The Conversation

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   John ED Barker

   (Adjunct Professor at Murdoch University)

   Thanks Dominique for a valuable contribution to the vexing conversation on energy and buildings. I would commend readers to the City of Melbourne report as a good example of properly conducted applied research. The report's findings support the less rigorous research that we conducted over 20 years ago.

   However, the report raises a number of concerns that I believe are more than 'academic nitpicking':

   First, although the report has many well-considered caveats, the overall impression is that…

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   Thanks Dominique for a valuable contribution to the vexing conversation on energy and buildings. I would commend readers to the City of Melbourne report as a good example of properly conducted applied research. The report's findings support the less rigorous research that we conducted over 20 years ago.

   However, the report raises a number of concerns that I believe are more than 'academic nitpicking':

   First, although the report has many well-considered caveats, the overall impression is that the use of commercial 'Cool Roof Paints' (CRPs) could make a significant contribution to energy flows and demand. The results are generally 'measurable', but not 'significant'. The likelihood, as discussed in the report, is that in most cases the heavy lifting has already been done by adequate insulation and the extra contribution by CRPs is negligible. At a scientific level, this is fine, but at a commercial level I can see the report being used and abused by CRP vendors. One only has to look at the website claims of these vendors (as quoted in the report) to see that most of their statements are (non)scientific gobbledegook. The roof coating industry has been notorious for decades for its predatory behaviour- a report with a prestigious university imprimatur is just what they want to impress more unwitting householders and to ultimately fleece them of thousands of dollars for negligible benefit. Try Googling 'roof coating scam' and peruse some of the more than 100,000 hits to get the gist of the problem.

   To the CRP issue one can add the 'rotating roof ventilator' myth. Certainly, a highly ventilated roof cavity will reduce cavity temperatures and consequently room temperatures. Again, most of the problem can be addressed with R4 insulation. Our research showed that ventilation rates from fans with ten times the ventilation rate of rotators still had a negligible (but measurable) effect on roof space temperatures. Open eaves, high pitches and louvred roof peaks are required to make a significant difference.

   The householder would be much better off insulating the ceiling and drawing the heat build-up INTO the house in winter (if they live in a cold, sunny region- probably not Melbourne).

   Which all points to the reason why, after 200 years of building in Australia, we still have a problem with building energy flows- it's simple, but it's subtle- that is, each element is scientifically measurable, but there are many factors to consider in real buildings that make it a dynamic, complex system.

   In my view the problem can be triaged- a lot can be dealt with by simple methods (insulation, orientation etc); some cases are pretty hopeless (ie can't be remedied cost-effectively by any known means); and a sizeable proportion of buildings need a 'house doctor' (technical background and significant training and experience) to deal with the complex symptoms. 'House paramedics' (ie a few weeks' training and a clipboard) of the kind recently sponsored by the Commonwealth can deal with the first group, but like conventional paramedics, they shouldn't be deluded that they can easily solve all problems.

   And we must beware of inadvertently providing sales material for CRP/snakeoil salespeople.

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      Paul Richards

      (logged in via Facebook)

      "And we must beware of inadvertently providing sales material for CRP/snakeoil salespeople." - I was right with you up until you used this high handed comment.

      To denigrate the ability to communicate with others is low brow. Individuals motives level of development cant' be lumped into your reference to sales of environmental products.

      Some of the most under evolved individuals have degrees, masters PhD and are friends as are some of the sales people I know.

      Surely the cultural centre of gravity will do with the knowledge University decimate as it's see fit. Who appointed anyone the keeper of knowledge?

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         John ED Barker

         (Adjunct Professor at Murdoch University)

         Sorry to upset you, Paul, although I'm not sure how my statement connects to your concerns. Maybe if you could explain it in sentences using conventional logic and grammar we could have a fruitful conversation.

         If you don't like university education, then you're going to have a sorry time trolling this website- as you would see if you read the masthead- this website is sponsored by Australia's leading universities. There are plenty of other websites I could recommend if you really feel like slagging education. This isn't one of them.

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            Paul Richards

            (logged in via Facebook)

            John my second reply, to clarify the poor explanation for the perspective you hold.

            Firstly,
            the comment made initially was regarding “And we must beware of inadvertently providing sales material for CRP/snakeoil salespeople.”
            To which your answer was “……. although I'm not sure”
            Is a redundant statement, as this was part of my opening comment.

            Secondly,
            the comment “Sorry to upset you ……” is debatable as you referred to “trolling” and “If you don't like university education”. So, the…

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            John my second reply, to clarify the poor explanation for the perspective you hold.

            Firstly,
            the comment made initially was regarding “And we must beware of inadvertently providing sales material for CRP/snakeoil salespeople.”
            To which your answer was “……. although I'm not sure”
            Is a redundant statement, as this was part of my opening comment.

            Secondly,
            the comment “Sorry to upset you ……” is debatable as you referred to “trolling” and “If you don't like university education”. So, the - “sorry statement” - doesn’t carry weight with anyone.

            Thirdly,
            Any comments made by anyone here is meant to be respectful, that is part of the “Community Standards: The 10 Rules”

            Fourthly,
            The issue of allusion to exclusive use of “The Conversation comments” by staff of Australia's leading universities is offensive to all who comment, and contrary to the principles this forum was founded on. The Conversation was designed as a conduit to the wider Australian Public, allowing the free flow of academic knowledge, findings, studies, opinion, and create a dialogue between academia, Australian's and others.

            Which is where exception was taken, see your statement encouraging Dr Dominique Hes to be frugal and selective with data. [she is her own woman and well qualified to know what and when to say anything, it is possible this machismo was offensive to her also]

            “ ……. we must beware of inadvertently providing sales material for CRP/snakeoil salespeople.” - John ED Barker

            This is an open forum, - encouraging - a colleague to be - sparse - with information is not appropriate in this venue and offensive to others. Not to mention judgmental of those who comment here. Cloistering of knowledge is ending, this mindset is dying, being opened up worldwide. Any attempt to squirrel data away as has been done for hundreds of years by academia will be met with extreme resistance.

            Fifthly,
            we all endeavour to accept each others perspective, some are highly intelligent, can hold multiple degree but their personal value systems are not developed. Same is true of the opposite, some hold no recognition, but have highly evolved value systems. Naturally the range between these extremes is large.

            Awareness of each others perspective is crucial in this forum. If this goes over your head, that may be because of the use of the language of “Foresight”, my area of study and experience. For this I apologise.

            Please take this reply in “comments” as encouragement to be open, honest and generous with data. As does your former colleague Dr Dingle.
            Wishing you well.

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               John ED Barker

               (Adjunct Professor at Murdoch University)

               Paul- I generally err on the side of more, rather than less information. In this case I was simply drawing attention to the point that Dr Hes is dealing with issues that are the feedstock of unscrupulous people. I have seen many cases of scientists becoming implicated simply because they replied to (and refuted) tricksters. The trickster's claim is then that they are "in close correspondence with Dr X at University Y" without telling the full story.

               In this case I think that Dr Hes's team could…

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               Paul- I generally err on the side of more, rather than less information. In this case I was simply drawing attention to the point that Dr Hes is dealing with issues that are the feedstock of unscrupulous people. I have seen many cases of scientists becoming implicated simply because they replied to (and refuted) tricksters. The trickster's claim is then that they are "in close correspondence with Dr X at University Y" without telling the full story.

               In this case I think that Dr Hes's team could have improved their report (and reduced the likelihood of misrepresentation) by providing a more detailed executive summary to the report that made it clear that in most cases CRPs don't perform any better than (much cheaper) standard white paint, particularly in common situations where the roof/ceiling is already insulated. Most of this data is in the report, but easy to miss or avoid.

               It's all a matter of balance and judgment of course and scientists can't be held responsible for the (verified) information they provide, although they-like others- can be held responsible for the advice they give. Scientists are often accused of not being sufficiently worldly. I'm just providing a bit of 'real world' information that might help their advice-giving.

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                  Paul Richards

                  (logged in via Facebook)

                  John - agreed, we aree on the same page. My response in comments are an illustration the difference between academic dialogue and this conduit to the wider public.

                  As a person who has been on the coal face of providing product information, awareness of deceptive practices is heightened. So respect your sensitives, while stressing the need to disseminate information freely and accurately. Thanks for the reply.

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               Paul Richards

               (logged in via Facebook)

               John - recommend you go easy on the language used, some of these people are highly intelligent and have a completely different value system to you.

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   Robert Nelson

   (Associate Director Student Experience at Monash University)

   Dominique Hess helpfully draws attention to the great potential for controlling temperatures through the reflectivity of building stock rather than energy consumption inside offices and houses.

   From a greenhouse point of view, however, the value of the research must be qualified. Shedding the heat in summer is a worthy objective but not necessarily if it means losing the warmth in winter, for which carbon is sacrificed in compensation. It would therefore seem logical to concentrate on architectural…

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   Dominique Hess helpfully draws attention to the great potential for controlling temperatures through the reflectivity of building stock rather than energy consumption inside offices and houses.

   From a greenhouse point of view, however, the value of the research must be qualified. Shedding the heat in summer is a worthy objective but not necessarily if it means losing the warmth in winter, for which carbon is sacrificed in compensation. It would therefore seem logical to concentrate on architectural skins that can be changed according to the weather rather than fix our designs with an invariable reflectivity through paint.

   It is perhaps a historical anomaly that we were able to create devices such as shutters on windows in the fifteenth century, where it seems an insuperable challenge for architects today to erect anything similar, with all our technological sophistication. Shutters or blinds may also mitigate the heat island effect with which Hess is primarily concerned; but they would have the additional benefit of a reduction in energy consumption all year ’round.

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      Alex Cannara

      (logged in via Facebook)

      The "heat in winter" thing misses the reality of current building standards. Even in arctic climes, we want reflective structures. The insulation requirements for any new/remodelled structure are, in US at least, such that even the rooms just beneath the roof have near zero thermal coupling to the roof.

      When an honest analysis is done, the effect of winter sun on a black roof, but over code insulation (R39...) is the same as one person entering the room with you, or turning on a 150W lamp (now illegal).

      And, the above result comes from assuming overhead sun, even in winter, at the rate of 1kW/sq meter -- obviously false.

      So, in any clime, there's so much human structure outside in the sun, making it reflective is key.

      Remember the 3 reasons: cooling (arctic or summer), avoidance of unnatural IR to GHGs; and, roof longevity.

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         John ED Barker

         (Adjunct Professor at Murdoch University)

         Alex- although the universal use of reflective structures might partly mitigate urban heat island problems (it doesn't reduce vehicle-based heat for example), much of what you have said simply doesn't apply in Australia.

         While some houses have reflective foil underneath the roof material, most houses only have bulk insulation on the ceiling, therefore not reducing heat ingress to the roof/ceiling cavity. R39 (US- or about R7 in Oz metric measure) is arguably appropriate in Minnesota (winter) or…

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         Alex- although the universal use of reflective structures might partly mitigate urban heat island problems (it doesn't reduce vehicle-based heat for example), much of what you have said simply doesn't apply in Australia.

         While some houses have reflective foil underneath the roof material, most houses only have bulk insulation on the ceiling, therefore not reducing heat ingress to the roof/ceiling cavity. R39 (US- or about R7 in Oz metric measure) is arguably appropriate in Minnesota (winter) or Phoenix (summer) but not in Australia- less than half that thickness will do the job.

         I can assure you that ceiling-space heating works- in fact there are companies in Australia and New Zealand providing retrofit services successfully- and cost-effectively. Some sunshine is required- but do the sums of even 200w/sqm over 200sqm and you have more heat than you need. Besides, sunny days often correlate with cold nights, so if one has a high thermal mass house (ie brick, stone etc) then the daytime energy can be stored. More complexity!

         While not discounting the possible effect of UHI's on amenity, in the greater scheme of things they make a negligible contribution to global albedo. Perversely, land clearing has a greater effect than white urban roofs and forests have the same effect as dark roofs. As I said- it's complex and I encourage discussion that adds more verified data- but CRPs are not a silver bullet.

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            Alex Cannara

            (logged in via Facebook)

            John, what's on the sun-exposed surface is what counts for reflectivity. Obviously, foil underneath sees no visible and can only deal with some IR.

            Also the vehicle reference is meant to show how large an effect a global improvement of structure reflectance is, not that it mitigates car heat. The effect is as if the GHGs from a decade of 600,000,000 petrol vehicles were not in the air. Obviously that;s not what the reflectance does, it simply avoids the IR heating that could also have been…

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            John, what's on the sun-exposed surface is what counts for reflectivity. Obviously, foil underneath sees no visible and can only deal with some IR.

            Also the vehicle reference is meant to show how large an effect a global improvement of structure reflectance is, not that it mitigates car heat. The effect is as if the GHGs from a decade of 600,000,000 petrol vehicles were not in the air. Obviously that;s not what the reflectance does, it simply avoids the IR heating that could also have been avoided by not emitting in the first place.

            Reflectivity increase buys time to limit warming a bit while we truly address GHG content of the air. It also saves HC outgassing & tons of petroleum materials in such roofs and dump space for the old stuff that wasn't reflective. Plus, it saves all the process/transport fuel, and $ for the owner -- ~$1000/year here in Calif.

            As to winter sun heating inside rooms, "200w/sqm over 200sqm" assumes 200 sqm get full sun. Unless the roof is mounted to face the sun. like a solar panel, and even moved to follow winter sun, the effect inside remains teeny. But, the bad effect of creating 10s of kW of unnatural IR to send back up to waiting GHGs is the truly foolish environmental choice. If there are folks selling this to homeowners, then they should also be responsible for the costs of short roof life, and an effective carbon tax for increasing GHG excitation & global warming.

            Your remark: "...forests have the same effect as dark roofs" is obviously false, as any biologist will tell you. Live plants don't assume higher temps than air, but dark surfaces do. Why? Surely you know about the spectrum of leaf reflectivity -- otherwise? Surely you know about leaf transpiration? Surely you know that a mature broadleaf tree is effectively a 50kW cooling system in the sun, while a dark roof is a 50kW heater. You can look up how plants work. They don't work like inert, dark materials. If you don't want a light roof, plant a tree or two -- even better.

            So, because >2% of all Earth's land is now covered by human structure, how reflective those surfaces are has an effect. The Earth's heat balance is now bout +1/2 Watt/sqm (heating). Given the net insolation of 86,000,000,000,000,000 Watts coming onto Earth from the Sun, having >2% of the 25% of Earth that's land be more reflective means a great deal, per sqm.

            Perhaps you're selling something that influences what you say, but facts are facts.

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               John ED Barker

               (Adjunct Professor at Murdoch University)

               Alex- I note your snide comment in your last sentence that is out of place on The Conversation.

               Albedo is a very complex matter- try reading the entry on Wikipedia as a starter. Different forests have different net heating or cooling effects depending on their associated transpiration. Eucalypts, for example, have a higher albedo than most deciduous forests, but have a lower transpiration, thus less cooling and less cloud-forming with less cloud-related albedo.

               The average Sydney and Perth roof (approximately horizontal) receives about 2kw/m2 in mid winter, thus providing a maximum of about 400kw on an average roof. Tapping a small fraction of this can heat the house.

               And to point out a further perverse complexity- PV panels convert about 15-20% of incident sunlight to electricity but have an albedo of about 0.2- ie very dark. So, what shall we do when our white painted roofs are covered with IR- producing PVs? The issue of significance is the key.

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                  Alex Cannara

                  (logged in via Facebook)

                  John.l sorry if you sensed something uncomfortable being said about what you said that was wrong, but you must expect this when you do say wrong things repeatedly in front of others who don't deserve misleading statements,

                  For example: "Perth roof (approximately horizontal) receives about 2kw/m2 in mid winter" -- no place on this planet gets 2kW/sqm. Why? Because even in near space, the max solar intensity is 1366W/sqm. At the surface, on the best days, it's about 1kW/sqm -- look it up…

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                  John.l sorry if you sensed something uncomfortable being said about what you said that was wrong, but you must expect this when you do say wrong things repeatedly in front of others who don't deserve misleading statements,

                  For example: "Perth roof (approximately horizontal) receives about 2kw/m2 in mid winter" -- no place on this planet gets 2kW/sqm. Why? Because even in near space, the max solar intensity is 1366W/sqm. At the surface, on the best days, it's about 1kW/sqm -- look it up.

                  Whether forests range from cooling to slightly warming, they do things we all need -- emit oxygen, maintain cool understories, absorb CO2 for as long as they live, and sustain wildlife, including birds, bats, insects, etc. that assist farmers in fighting undesirable insects, etc.

                  You're right about PV panels, except that, if you paint the roof, then put panels on that are at least 20% efficient (e.g., Sunpower E20), you'll at least have electricity taking place of whatever emitting generator you use, to the tune of 0.8lb/kWHr for gas, ~1.2x that for oil & ~1.8 that for coal. So, there's a tradeoff, but paint the roof to get started. >20% efficient cells are now in our military & space systems & will be coming to your neighborhood in a couple of years.

                  No other 'renewable' has one or two efficiency/power-density doublings in its future. That's why efficiency, on-structure solar PV, EV/storage & nuclear are the environmentally wise futures.

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                     John ED Barker

                     (Adjunct Professor at Murdoch University)

                     Alex- I don't expect respondents on TC to imply (without foundation) that I have an undeclared vested or commercial interest in a particular outcome. That's called trolling. Can I assume that you do not have a commercial interest in Sunpower PVs or CRPs?

                     As to rooftop radiation- it is pretty obvious from the whole sentence that I meant 2kwh/m2/DAY.

                     You have not explained how the colour of the roof surface is going to make any difference if it is covered with PVs.

                     I'd prefer if you kept this conversation to albedo issues and left the forest birds and bats to another forum.

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                        Alex Cannara

                        (logged in via Facebook)

                        John thanks for your 'cleanliness' of advice concern. I don't car what anyone uses for solar PV as; long as it's the most efficient available. What's CRP? If I'm not selling anything what are you?

                        Pardon my reading that I didn't divine the "obvious from the whole sentence that I meant 2kwh/m2/DAY." -- that's high anyway -- if your system doesn't track the sun, it won't get 10 hours of 20% of 1kW/sqm anyway.

                        As to roof under PVs, well, remember the 3 reasons for lightening roof color? One is life extension. PV panels don't cover every sq inch, nor are they flush -- can't be, due to their framing, inverters, thermal dissipation & back IR. So indeed, the roof treatment will help a little to save you $, even under the panels. But, you knew this already, didn't you, you sly dog?

                        What you or I "prefer" can't be allowed to interfere with relevant fact -- that's the purpose of any "forum", John. We know you know we know you know this.
                        ;]

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                           John ED Barker

                           (Adjunct Professor at Murdoch University)

                           Alex- If you had read even the introduction of the report upon which Dominique's article is based- (Cool Roofs: City of Melbourne Research Report September 2011 The University of Melbourne)- you would know that CRP stands for 'Cool Roof Paint'.

                           If you cared to look at any of the readily available data for Australia you would see that I am quoting verified data. Try http://www.energymatters.com.au/climate-data for example.

                           Flush or not, the PV panels will obscure the roof from direct solar…

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                           Alex- If you had read even the introduction of the report upon which Dominique's article is based- (Cool Roofs: City of Melbourne Research Report September 2011 The University of Melbourne)- you would know that CRP stands for 'Cool Roof Paint'.

                           If you cared to look at any of the readily available data for Australia you would see that I am quoting verified data. Try http://www.energymatters.com.au/climate-data for example.

                           Flush or not, the PV panels will obscure the roof from direct solar radiation. The roof surface would need high reflectance in the IR to have any effect at all on any IR radiation from the back of the PV panels- this would mean a metallic surface- which would usually have a low emissivity, making a complex situation with a net heat buildup. "Helping a little" is not good enough if the cost is high.

                           The rapidly reducing costs of PVs means that homeowners are going to cram as much as possible on to their roofs, thereby minimising the exposed areas.

                           Please explain to me why forest bats are relevant to rooftop albedo. Suburban bats might be, particularly in Sydney where their droppings reduce rooftopp abedo.

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                              Alex Cannara

                              (logged in via Facebook)

                              Aw, you got me, John. I recalled CRP after I sent the comment. Never heard it before. Forgive me? Please? Please?

                              Indeed ,metallic paint under panels is fine, simply because it's just aluminized, thus meeting your "metal" requirement. And, it's relatively lots cheaper than elastomerics used for white roof painting. It also lasts a very, very long time in the sun or under a panel -- aluminium, you know?

                              You seem to have picked up a term or two, but miss key facts -- emissivity is not what's wanted when you're reflective and without frequency shifting -- hold a mirror to the sun or touch a white car -- emissivity takes 2nd place to reflectivity (albedo -- since you learned that one too).

                              Emissivity is what an absorbing surface uses to keep the interior a bit cooler while not caring about the great amount of unnatural IR the surface radiates back up to GHGs.

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                                 John ED Barker

                                 (Adjunct Professor at Murdoch University)

                                 Alex- Your condescension is rather misplaced. I think that with a PhD in physics and 40 years of researching and teaching in solar energy and especially thermal design of buildings, that I might have "picked up a term or two".

                                 ...which is not an attempt to pull rank on you, but to point out that smart-ass comments like "You seem to have picked up a term or two" don't go down well around here- TC has many very well-informed readers who are trying to extend their knowledge-as I am.

                                 To address…

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                                 Alex- Your condescension is rather misplaced. I think that with a PhD in physics and 40 years of researching and teaching in solar energy and especially thermal design of buildings, that I might have "picked up a term or two".

                                 ...which is not an attempt to pull rank on you, but to point out that smart-ass comments like "You seem to have picked up a term or two" don't go down well around here- TC has many very well-informed readers who are trying to extend their knowledge-as I am.

                                 To address the point that I think that you are making- if the back of a PV panel is hot and not highly ventilated (like most installations), then heat will be transferred to its surrounds (mainly the roof) by conduction, convection and radiation. In this kind of space, conduction and convection will be significant and it is likely that the roof will be at close to the same temperature as the back of the panel, irrespective of its colour, albedo, or material. In turn, the roof will transfer heat to its surrounds, part of which is the downward direction. Ventilation will help, but absorption and re-radiation in the near-IR (ie 'heat') will remain important.

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                                    Alex Cannara

                                    (logged in via Facebook)

                                    Oh John, there you go again. Read your own mildly "smart-ass" comments.

                                    Glad you have a degree or two. Me too, maybe more.
                                    ;]
                                    Doesn't mean I should drop terms when unnecessary. I'm not selling my consulting or products here.

                                    The point you seem needing to miss is that under a hot panel where inverters are rated at 85C) it's better to have some reflectivity in the IR to save the roof (if petroleum composite) from deteriorating/outgassing pollutants, etc. That's part of the life-extension factor -- very important to long-term costs & petroleum consumption from re-roofing.

                                    But, tell folks not to paint before the panels go on & paint afterward, if you like.

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                                       John ED Barker

                                       (Adjunct Professor at Murdoch University)

                                       ...and the point that you seem to miss, Alex, is that here in Australia asphalt roof tiling is rarely used. It's mainly terracotta or clay tiles or corrugated iron- often powder-coated.

                                       ...which serves to demonstrate that one should take care to find out whether there are common basic premises before entering a debate.

                                       Am I 'dropping terms' when they are terms used by the author? Use of terms like R39 are pretty meaningless here- only the Republic of the USA uses this old Imperial measure.

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                                          Alex Cannara

                                          (logged in via Facebook)

                                          We have tile roofs here too, John. We've metal roofs, we've tar & gravel roofs, we've asphalt=composite roofs -- name a roof, we've got in in Calif!

                                          What you hope others missis that it doesn't matter what the roof material is as far as reflectance -- that's a property of the first layer of molecules, as JohnN agrees as well.

                                          But, I'll explain more in response to your other comment somewhere below. At least now we all know you're selling something.
                                          ;]

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      Dominique Hes

      (Senior Lecturer in Sustainable Architecture at University of Melbourne)

      Thanks Robert, in the full report we discuss this very important point. We did 12 months of monitoring to see the overall summer/winter benefit and we did the sensitivity on various aspects to ensure net benefit, and as you say for Melbourne residential has the least benefit. Though there is still some while for commercial and industrial building the benefit is clear.
      In the larger study, where the model will be developed, we will be able to give more detailed analysis on the contribution to the heat island effect – both positive and negative.

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   Douglas Cotton

   Climate Research (logged in via email @hotmail.com)

   When you are developing that "urban microclimate model" I am somewhat curious as to whether you envisage studying purely the temperatures within buildings, or whether you expect to somehow control outside air temperatures to any degree.

   If it is the latter, then I would suggest there is now evidence that humans can have no significant control over such. The concept of an atmospheric greenhouse effect has now been proven by Professor Claes Johnson* to be a physical impossibility, and 31,000…

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   When you are developing that "urban microclimate model" I am somewhat curious as to whether you envisage studying purely the temperatures within buildings, or whether you expect to somehow control outside air temperatures to any degree.

   If it is the latter, then I would suggest there is now evidence that humans can have no significant control over such. The concept of an atmospheric greenhouse effect has now been proven by Professor Claes Johnson* to be a physical impossibility, and 31,000 scientists so far have signed a statement to the effect that anthropogenic global warming is greatly overstated.

   The backradiation that is supposed to be warming the ground cannot do so because its frequency is below the cut-off frequency of the warmer surface. As a result it is not converted to thermal energy at all, as Johnson proves computationally. In fact, as we can observe, it can't even melt a bit of frost in a shady spot, let alone warm the oceans.

   Whilst controlling the absorptivity of, for example, road surfaces may appear to have an effect, you will at the same time alter emissivity in such a way that the net effect over a 24 hour cycle will be nil. More thermal energy flows into a road surface on a hot sunny day than on a cold one. But it cools back down to a similar temperature at night. Changing the colour would be similar to such a variation in sunlight.

   Having been through the home-building process four times in my life, I know the nature of personal decisions that are involved in making all the colour choices etc - including of course the roof colour. I really can't see the government having much control over such, and that, I suggest, is a good thing.

   I'm sorry, but if I had a say in funding your research my response would be in the negative.

   * http://climate-change-theory.com/RadiationAbsorption.html

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      Alex Cannara

      (logged in via Facebook)

      Uh oh, Mr. Cotton is back here too, but now without his picture.

      His citings are more often wrong than right & this one, that surface heating/reflectivity have no upward contribution to the greenhouse effect is similarly wrong. But, his other posts on overall effects show why he makes such a physically-impossible assertion -- to cover other impossible assertions.

      The effect on global warming of both absorption & reflection on surfaces (human or natural) has been understood for decades, notably…

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      Uh oh, Mr. Cotton is back here too, but now without his picture.

      His citings are more often wrong than right & this one, that surface heating/reflectivity have no upward contribution to the greenhouse effect is similarly wrong. But, his other posts on overall effects show why he makes such a physically-impossible assertion -- to cover other impossible assertions.

      The effect on global warming of both absorption & reflection on surfaces (human or natural) has been understood for decades, notably by the work at Lawrence Berkeley Labs, the Heat Island Group, Calif. Energy Commission, DoE, etc.

      It's quite simple: GHGs absorb various frequencies of light, below visible -- infrared (IR). And so anything that gets hot under/in the air re-radiates IR, thus being much absorbed, mostly by the broad frequency bands of water vapor.

      The key is to reflect surface sunlight back to space without alerting its spectrum -- without filling in energy (IR) bands already depleted by GHGs on the way down. White/aluminized roofs do this, as do living plants, especially broadleaf trees (they look green because they use blue & red for their own energy needs), which directly reflect much IR.

      So a typical home roof, if dark & rough, can be a 50kW heating element to the air directly, and return IR radiation to GHGs above it at an equivalent temperature far above ambient. What's also happening bad is converting visible light frequencies to IR. Those frequencies could have largely passed upward to space, if linearly reflected (no frequency shifts), but moved down to IR allows them to re-excite GHGs above and add to atmospheric heating unnaturally.

      And, another reason for light-colored, reflective roofs is that they last longer. A typical composite-shingled roof lasts under 40 years, but if made reflective, will about double its life. It contains a few tons of petroleum-derived material, so doubling roof life not only saves fossil input material, it saves on transport & dump space.
      
      Even discounting life extension, just raising the average reflectivity of human structures (including parking lots) around the world by ~40% reduces atmospheric GHG warming equivalent to removing the GHGs produced by all fuelled vehicles in the world to zero, for a decade. The effect is large.

      Cultures in sunny climes have long known about the cooling benefits of white/roofs/structures, and glider pilots have long known how to exploit the opposite.
      ;]

   2. Permalink

      

      Dominique Hes

      (Senior Lecturer in Sustainable Architecture at University of Melbourne)

      we will be looking at the urban heat island and the contribution of decisions to it, this is within our control as we can show what we add to the impact..

      1. Permalink

         

         Paul Richards

         (logged in via Facebook)

         Dominique - thanks.
         The issues you have been challenged or diverted to, are simply not worthy of a response. Your article is clear and concise, appropriate for discussion amongst evolved critical thinkers and sound.

         Having consulted in the energy control business since 1978, and anecdotally having had a working life observing this very issue, making a living from people who had contrary views your article and content is correct.

         With this perspective I have read the usual scientific piffle espoused and can assure you these individuals are simply trying to cling onto there redundant value systems, bolster their "story", their intelligence is not in question.

      2. Permalink

         

         Douglas Cotton

         Climate Research (logged in via email @hotmail.com)

         Could you clarify how you can show what you add to the impact? You make reference to the current belief by many that there is a greenhouse effect, but the point of my comment was to draw your attention to Prof. Claes Johnson's "Computational Blackbody Radiation" which proves that such is a physical impossibility. When someone proves empirically that so-called backradiation actually warms anything that's already warmer than the cold atmosphere it came from, then Johnson and I will be proved wrong. But while it doesn't even melt a bit of frost shaded from the Sun, I'm backing Johnson and those who have demonstrated empirically that he is right.

         For more detail, see my post here: https://theconversation.edu.au/durban-did-too-little-here-are-alternatives-to-the-un-process-5010
         

         1. Permalink

            

            Dominique Hes

            (Senior Lecturer in Sustainable Architecture at University of Melbourne)

            In about 18 months we will be able to clarify definitively what we can show... our intension is to produce a tool to help with planning and development decision making at a urban level.. for example... if we use tree 'x' instead of tree 'y', if we place them every 10m apart or every 50m; if we use concrete instead of bitumen; if we use white or light coloured roofs instead of dark; etc... What is the impact on the heating up of the city and therefore the assumed cooling and energy use? It remains about Urban Heat Island a demonstrated phenomenon…
            To respond specifically to your reference of Prof. Claes Johnson's "Computational Blackbody Radiation" I am not qualified to give meaningful opinion.
            This article was about high albedo roofs reducing temperature in and around the building and therefore leading to less energy required for cooling... in Melbourne that means less burning of brown coal and CO2 emissions.

4. Permalink

   

   Douglas Cotton

   Climate Research (logged in via email @hotmail.com)

   In regard to temperatures inside houses, I would suggest that it's obvious why people use more energy on warming than cooling in Melbourne. (One year of my life living in Melbourne was quite enough.) Simple heating devices will always be cheaper to buy than ducted air-conditioning.

   So, yes, it does make good sense to keep a house cooler. But it is also obvious that ceiling insulation and ventilation can achieve this.

   I made the mistake of choosing raked ceilings in my previous house. On reflection, it's obvious that such a home would get hot without a ventilated roof space. So perhaps one thing the government could do would be to outlaw such designs.

   There, I've done all the research you need. Get another job.

   1. Permalink

      

      Dominique Hes

      (Senior Lecturer in Sustainable Architecture at University of Melbourne)

      Agreed, but using passive techniques we can do very well heating and cooling. The white roofs project just added to the options you can choose from. Ventilating roof stape is also a good option, and even cheaper than the paint.

      1. Permalink

         

         Douglas Cotton

         Climate Research (logged in via email @hotmail.com)

         I would go along with a suggestion that more people drive white cars which would reduce fuel consumption for their air conditioners and also reduce risk of accidents due to better visibility.

         But I can't see many people wearing the cost of painting and re-painting their roof tiles which should not need painting at all. At least insulation serves a dual purpose both in summer and winter.

         We just need fans in the roof that can be turned on when it's hot and off when cold, perhaps automatically.

         P.S. We also need instant microwave hot water services under each sink in the house as these would heat far more efficiently and save water too. There - make a fortune if you can patent such.

         1. Permalink

            

            Douglas Cotton

            Climate Research (logged in via email @hotmail.com)

            P.P.S. Connect those electric roof fans to a small solar generator and they will automatically operate when the Sun shines - just what you want.

            1. Permalink

               

               Michael J. I. Brown

               (ARC Future Fellow and Senior Lecturer at Monash University)

               Doug Cotton is may be many things (e.g., dental software salesman) but he is not a climate researcher. His climate websites are largely pseduo-science gibberish.

               1. Permalink

                  

                  John Nicol

                  (logged in via Facebook)

                  Michael,

                  You should be very grateful to Doug. By making a well balanced and accurate comment, he gave you another opportunity to be rude, which s something you love doing! John Nicol

                  1. Permalink

                     

                     Alex Cannara

                     (logged in via Facebook)

                     John! You've not responded to the email conversation you started with me about your misinformation on GHG effects. Where have you been? Is non-response also "rude" in your mind?
                     ;]
                     cannara at sbcglobal dot net or just call 650-400-3071 any time John!

      2. Permalink

         

         Alex Cannara

         (logged in via Facebook)

         Unfortunately, as John Nicol agreed, the reflectivity of the first sunlit surface is what counts. Anything done below that can't make up for the air/GHG warming above a dark surface. As to winter heating, the angle of winter sun makes it absurd, even if one wanted to leave the roof & rooms under it totally uninsulated.

         We have such homes here in Calif. -- made by Eichler decades ago for low cost. Their interior ceilings are the roof. Many of these now have white or aluminized roofs. One in particular has been studied and while the occupants used to need air conditioning or fans in summer, they need them not at all now. In winter, they see no addition to their heating bills, which, of course, makes engineering, as well as common, sense.

         All these effects are easily measured with common radiance & thermal tools.

         What's mystifying is why this seems to be controversial. Are some folks here making $AU off customers whom they mislead?

5. Permalink

   

   Derek Fiddler.

   Albedo Australia (logged in via email @albedoaustralia.info)

   This research appears to be redundant in that this ground has been covered in depth by the Heat-Island Group, Hashem Akbari et al., as well as many other research groups. The landmark study was the modelling of a 0.075 (7.5%) increase to urban albedo, along with the strategic planting of trees to shade buildings, in 1998. Melbourne Uni Earth Sciences also mapped Melbourne's UHI in that year.

   Last year a study showed that increasing urban albedo via painting roofs and footpaths is even more effective…

   show full comment

   This research appears to be redundant in that this ground has been covered in depth by the Heat-Island Group, Hashem Akbari et al., as well as many other research groups. The landmark study was the modelling of a 0.075 (7.5%) increase to urban albedo, along with the strategic planting of trees to shade buildings, in 1998. Melbourne Uni Earth Sciences also mapped Melbourne's UHI in that year.

   Last year a study showed that increasing urban albedo via painting roofs and footpaths is even more effective than the models predicted. The study also measured the cooling effect of green roofs vs painted roofs and found that the painted roofs cooled urban areas more effectively than green roofs. There is also the problem of maintenance and where to put shrubbery in most urban areas. High albedo roofs win hands down.

   You did not mention in your study the benefits of increasing urban albedo with regards to their effect upon local temperatures and thereby an effect on air-conditioning energy consumption? By lowering urban temperatures one then gain expected reductions of over 50%, not the 3-15% that you measure for an individual building.

   However, save the taxpayer some money and look at the research that has already been done in this area. e.g. Real World Evidence of the Effevts of HIgh Albedo vs Green Roofs in Chicago
   by Cris Mackay et al.. Instead of spending $25 million openning or closing Swanston Street perhaps some funds could be directed towards increasing Melbourne's urban albedo in order to save lives, electricity and it's associated emiisions along with healthier longer lives for residents due to the reduced amount of and number of days of photochemical smog.

   As is mentioned in the article we lost over 374 people due to the last heatwave. How much longer must we procrastinate before we "do something" to reduce Melbourne's quite pronounced urban heat island?

   ... Derek Fiddler.
   Albedo Australia

6. Permalink

   

   Lorna Jarrett

   PhD candidate, science education; Physics teacher (logged in via email @diment.org)

   I'm frankly astonished by the suggestion that dark roofs might be a good idea. I'd be grateful if Dominique can explain in very simple terms that a physicist can understand!

   My reasoning is as follows:
   1. Yes, a dark roof will collect more heat in winter, but this heat will only be transferred into the house if the roof insulation is poor. The same poor insulation will allow heat loss at night. A black roof will radiate heat at a higher rate at night.
   2. In summer, the black roof and poor insulation…

   show full comment

   I'm frankly astonished by the suggestion that dark roofs might be a good idea. I'd be grateful if Dominique can explain in very simple terms that a physicist can understand!

   My reasoning is as follows:
   1. Yes, a dark roof will collect more heat in winter, but this heat will only be transferred into the house if the roof insulation is poor. The same poor insulation will allow heat loss at night. A black roof will radiate heat at a higher rate at night.
   2. In summer, the black roof and poor insulation will make the house a hot box, requiring more energy for cooling than if the roof had been light and the insulation good.
   3. In summer the energy intensity and daylight hours are both longer than in winter, so the amount of unwanted heat gain in summer will be greater than the amounted of desired heat gain in winter.
   4. Also, in winter the Sun's at a lower angle. With a typical (in Australia) shallow roof, more of the Sun's energy will be reflected during winter and absorbed during summer (this has led to advice to mount solar hot water systems at 60o to horizontal in Melbourne rather than directly on roofs - because they overheat in summer and under-perform in winter. I own one and can confirm this). Everyone knows the advantage of putting windows on the North side of the house as they collect most heat in winter when the Sun is low in the sky. It seems to me that roofs have the opposite effect - gaining most heat in summer.

   I think my reasoning is correct but realise it lacks quantification. If anyone is able to provide such quantification I'd very much appreciate it.

   Especially as I'm designing a house.

   1. Permalink

      

      Dominique Hes

      (Senior Lecturer in Sustainable Architecture at University of Melbourne)

      Thanks Lorna,

      Derek, we were asked to study it for Melbourne because of its unique climatic conditions - very high UV, high residential heating load, etc. Also, Derek, we referenced and looked at the work you mentioned. Finally, these results are measured, we saw real benefits, and we are comparing this to a dark roof now and will report on it openly and honestly in 6 months time. There is no agenda; we just want to see if it makes sense and for the roofs we have tested, given the outline in the research, it does.

      1. Permalink

         

         Alex Cannara

         (logged in via Facebook)

         Sounds good Dominique. Why do you say Melbourne is unique? Many other cities around the world have extremes you mention, such as Denver Colorado, Salt Lake City Utah, and many more at high altitudes with often clear skies that I don't know. And I hope you're aware of much historical work...
         www.climatechange.ca.gov/events/2008_conference/presentations/2008-09-09/Hashem_Akbari.pdf
         www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/02/19/DDTL15VQAG.DTL
         http://heatisland.lbl.gov/
         www.energy.ca.gov/commissioners/rosenfeld_docs/index.html
         www.energy.ca.gov/2007publications/CEC-999-2007-034/CEC-999-2007-034.PDF

         And many more.

   2. Permalink

      

      John ED Barker

      (Adjunct Professor at Murdoch University)

      Lorna- you raise a series of commonly-made claims. In the absence of any other response, I'll answer them, in turn:

      "I'm frankly astonished by the suggestion that dark roofs might be a good idea. I'd be grateful if Dominique can explain in very simple terms that a physicist can understand! My reasoning is as follows: 1. Yes, a dark roof will collect more heat in winter, but this heat will only be transferred into the house if the roof insulation is poor".

      • If the roof insulation is poor…

      show full comment

      Lorna- you raise a series of commonly-made claims. In the absence of any other response, I'll answer them, in turn:

      "I'm frankly astonished by the suggestion that dark roofs might be a good idea. I'd be grateful if Dominique can explain in very simple terms that a physicist can understand! My reasoning is as follows: 1. Yes, a dark roof will collect more heat in winter, but this heat will only be transferred into the house if the roof insulation is poor".

      • If the roof insulation is poor, then most of your conclusions are right. But this is not the reality in most cases in Australia. Even before the Rudd Government's "Pink Batts" program, about three-quarters of Australian houses were insulated. The proportion uninsulated now would be very small. As, in most circumstances, ceiling insulation is "a good thing", then we should start from the assumption of a ceiling insulated to at least R2.

      "The same poor insulation will allow heat loss at night."

      • Correct.

      "A black roof will radiate heat at a higher rate at night".

      • Negligible difference against other coloured tiles or paint. Aluminium slightly less but conductive and convective losses far more important.

      2. "In summer, the black roof and poor insulation will make the house a hot box, requiring more energy for cooling than if the roof had been light and the insulation good."

      • Yes, but there is a matrix of possibilities: black roof and good insulation is better than white roof and no insulation (see below). Further complications from building materials and window orientation eg a well-insulated brick house with west facing windows will remain hotter in the evening than a similar timber frame house without ceiling insulation.

      3. "In summer the energy intensity and daylight hours are both longer than in winter, so the amount of unwanted heat gain in summer will be greater than the amounted of desired heat gain in winter."

      • Yes, but only significant if ceiling is uninsulated. Ceiling heat gain in winter can be done by ducting roofspace heat down with a fan during the day (see my earlier posting).

      4. "Also, in winter the Sun's at a lower angle. With a typical (in Australia) shallow roof, more of the Sun's energy will be reflected during winter and absorbed during summer (this has led to advice to mount solar hot water systems at 60o to horizontal in Melbourne rather than directly on roofs - because they overheat in summer and under-perform in winter. I own one and can confirm this)".

      • Yes, but even in winter the energy on a horizontal surface (at Sydney latitude) is very significant (2kw/m2/day). Try staying in the ceiling of a dark-roofed house on a sunny winter's day and you'll confirm this!

      (5). "Everyone knows the advantage of putting windows on the North side of the house as they collect most heat in winter when the Sun is low in the sky."

      • I wish that they did. After 40 years of researching and talking my head off to thousands of people (from laypeople to architects), I wonder how 3 billion years of evolution under the sun as has a negligible effect on our collective understanding of this elementary observation.

      (6) "It seems to me that roofs have the opposite effect - gaining most heat in summer. I think my reasoning is correct but realise it lacks quantification."

      • Here's a simple example: Assume: summer- dark roof 70°C, white roof 50°C, inside temp 25°C; Uninsulated U-value 1.35, insulated U value 0.36 (R2 batts, no foil). E = UxAx(Tout-Tin). Giving: White (uninsulated)- 34w/m2; black (uninsulated)- 68w/m2; white (insulated)- 9w/m2; black (insulated)- 18 w/m2. Ergo- black (insulated) about twice as effective as white (uninsulated).

      There are a few qualifications to these figures and statements (eg R3 roof insulation now recommended), but they are broadly the situation that most people will experience.

      (7) If anyone is able to provide such quantification I'd very much appreciate it. Especially as I'm designing a house.

      • I'd always recommend getting an architect- with solar design experience. (Disclaimer- I am not an architect)

      1. Permalink

         

         Alex Cannara

         (logged in via Facebook)

         This all misses that the effect of a hot roof, re-radiating unnatural IR is far worse environmentally than having to burn a little more gas, or even coal, at the power plant, or inside the house.

         Using this imagined AU winter figure of 2kW/sqm/day, which isn't even a sensible engineering unit -- what's the hourly rate, how long is the day? How was the power measured at the roof surface? And so on.

         1. Permalink

            

            John ED Barker

            (Adjunct Professor at Murdoch University)

            Alex- It is difficult to converse with you on this matter when you don't read my posts with a reasonable degree of attention and you choose to be perverse over trivial points. OK- the units are KWH/sqm/day- I am sure that most people would have realised that point. I gave a reference to the data before (Try http://www.energymatters.com.au/climate-data). There are many such sites. The 2KWH/m2/day was an average mid-winter (June) value for Sydney. If you know how to do the rest of the sums (as you…

            show full comment

            Alex- It is difficult to converse with you on this matter when you don't read my posts with a reasonable degree of attention and you choose to be perverse over trivial points. OK- the units are KWH/sqm/day- I am sure that most people would have realised that point. I gave a reference to the data before (Try http://www.energymatters.com.au/climate-data). There are many such sites. The 2KWH/m2/day was an average mid-winter (June) value for Sydney. If you know how to do the rest of the sums (as you seem to claim in your response to Lorna) then you would know that you don't need to know the hourly rate or the length of the day. This kind of solar design can only be done on averages.

            As to "a hot roof, re-radiating unnatural IR is far worse environmentally than having to burn a little more gas, or even coal, at the power plant, or inside the house."- I disagree with you. Here's why- if the roof-space heater is cost-effective (see commercial references in post above), then it is likely that it will be energy-effective as well. As I have discussed in an earlier article in TC, the issue of net energy analysis requires further work, but "lower cost means less carbon" seems to be a durable rule-of-thumb.

            You also seem to be equating infra-red radiation with greenhouse gases. Certainly, a white roof is going to bounce more visible radiation straight back into space, thus not being potentially trapped by GHGs. But as Paul Nicol pointed out (read his calculations carefully) the difference likely to be made by rooftop colour to global warming is trivial. Which is not to say that dark surfaces (particularly roads) won't exacerbate (local) UHIs.

            1. Permalink

               

               Alex Cannara

               (logged in via Facebook)

               Sorry John, you use units that aren't energy & don't exist in science/engineering, then someone who queries it gets accused of being: "difficult to converse" .

               Ok, so 2kWHr/sqm per day is the average daily energy you meant. That's 200kWHrs/day for a typical home roof, assuming 100sqm get sun -- a big assumption, but let's go with it. For a room under the roof that's say 30sqm in area, that's 60 KWHr delivered to the room per day.. That's 2500 Watts, average. ..

               For 14 hours, it's zero…

               show full comment

               Sorry John, you use units that aren't energy & don't exist in science/engineering, then someone who queries it gets accused of being: "difficult to converse" .

               Ok, so 2kWHr/sqm per day is the average daily energy you meant. That's 200kWHrs/day for a typical home roof, assuming 100sqm get sun -- a big assumption, but let's go with it. For a room under the roof that's say 30sqm in area, that's 60 KWHr delivered to the room per day.. That's 2500 Watts, average. ..

               For 14 hours, it's zero, or negative, if the outside is colder than inside. Since the sun heats but 10 hours at best, you assert the room gets 6kW of heating average, over 10 hours. That's indeed toasty!

               The maximum solar input, at solar noon is 1kW/sqm, so that means the room with no roof at all might get 30kW in summer for more than 10 hours.

               Ok, so you say the room could get 1/5 the summer power for maybe 10 winter hours, if there were no roof. .

               Let's put the roof in. the insulating factor for a plywood roof deck is about 0.14. Let's assume a tile roof covering and say it's not a factor, despite any air spaces underneath it or any tar paper, etc. So now, if, like our Eichlers here, there's just that one wood layer between room & hot roof, we have 1/7 the thermal flow into the room under the roof. So instead of 6kW, we feel less than 1kW (actually mucj less because of the math relating power flow through thermal resistance, but ok.

               So this 30sqm room, with an 3m ceiling gets less than 800 Watts of heating for 10 hours on a winter day. That's trying to heat a 90cubic meter room with a hair dryer that's only on for 10 hours a day.

               It might be nice to at least let the resident run the hairdryer every other hour or so, but, oops, can't do that. Then, when we add in the thermal inertia and nighttime temps, we'll see just how chilly it'll be for how long each morning and how soon it's time to get under covers after dinner!

               All that 'benefit' to: ignore the environmental cost every sunlit hour every day and to force vast electrical consumption each summer day to fight the 'desired' roof heating, adding still more emissions because of the thermodynamic loss in any A/C system.

               So some folks make $ off doing this, eh?
               ;]
               How about insulating the house well, as even Australia must be thinking of requiring, have or paint a light-colored roof and enjoy the $ savings for decades, as well as the knowledge you're husbanding the effects of global warming, sea rise & ocean acidification (now sensed on the Great Barrier Reef, I hear.

               But, to do a good solar heating job, copy a design done years ago -- add a solarium to the sunny side of the house. For the sunlit part of the floor, install a heavy rock bed. Inside the exterior glass, add a second glass layer. Install reversible ventilation fans between main house & solarium. Install a polystyrene-foam blower that can fill the space between all the glass. Connect all this to a temp/time sensor & controller, and enjoy the warmth on sunny winter day, as the fans blow in. Enjoy the retained warmth overnight, as the air is driven over the rocks, and as the foam machine fills the glass interspace, then empties it when the sun comes out/up. It's a great show any day of the year, and the white styrofoam reflects most summer sunlight, as desired. Now that's an architectural product with environmental legs.

               Re general building stuff, here's one ref...
               www.climatechange.ca.gov/events/2008_conference/presentations/2008-09-09/Hashem_Akbari.pdf

               1. Permalink

                  

                  John ED Barker

                  (Adjunct Professor at Murdoch University)

                  Alex- I'll provide a simplified calculation for you, of the kind used by solar design professionals. Assume 100m2 collection area (average Australian house is over 200m2 and 'bungalow' with little roof shading, but let's go with your number to be conservative.) Assume mid-winter 2kwh/m2/day, giving a maximum of 100kwh/day on the top of the roof. Assume 60m2 to be heated. We need to find the heat loss from the room- assume 10mx6mx3m=160m2 of surface area (floor is considered neutral in most of Australia…

                  show full comment

                  Alex- I'll provide a simplified calculation for you, of the kind used by solar design professionals. Assume 100m2 collection area (average Australian house is over 200m2 and 'bungalow' with little roof shading, but let's go with your number to be conservative.) Assume mid-winter 2kwh/m2/day, giving a maximum of 100kwh/day on the top of the roof. Assume 60m2 to be heated. We need to find the heat loss from the room- assume 10mx6mx3m=160m2 of surface area (floor is considered neutral in most of Australia.) Assume average R-value of 1.5 (SI units) ie U-value of about 0.6. Assume average (24hour) "delta T" ie inside vs outside temp of 5°C (inside 20°C outside average 15°C). UxAxdeltaT= 0.6x160x5 =0.48kwh/h = (say) 12kwh over 24hours. This means that the heater would have to be only 12% efficient to meet these heating needs. Such systems are more like 20-30%. As the system could pressurise the space, no air change heat loss is assumed. Australian houses are mainly brick, so heat can be effectively stored during the day for night time warmth.

                  These figures are conservative, but realistic for much of Australia. The proof of the pudding is that the companies that I referred to are doing a good business and are subject to Australian law with regards to truth of claim (ie consumer protection.)

                  1. Permalink

                     

                     Alex Cannara

                     (logged in via Facebook)

                     Ok John, I'm glad you understand the reason for reflectivity being to "bounce" visible (and IR) back to space, unchanged in frequency -- that latter is key. Aliens are checking to see if we're smart enough to be worth contact.

                     But, let's go to your calcs above and why they're wrong. If anyone here wants to do this they can -- take two equal cardboard boxes, put them out in the sun, bottom up and put any sort of thermometer inside (a recording one would be great). Now paint the top of one box…

                     show full comment

                     Ok John, I'm glad you understand the reason for reflectivity being to "bounce" visible (and IR) back to space, unchanged in frequency -- that latter is key. Aliens are checking to see if we're smart enough to be worth contact.

                     But, let's go to your calcs above and why they're wrong. If anyone here wants to do this they can -- take two equal cardboard boxes, put them out in the sun, bottom up and put any sort of thermometer inside (a recording one would be great). Now paint the top of one box white/silver & leave the other alone or spray it brown or black. Through a (low-wind) day, note the inside temps, say every 1/2 Hr. We can all imagine the result -- blacky gets hottest midday, whitey always is cooler, and both end up about the same temp before sun-up.

                     Now make your Aussie 'house' by putting thin bricks/tiles around the outside, to simulate your uninsulated house with heat storage outside the walls.
                     On the white box, add some thin insulation (say 1/2" fiberglass) to the inside walls and on the 'floor'. Repeat the measurements for another day/night.

                     Both times, the black-top box will be hotter inside, but the effect of the bricks outside the inner 'wall' will not improve the temp before dawn. The insulated box will be cooler in sun & warmer by sunrise.

                     Repeat the experiment putting insulation under whitey's 'roof'. Now, it won't be at all warm anytime, but still will be warmer at sunrise, than uninsulated blackie.

                     Now for la piece de la resistance -- place identical lightbulbs inside each box, say 40-60W, and have each on separate dimmers. Get some beer & snacks, and all day & all night, adjust each dimmer so each box has the same internal temp as a home -- 20C or whatever. Record the dimmer settings every 1/2 hour, or better, use a Watthour meter ($15) from the hardware store. At the end of the experiment, add up all the WHr readings taken in each 1/2-hour period.

                     Now you'll see why insulation trumps Winter, low-angle solar input. You could repeat in Summer, with overhead sun, but we all know how bad the result will be for blackie.

                     Note that this expt. even ignores the waste effect of the roof-space fan, which brings in cooler, outside air. It must, of course, because under roof spaces, if sealed, are polluted by building material chemistry -- phenyls, etc. Of course, buyers of such systems still get some inside pollution -- fun fact! Do you tell your customers John?

                     You can also just take solar power info from common solar panels, to estimate how much heating a Winter day could give -- here's a large one: http://tinyurl.com/3znad4b of ~20% efficient panels, so divide the total daily output on right by 5. This is larger than a home installation by a factor of about 3, since each 1/2-Hr bar is 10kWHr max today. So the 107kWHr total for today's raw sun power on a home in Fresno, Calif. would be about 180kWHr -- much as you assumed.

                     If that solar energy were used to both heat the home & power the grid, the net result would be far less energy waste than leaving the home uninsulated and with a dark roof.

                     Of course, the analysis above doesn't even cover the climate damage of both the dark roof and the extra heating power required for blackie, as measured by the bulb-dimmer-Watthour meter expt.

                     Bottom line is what you've been selling folks is like the old shell game at Coney Island -- where's the pea under the cups? The "pea" of truth in this case. As scientists & engineers, we don't actually swear the physician's oath to "do no harm", but we implicitly do swear to serve humanity with honesty.

                     So, give me your trade association's name & address, and the Australian agency that provides regulatory oversight, and I'll explain to them what's going on here to mislead Australians & maybe others.

                     As Lorna observes, there seemingly are requirements for new Aussie homes' roofs to be reflective, and likely to have excellent insulation all 'round the interior. So selling roof-space fans may simply be a dying opportunity that customers don't have explained to them by fan salesmen. Could be? Does saying it's "complex" help? Whatcha think?
                     ;]

                     1. Permalink

                        

                        John ED Barker

                        (Adjunct Professor at Murdoch University)

                        Alex- Your response is unscientific and incomprehensible and it would seem that you are not able to follow the norms of reasoned discourse. Furthermore I deeply resent your ongoing imputation that I have vested interests. I will not be responding any further to your comments.

                        1. Permalink

                           

                           Alex Cannara

                           (logged in via Facebook)

                           Facts are facts, John. Not knowing anything about your range of "vested interests", you make clear that honest scientific study isn't among them.

      2. Permalink

         

         Lorna Jarrett

         PhD candidate, science education; Physics teacher (logged in via email @diment.org)

         Thanks for the detailed response John, but the original idea - that dark roofs are good because they warm up a house - is still unaddressed.

         I'm guessing we all agree a well-insulated roof is a good thing. That means minimising heat transfer from the roof into the house. As far as I can see, a well-insulated roof won't bring much heat into the house whatever its colour - but dark will always bring more heat in than light (insulation being equal).

         Next point - a roof will always gain more heat…

         show full comment

         Thanks for the detailed response John, but the original idea - that dark roofs are good because they warm up a house - is still unaddressed.

         I'm guessing we all agree a well-insulated roof is a good thing. That means minimising heat transfer from the roof into the house. As far as I can see, a well-insulated roof won't bring much heat into the house whatever its colour - but dark will always bring more heat in than light (insulation being equal).

         Next point - a roof will always gain more heat in summer than in winter - when it's not wanted. As opposed to well-sited windows which are shaded by eaves in summer and exposed to the Sun in winter. Any passive element of a house that gains more heat in summer than winter is an element you want to reduce - hence paint the roof white and bring the heat gain down as low as possible.

         Architects definitely know lots about building that I don't - but this looks to me like a physics problem and while physicists are often guilty of oversimplifying real-world problems (as the in the"spherical chicken in a vacuum" joke) I am sure this is one where a reasonable approximation should be obtainable. So my options are to
         (a) get on with it myself
         (b) ask my supervisor, he's probably done the calculations or
         (c) see if anyone here has done them.
         Being a lazy student I'm working backwards from (c)

         1. Permalink

            

            John ED Barker

            (Adjunct Professor at Murdoch University)

            Lorna- Let's not mix up two (interrelated) issues: Certainly, the best way to design a house- if conditions permit- is to follow the simple "large north windows, minimise east, west and south widows, insulate ceiling" approach.

            But in this thread we are trying to focus on roof albedo issues. My point about dark ceilings is that if the ceiling is insulated, hot air from the ceiling space can be drawn into the house in winter for heating. To see how this is done, Google "solar air heating roof…

            show full comment

            Lorna- Let's not mix up two (interrelated) issues: Certainly, the best way to design a house- if conditions permit- is to follow the simple "large north windows, minimise east, west and south widows, insulate ceiling" approach.

            But in this thread we are trying to focus on roof albedo issues. My point about dark ceilings is that if the ceiling is insulated, hot air from the ceiling space can be drawn into the house in winter for heating. To see how this is done, Google "solar air heating roof space"- you'll find a number of companies offering to retrofit your house with such a system. I did it myself on my own house twenty years ago.

            Secondly, as I pointed out in the little maths exercise before, ceiling insulation (R2-R3) will keep out most of the heat, irrespective of the roof colour. Certainly, white beats black, but the difference is usually not worth worrying about, other things being equal. Those things include, as I commented before, not falling prey to roof-coating scammers, dazzling white roofs in suburbia (some places don't allow them), skillion and cathedral roofs (more insulation required or light coloured paint).

            As a physicist, I pioneered solar housing education in Western Australia. I made sure that I transferred most of the design aspects to architects, as my design capabilities generally produce "spherical chickens in a vacuum". The calculations are an important first step, but you ultimately want a home to live in, not a research test-cell.

            1. Permalink

               

               Lorna Jarrett

               PhD candidate, science education; Physics teacher (logged in via email @diment.org)

               Thanks for the clarification about drawing the air in. As for dazzling white roofs, they're what all the new houses in my area have.

         2. Permalink

            

            Paul Richards

            (logged in via Twitter)

            Lorna - in business the opportunity came up weekly during my career to have real world experience of this issue.

            Firstly - a dark, fashionably "Charcoal" roof cavity is hotter.
            Secondly - a dark, fashionably "Charcoal" roof cavity is hotter and roof insulation reduces the "Heat Gain".
            Thirdly - a light roof cavity is cooler, a lot - more than 10º C. [subject to day, time, angle of incidence etc.etc.]
            Fourthly - a light roofed home is cheaper on energy with insulation or not.

            Other factor…

            show full comment

            Lorna - in business the opportunity came up weekly during my career to have real world experience of this issue.

            Firstly - a dark, fashionably "Charcoal" roof cavity is hotter.
            Secondly - a dark, fashionably "Charcoal" roof cavity is hotter and roof insulation reduces the "Heat Gain".
            Thirdly - a light roof cavity is cooler, a lot - more than 10º C. [subject to day, time, angle of incidence etc.etc.]
            Fourthly - a light roofed home is cheaper on energy with insulation or not.

            Other factor come into play, thermal mass of the walls, and glass insulation.
            Heat gain through glass or walls - will retain heat - with insulation.

            Putting all that together in all parts of Australia, except where there is low summer average temperatures, building any home with a dark roof is asking for trouble.
            Now and in the future. Energy cost will be higher, and roof paint replacement cost will be more frequent.

            Make sure the home's glass is insulated with either drapes, thermal break glass or window insulation film to suit. Combinations of glass insulation work, the window film protects drapes, as does thermal break glass. Choose a suitable wall construction always, crucial.

            RECOMMENDATION FOR CONSTRUCTION
            If cost and location was not an issue an Earth Covered home is our best choice.
            The thermal mass of ground can keep the home at a constant temperature year round without expending energy and they are cyclone and fire resistant making tem suitable Australia wide. Approximately 10% higher constructions costs, saleability - fast.

            If an Earth Covered building is good enough for politicians it is good enough for us all.
            Parliament House in Canberra is our most famous Earth Covered Building.

            But does my experience count? Over thirty years in the energy control business, actually applying solutions created by builders and architects, probably not.

            "Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth." ~ Marcus Aurelius ~

            1. Permalink

               

               Lorna Jarrett

               PhD candidate, science education; Physics teacher (logged in via email @diment.org)

               Paul, I had a look at the concept last year and I'd love to build an earth-sheltered house. But geotech, planning laws, block-size constraints and $$$ all say otherwise.

               1. Permalink

                  

                  Paul Richards

                  (logged in via Twitter)

                  Same here, we must have hope. Biggest issue is consultant / architects who are ECH builders are well booked up.

                  Currently working toward Toodyay home/workshop Earthship. Having built retaining walls using the tyres as done in the building method, I know the structure is very strong, earthquake resistant, bushfire resistant and qualifies as an Earth Covered Building. Design work in appearance to remove the Adobe look is simple and essential for me. Design course here in Brunswick where I am working at the moment, will be interesting.

                  http://earthship.com/
                  http://en.wikipedia.org/wiki/Earthship

                  As for the roof colour issue, have found myself discenting with academics frequently and recommend you approach house owners. Talk about the issue, people when approached are often only to happy to talk.

                  Real world issues will help, even get John to give you some of the people he knows and ask a few of your own.

            2. Permalink

               

               Paul Richards

               (logged in via Twitter)

               I might add my time was working in the Perth and country Western Australia. Solutions sought were after the Architect and Builders liability was encountered. The owner has to live with the building ultimately so "practical solutions" were often needed. My experience of the WA building scene is the best energy consultants were in the private sector, developing, buildings and designing energy efficient buildings.

               John's idea of draw down of heat is interesting, but if we have the ceiling insulated, the walls and glass. Why do we need to draw on the ceiling heat during winter?

               There are many forms of intelligence, many have forté in one. I admit my forté is not academic intelligence.

               1. Permalink

                  

                  John ED Barker

                  (Adjunct Professor at Murdoch University)

                  Paul- As an empiricist-probabilist, I've joined the dots on your comments in this thread- I infer that you have some sort of grudge against academics and you seem to imply that I'm some "cloistered" academic.

                  Your quote: "Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth." ~ Marcus Aurelius ~ does not mean that all opinions are equally reliable when dealing with the world of shared reality. Scientists these days don't deal with "truths" and "facts…

                  show full comment

                  Paul- As an empiricist-probabilist, I've joined the dots on your comments in this thread- I infer that you have some sort of grudge against academics and you seem to imply that I'm some "cloistered" academic.

                  Your quote: "Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth." ~ Marcus Aurelius ~ does not mean that all opinions are equally reliable when dealing with the world of shared reality. Scientists these days don't deal with "truths" and "facts"- they deal with probabilities related to observations. Dominique's research is an example of this. Scientific findings are essentially the most concise and reliable statements that account for observed data. "Reliable" means that they are testable.

                  I have a very diverse background, including manufacturing, consulting, lecturing and public service. In this area I have worked closely with multi-award-winning architects for more than 30 years. Many of my "academic" colleagues also have similar experiences and many of my "business" colleagues are also part-time academics. The "real world" of universities is very different from the one that you seem to have experienced.

                  1. Permalink

                     

                     Paul Richards

                     (logged in via Twitter)

                     John - you have made some very broad assumptions, that is to be expected.

                     If walls are insulated, ceiling is insulated, glass is insulated, my point stands unanswered; "Why do we need to draw on the ceiling [roof cavity] heat during winter?"

                     "Science is the belief in the ignorance of experts" ~ Richard Feynman ~

                     1. Permalink

                        

                        Paul Richards

                        (logged in via Twitter)

                        John - The point is crystal clear and anecdotally for what it's worth I agree with your statement.

                        "......... roofspace heating could do the job as well"

                        With the caveat, other forms of heating may be still needed at night.

                        With many variables in actual application having a roof heat sink is one option when conditions are suitable. A very good one at that, so finally you have made your point.

                        As for the companies doing it, the sales method and cost is questionable. Thank you for all your replies.

                        "We've learned from experience that the truth will come out."
                        ~ Richard Feynman ~

                        1. Permalink

                           

                           Alex Cannara

                           (logged in via Facebook)

                           It's intriguing that "academics" aren't to be trusted, but we get quotes from Feynman -- both an academic and a deceiver (at least in his youth). apparently, if an opinion or statement of fact comes by that is uncomfortable, it can simply be rejected to preserve self comfort.

                           That's dead-end thinking no one can afford.

                     2. Permalink

                        

                        John ED Barker

                        (Adjunct Professor at Murdoch University)

                        Paul- I have assumed a winter's day with an average temperature of 15°C, which is below the comfort range- generally accepted to be 18-25°C. With the assumption of R1.5 (current design standard) then some heating is required from somewhere. I have assumed, for this illustration, that no solar gain was possible (R1.5 assumes some windows in the mix). Of course there are many ways of heating the space- I am simply showing that roofspace heating could do the job as well. There are many houses (look…

                        show full comment

                        Paul- I have assumed a winter's day with an average temperature of 15°C, which is below the comfort range- generally accepted to be 18-25°C. With the assumption of R1.5 (current design standard) then some heating is required from somewhere. I have assumed, for this illustration, that no solar gain was possible (R1.5 assumes some windows in the mix). Of course there are many ways of heating the space- I am simply showing that roofspace heating could do the job as well. There are many houses (look around Subiaco) where significant direct gain is not possible. Roofspace heating could be an option. I'm not advocating it- simply pointing out in my customary scientific way that it is technically viable. I have personally tried and used it and as I pointed out, there are a number of companies doing it.

                        BTW- I still don't get your ongoing derision of scientists. If you read your Feynman Physics Lectures (3 vols), his various autobiographical works and James Gleick's 532-page biography, you would understand that his take on the "ignorance of experts" is somewhat different from the "ignorance of non-experts". Scientists generally say that they are ignorant, meaning that their knowledge is small compared with what is to be known and they are never absolutely certain of anything. Try participating on TC without the fruits of these "ignorant" people.

                        1. Permalink

                           

                           Alex Cannara

                           (logged in via Facebook)

                           Ahh, name dropping there, eh John? One sign of a lost argument, y'know?

                           Indeed. we're all ignorant, as the Greek & Latin roots of "science" suggest we engage in: "learning" or "clarifying", and so gaining "knowledge".
                           
                           Since you're facile with Feynman, you must know he was something of a magician, even a charlatan, as a youngster in NY. He fixed neighbors' radios without explaining to them the simple knowledge he used but wouldn't share -- ego & profit motive at work!

                           Something like what you advocate to unsuspecting home owners/builders?

                     3. Permalink

                        

                        Alex Cannara

                        (logged in via Facebook)

                        Indeed, there's no point in cavity air circulation into the home, especially given the volatiles common in many building materials. It is, in fact, illegal in many jurisdictions in the US.

                        There's indeed one other source of heat that is available, via heat exchange from cooking. The products available for that ensure safe recirculation of internal home air, while losing minimal useful heat to the cooking-exhaust path to outside.

         3. Permalink

            

            Alex Cannara

            (logged in via Facebook)

            The calculations have been done many times over decades, Lorna. If you wish, send me an email for pointers & examples.

            cannara at sbcglobal dot net

         4. Permalink

            

            Alex Cannara

            (logged in via Facebook)

            Lorna, we have one guy admitting light roofs lower temps inside, another saying "white beats black, but the difference is usually not worth worrying about", and some apparently selling things like attic fans for winter heating.

            So caveat emptor definitely seems to apply here. But the facts remain...

            1) reflective roofs save internal energy in summer.
            2) reflective roofs reduce atmospheric heating.in any clime
            3) light roofs of petrol base last far longer, even if simply painted
            4) trees…

            show full comment

            Lorna, we have one guy admitting light roofs lower temps inside, another saying "white beats black, but the difference is usually not worth worrying about", and some apparently selling things like attic fans for winter heating.

            So caveat emptor definitely seems to apply here. But the facts remain...

            1) reflective roofs save internal energy in summer.
            2) reflective roofs reduce atmospheric heating.in any clime
            3) light roofs of petrol base last far longer, even if simply painted
            4) trees shading roofs & parking let you have any color roof you want.

            I posted the example of one home carefully monitored. Another nearby shows outstanding results as well, adding a decade so far to to roof life and lowering surface temp by over 50F in direct sun, while already saving the cost of the painting -- aluminized, in this case -- within 3 years...

            So the physics of all that's going is clear, most has been clear for decades, or centuries, depending on whether we give older cultures credit for brains. Using a dark roof in winter to get a little hot air for the home, makes no scientific or engineering sense over a year, though it may offer sales opportunities for some.
            

7. Permalink

   

   Dale Bloom

   Laboratory analyst (logged in via email @mail.com)

   Great work.

   If a building is located in a rural setting surrounded by trees or scrub, a white roof is easily seen, and the building looks completely unnatural. In fact, a white roof in such a setting could be considered a form of visual pollution. The situation may be different in more built up areas, or may be different in housing estates.

   Perhaps the best way of getting efficient heating in cold climates, is for people to wear warmer clothes, such as thermal underwear. It would be interesting to know if a company pays its employees extra money to wear thermal underwear, and then turns down the heating.

   1. Permalink

      

      Dominique Hes

      (Senior Lecturer in Sustainable Architecture at University of Melbourne)

      Thanks, if you read the full report available on the City of Melbourne website you will see we did do a sensitivity study using different colours, it shows there is still a significant benefit to using the special engineered paints even if it is not white.

      1. Permalink

         

         Dale Bloom

         Laboratory analyst (logged in via email @mail.com)

         Thanks Dominique, I have read the report and regard it as a very good report.

         It would be interesting to know the energy consumption in different climate areas of Australia, or if more energy is being used for cooling buildings or for heating.

         In regards to ventilated roofs, a gable roof can be used to both heat and cool the house. I once had a pole house and the main living room had a Dutch gable roof (about 25 degrees) with exposed beams and tongue and grove ceiling. Underneath the peak at each end were louvers, and on hot days the louvres could be opened to let hot air out, and on cooler days they could be closed to retain heat under the roof and subsequently heat the room below.

         Adjusting the louvres could alter the temperature inside the room by about 3 – 5 degrees, but unfortunately it was in the tropics, with few cold or even cool days.

      2. Permalink

         

         John Nicol

         (logged in via Facebook)

         It seems to me that the only significant effect on the environment, without considering warming or cooling of the building, is to change the surface that the initial sunlight falls upon. Once the energy ids absorbed, even if arrested by insulation, it will only be removed by either IR radiation or by wind cooling, both of which end up with the energy being taken into the atmosphere. Shiny foot paths and walls are also totally impractical and their characteristics would need to be managed by trees…

         show full comment

         It seems to me that the only significant effect on the environment, without considering warming or cooling of the building, is to change the surface that the initial sunlight falls upon. Once the energy ids absorbed, even if arrested by insulation, it will only be removed by either IR radiation or by wind cooling, both of which end up with the energy being taken into the atmosphere. Shiny foot paths and walls are also totally impractical and their characteristics would need to be managed by trees or other shade.

         The ideal system, though probably totally impractical, would be to have double sided, reversable, adjustable, louvres covering a flat roof, being flat to avoid visual pollution if the edges were slightly raised. The "louvres" could be very shiny (reflective) on one side and black on the other and when flat on the roof, be in contact with a conducting material which thermally connects them to the buiolding. In summer, the louves would be turned so that the bright side faced upwards, and in winter, the black side would absorb sunshine. In any case, the reduction of the albedo, requires reflection of sunlight which can then pass directly back to space, not being converted to IR before being directed upwards.

         Insulation and flushing the roof cavity with air will only have a benefit for the building, not the albedo of the earth.

         It is instructive to see how much difference change to the built albedo, could make to the earth's total heat balance. Since 30% of the earth's surface is land and according to someone on this blog, above, 2% of this has been built on, the total surface area built upon, is 0.006 of the earth's surface. Without allowing for the fact that buildings North or South of about 45 degrees will have their effect reduced by a factor of <0.7, the average reduction of sunlight, if the whole of the built up area is now black and the surfaces were changed to ensure that they all became 100% reflective, would be 2 W/m2 in 1300 Watts. This could well be significant, but one needs to put in the real numbers allowing for the fact that everything is not now black and could not be made anywhere near 100% reflective, and clouds currently help to reduce sunlight but would also block some of the reflected light from roofs.

         This would reduce the change from 2 W/m2 to what I expect would be a very insignifcant number.

         1. Permalink

            

            Alex Cannara

            (logged in via Facebook)

            It may "seem" to you John, but you're incorrect because you ignore the reality that unnaturally absorbing visible light, which is not much absorbed on the way in, and converting it to IR, some bands of which were absorbed on the way down, will re-radiate this unnatural IR back up for a second shot at GHG absorption. This will depend on the surface temperature, but for common rises of 50C or so, the IR is radiated as a >320K body, which hits a number of broad water-vapor GHG absorption bands.on the…

            show full comment

            It may "seem" to you John, but you're incorrect because you ignore the reality that unnaturally absorbing visible light, which is not much absorbed on the way in, and converting it to IR, some bands of which were absorbed on the way down, will re-radiate this unnatural IR back up for a second shot at GHG absorption. This will depend on the surface temperature, but for common rises of 50C or so, the IR is radiated as a >320K body, which hits a number of broad water-vapor GHG absorption bands.on the way back up.

            Your blackened-back louvers idea misses the reality that in winter/arctic as well, avoidance of down-conversion of visible frequencies to IR is exactly what's unwanted. Plus, low-angle winter sun (up here) makes for useless heat addition to the building, which must have code insulation under the roof anyway.

            Yes, trees are ideal ways to improve the situation on any human structures shorter than they are. That last is a rub in any urban locale.

            Thanks for the calculation of the effect of >2% land being human stuff, but "2 W/m2 in 1300 Watts" is overblown, when the actual solar intensity at the surface is about 1000W/sqm. Even so, yes, "This could well be significant". The earth's imbalance as measured by satellite & other methods is now +1/2W/sqm toward net warming, so indeed, "2W/m2" is more than "significant" -- if it occurred, it would be fatal. The only saving grace right now is moderate sunspot cycle and the huge cloud of particulates from SE Asia that's doing some reflecting and altering the monsoon as well. So much for unintended planetary experimentation, rather than husbandry! But heck, we're now 'only' 1.2GWe per day behind in starting up new, emissions-free power. Or, as the IEA explains
            http://tinyurl.com/bueq2ev

            And honest folks try to tell us all...
            www.sfgate.com/cgi-bin/article.cgi?f=/g/a/2012/01/27/prweb9143858.DTL
            www.world-nuclear-news.org/NP_Japanese_trade_figures_reveal_cost_of_nuclear_shutdown_2501121.html
            www.pointcarbon.com/aboutus/pressroom/pressreleases/1.1552105 (extra emissions)
            www.reuters.com/article/2012/01/17/us-siemens-energy-idUSTRE80G10920120117
            http://spectrum.ieee.org/energywise/energy/nuclear/siemens-says-germany-nuclear-phase-out-to-cost-trillions/?utm_source=techalert&utm_medium=email&utm_campaign=011912
            www.world-nuclear-news.org/NP_Eye_watering_cost_of_renewable_revolution_2301121.html?utm_so

            1. Permalink

               

               John Nicol

               (logged in via Facebook)

               Alex,

               We are indeed on the same page here. If you read the top part of my comment again, you will see that what I said is exactly that the sunlight must be reflected directlyto space and NOT allowed to be converted to IR.

               I understand that some parts of the world such as the Arctic regions will be quite different from the rest. The majority of world buildings are most likely in the mid to higher latitudes but not much above 75 degrees? I don't really know. The most significant effects will…

               show full comment

               Alex,

               We are indeed on the same page here. If you read the top part of my comment again, you will see that what I said is exactly that the sunlight must be reflected directlyto space and NOT allowed to be converted to IR.

               I understand that some parts of the world such as the Arctic regions will be quite different from the rest. The majority of world buildings are most likely in the mid to higher latitudes but not much above 75 degrees? I don't really know. The most significant effects will be in the tropics.

               John Barker and Dominique Hes have presented us with a very interesting discussion of the realities of this aspect of proper and practical urban design. Well done both of you. No amount of theoretical navel gazing will lead to the solution of any complex problem - you have to get out there as you have done and look closely at the real data, the real situation and the real costs. This will provide the information needed for sound decisions which also make economic sence.

               1. Permalink

                  

                  Alex Cannara

                  (logged in via Facebook)

                  Yes John, I see that your first sentence does in fact agree -- I misread.

                  One of the things all here can do is follow back to the great deal of research on structural effects done by the international Heat Island Group, earlier work by Lawrence Berkeley Labs (Ashem Akbari, etc.) and take care to evaluate many of the commercialized policies & practices coming out of semi-commercial groups, such as the LEED rating systems. Most, if not all that influence construction in the US, are blind to the…

                  show full comment

                  Yes John, I see that your first sentence does in fact agree -- I misread.

                  One of the things all here can do is follow back to the great deal of research on structural effects done by the international Heat Island Group, earlier work by Lawrence Berkeley Labs (Ashem Akbari, etc.) and take care to evaluate many of the commercialized policies & practices coming out of semi-commercial groups, such as the LEED rating systems. Most, if not all that influence construction in the US, are blind to the overall environmental effects & the results of a finally-constructed building.

                  We had such a wasteful result here at Stanford a few years back, where a highly LEED-rated, multi-million $ building was found to underperform on most everything but water use. A study revealed silly things like no caulk around office windows, computer-controlled vents that were non-functioning or connected backwards, and so on. The design was expensive. the construction was expensive. The final evaluation was lacking...
                  www.stanford.edu/group/CIFE/online.publications/TR183.pdf

                  This is all too common -- ratings mean $ and follow up to check actual performance costs $. Very few environmental raters follow up. And, almost none understand the multiple reasons for surface reflectivity, so a highly-LEED rated new factory, with beautiful white Calif. AB32 roof, with some of that covered by good solar PV, will have an even larger parking lot around it made of asphalt and few trees.

               2. Permalink

                  

                  John ED Barker

                  (Adjunct Professor at Murdoch University)

                  Thanks, John Nicol. On reflection, I think that we have all contributed more light than heat to the conversation.

   2. Permalink

      

      Alex Cannara

      (logged in via Facebook)

      As to light roofs being "unnatural" or somehow undesirable, this indeed is a common feeling in some places. But, if one flies over various countrysides one sees how often folks like farmers, who must deal with reality, have reflective roofs on their structures. A short hop over Caribbean, Greek & similar islands gives the same picture. The benefit of reflective roofs & structures is over 1000 years old.

      Of course, those folks may not get all 3 reasons for reflectivity, but, just like our own AB32's requirements on commercial roofing, 1 out of 3 ain't bad.
      ;]