[HN Gopher] Ultra-white ceramic cools buildings with high reflec...
___________________________________________________________________
Ultra-white ceramic cools buildings with high reflectivity
Author : thunderbong
Score : 150 points
Date : 2023-11-14 14:51 UTC (8 hours ago)
(HTM) web link (newatlas.com)
(TXT) w3m dump (newatlas.com)
| hospitalJail wrote:
| I've wanted blankets like this for my roof in the summer and the
| black alternative for winter. (I suppose my roof is black, but
| the equivalent for the exterior walls for my home)
|
| I'm almost surprised this isnt already a thing.
| craftkiller wrote:
| Sounds like you want trees. In the summer they have leaves
| which provides shade to your roof. In the winter they lose
| their leaves and let the sun through. Best of all: its
| automated.
| ceejayoz wrote:
| The gutter cleaning and leaf raking/mulching that results
| most certainly is _not_ automated, lol.
| HelloMcFly wrote:
| You can install nearly-perfect gutter guards.
|
| I've also personally just stopped raking leaves entirely.
| Where I want some grass in my front yard I'll mulch with my
| mower which is good for the grass, but otherwise I just
| leave the leaves alone and it results in a soft, typically
| non-muddy ground like a forest floor.
|
| I'm not proselytizing this course of action, do as you
| please. But I think it's nice and something most don't
| consider.
| a_wild_dandan wrote:
| I received an HOA fine for reading this comment.
| sumtechguy wrote:
| You will receive a 75 dollar per day fine until the issue
| is resolved.
| cvccvroomvroom wrote:
| Yep. Pine needles are the worst. Gutter guards are a
| timesaver.
| lostlogin wrote:
| Compared to putting a blanket on the house, cleaning
| gutters sounds trivial.
| giardini wrote:
| Trees large enough to shade your home will tear up your
| foundation and house rodents (squirrels) that will nest in
| the walls and A/C units. Trees and pests will deposit leaves,
| branches and nuts on the roof which will clog gutters and
| rainspouts. In storms, trees will tear the building down.
|
| If you want a building then remove the trees. If you want
| trees then create a park and put trees there. Separate the
| treed areas from the buildings with distance and/or
| (maintained) root barriers. Otherwise the trees et al will
| tear the buildings down.
|
| I saw a 12-story high-rise last week whose foundation has
| been penetrated by "nice hardwood trees" they planted at the
| base 20-odd years ago.
|
| Similarly buildings don't belong on beaches or on cliffs. The
| water/wind will always win. Camp on the beach, party on the
| cliff but _never_ build on the beach or cliff.
| lostlogin wrote:
| This is a very dystopian approach to living.
|
| Plenty of us live with a bit of nature nearby without
| destroying each other.
| craftkiller wrote:
| I live in a building that was constructed 92 years ago.
| There are plenty of trees around it and the building is
| doing just fine.
| cvccvroomvroom wrote:
| Yep. It's usually the wrong tree species, wrong
| placement, or poor maintenance that leads to problems. I
| had 100'+ pine trees in my hard. Beetles were somewhat of
| a problem but the woodpeckers were all over them and
| systemics helped.
|
| Grew up in an house with 60' Australian willows that
| became too fragile and messy and were too close to a
| structure. Also, never get lemon trees because thorns
| from hell.
| jskrablin wrote:
| Big trees very close to a house? Not the best idea, you're
| always a storm away from serious damage to the house. Tree
| roots will also eventually damage any kind of surface around
| the house or house foundation. And trees with shallow roots
| are really probe to get knocked over in heavy wind.
| cvccvroomvroom wrote:
| There are different types of large trees with variations in
| structural strength of root systems that can be planted far
| enough away to not be a fire or mechanical hazard but close
| enough for shade. Minimizing surface roots by choosing the
| right species. Where I grew up, there was a storm with
| straight line winds 110 mph that took out every fence but
| only half of the trees and very few of the old trees.
| throwaw33333434 wrote:
| why not solar panels?
| justinclift wrote:
| > the black alternative for winter.
|
| Vantablack maybe?
|
| Though, you'd probably need good connections in the US DoD to
| arrange it. ;)
| willcipriano wrote:
| Anyone who isn't Anish Kapoor can use Black 3.0 instead since
| he refuses to share Vantablack.
|
| https://www.culturehustleusa.com/products/black-3-0-the-
| worl...
| chipsa wrote:
| Vantablack is only limited to Anish Kapoor for artwork.
| This isn't artwork. However, it's also finicky to apply, so
| Black 4.0 is much easier.
| justinclift wrote:
| Black 2/3/4 all have problems with reflectance. Apparently
| Vantablack doesn't.
|
| Haven't seen Vantablack in person, so not super sure. Black
| 2.0 and 3.0 I've used though, and wasn't super impressed.
| willcipriano wrote:
| I 3d print busts to paint and give to friends and family.
| If I put a few coats of black 3.0 on it gets very hot in
| the sun to the point it can melt the glue that holds the
| parts together (the plastic isnt thermoplastic so that's
| fine). I think it would work great for this purpose.
| alberth wrote:
| While this material is very exciting, wherever the reflection
| lands upon can cause real damage and is a problem.
|
| It's not uncommon for developers of office buildings that use a
| lot of glass, get sued (and win) by neighbors because the light
| reflected from the glass building causes damage to their
| property.
| tecleandor wrote:
| In this case it's diffuse reflection, not a mirror, so it
| doesn't cause any burns, hot spots or similar stuff on near
| locations. It would just look like a very white surface.
| alberth wrote:
| I might be missing it, but where in the article do you see it
| diffuses the reflection?
| josephcsible wrote:
| The picture, where it looks white and not like a mirror.
| tecleandor wrote:
| It says it 'efficiently scatters almost the entire spectrum
| of sunlight'. Due to the scattering, the reflection is
| diffuse.
|
| It's also inspired in a beetle that has a beautiful matte
| but very bright white shell: https://newatlas.com/beetle-
| scales-white/53789/
| alberth wrote:
| I'm curious to know how effective this becomes after your
| roof gets dirt & dust on it.
|
| Having a "white" roof isn't a new thing. But most don't
| do it because they quickly become dirty and look bad.
| jacquesm wrote:
| An extreme case of this sort of thing:
|
| https://www.nbcnews.com/sciencemain/london-skyscraper-can-me...
| jona-f wrote:
| The youtuber NightHawkInLight made a video about a similar
| coating (he is using CaCO3 whereas this here is using Al2O3)
| https://www.youtube.com/watch?v=KDRnEm-B3AI
|
| It was also discussed here
| https://news.ycombinator.com/item?id=36579995
|
| Would be interesting to know how the performance compares.
| trickstra wrote:
| Tech Ingredients youtube channel made something similar:
| https://www.youtube.com/watch?v=dNs_kNilSjk
| vanderZwan wrote:
| The top comment there is actually by NightHawkInLight, so
| they seem to be having a friendly competition/mutual
| inspiration in pushing this DIY technology forward :)
|
| EDIT: curious to see if Tech Ingredients' barium sulfate or
| NightHawkInLight's calcium carbonate will work out better in
| the long run. The latter looks a lot easier to manufacture
| though.
| bell-cot wrote:
| For regular buildings, the differences between 99.5%, 99.6%, etc.
| mostly matter to the supplier's Marketing Dept. and Sales Dept.
| (Vs. whoever's in charge of HVAC for the building it's installed
| on.)
|
| Though some of the other properties - especially withstanding
| ~1,000 degC - make it sound pretty useful for military equipment
| which might be facing weapon-grade lasers or nuclear fireballs.
| lm28469 wrote:
| > For regular buildings, the differences between 99.5%, 99.6%,
| etc.
|
| It's going to be <80% after a week in real life due to dust &co
| anyways
| bell-cot wrote:
| Reaction I: Point...but no way it'll be <80% after a week!
|
| Reaction II: OTOH, the article says zilch about the stuff
| being dirt-repelling, or trivial to clean. And considering
| just _how_ bad the air often gets, in some of the world 's
| largest cities...
| lm28469 wrote:
| > the article says zilch about the stuff being dirt-
| repelling
|
| They talk about "nanostructures", I read it as "dust traps"
|
| Just looking at my window stills give me a good idea of how
| they'll look if they're anywhere remotely close to a road,
| and that's in a "clean" western european city
| instagib wrote:
| I was reading that in some humid areas they pipe out their
| grey water or fresh water and disperse it onto their roofs to
| combat radiant heat from the sun to keep homes cooler.
| WaitWaitWha wrote:
| Can you give some references to this? I might have a place
| I could use this.
| lostlogin wrote:
| Installation method is going to make more difference than
| that too I'd have thought.
| joosters wrote:
| What the article needed was a comparison with 'normal' white
| paint, otherwise reporting 99.6% is not meaningful. The linked
| story https://newatlas.com/materials/super-white-paint-
| teflon-98-s... mentions that traditional paint reflects 85% of
| solar radiation.
|
| 85% -> 99.6% is an improvement, but not like a game-changer.
| bell-cot wrote:
| 85% -> 99.6% is a ~35X reduction is absorbed solar energy.
| _Definitely_ a game-changer. (Assuming it holds up in real-
| world use, etc.)
| jerf wrote:
| No, it isn't necessarily. 99.6% to 99.9999996% would be a
| "one million X" reduction in absorbed solar energy, but it
| would be of no consequence whatsoever because it would be
| well below the noise floor of any useful effect (see other
| people's comments about dust, etc.). The multiplicative
| factor of the reduction itself is not the relevant thing
| here. The real effect on a building would have to be
| measured.
| 4gotunameagain wrote:
| yes, but when buildings painted white already get warm
| from sunlight, we can safely say that a ~35x reduction
| will be meaningful, as opposed to the example you
| provided where there will be no observable effect as you
| correctly pointed out.
| hinkley wrote:
| Roofing your house in a fire prone area. Combined with
| hardyboard siding and you could survive quite a bit.
| jonhohle wrote:
| Roofing tile was the first thing I thought of as well. In
| Phoenix having a ceramic, heat tolerant, moldable, reflective
| material seems optimal for tiled roofs, or even as an
| addition to flat roofs.
|
| I wonder if it can be used in spray applications like other
| ceramic coatings.
| carreau wrote:
| While I agree this is marketing stunts in general, sometime the
| difference between 99.5 and 99.6 reemission is 0.5 vs 0.4
| percent absorption. so one way of seeing it the second one is
| 20% better than the first one at not heating the building.
|
| This is often the case for percentages "close" to 100%, e.g:
| with LED efficiency, for powerful LEDs the problem is not the
| quantity of light emitted but dissipating the heat that may
| need active cooling, so what may look like a few percent
| improvement is luminosity may actually be a much stronger
| decrease of the size of active cooling,
|
| Or semi-transparent mirrors in physics, where you really make a
| difference between 99.95 and 99.96% reflectance, because what
| you really look at the transmitance.
| Aeroi wrote:
| Yeah, I mean how does this material actually perform on a roof?
| Is there a measurable difference in the marginal gain of 95% to
| 99.6% when analyzing inside temperature of a house or energy
| reduction as a result?
|
| There seems to be many factors when looking at the actual cause
| and effect especially when cost is introduced.
| somedude895 wrote:
| Funny that in a lot of Sci-Fi of the non-dystopian type white and
| shiny materials often seem to be widely used. I suppose they made
| it like that due to white looking clean, sleek and welcoming, so
| it would be cool if it actually turned out that way.
| _jal wrote:
| It codes as "clean" and "controlled".
|
| It also implied clean energy tech at a time when that was also
| mostly science fiction.
| Gys wrote:
| Ideally this could switch to ultra-black for the Winter months ;)
| Spivak wrote:
| I mean you joke but there's no reason you couldn't.
| BizarroLand wrote:
| There's an old solar heating method that does something
| similar. Build a large glass box with a wooden frame, and in
| the middle of that box place a bunch of bricks that have been
| painted black.
|
| Place an air vent at the bottom and a tube out of the top, and
| route that tube into your house, and cover the inlet with a
| heavy sheet of plastic.
|
| Place the entire contraption in the sunniest spot on your
| property. When the sunlight hits the bricks they will heat up,
| and the convection will cause an updraft.
|
| Once the updraft pressure is high enough to lift the plastic,
| it will spray hot air into your home, and when it is too cold
| the plastic will stop a backdraft from drawing air out of your
| home.
|
| Additionally, the bricks serve as thermal mass so the heat will
| continue for several hours after sundown.
|
| You can improve the performance by replacing the open air inlet
| with a tube that goes to a colder place in your home so that
| the convection circulates the air in your house.
| teachrdan wrote:
| This is an amazing demonstration of low-technology. Is this
| documented anywhere with diagrams?
| BizarroLand wrote:
| IDK, I read about it in an issue of Mother Earth News I
| think?
| BizarroLand wrote:
| Found one of the ones I've read:
|
| https://www.motherearthnews.com/sustainable-
| living/renewable...
| dntrkv wrote:
| I recently bought a property that has a cooling system
| similar to this. The difference in my case is that there are
| tunnels underneath the foundation containing rocks. Once the
| temp inside the house reaches a certain point, there are fans
| that blow the accumulated hot air in the "greenhouse" through
| those tunnels. It works, but I'm tearing it all out. It's an
| eyesore and I rather have proper temp control.
| fudged71 wrote:
| This is the state of the art type of system for greenhouse
| heat retention, one that I dream of owning. I can't imagine
| how an underground system would be an eyesore, the ducts
| going to the roof?
| dntrkv wrote:
| The glass panels lean against the side of the house. It
| was built in the 80s and wasn't all that well
| implemented.
| fudged71 wrote:
| I wonder if e-ink technology can scale to large sized roof
| tiles.
|
| I live in the north and I think it's remarkable that we don't
| use some form of white/black transitions or convertible awnings
| etc for regulating temperature.
| Synaesthesia wrote:
| Black is a better emitter of heat, so if your home is warmer
| than the surroundings, it will actually make you colder. That
| said, infrared radiation is a small contributor to cooling at
| those temperatures, good insulation is the biggest factor by
| far.
| tromp wrote:
| These ceramic tiles were also discussed 2 days ago at
| https://news.ycombinator.com/item?id=38227486
| agilob wrote:
| >But these coatings have their issues, including durability.
|
| Was thinking if that would be a good solution for frying pankings
| made from dark bricks that's 50'C during summer, but probably
| not?
| lostlogin wrote:
| It might be a good coating for the inside of fires, kilns etc.
| though only for ones that are under the temperature rating.
| satvikpendem wrote:
| Will it cause something like snow blindness if I look at it?
| kristiandupont wrote:
| Is this better than mirrors or space blankets?
| theultdev wrote:
| Mylar will shred and is loud. Might as well do an aluminum roof
| if you don't mind the noise.
|
| Mirrors will crack and can reflect sunlight in unwanted ways
| (directly into your neighbor's line of sight, into planes,
| etc.)
| kristiandupont wrote:
| Right, I meant in terms of reflectivity.
| ChrisMarshallNY wrote:
| I predict the rise of the "Roof Cleaner," as a vocation.
|
| That stuff will need to be kept pristine.
| switchbak wrote:
| That already exists though, I just paid a guy in a truck a
| bundle of money to clean my roof. Maybe this is mostly a thing
| in the PNW though?
| kube-system wrote:
| Building exteriors are regularly cleaned all over the world.
| It's over a billion dollar industry in the US alone.
|
| It would probably be even larger if more US roofs were
| pristine white instead of dark asphalt.
| ChrisMarshallNY wrote:
| Yeah, but these will be a different breed. I know a number
| of folks that power-wash buildings and roofs. It's a
| cottage industry, hereabouts.
| nvy wrote:
| Definitely a PNW thing. The rain here causes moss and other
| problems that aren't prevalent back east.
| josefx wrote:
| I can't wait for more molten car incidents when it becomes even
| easier for curved designer buildings to focus massive amounts
| of light at random points on the ground.
| csours wrote:
| This is diffuse reflection (rough), not specular like a
| mirror.
| TeMPOraL wrote:
| Diffuse reflections still scare roughly with cos of
| incidence angle, so diffuse-only panels arranged into
| parabolic or spherical shell would still focus light, even
| if much less efficiently.
| soco wrote:
| I assume you're referring to the walkie-talkie building in
| London: https://globalnews.ca/news/1334377/car-melting-
| london-skyscr...
| throwaway20222 wrote:
| Already lots of groups doing solar panel cleanings. I imagine
| the venn diagram between people who invest in solar and in
| these roofs may have some overlap.
| javajosh wrote:
| The iRobot Roofba!
| contemporary343 wrote:
| There's been a ton of development in super reflective materials
| since the first demonstration of daytime radiative cooling at
| Stanford in 2014. Ultimately though, reflectivity does drop with
| dirt and pollution exposure over time, even for these kinds of
| materials. So most super reflective materials plateau at a lower
| number long term outdoors.
|
| Also, just for reference, Spectralon, a sintered PTFE reflectance
| standard has had this level of solar reflectance for decades. So,
| in a sense, not that much new here. a sintered ceramic is gonna
| be expensive and will have a hard time competing with the
| simplicity of a paint based approach. Super white paints using
| various pigments have been well studied the last 5 years.
| gorkish wrote:
| IMO simply being reflective is a dead end. Future materials
| will have to absorb wideband energy and actively emit it in an
| atmospheric bandgap to be effective enough to matter. I would
| think this would be an excellent application for quantum dots
| and have been sort of low-key waiting for an announcement or
| paper to drop for the last year or two.
| rickydroll wrote:
| We also need to reduce aircraft contrails. Contrails increase
| high-altitude clouds (cirrus and related), which blocks the
| heat that would have been lost by radiative cooling. It isn't
| hard to reduce contrails. We have the atmospheric data
| telling us the height of and where clouds are likely to form.
| Aircraft need to change altitude by 2000 ft from what was
| planned to avoid the cloud-forming regions.
|
| research paper
| https://acp.copernicus.org/articles/19/8163/2019/
|
| AI is helping reduce the problem
| https://blog.google/technology/ai/ai-airlines-contrails-
| clim...
| piyh wrote:
| Reducing contrails would cause more warming unless we have
| a ton of these coatings out there
| kulahan wrote:
| We already pay to clean lots of buildings, and rain should help
| with that too, no? Seems like this would be a very solvable
| problem to me, but maybe I'm misunderstanding the problem
| fundamentally.
| zdragnar wrote:
| The less rain you get (i.e. during a drought) the more you
| tend to get dust in the air. We went through this last
| summer; my dog would kick up clouds of dirt dust running
| through our yard.
|
| Worse than this, though, is the durability of the material.
| Lots of these super reflective paints don't hold up very well
| to rainwater (which itself is not especially clean or PH
| neutral) or seasonal extremes.
|
| Typically, you wouldn't want to paint the sides of buildings,
| as that'll just reflect the light mostly down. You want it on
| rooftops, which most people don't pay to clean frequently or
| at all.
| kulahan wrote:
| This makes sense; I guess it just becomes a new added
| expense with no _major_ benefit aside from maybe saving on
| some cooling costs? Seems like a thing you 'd be able to
| convince a company to buy into completely, but only once
| it's cheap and durable.
| wongarsu wrote:
| Maybe it's just dirty coal plants and the nearby streets, but
| rain seems to be the main reason why our windows get dirty.
|
| You could add a lotus-effect coating, but given that window
| cleaners are still in business I assume that is quite
| expensive at scale.
| lawlessone wrote:
| >Ultimately though, reflectivity does drop with dirt and
| pollution exposure over time, even for these kinds of
| materials.
|
| I guess this will be the new white washing?, like people used
| to do on buildings 100 years ago.
| felipemnoa wrote:
| I wonder if you could just use mirror tiles? What would be the
| reflectivity then?
| hgomersall wrote:
| I initially thought the same, but my current model is that the
| mirror would also have a very low emissivity so you can't
| passively cool (only not heat so much).
| the_jeremy wrote:
| Standard mirrors are only ~98% reflective
| (https://en.wikipedia.org/wiki/Mirror#Reflectivity). For
| example, "infinity mirrors" will fade as the number of
| reflections increase
| (https://physics.stackexchange.com/questions/305329/are-
| infin...).
| torusle wrote:
| I want this as a paint pigment please...
| dgacmu wrote:
| This article is a fairly terrible summary, particularly when it
| comes to explaining the really neat thing about these coatings:
| It's not just that they reflect a lot of inbound light, they also
| radiate heat in a part of the infrared spectrum that can pass
| transparently through the atmosphere.
|
| https://en.m.wikipedia.org/wiki/Passive_daytime_radiative_co...
|
| Which is one of the major reasons that these specialized coatings
| are better than just white paint or mirrors or things like that.
| They can actually cool the structure to below ambient
| temperature.
| HPsquared wrote:
| This is because the blue sky is very "cold". Point an infrared
| thermometer up there and see... Very cold indeed.
| wongarsu wrote:
| Which usually objects can't fully exploit, because the heat
| they radiate away is absorbed by their immediate
| surroundings, which radiate part of it back towards them. You
| can "cheat" that by radiating away heat in a spectrum that
| isn't absorbed by anything, removing it from the area.
| jessriedel wrote:
| Basically. To be clear, it's not that you are worried about
| getting "the same" heat reflected or otherwise radiated
| back toward you. (The radiation emitted by your roof
| doesn't appreciably change the radiation incident on your
| roof from the atmosphere.) It's that if you are passively
| emitting at some frequency you are _necessarily_ absorbing
| at that frequency too (by the 2nd law). And you don 't want
| to be absorbing at the frequency where the atmosphere is
| opaque and hence warm. In contrast, it's fine to be
| absorbing at the frequency where the atmosphere is
| transparent, because then you're just exposed to cold outer
| space.
| dragontamer wrote:
| I had no idea what you were talking about until I
| remembered that infrared is just a Radio wave and
| therefore everything is an antenna.
|
| Antennas that are good at transmit at X frequency tend to
| also be good at receiving X frequency necessarily. And
| different 'colors' are nothing more than different
| antenna resonance points.
| eptcyka wrote:
| You could use _chimneys_ that are coated by the irradiative
| material on the inside, pointing all the IR up into the
| sky.
| dontwearitout wrote:
| I had to look this up - apparently it's around 0C if you do
| this! https://mynasadata.larc.nasa.gov/sites/default/files/20
| 18-12...
| bilsbie wrote:
| It would be interesting to put these out at night and have them
| drop a designated area below the dew point and collect water.
|
| As I understand it, nighttime temps get near the dew point but
| often don't hit it because water in the air releases so much
| heat.
| deepsun wrote:
| Mold/algae will grow on the wet surfaces in a matter of days,
| destroying the main promise of the material.
| hamandcheese wrote:
| Im not so sure. Mildew has to eat something. Assuming the
| surface is kept clean and water is collected regularly, it
| shouldn't be a major problem.
|
| You don't see mildew growing on cars very often, do you?
| Yet, growing up in Florida, I'd see few covered cars in the
| morning all the time.
| j-a-a-p wrote:
| At night they would do the opposite what you suggest. A very
| white surface would stay warmer, a black (in the sense of IR
| black) surface would radiate heat better and cool below dew.
| sandworm101 wrote:
| And literally cool the planet. That ir that passes through the
| atmosphere is heading into space, at least in clear days.
| jessriedel wrote:
| Even the wikipedia page is confusing for someone who knows
| basic thermodynamics.
|
| > PDRCs can be broadband in their thermal emittance capacity,
| meaning they possess high emittance in both the solar spectrum
| and atmospheric LWIR window (8 to 14 mm), or selective
| emitters, meaning they narrowband emit longwave infrared
| radiation only in the infrared window
|
| It's not really that you want to avoid emitting thermal
| radiation _per se_ at the frequencies where the atmosphere is
| opaque. It 's that by the second law your _thermal_ (i.e.,
| passive) emissivity is equal to your absorptivity, and you want
| your absorptivity to be low in frequencies where the atmosphere
| is opaque and hence is warm. In other words, by basic thermo
| your passive behavior at each frequency is some value ranging
| between insulative (reflective) to absorbtive (transparent). If
| insulative, you will neither thermally emit nor absorb at that
| frequency. If absorbtive, you will both thermally emit and
| absorb at the frequency. So you want to be insulative at the
| frequencies where you would be thermally coupled to the warm
| atmosphere and you want to be conductive at the frequencies
| where you would be thermally coupled to cold outer space.
| contemporary343 wrote:
| Most materials, aside from metals, of sufficient thickness have
| high high infrared emissivity. All white paints, for example,
| already did radiate heat upwards through the atmospheric
| window. These more reflective films are no more emissive than
| previous paints (they're all quite emissive to begin with!)
|
| The only difference, optically speaking, really is that they
| are better solar reflectors.
| yownie wrote:
| DIY version.
|
| https://hackaday.com/2023/07/22/that-ultra-white-paint-that-...
| medion wrote:
| Meanwhile, in places like Australia - councils regulate roof
| colours and there are laws against light and reflective roofs -
| dark roofs are actually forced upon.
| amne wrote:
| how can they justify teh cost of cooling in the summer?
| aregue wrote:
| How do these tiles compare to a green roof where there is some
| cooling via water evaporation through plants?
| nfriedly wrote:
| My dad lived in a trailer for a little while, and he painted the
| roof white one summer. It lowered the inside temperature by a few
| degrees - I don't recall the exact number, but enough that it was
| noticeable.
| Mistletoe wrote:
| I kind of just wish we would skip it and put solar panels on
| everything.
|
| https://www.frontiersin.org/articles/10.3389/fenvs.2014.0001...
|
| "Solar panels reduce both global warming and urban heat island."
| cvccvroomvroom wrote:
| Interesting. Barium Sulfate (Spectraflect) was likely the
| previous record holder at 98%.
| tomkinstinch wrote:
| Depending on the wavelength, Spectralon (sintered PTFE powder)
| is a bit better. At least until it gets dirty.
| DontchaKnowit wrote:
| Can you imagine how awful a city with buildungs made out of this
| material would be? It would be completely blinding.
| dzonga wrote:
| in places like Taiwan - buildings tend to be covered with tile
| outside.
|
| now it occurs to me - must be way for passive cooling.
| next_xibalba wrote:
| But can I put it on my teeth?
| jwineinger wrote:
| Would ultra-black siding help warm my house appreciably in
| Minnesota winter?
| deepsun wrote:
| Wouldn't mold/algae grow on its surface, almost immediately
| disrupting its magic feature?
| smileysteve wrote:
| We have so much to do before "ultra-white" really matters;
|
| Most buildings aren't white, or even close to white;
|
| Streets -- and parking lots in many areas take up much more
| surface area, and they're mostly painted black, and they create
| heat islands. Phoenix changed the color _slightly_ and saw great
| results https://www.fox10phoenix.com/news/is-phoenixs-cool-
| pavement-...
| kadoban wrote:
| Extra passive cooling on a building has more immediate local
| effects, namely if my house is cooler I don't have to run the
| A/C as much. A/C is a _huge_ power suck, so avoiding even a
| little is huge.
| j-a-a-p wrote:
| One bummer is that modern building codes ask for better
| insulating roofs. Think 15 cm mineral wool. Because of this it
| does not so much matter anymore how hot the roof becomes at the
| exterior.
|
| I doubt if you earn back the investment.
___________________________________________________________________
(page generated 2023-11-14 23:01 UTC)