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There is plenty of opportunity in being more efficient. To give an example, houses in the Bay Area has gray/black roofs. In the summer such roof receives abou

There is plenty of opportunity in being more efficient. To give an example, houses in the Bay Area has gray/black roofs. In the summer such roof receives about 10kW of energy and readily converts it into heat. Heat, which we are trying to evacuate from the house with our super-efficient heat pumps in the air-conditioning units. If only we'd painted these roofs with white reflective roof paint (~92% reflection). We would have removed ~8kW of heating from such roofs! And then, maybe, we wouldn't have to pump all that energy into air-conditioning. So the surrounding air would be cooler, less noise would be heard from air conditioning, less energy would be spent. And the cost? 4 gallons of white reflective paint and a couple of hours of work, painting the roof...

mrfusion 4y ago
But that 10kw isn’t going directly into your house. The attic is designed to vent the air and let that hot air escape.
- cy_hauser 4y ago
  For my house the problem is that the sun's energy is converted to radient heat which makes its way hours after the air has cooled. The HVAC people have said no amount of insulation or attic fans will help. They suggest radiant barrier roofing of varoius types. The simplest being reflective paint, which the HOA won't allow.
MobileVet 4y ago
Black / dark tile roofs across the south are completely ridiculous. I doubt people understood this when shingles were first developed but we do now and we should adjust accordingly
- hsbauauvhabzb 4y ago
  Pretty sure they were recently banned in Sydney, Australia.
  - josh64 4y ago
    Not quite unfortunately - the new Planning Minister caved to the property developer lobby: https://www.theguardian.com/australia-news/2022/apr/09/plan-to-ban-dark-roofs-abandoned-as-nsw-government-walks-back-sustainability-measures https://www.theguardian.com/australia-news/2022/apr/09/plan-...
    - jdironman 4y ago
      What exactly are the challenges with producing lighter colored roofing?
      - freen 4y ago
        People who are happy to let the world burn so they can have their roof look the way British roofs look.
      - ip26 4y ago
        Asphalt is black, and a high albedo is hard for anything to maintain with dirt, dust, and age.
        Tagbert 4y ago
        I had assumed that the white color would come from a white granular material impressed into the asphalt base
        stephen_g 4y ago
        That’s not it in Australia - we don’t use asphalt roofing. Normal roofs are tile, steel or (more rarely) zinc here. I think the US is fairly unique in that regard. I’m so used to our houses here that the idea of using shingles made of asphalt just seems bizarre to me.
- Hellbanevil 4y ago
  The main reason they are dark is because they are made with oil. Asphalt tiles are fairly cheap, and that's a good thing. It's the labor that makes up most of the cost of a roof. I'm trying to get up the nerve to shingle my four bedroom home, and it's not the cost of materials I'm worried about. It's my body. My fear with global warming measures is the poor, and middle class, will be required to bear the brunt of the preventative measures. I guess the race is on to develop a 50 year life expectancy, but reasonably priced, white shingle? They might be out there? I really haven't researched them. If anyone knows a cheap roofing contractor in the Bay Area, please divulge? Twenty years ago I had a estimate of $25,000. I think that's too much now. I'm a ex General Contractor.
  - Wowfunhappy 4y ago
    > My fear with global warming measures is the poor, and middle class, will be required to bear the brunt of the preventative measures. They'll also bear the brunt of the effects of global warming, and those will be worse. We should try to make environmental programs as equitable as possible. But first and foremost we need to do them!
    - Hellbanevil 4y ago
      Yea, but trying to squeeze more out of the lower middle class, and poor, dosen't seem kind at this point in history. I see a lot of virtue signaling out there. Most of us can't afford a electric vechicle, and those federal credits seemed to just go to people whom could afford any vechicle. I can't even afford the smog check, and registration, on my 4 banger toyota. A Truck I've keep going 20 years. It uses very little gas. (My vechicle has always been tuned up properly. I thought by now we would have had free smog checks for the poor? In CA we have a low income deal that was enacted when CA decided to require smog checks. It's so complicated most people don't use the "gift". You need to bring your car to a mechanic in order to get any money back. Shade Tree mechanics are out of luck. My point is the corporations/government will pass any Global Warning measures down to us. We are already tapped out. If we are really serious about Global Warming lets go after the wealthy boys first. Take away their private jets. And enough with their Globalization. If they can make a product that dosen't need to be shipped long distances, have them make it here. I'm a Democrat, and winced when Biden pretty much gave a FY to the oil companies in order to sound Progressive. I knew at the time, the poor can't afford to pay more for gas, and natural gas. Now--I don't blame the president for this spike in gas prices, but I would have rather have him say this is a big problem, and we can't just do away with oil. Be it my PG&E bill that just seems to go up, and the $6.69 gas at my Chevron station, the poor are already paying to much of their income on a complex problem. (My gas station raised their prices the minute they started talking about inflation, and the Russia sanctions. It is pure greed. They made a record profits in the past few years. Sorry about my rant. I just don't like being squeezed so much, while my wealthy neighbors buy crap from Amazon, and think they are doing their part by driving a Tesla.
- SoftTalker 4y ago
  I think people understood. It's just that tar/asphalt is cheap and makes a very good roofing material.
amluto 4y ago
If the roof assembly is decently insulated, then relatively little of that 10kW heats the house. So, while improvement is available, it’s not nearly that large.
- hn_throwaway_99 4y ago
  Still, though, I have to wonder what the equivalent "CO2 reduction" would be considering that a white roof is likely to radiate most of the incoming sunlight back into space, where if it is radiating in infrared then that heat is more likely to be trapped on Earth.
  - throwaway3334 4y ago
    For now, everyone is free to pump out kilowatts of heat with their roofs, parking lots, air conditioners into the surrounding air. It is not considered pollution, even when it is already 100 °F outside. On the days when there is an inversion in the atmosphere, the hot air stays trapped. People have to run ACs in their houses, stores and offices. And that results in even more heat routed to the place, with ACs units, literally pumping energy from the solar arrays somewhere in the desert into the city.
    - rocqua 4y ago
      My intuition says that the volume of inside vs outside air is so big that it has little effect.
      - throwaway3334 4y ago
        You can look at how much space roofs cover in the suburb in the Bay Area. It'd be roughly 25% streets, 40% roofs, 30% backyard, 5% front-yard. Adding white reflective coating increases "Solar Reflectance" and decreases "Thermal Emittance" and absorption. Most dark roof materials reflect 5 to 20% of incoming sunlight, while light-colored roof materials typically reflect 55 to 90%. A white roof coating that you can purchase at your regular home improvement store would do that 90%. So effectively, in the suburban area there is an opportunity to change our average solar reflectance by ~32% [(90% - 10%) * 40%]. If we just abandon the idea that a good house should look like a house in Normandy and have a black roof. [edit: I've opened a section of sat map (in Sunnyvale, near Reed Ave/Sequoia Dr.) and estimated roof/street/backyard/front-yard by area, for a lot of 2 houses and adjacent street. The numbers above are from that estimate. Heat and noise of ACs is somewhat local (urban heat island effect, etc), so that local estimate is what counts. It is not surprising that we can have 40% roofs. Land is expensive in the suburb like that.] As per: https://en.m.wikipedia.org/wiki/Reflective_surfaces_(climate_engineering) https://en.m.wikipedia.org/wiki/Reflective_surfaces_(climate... - "If all urban, flat roofs in warm climates were whitened, the resulting 10% increase in global reflectivity would offset the warming effect of 24 gigatonnes of greenhouse gas emissions, or equivalent to taking 300 million cars off the road for 20 years. So it seems, there is not only local/urban heat island effect, but even some global effect. To put this into perspective, Tesla sold 2 million vehicles. No idea, if the Wiki numbers are correct...
rayiner 4y ago
Would that work in terms of all the other stuff? Rain snow etc.
recuter 4y ago
Imagine instead of paint if we could come up with some sort of material that generates electricity. P.S. - If you look into the white paint thing more carefully you'll be rather disappointed.
- highwaylights 4y ago
  Wouldn't a reflective coating work better? Given it's a once off cost it seems like this should be doable.
  - thombat 4y ago
    Neighbors and pilots may complain
    - highwaylights 4y ago
      I dislike people and planes are noisy. I take your point, I’m doing it anyway.
- throwaway3334 4y ago
  Actually, I was looking into installing solar, to offset $400/month of air-conditioning costs, during the summer. I could have had around 1.5kW of solar. But the cost of this is north of $25k, plus all the hassle to get the permits, plus all the extra complexity. While the cost of painting the roof is $100 + work. And now it is very rare that I have to run the AC.
  - sxates 4y ago
    Do you mean 15kw? 1.5 is only like 4 panels, it wouldn’t make $400 per month and wouldn’t cost anywhere near $25k.
    - throwaway3334 4y ago
      I was looking at installing a very small solar array, just to offset the AC costs. The quote for the solar kit that could produce ~1.5kW (2170W Solar Kit: 7xURE NSP 310W - Mono 60 Cell - All Black Panels + 7xEnphase IQ7 60-Cell Microinverters w/QCables + 1x Enphase IQ Combiner 3 + Wireless Monitoring) was $6.5k. But, I was also considering having a 10kW battery to store that energy and to have a backup power, like Tesla Powerwall - $10k. And then there was work to install, permits, my time. Overall my estimate was, realistically it'd be ~$25k. Maybe I was wrong. On my house I have two sections of roof that are flat/horizontal. Roof is pretty thin there and although there is insulation, on hot days ceiling was getting worm in the 2 rooms under these sections. I also was hoping that an extra layer of solar would insulate my roof a bit more. So I wouldn't have to run AC that much. So the hope was to stop wasting annoying $400 on AC in the hottest months. But the cost of installing solar felt prohibitive. So I've made a quick calculation and spent $100 on the reflective roof paint instead...
joshocar 4y ago
This is one of the reasons metal roofs a nice, they reflect heat and you don't need to paint them white, they make special paints for metal roofs that help reflect the heat and also look nice.
csomar 4y ago
Yeah this was figured out in the Mediterranean probably a few hundred years ago: https://www.santorini-view.com/white-houses-of-santorini https://www.santorini-view.com/white-houses-of-santorini Unfortunately, we are losing some of this cumulative knowledge due to it not being documented, and due to the looks of alternatives (although the grey buildings in the US are as ugly as it can get)
- drjasonharrison 4y ago
  Well also asphalt tiles being cheaper material and cheaper installation on sloped roofs (snow!) over wood frame construction.
  - jacquesm 4y ago
    They're only cheaper in the short term. Long term energy costs and replacement costs factor in strongly, and chances are that once you make that calculation you'll end up with old fashioned terracotta roofs being cheaper over the life of the house.
    - petre 4y ago
      I don't really like how the old fashioned terracota roofs behave during the summer. They heat up during the day and release that heat in night time, driving the inabitants crazy with heat. Maybe with some kind of ceramic coating to increase the albedo they'd be okay.
- JasonFruit 4y ago
  We're not losing the information that light colors heat less in the sun. Neither could anyone who spent five minutes on a black roof in the sun forget that tidbit. It's just that other factors than the energy required to cool a building took precedence in the past.
  - kjkjadksj 4y ago
    Anecdotally it seems like we are. The rad thing to do in my area of california is to paint your white washed spanish style home mud brown or ozzy osbourne black. Then you have to install a much more powerful AC system when in the past maybe just opening windows and getting crossbreeze was enough. All these houses used to have awnings over sun facing windows when they were build in the 1920s but at some point that must have been seen as ugly and its now pretty rare to see.
foobiekr 4y ago
Hell most of the 1950s and 1960s Bay Area housing stock is worse - it’s tar and gravel roofs without any significant insulation thereby turning houses into ovens. The right answer to most of them is a new foam roof which both provides insulation and reflectivity being white but people get quite upset about the foam roof thing, especially with Eichlers.
seltzered_ 4y ago
Changing how roofs are approached (color, materials) may also have a (possibly beneficial) hydrological effect, even better would be some form of vegetation grown on roofs (likely called 'green roofs' to some) to help with evapotranspiration for facilitating a small water cycle (helping water vapor travel inland) and reduce the 'urban heat dome' effect. (see Millan Millan's papers like https://academic.oup.com/bioscience/article/69/2/143/5254231 https://academic.oup.com/bioscience/article/69/2/143/5254231 , can link to some other newer stuff if desired)
epmatsw 4y ago
There’s actually a $500 tax credit to install reflective shingles for this very reason. https://www.energystar.gov/about/federal_tax_credits/roofs_metal_and_asphalt https://www.energystar.gov/about/federal_tax_credits/roofs_m...
drusepth 4y ago
What happens to the "heat" energy that gets reflected by white/reflective roofs? It seems like it'd stay in the relative vicinity of the house, heating up the outside air further (even by a small amount), right? If that's the case, are there diminishing returns to worry about with effectively just moving heat from one place to another, assuming the (hotter) outside air will probably continue to warm up the house anyway? Do we just bank on something else absorbing the energy instead? Does it leave the area/atmosphere if nothing absorbs it? (Please don't take this as a rhetorical "this is why X solution doesn't work" -- I'm no expert here and am just curious where all that reflected heat/energy goes!)
- jliptzin 4y ago
  I would assume those light rays reflect off the roof instead of getting absorbed…in that case the heat is absorbed into the atmosphere, I have a hard time believing it sits around the house and lingers there for any significant amount of time (doesn’t heat rise?)
  - oneoff786 4y ago
    Heat rises is short for hot air rises. The light would not be completely absorbed by the atmosphere more than it did on the way down.
- extra88 4y ago
  With a light or reflective surface, a lot of the energy is reflected as light so it's not converted to heat. Relatively little will be absorbed by the air near ground level, heating the air only a little.
- dexwiz 4y ago
  “Heat” from the sun that we feel is mostly IR/Visible light. Mix of stuff happens if we reflect it with white surfaces. Some of it does go back into space. Some of it will get reflected by the atmosphere back towards the ground. IR light is also directly absorbed by the air molecules, but very little. Air is mostly transparent at visible wavelengths so it absorbs very little energy. Solids are much better at converting IR to thermal energy. Realistically air conditioning is just moving heat from one side of a wall to another. Overall painting buildings white won’t change the temperature of Earth, but it does help the building in question, which is all air conditioning cares about anyways.
gumby 4y ago
> To give an example, houses in the Bay Area has gray/black roofs. Those are no longer legal. Title 24 requires a “cool roof” * When I had my roof re-covered a couple of years ago the roofer apologized and said he had to use a light color. Which wasn’t a problem for me so no apology was needed. * https://coolcalifornia.arb.ca.gov/cool-roofs-codes-and-standards https://coolcalifornia.arb.ca.gov/cool-roofs-codes-and-stand...
- hedora 4y ago
  That's strange. We just built a house in the Bay Area with a black roof, and have never heard of this. It passed planning/inspection, and the thing you linked says we are in a title 24 zone. We hadn't thought about it, and would likely have opted for a lighter roof, had someone pointed it out to us.
  - fnordpiglet 4y ago
  - oefnak 4y ago
    Well, I assume you covered it with solar panels, so it doesn't really matter.
- zbrozek 4y ago
  My understanding is that you can insulate your way to Title 24 compliance. You just have to have a total ingress performance over some level. Now that said, it would still be better for our communities to reflect this energy back out into space to reduce environmental heating. Houses in my area at solar noon have almost half a megawatt of heating potential. By municipal code they are not allowed a roof reflectivity of more than 40%.
  - gumby 4y ago
    I guess having mirrors on all the houses could cause problems for other people, even for flat roofs. But I agree: reflecting the incident beams is important: when it emerges as heat (IR) it can be trapped by GHGs. I had been thinking of the reflectivity benefit rather than the reduction in air comditioning.
WhompingWindows 4y ago
In northern New England, we see a lot of homes using heating oil and woodstoves. These create a lot of local emissions and can be expensive or use a lot of time/effort (woodstoves). Heat pumps that work especially well in cold climates would be a huge efficiency gain over oil, woodstoves, and electric resistive space heaters which are also commonly used as stop-gaps in the region.
wolverine876 4y ago
Agreed, though you still need to account for cold days when you want more heat in the house.
sundvor 4y ago
Seems like a better idea to cover the roofs with PV panels, to be honest. This would reflect heat and provide power for the cooling / travel / regular house electricity.
- stephen_g 4y ago
  Why not both? If you have a light colour roof, you can use bifacial panels and get additional generation for the same surface area!
baybal2 4y ago
jacquesm 4y ago
I always wondered why in such climates we don't simply stick mirrors on the roof (cheap) but solar panels would seem to be the best option in the longer term (much more expensive than either mirrors or white paint). But you are absolutely right: black or dark gray roofs are quite silly in a hot climate.
- maigret 4y ago
  I have the same question, it would seem a quick win to have optimized house colors for the current temperatures. Many hot countries do it right, but especially northern architecture hasn’t adapted as well. Also, too much unshadowed windows. There’s a lot to win with well thought architecture.
deleted 4y ago
[deleted]
an9n 4y ago
Couldn't agree more. I'm in the UK and in the process of installing underfloor insulation in a house built around 1890. It is a flooboards-up job involving a windproof one way moisture permeable membrane above the joists, with hygroscopic insulation on top, and then a vapour control barrier on top of that, with all edges of layers taped to the joists where possible, all holes for wires, pipes etc. sealed with tape, and finally membranes brought up to wall behind the skirting boards. It's going to cost around £1k for a room of about 25m2. We have double glazing, the walls aren't particularly cold in winter, and the roof is insulated. I'm convinced most of our cold is coming through the floor and I reckon this job (along with the rest of the house in time, ugh) will make a huge difference. But I'm having to do it myself because there are literally no specialist fitters where I live, and there are no government incentives that I am aware of. Why aren't the government going hell-for-leather for insulation etc.?

mrfusion 4y ago

But that 10kw isn’t going directly into your house. The attic is designed to vent the air and let that hot air escape.

cy_hauser 4y ago
For my house the problem is that the sun's energy is converted to radient heat which makes its way hours after the air has cooled. The HVAC people have said no amount of insulation or attic fans will help. They suggest radiant barrier roofing of varoius types. The simplest being reflective paint, which the HOA won't allow.

MobileVet 4y ago

Black / dark tile roofs across the south are completely ridiculous. I doubt people understood this when shingles were first developed but we do now and we should adjust accordingly

hsbauauvhabzb 4y ago
Pretty sure they were recently banned in Sydney, Australia.
- josh64 4y ago
  Not quite unfortunately - the new Planning Minister caved to the property developer lobby: https://www.theguardian.com/australia-news/2022/apr/09/plan-to-ban-dark-roofs-abandoned-as-nsw-government-walks-back-sustainability-measures https://www.theguardian.com/australia-news/2022/apr/09/plan-...
  - jdironman 4y ago
    What exactly are the challenges with producing lighter colored roofing?
    - freen 4y ago
      People who are happy to let the world burn so they can have their roof look the way British roofs look.
    - ip26 4y ago
      Asphalt is black, and a high albedo is hard for anything to maintain with dirt, dust, and age.
      - Tagbert 4y ago
        I had assumed that the white color would come from a white granular material impressed into the asphalt base
      - stephen_g 4y ago
        That’s not it in Australia - we don’t use asphalt roofing. Normal roofs are tile, steel or (more rarely) zinc here. I think the US is fairly unique in that regard. I’m so used to our houses here that the idea of using shingles made of asphalt just seems bizarre to me.
Hellbanevil 4y ago
The main reason they are dark is because they are made with oil. Asphalt tiles are fairly cheap, and that's a good thing. It's the labor that makes up most of the cost of a roof. I'm trying to get up the nerve to shingle my four bedroom home, and it's not the cost of materials I'm worried about. It's my body. My fear with global warming measures is the poor, and middle class, will be required to bear the brunt of the preventative measures. I guess the race is on to develop a 50 year life expectancy, but reasonably priced, white shingle? They might be out there? I really haven't researched them. If anyone knows a cheap roofing contractor in the Bay Area, please divulge? Twenty years ago I had a estimate of $25,000. I think that's too much now. I'm a ex General Contractor.
- Wowfunhappy 4y ago
  > My fear with global warming measures is the poor, and middle class, will be required to bear the brunt of the preventative measures. They'll also bear the brunt of the effects of global warming, and those will be worse. We should try to make environmental programs as equitable as possible. But first and foremost we need to do them!
  - Hellbanevil 4y ago
    Yea, but trying to squeeze more out of the lower middle class, and poor, dosen't seem kind at this point in history. I see a lot of virtue signaling out there. Most of us can't afford a electric vechicle, and those federal credits seemed to just go to people whom could afford any vechicle. I can't even afford the smog check, and registration, on my 4 banger toyota. A Truck I've keep going 20 years. It uses very little gas. (My vechicle has always been tuned up properly. I thought by now we would have had free smog checks for the poor? In CA we have a low income deal that was enacted when CA decided to require smog checks. It's so complicated most people don't use the "gift". You need to bring your car to a mechanic in order to get any money back. Shade Tree mechanics are out of luck. My point is the corporations/government will pass any Global Warning measures down to us. We are already tapped out. If we are really serious about Global Warming lets go after the wealthy boys first. Take away their private jets. And enough with their Globalization. If they can make a product that dosen't need to be shipped long distances, have them make it here. I'm a Democrat, and winced when Biden pretty much gave a FY to the oil companies in order to sound Progressive. I knew at the time, the poor can't afford to pay more for gas, and natural gas. Now--I don't blame the president for this spike in gas prices, but I would have rather have him say this is a big problem, and we can't just do away with oil. Be it my PG&E bill that just seems to go up, and the $6.69 gas at my Chevron station, the poor are already paying to much of their income on a complex problem. (My gas station raised their prices the minute they started talking about inflation, and the Russia sanctions. It is pure greed. They made a record profits in the past few years. Sorry about my rant. I just don't like being squeezed so much, while my wealthy neighbors buy crap from Amazon, and think they are doing their part by driving a Tesla.
SoftTalker 4y ago
I think people understood. It's just that tar/asphalt is cheap and makes a very good roofing material.

amluto 4y ago

If the roof assembly is decently insulated, then relatively little of that 10kW heats the house. So, while improvement is available, it’s not nearly that large.

hn_throwaway_99 4y ago
Still, though, I have to wonder what the equivalent "CO2 reduction" would be considering that a white roof is likely to radiate most of the incoming sunlight back into space, where if it is radiating in infrared then that heat is more likely to be trapped on Earth.
- throwaway3334 4y ago
  For now, everyone is free to pump out kilowatts of heat with their roofs, parking lots, air conditioners into the surrounding air. It is not considered pollution, even when it is already 100 °F outside. On the days when there is an inversion in the atmosphere, the hot air stays trapped. People have to run ACs in their houses, stores and offices. And that results in even more heat routed to the place, with ACs units, literally pumping energy from the solar arrays somewhere in the desert into the city.
  - rocqua 4y ago
    My intuition says that the volume of inside vs outside air is so big that it has little effect.
    - throwaway3334 4y ago
      You can look at how much space roofs cover in the suburb in the Bay Area. It'd be roughly 25% streets, 40% roofs, 30% backyard, 5% front-yard. Adding white reflective coating increases "Solar Reflectance" and decreases "Thermal Emittance" and absorption. Most dark roof materials reflect 5 to 20% of incoming sunlight, while light-colored roof materials typically reflect 55 to 90%. A white roof coating that you can purchase at your regular home improvement store would do that 90%. So effectively, in the suburban area there is an opportunity to change our average solar reflectance by ~32% [(90% - 10%) * 40%]. If we just abandon the idea that a good house should look like a house in Normandy and have a black roof. [edit: I've opened a section of sat map (in Sunnyvale, near Reed Ave/Sequoia Dr.) and estimated roof/street/backyard/front-yard by area, for a lot of 2 houses and adjacent street. The numbers above are from that estimate. Heat and noise of ACs is somewhat local (urban heat island effect, etc), so that local estimate is what counts. It is not surprising that we can have 40% roofs. Land is expensive in the suburb like that.] As per: https://en.m.wikipedia.org/wiki/Reflective_surfaces_(climate_engineering) https://en.m.wikipedia.org/wiki/Reflective_surfaces_(climate... - "If all urban, flat roofs in warm climates were whitened, the resulting 10% increase in global reflectivity would offset the warming effect of 24 gigatonnes of greenhouse gas emissions, or equivalent to taking 300 million cars off the road for 20 years. So it seems, there is not only local/urban heat island effect, but even some global effect. To put this into perspective, Tesla sold 2 million vehicles. No idea, if the Wiki numbers are correct...

rayiner 4y ago

Would that work in terms of all the other stuff? Rain snow etc.

recuter 4y ago

Imagine instead of paint if we could come up with some sort of material that generates electricity. P.S. - If you look into the white paint thing more carefully you'll be rather disappointed.

highwaylights 4y ago
Wouldn't a reflective coating work better? Given it's a once off cost it seems like this should be doable.
- thombat 4y ago
  Neighbors and pilots may complain
  - highwaylights 4y ago
    I dislike people and planes are noisy. I take your point, I’m doing it anyway.
throwaway3334 4y ago
Actually, I was looking into installing solar, to offset $400/month of air-conditioning costs, during the summer. I could have had around 1.5kW of solar. But the cost of this is north of $25k, plus all the hassle to get the permits, plus all the extra complexity. While the cost of painting the roof is $100 + work. And now it is very rare that I have to run the AC.
- sxates 4y ago
  Do you mean 15kw? 1.5 is only like 4 panels, it wouldn’t make $400 per month and wouldn’t cost anywhere near $25k.
  - throwaway3334 4y ago
    I was looking at installing a very small solar array, just to offset the AC costs. The quote for the solar kit that could produce ~1.5kW (2170W Solar Kit: 7xURE NSP 310W - Mono 60 Cell - All Black Panels + 7xEnphase IQ7 60-Cell Microinverters w/QCables + 1x Enphase IQ Combiner 3 + Wireless Monitoring) was $6.5k. But, I was also considering having a 10kW battery to store that energy and to have a backup power, like Tesla Powerwall - $10k. And then there was work to install, permits, my time. Overall my estimate was, realistically it'd be ~$25k. Maybe I was wrong. On my house I have two sections of roof that are flat/horizontal. Roof is pretty thin there and although there is insulation, on hot days ceiling was getting worm in the 2 rooms under these sections. I also was hoping that an extra layer of solar would insulate my roof a bit more. So I wouldn't have to run AC that much. So the hope was to stop wasting annoying $400 on AC in the hottest months. But the cost of installing solar felt prohibitive. So I've made a quick calculation and spent $100 on the reflective roof paint instead...

joshocar 4y ago

This is one of the reasons metal roofs a nice, they reflect heat and you don't need to paint them white, they make special paints for metal roofs that help reflect the heat and also look nice.

csomar 4y ago

Yeah this was figured out in the Mediterranean probably a few hundred years ago: https://www.santorini-view.com/white-houses-of-santorini https://www.santorini-view.com/white-houses-of-santorini Unfortunately, we are losing some of this cumulative knowledge due to it not being documented, and due to the looks of alternatives (although the grey buildings in the US are as ugly as it can get)

drjasonharrison 4y ago
Well also asphalt tiles being cheaper material and cheaper installation on sloped roofs (snow!) over wood frame construction.
- jacquesm 4y ago
  They're only cheaper in the short term. Long term energy costs and replacement costs factor in strongly, and chances are that once you make that calculation you'll end up with old fashioned terracotta roofs being cheaper over the life of the house.
  - petre 4y ago
    I don't really like how the old fashioned terracota roofs behave during the summer. They heat up during the day and release that heat in night time, driving the inabitants crazy with heat. Maybe with some kind of ceramic coating to increase the albedo they'd be okay.
JasonFruit 4y ago
We're not losing the information that light colors heat less in the sun. Neither could anyone who spent five minutes on a black roof in the sun forget that tidbit. It's just that other factors than the energy required to cool a building took precedence in the past.
- kjkjadksj 4y ago
  Anecdotally it seems like we are. The rad thing to do in my area of california is to paint your white washed spanish style home mud brown or ozzy osbourne black. Then you have to install a much more powerful AC system when in the past maybe just opening windows and getting crossbreeze was enough. All these houses used to have awnings over sun facing windows when they were build in the 1920s but at some point that must have been seen as ugly and its now pretty rare to see.

foobiekr 4y ago

Hell most of the 1950s and 1960s Bay Area housing stock is worse - it’s tar and gravel roofs without any significant insulation thereby turning houses into ovens. The right answer to most of them is a new foam roof which both provides insulation and reflectivity being white but people get quite upset about the foam roof thing, especially with Eichlers.

seltzered_ 4y ago

Changing how roofs are approached (color, materials) may also have a (possibly beneficial) hydrological effect, even better would be some form of vegetation grown on roofs (likely called 'green roofs' to some) to help with evapotranspiration for facilitating a small water cycle (helping water vapor travel inland) and reduce the 'urban heat dome' effect. (see Millan Millan's papers like https://academic.oup.com/bioscience/article/69/2/143/5254231 https://academic.oup.com/bioscience/article/69/2/143/5254231 , can link to some other newer stuff if desired)

epmatsw 4y ago

There’s actually a $500 tax credit to install reflective shingles for this very reason. https://www.energystar.gov/about/federal_tax_credits/roofs_metal_and_asphalt https://www.energystar.gov/about/federal_tax_credits/roofs_m...

drusepth 4y ago

What happens to the "heat" energy that gets reflected by white/reflective roofs? It seems like it'd stay in the relative vicinity of the house, heating up the outside air further (even by a small amount), right? If that's the case, are there diminishing returns to worry about with effectively just moving heat from one place to another, assuming the (hotter) outside air will probably continue to warm up the house anyway? Do we just bank on something else absorbing the energy instead? Does it leave the area/atmosphere if nothing absorbs it? (Please don't take this as a rhetorical "this is why X solution doesn't work" -- I'm no expert here and am just curious where all that reflected heat/energy goes!)

jliptzin 4y ago
I would assume those light rays reflect off the roof instead of getting absorbed…in that case the heat is absorbed into the atmosphere, I have a hard time believing it sits around the house and lingers there for any significant amount of time (doesn’t heat rise?)
- oneoff786 4y ago
  Heat rises is short for hot air rises. The light would not be completely absorbed by the atmosphere more than it did on the way down.
extra88 4y ago
With a light or reflective surface, a lot of the energy is reflected as light so it's not converted to heat. Relatively little will be absorbed by the air near ground level, heating the air only a little.
dexwiz 4y ago
“Heat” from the sun that we feel is mostly IR/Visible light. Mix of stuff happens if we reflect it with white surfaces. Some of it does go back into space. Some of it will get reflected by the atmosphere back towards the ground. IR light is also directly absorbed by the air molecules, but very little. Air is mostly transparent at visible wavelengths so it absorbs very little energy. Solids are much better at converting IR to thermal energy. Realistically air conditioning is just moving heat from one side of a wall to another. Overall painting buildings white won’t change the temperature of Earth, but it does help the building in question, which is all air conditioning cares about anyways.

gumby 4y ago

> To give an example, houses in the Bay Area has gray/black roofs. Those are no longer legal. Title 24 requires a “cool roof” * When I had my roof re-covered a couple of years ago the roofer apologized and said he had to use a light color. Which wasn’t a problem for me so no apology was needed. * https://coolcalifornia.arb.ca.gov/cool-roofs-codes-and-standards https://coolcalifornia.arb.ca.gov/cool-roofs-codes-and-stand...

hedora 4y ago
That's strange. We just built a house in the Bay Area with a black roof, and have never heard of this. It passed planning/inspection, and the thing you linked says we are in a title 24 zone. We hadn't thought about it, and would likely have opted for a lighter roof, had someone pointed it out to us.
- fnordpiglet 4y ago
- oefnak 4y ago
  Well, I assume you covered it with solar panels, so it doesn't really matter.
zbrozek 4y ago
My understanding is that you can insulate your way to Title 24 compliance. You just have to have a total ingress performance over some level. Now that said, it would still be better for our communities to reflect this energy back out into space to reduce environmental heating. Houses in my area at solar noon have almost half a megawatt of heating potential. By municipal code they are not allowed a roof reflectivity of more than 40%.
- gumby 4y ago
  I guess having mirrors on all the houses could cause problems for other people, even for flat roofs. But I agree: reflecting the incident beams is important: when it emerges as heat (IR) it can be trapped by GHGs. I had been thinking of the reflectivity benefit rather than the reduction in air comditioning.

WhompingWindows 4y ago

In northern New England, we see a lot of homes using heating oil and woodstoves. These create a lot of local emissions and can be expensive or use a lot of time/effort (woodstoves). Heat pumps that work especially well in cold climates would be a huge efficiency gain over oil, woodstoves, and electric resistive space heaters which are also commonly used as stop-gaps in the region.

wolverine876 4y ago

Agreed, though you still need to account for cold days when you want more heat in the house.

sundvor 4y ago

Seems like a better idea to cover the roofs with PV panels, to be honest. This would reflect heat and provide power for the cooling / travel / regular house electricity.

stephen_g 4y ago
Why not both? If you have a light colour roof, you can use bifacial panels and get additional generation for the same surface area!

baybal2 4y ago

jacquesm 4y ago

I always wondered why in such climates we don't simply stick mirrors on the roof (cheap) but solar panels would seem to be the best option in the longer term (much more expensive than either mirrors or white paint). But you are absolutely right: black or dark gray roofs are quite silly in a hot climate.

maigret 4y ago
I have the same question, it would seem a quick win to have optimized house colors for the current temperatures. Many hot countries do it right, but especially northern architecture hasn’t adapted as well. Also, too much unshadowed windows. There’s a lot to win with well thought architecture.

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an9n 4y ago

Couldn't agree more. I'm in the UK and in the process of installing underfloor insulation in a house built around 1890. It is a flooboards-up job involving a windproof one way moisture permeable membrane above the joists, with hygroscopic insulation on top, and then a vapour control barrier on top of that, with all edges of layers taped to the joists where possible, all holes for wires, pipes etc. sealed with tape, and finally membranes brought up to wall behind the skirting boards. It's going to cost around £1k for a room of about 25m2. We have double glazing, the walls aren't particularly cold in winter, and the roof is insulated. I'm convinced most of our cold is coming through the floor and I reckon this job (along with the rest of the house in time, ugh) will make a huge difference. But I'm having to do it myself because there are literally no specialist fitters where I live, and there are no government incentives that I am aware of. Why aren't the government going hell-for-leather for insulation etc.?