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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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      CommentAuthorfostertom
    • CommentTimeApr 16th 2021 edited
     
    https://www.theguardian.com/environment/2021/apr/15/whitest-ever-paint-could-help-cool-heating-earth-study-shows

    "... a comparison of the carbon dioxide emitted by the mining of barium sulphate with the emissions saved from lower air conditioning use would be needed to fully assess the new paint. He also said green roofs, on which plants grow, could be more sustainable where practical.

    Project Drawdown, a charity that assesses climate solutions, estimates that white roofs and green roofs could avoid between 600m and 1.1bn tonnes of carbon dioxide by 2050, roughly equivalent to two to three years of the UK’s total annual emissions."

    Anyone know anything about large quantities of barium sulphate (instead of titanium dioxide) as pigment?
    •  
      CommentAuthordjh
    • CommentTimeApr 16th 2021 edited
     
    The main problem applying it in many countries would be the same as here - "Roofs should be tiled/slated/dark in colour. Light-coloured roofs look wrong."

    The paint will suffer from the other problem that applies to light-coloured roofs. In order to keep them effective at reflecting light, they need to be cleaned very often. How often are roofs ever cleaned, except by rain? How much water is needed to wash a roof?

    Not that I'm against the idea at all. I do have a shiny aluminium roof, although it is now somewhat less shiny after five years. :bigsmile:

    PS https://en.wikipedia.org/wiki/Baryte describes how it is obtained.
    • CommentAuthorphiledge
    • CommentTimeApr 16th 2021
     
    Id be more concerned about 'snow blindness' and cataracts if the world was painted white.
  1.  
    Insulate the roof and walls instead. Nobody is going to clean them, nor should they have to.

    Though some buildings would be cooler, if their excessive glazing was coated with white paint.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 16th 2021 edited
     
    Ah - baryte. Incredibly dense and heavy, it was mined all down the Teign Valley next to here, along with arsenic, lead, heavy metals. Now overgrown/back to nature, numerous sterile zones, horrendous toxic runoff from spoil heaps into the river, destination Teignmouth holiday beaches.

    Pilks make glass self-cleaning that's coated with a catalyst that causes organic deposits to decompose under UV and then wash off with rain.

    What struck me was that here's a highly reflective surface that can also be a high radiator of heat. I understood that anything that's a good radiator is also a good absorber, as both are the same process, just radiant/temp reversed. Absorbency is the measure of how much radiation it exchanges with its environment for given radiant-delta-t. So white/chrome would absorb v little and radiate v little, while black would both absorb and radiate a lot.
    • CommentAuthorEd Davies
    • CommentTimeApr 16th 2021 edited
     
    Posted By: fostertom: “I understood that anything that's a good radiator is also a good absorber”

    Yes, that's right but only for a particular wavelength. https://en.wikipedia.org/wiki/Kirchhoff%27s_law_of_thermal_radiation Things absorb or reflect differently at different wavelengths, as you've probably noticed unless you're 100% colour blind. This stuff seems to be a good reflector at short wavelengths (near IR, visible and UV - around 1 or 2 μm or shorter) while being a good emitter at thermal wavelengths (around 10 μm).

    What'd also be nice for more poleward climates would be the opposite: something which is good absorber of short wavelength radiation while having a low emissivity for thermal IR.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 16th 2021
     
    Brilliant! We could put in a Feature Request to the guy.
    • CommentAuthortony
    • CommentTimeApr 16th 2021
     
    What proportion of the Earths surface could be covered? Infitemisally small I think
    •  
      CommentAuthordjh
    • CommentTimeApr 16th 2021 edited
     
    Posted By: WillInAberdeenInsulate the roof and walls instead.

    Insulate the roof and walls AS WELL!

    Posted By: fostertomPilks make glass self-cleaning that's coated with a catalyst that causes organic deposits to decompose under UV and then wash off with rain.

    But I wonder whether that would interfere with the 'miracle' paint?

    The most non-shiny bit of our aluminium roof is green BTW, exactly because that is the bit the sun never shines on.

    What struck me was that here's a highly reflective surface that can also be a high radiator of heat. I understood that anything that's a good radiator is also a good absorber, as both are the same process, just radiant/temp reversed.

    That's true but not a contradiction. It's true for each wavelength/frequency individually. So most of the sun's radiation is at visible frequencies and some short infra-red etc, whereas I'll bet the paint is a good radiator of long-wave IR (i.e. thermal radiation). There are somewhat similar frequency-selective paints used in some solar thermal collectors and window coatings.

    edit: cross-posted with Ed.
    • CommentAuthorEd Davies
    • CommentTimeApr 16th 2021
     
    Posted By: tonyWhat proportion of the Earths surface could be covered? Infitemisally small I think
    Yes, but the point is to reduce the air conditioning load thereby reducing CO₂ emissions, not to cool the planet directly.

    But, as DJH has already pointed out, the problem in places like the US SW is not the unavailability of light-enough-coloured roofs but the legal blocks put on using them.
  2.  
    https://www.bbc.co.uk/news/science-environment-56749105

    "said Prof Ruan. "And we estimate we would only need to paint 1% of the Earth's surface with this paint - perhaps an area where no people live that is covered in rocks"

    It's definitely an April Fool story.

    Edit: would anyone like to suggest a residual wilderness area of this poor planet which has so far escaped occupation by humans, where the habitat would be improved by painting everything white? Looking for somewhere about the size of Western Europe. Perhaps Australia would do?
    •  
      CommentAuthordjh
    • CommentTimeApr 16th 2021
     
    Posted By: WillInAberdeenIt's definitely an April Fool story.

    Seems a bit past its best-before date if it is?

    The man is right though, isn't he? Increasing the reflectivity of the earth is one approach to decreasing/eliminating/reversing (take your pick) climate change. The usual proposal is to seed the air to increase cloud cover and thus the albedo of the earth.

    I confess I can't be bothered to try to check the figures or even the source of the story, though Project Drawdown looks vaguely real? https://drawdown.org/
  3.  
    "In response, UK-based artist Stuart Semple created a pigment that he claimed to be the world's "pinkest pink" and made it available to purchase on his website for "everyone but Anish Kapoor"."

    Nice touch.
    • CommentAuthorEd Davies
    • CommentTimeApr 16th 2021
     
    While I can see that increasing the reflectivity of the Earth might decrease/eliminate/reverse global warming I find it harder to see how it could eliminate climate change.
    •  
      CommentAuthordjh
    • CommentTimeApr 17th 2021
     
    Posted By: WillInAberdeen"In response, UK-based artist Stuart Semple created a pigment that he claimed to be the world's "pinkest pink" and made it available to purchase on his website for "everyone but Anish Kapoor"."

    Nice touch.

    Sorry, but that was in response to Vantablack, which appears to be a real product, so I'm not sure what your point is?

    https://www.surreynanosystems.com/purchasing
    •  
      CommentAuthordjh
    • CommentTimeApr 17th 2021
     
    Posted By: Ed DaviesWhile I can see that increasing the reflectivity of the Earth might decrease/eliminate/reverse global warming I find it harder to see how it could eliminate climate change.

    True, I was careless in my choice of phrase and global warming does fit the case much better :bigsmile:
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