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I assume this could be useful to shield something in space with extremely specific temperature tolerances. I'm not sure about the suggestion that people are go
by SamBam 6y ago
I assume this could be useful to shield something in space with extremely specific temperature tolerances.
I'm not sure about the suggestion that people are going to paint their roofs with it. People already have the opportunity to paint their roofs with cheap white paint which would provide nearly all the benefits this would, and still choose not to do it.
- yetihehe 6y agoNot as much benefits as their paint > Commercially available white paints reflect between 80% and 90% of sunlight, according to lead researcher Prof Xiulin Ruan from Purdue, in West Lafayette, Indiana. "It's a big deal, because every 1% of reflectance you get translates to 10 watts per metre squared less heat from the Sun," he explained.
- SamBam 6y agoYes, sure, but if you painted just two roofs white with regular paint, you're already doing much better than painting a single roof white with super-fancy paint. And yet it's hard enough even to do that.
- rtkwe 6y agoWhite roofs don’t look great which is why I think they’re largely relegated to commercial buildings instead of residential ones. They get dirty fast, are super bright and don’t fit with the traditional look for houses. On commercial flat top roofs they are hidden so it doesn’t matter if they’re blindingly bright or stained because they’re not visible.
- bryanrasmussen 6y ago>They get dirty fast do they get dirty fast in both humid and not humid climates? I would think in not humid, dry climates it might be more useful?
- frabert 6y agoDust would settle on them despite of humidity levels I think
- Retric 6y agoIt likely rains enough in humid environments to make dust a non issue. Both because you get vastly less dust in the air and because it washes away most dust that does show up as long as the roof has a significant slant to it. However you don’t need white to see significant benefit over a black roof, even just green helps.
- bryanrasmussen 6y agoI think they mean in non-humid environments the dust would be an issue.
- rtkwe 6y agoThey show any dirt really clearly so for houses it’s a crummy choice because it’s not hidden on out of view (on most houses, if it’s a modern house with a flat roof you could potentially use a flat white painted roof) which means cleaning a lot.
- bryanrasmussen 6y agoarchitecturally is a non-flat roof good for dry, hot environments? I think I tend to associate flat roofs with a dry and hot environment.
- iamthepieman 6y agoIt's bad for wet environments and snowy ones. You need to be super vigilant about inspection and maintenance if you have a flat roof where I live in northern U.S. While two feet of snow on the roof will provide a small amount of insulation, every material in contact with it needs to be rubberized or sealed every couple of years or both. Shovelling your roof with a flexible waterproof membrane can lead to gouges which defeat the impermeability. And one small leak can go unnoticed until it has seeped into the visible part of the house and rotted rafters and supporting timbers. Drainage on flat roofs get clogged and need to be cleaned or you end up with standing water. A sloped metal roof will last for 30+ years without any maintenance. A flat roof of any type will require several maintenance operations a year and last half that unless you have a commercial tar and gravel roof which is heavy and imposes additional load bearing requirements on the structure.
- everybodyknows 6y agoI'm recalling a technology from 70s Southern California: low-slope, tar paper for water seal, half-centimeter fragments of broken light-colored rock scattered on top. Dust falls through the gaps onto the tarpaper. One downside being that after a heavy rain, some fraction of the gravel makes its way down from the roof.
- citrin_ru 6y ago> White roofs don’t look great What looks great and what is not significantly affected by what are you used to see. In the place I've ground up galvanized steel roofing was common and I think it looks fine. But someone who used to dark roofs likely would tell that galvanized steel looks ugly.
- ebiester 6y agoWhat we really need is white paint in the summer, black paint in the winter - reversible roofs, if you will. That said, in the desert southwest and many places in the world, white roofs are common. I wish it were more common in the southeast...
- fullstop 6y agoCouldn't solar panels be used to achieve both benefits?
- beauzero 6y agoIf you look at old architecture in rural Georgia and Alabama. Houses are on rocks raised above the ground (air circulates underneath), 10 ft ceilings, a huge attic fan to pull cool air in in the evening, tall trees planted next to the house for shade (we have 4 pecan trees), and reflective tin roofs (if still shiny). This helped significantly to cooling in the summer. Winters aren't cold enough to warrant more than a fireplace in the common area. We have an old farm house built in the 1920's...the old original part of the house doesn't get uncomfortable until the temperatures outside get above 100. A newer part of the house with standard 9ft ceilings built in the 70's gets very warm and uncomfortable.
- gerikson 6y agoThe same kind of ideas were present in bungalows in British India and other parts of Asia. In general I think a lot of energy savings can be realized by accommodating buildings to the prevailing climate, and using passive means of heating and cooling.
- quercusa 6y agoWide eaves help as well to keep summer sun off windows and to provide a place for a porch. A gentle rain on a tin roof is a sure ticket to sleep; a strong one not so much. I'd never thought about ceiling height - that makes a lot of sense.
- theluketaylor 6y ago
- beauzero 6y agoThere are even tax benefits for doing this in the USA. https://www.energystar.gov/about/federal_tax_credits/roofs_metal_and_asphalt https://www.energystar.gov/about/federal_tax_credits/roofs_m... We decided to not use shingles on our new roof but go with silver galvalum. Galvalum does not provide the initial reflectivity but over a 5 year period shingles lose much of their reflectivity https://homeenergysaver.lbl.gov/consumer/help-popup/content/~consumer~nrr~cool-roofs https://homeenergysaver.lbl.gov/consumer/help-popup/content/... https://web.ornl.gov/sci/buildings/tools/cool-roof/ https://web.ornl.gov/sci/buildings/tools/cool-roof/ ...there are many other resources out there. It made a huge difference in our home in rural Georgia.
- purple_ferret 6y agoNYC roofs are definitely painted with reflective paint. They're usually silver-ish though.
- nerdponx 6y agoDisappointingly few of them, still. It's always depressing to fly over an area and see nothing but black rooftops, devoid of anything but HVAC equipment. I know green roofs have engineering issues but I hope one day I will instead look out my airplane window and see a sea of solar panels, small wind turbines, and rooftop gardens.
- JackFr 6y agoThe thing is, tar is an inexpensive and excellent sealant.