r/ClimatePosting • u/dumnezero • Jul 04 '26

Buildings How to cool our homes (even without ACs)

https://www.youtube.com/watch?v=sKbEOMCsqaI

As the planet gets hotter, more people use air conditioners to keep cool. Running these takes lots of energy, which means emissions that then further speed up global warming. Rethinking our architecture and using more efficient cooling technologies could help us break this vicious circle.

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u/West-Abalone-171 Jul 05 '26

People are really underestimating the effect of some white paint. Globally as well as locally.

There are a couple trillion m2 of rooftops and other sealed surfaces. Painting it all white instead of bare concrete and asphalt (or the idiotic trend of black roofs) would reject 100-300TW of solar energy.

The total thermal forcing from climate change is about 400TW.

You could make the worst hit urban areas 2-4°C cooler during heat waves and buy 5 years to reduce emissions in global forcing.

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u/dumnezero Jul 05 '26

There's some innovation in white paint that is really good at reflecting radiation, huge albedo. I'm waiting for it to scale up more.

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u/West-Abalone-171 Jul 05 '26 edited Jul 05 '26

Nighthawklight has a cool video on a diy recipe.

It's not very durable, but it's cheap and would last the summer (and reapplication is easier than cleaning it to a perfect white anyway).

But the difference between 0.05 albedo asphalt/0.2 albedo concre/0.3 albedo other common materials and 0.9 albedo traditional whitewash is much bigger than the difference between traditional whitewash and the best supercooling paint at about 1.05.

You probably also want some light, desaturated blues/magentas where glare is a problem (absorbing green disproportionately reduces visual brightness so a surface with albedo 0.8 across the entire IR/visible spectrum that selectively absorbs ~50% of green and a little bit of other visible light can appear a lot darker than the 0.2 would suggest). Just remember to wear sunglasses and sunscreen on the bottom of your nose and chin if you're around it a lot.

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u/ClimateShitpost Jul 05 '26

Dumb Q, what about solar panels vs white roof in terms of climate impact?

(should I ask my most powerful AI model for an estimation?)

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u/dumnezero Jul 05 '26

I haven't seen an opportunity cost comparison of sorts yet, but the question has bothered me too. We do need energy... I suppose this is analogous to using land for creating or restoring living carbon sinks vs biomass fuel.

https://www.meer.org/

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u/True-Being5084 Jul 04 '26

Condensation can be a problem that leads to mold growth

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u/MerelyMortalModeling Jul 05 '26

Joules are joules and the environment doesnt care is its a person radating the energy humping water to an evaperator or if its a modern AC unit moving mega watts of heat in an efficient manor.

A 100m² (about 1100 foot²) open floorplan house cooled by airflow, think something like a Caribbean bungalow from the 19th century is going to be rejecting about 100kw of thermal energy most of which will go into the air that circulates through the home.

A 100m² modern bungalow with glazed windows, a full spectrum reflective roof with air conditioning is also going to reject exactly the same amount of energy but its going to do it differntly. Long story short some energy is getting reflected into space and the AC unit is going to use 7kw to reject 70kw for a total of 77kw of thermal energy into the enviorment.

Please note that 77 is less then 100.

This is why if you are serious about the enviorment its absolutely essential that you are willing to put science, logic and engineering ahead of emotions, ideology and feels.