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Science Technology

Smart Glass Blocks Infrared - But Only When It's Hot 303

Posted by michael from the light-reading dept.
klevin writes "New Scientist has an article about a new way of making sheets of glass so they block infrared energy at temperatures above 29C (84.2F). Just so long as it doesn't have to get that hot on both sides of the glass. My AC comes on way before 84F. I suppose that with double or triple paned glass, you'd only treat the exterior pane."
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Smart Glass Blocks Infrared - But Only When It's Hot More

Smart Glass Blocks Infrared - But Only When It's Hot

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  • Safe? Lifespan? (Score:5, Interesting)

    by ackthpt ( 218170 ) * on Tuesday August 10, 2004 @12:29PM (#9931354) Homepage Journal
    However, a number of issues still need to be overcome. Firstly, the substance is not permanently fixed to the glass. Also, the coating itself currently has a strong yellow tint.
    Anyone know toxicity of Vanadium dioxide? How would it hold up to acid rain (H2S) and what byproduct is likely if it comes away and combines with other compounds. (Remember the good old days when car brake pads were asbestos and people pissed about asbestos being in the vents, but didn't realize the city air was awash with it?) What kind of lifespan will it have under nominal outdoors conditions, including periodic cleaning?

    How's that yellow tint going to look where indoor light is already greenish from fluorescent lighting? Will we walk outside and everything will look pink or purple? Fun!

    Hopefully in three years they'll give some answers to these questions and more. I've got a couple windows, but we've got no air conditioning and the heat reflects off an earthen bank, most of the heat comes through the walls.

    • Re:Safe? Lifespan? (Score:4, Funny)

      by Leffe ( 686621 ) on Tuesday August 10, 2004 @12:34PM (#9931406)
      How's that yellow tint going to look

      Oh, that's easy, the opposite of yellow is blue, just use blue glass!

    • Re:Safe? Lifespan? (Score:5, Funny)

      by cephyn ( 461066 ) on Tuesday August 10, 2004 @12:39PM (#9931481) Homepage
      Yellow tint, ew, but as for the Vanadium, if you have a double paned window, treat the inner side of the outer pane. No leakage or exposure to Vanadium, unless you break the glass. And no exposure to H2S rain.

      If you've got heat coming through the walls, just get some old-fashioned IR reflectors -- Aluminum Foil! Put it up to reflect heat away from your walls, and maybe an old fan to blow the heat off of it. Oh, and ripple it. Your very own House Heat Sink. Overclock your house!
      • As a side benefit you won't have to wear your tin foil hat inside anymore!
      • If you've got heat coming through the walls, just get some old-fashioned IR reflectors -- Aluminum Foil! Put it up to reflect heat away from your walls

        I hear this also helps with the mind control rays.
      • If you've got heat coming through the walls, just get some old-fashioned IR reflectors -- Aluminum Foil! Put it up to reflect heat away from your walls, and maybe an old fan to blow the heat off of it. Oh, and ripple it.

        Actually, we used this technology on a west-facing window whose transparency was a bug, not a feature. It gave a great view of the neighbor's bathroom window, but was perfectly situated for the summer sun to beat down on the dining room table (and all its occupants).

        A layer of aluminum f
        • not to mention overrated. ;)

          the ripple thing was a joke. if you were actually trying to bleed heat off from the inside, you would want it rippled with a fan, and attached to your house with heat-conductive goo. ;)
    • Some quick Googling didn't turn up safety or toxicity data. That's kind of disquieting, since it implies that the material hasn't been deployed or tested much.

      I try to avoid brand new construction materials. Let other people find the problems that show up ten years down the road.

      Hope it works -- nifty idea!

      • It's safe (Score:5, Informative)

        by Engineer-Poet ( 795260 ) on Tuesday August 10, 2004 @02:48PM (#9933036) Homepage Journal
        Vanadium is a common alloying element in steel. The two MSDS [espimetals.com] pages [ox.ac.uk] I found indicate that the powdered oxide isn't very good to breathe or eat, but the amount released by breaking a window is probably so small that you wouldn't notice. The biggest hazard would be to people working in the manufacture of such windows.

  • Damn, that's unfortunate (Score:5, Funny)

    by Anonymous Coward on Tuesday August 10, 2004 @12:31PM (#9931374)
    This will severely hamper my illicit recordings of my neighbors having sex using my hidden wireless camera.

  • window tinting? (Score:4, Insightful)

    by natron 2.0 ( 615149 ) <ndpeters79NO@SPAMgmail.com> on Tuesday August 10, 2004 @12:33PM (#9931395) Homepage Journal
    Sounds very similar to Ceramic window tinting film that is found on cars

  • can be used in cars (Score:4, Interesting)

    by Anonymous Coward on Tuesday August 10, 2004 @12:33PM (#9931403)
    If this technology comes out, a good application is to use it in cars (especially in hot areas).
    • I haven't RTFA yet, so maybe they discuss this. But my (limited) understanding of why cars get so hot is because sunlight comes in in the visible range (to which the glass is fully transparent). It gets absorbed by stuff in the car and then re-emitted mostly in the IR range. Because the glass is already more transparent to visible light than to IR the heat gets trapped in the car.

      If I am right about this, then cars would be exactly where you don't want this stuff.

    • I've often wondered why car-makers (NOT the aftermarket!!) don't design for places like Miami rather than just Detroit/Tokyo/Munich and similar latitudes. Then they try to compensate for baking the contents of your car for hours with too much air-conditioning, which wouldn't be needed with proper design (and I'm not even a professional car designer, the following is off the top of my head!)

      For example: I would LOVE to have a cartop solar cell harnessed to a fan helping to cool the car -- better yet would a
    • I know my Honda Insight uses some IR blocking in the windows, but not sure what it is right now. Gives a slight green tint. The goal is to take a load off the A/C.

  • 84 degrees is okay for some things. (Score:5, Informative)

    by lpangelrob2 ( 721920 ) on Tuesday August 10, 2004 @12:34PM (#9931420) Journal
    First poster brought up good points about toxicity... I'll address the temperature question.

    (sidenote: I guess there's a new geek test out on how to actually post to this story... the Read More link being wrong and everything...)

    84 degrees actually is pretty comfortable for people in the south, especially if it's going to be a dry 84 degrees, which air conditioning can help with. This can be useful, if it's not as expensive as gold, and if it really works as advertised, for people living in dry climates (read: desert southwest) who don't want to run A/C bills through the roof.

    That said, I recall that while a significant percentage of heat comes from solar energy through windows... when the house is sitting in a 110 degree plain, it may not be quite as good as first thought.

    • These are good points, especially for southerners. If your a/c kicks on "way before" 84, you have it set to too low a temperature.

      This would, however, be an additional piece of equipment in the effort to keep cooling costs down. You can insulate your building's walls and ceiling to keep the 110-degree ambient air from getting too much heat in, along with double- or triple-paned glass. But since we all don't like to live in dark caves with no windows, this would help keep IR light from heating up the ins
      • ... for the old ways of construction. 3 foot thick earth-type walls, low deep overhangs for shade. Maybe those old original settlers in the southwest weren't as backwards as we think, just because they didn't have cheap electricity.......

    • Re:84 degrees is okay for some things. (Score:5, Insightful)

      by value_added ( 719364 ) on Tuesday August 10, 2004 @12:52PM (#9931665)

      That said, I recall that while a significant percentage of heat comes from solar energy through windows... when the house is sitting in a 110 degree plain, it may not be quite as good as first thought.

      What amazes me to this day is that a less hi-tech approach would be to plant a frigging tree. Cities here in Southern California still insist on cutting them down (ostensibly to save money from the city maintenance budgets). Without the shade, you get roofs and attic spaces that easily heat up to over 100 degrees and don't cool until 6-7 hours after nightfall.

      • What amazes me to this day is that a less hi-tech approach would be to plant a frigging tree.

        Given that they seemed most interested in using this glass on skyscrapers, those would need be some mighty tall trees! That, and I don't think I'd want to hang a smaller tree in front of my car either. :)

      • Roof gardens. (Score:5, Interesting)

        by Anonymous Coward on Tuesday August 10, 2004 @01:32PM (#9932187)
        In Tokyo, law requires large buildings to have roof gardens to prevent the roofs from getting so hot. Plants will use that energy to grow, instead of letting that energy hit concrete, metal, etc and become heat. Its estimated that tokyo would be 10 degrees hotter on average without the roof gardens.

        • Re:Roof gardens. (Score:3, Interesting)

          by Grishnakh ( 216268 )
          Sounds great, but we can't have laws like this in the US. It would make too much sense, and would also increase building costs, reducing profits for construction companies.

          • Re:Roof gardens. (Score:4, Insightful)

            by valkraider ( 611225 ) on Tuesday August 10, 2004 @02:13PM (#9932646) Journal
            Here in Portland, OR - they try and implement things like this, but then people just complain about the extra cost up-front.

            When will Americans learn - if we build stuff cheap up front it is more expensive long term. If we spend more money up front, we save LOTS of money in the long term...

            Oh, wait. That would be smart...

            • Re:Roof gardens. (Score:4, Interesting)

              by Grishnakh ( 216268 ) on Tuesday August 10, 2004 @02:30PM (#9932802)
              It's the American Way. Buy cheap crap, then spend even more money to fix or replace it. It's why ultra-cheap inkjet printers (with their absurdly priced replacement cartridges) are so popular. I got a laser printer instead, which only costs a penny or two per page, so I'm UnAmerican.

    • Re:84 degrees is okay for some things. (Score:5, Informative)

      by hummassa ( 157160 ) on Tuesday August 10, 2004 @01:00PM (#9931777) Homepage Journal
      Where I live (Belo Horizonte, southwestern Brasil) 84F (29C) is room temperature 9 out of the 12 months of the year. In the northern states, it's 11/12. We usually only turn our ACs on at home when it's 37C (100F) and above.

      Notwithstanding, this is _great_ (if the yellow tint and the toxicity when broken issues are solved) for car windows. AC won't kick in as often (less gas spent), seats/steering wheel won't get ultra-hot when the vehicle is left under the sun (the beach!!), baby-left-in-the-car dehidration deaths won't happen.

    • 84? (Score:2)

      by siskbc ( 598067 )
      84 degrees actually is pretty comfortable for people in the south, especially if it's going to be a dry 84 degrees

      Except that a dry 84 degrees never occurs in the south, assuming we're talking the southern part of the US. If it''s 84, teh humidity is 90%+.

      • Comment removed based on user account deletion
        • I think Mississippi counts as "the south" in anbody's book.

          Of course, it would have to be one of those rare nice summer days as soon as I open my mouth. Trust me, it's rare. The south in summer is freaking miserable. Humidity by 4pm is usually 100% accompanied frequently by pop-up thunderstorms. I'm from KY, and everything south of that is even worse.

          And no, Austin ain't the south. ;)

  • I'll sum it all up in one word... (Score:4, Funny)

    by FooAtWFU ( 699187 ) on Tuesday August 10, 2004 @12:34PM (#9931421) Homepage
    Cool!

  • Dye to change the color? (Score:3, Interesting)

    by tmasssey ( 546878 ) on Tuesday August 10, 2004 @12:35PM (#9931424) Homepage Journal
    According to the article, they want to add dye to get it to 'change color'. Given the subtractive properties of such a dye, won't that cause the glass to let in less light, just like the tinting they're trying to replace?

    I don't see how you *add* dye to get the coating to let in the light that the coating is currently blocking...

    • Given the subtractive properties of such a dye, won't that cause the glass to let in less light, just like the tinting they're trying to replace?

      One advantage that I can see would be that in low-light situations there would be no visible tint...?
    • It is called color compensating. You tint with complementary colors to neutralize a color cast. Yes it will make the window appear a bit tinted as less total light gets through, but it would be less yellow.
  • Depending on the cost of the material, which is not mentioned in the article, it could be a great way to insulate from heat in the summer, while helping trap heat in winter. Specially for big glass buildings, this could translate into big savings in energy and money.

  • Temperature of Glass (Score:5, Insightful)

    by Crazy Man on Fire ( 153457 ) on Tuesday August 10, 2004 @12:36PM (#9931433) Homepage
    My AC comes on way before 84F.
    Looking at the article, it seems that it is the temperature of the glass that must reach 84F, not the temperature of the air inside the room. I would imagine that the glass reaches 84 much faster than the air inside, so your AC shouldn't be much of a factor unless it is cold enough to have a larger impact on the glass temp than the outside air and the solar energy.

    • Re:Temperature of Glass (Score:4, Interesting)

      by Tranzig ( 786710 ) <voidstar@freemail.hu> on Tuesday August 10, 2004 @01:03PM (#9931815)
      Actually everything else in the room hit by the sunlight get way beyond 84F before either the window glass or the air inside the room. They start to radiate and heating up the air, much sooner than glass. And a typical window glass has neligible surface connection with other material than air and air has poor heat conduction and storage (sorry I don't know the exact English name of these physic attributes) capabilities, I think it is an educated guess that glass gets hot slower than air, thus this temperature boundary can be a real issue. (Though I have never made such measurements.)
      • Hmm. Seems reasonable, but I haven't seen this in practice. When I touch my window on a cold winter day, it is cold (much colder than the air inside my house). When I touch my window on a hot day in the summer, it is very warm (much warmer than the air inside my house). Can anybody with more knowledge on this subject offer some insight?
        • When you touch your bathroom tile, it typically feels colder than the surrounding air. This is not because the tile is somehow cooled with respect to its surroundings, but because the tile is much more efficient at carrying away heat from your body. An air temperature of 70 degrees F can feel very comfortable, since air is a very poor conductor of heat, but 70 F water feels decidedly cool to the skin. Having said that, it still may be the case that your window is cooler or hotter than the inside of your
  • Next step is glass that turns transparent to visible light when it's hot, for example, a bathroom window what turns transparent when a hot woman (or a hot man) gets on the other side...

  • recycle (Score:5, Interesting)

    by Doc Ruby ( 173196 ) on Tuesday August 10, 2004 @12:36PM (#9931449) Homepage Journal
    How about some electronics grounding that vanadium dioxide? If set up right, when the VO2 transitions to "metallic" above 29C, the panel's photoelectric effect could harness the solar power now more highly available. That in turn could power other devices, like awnings, vent covers, or even fans, to mitigate the heat, using the sun's power against itself.

    • Re:recycle (Score:5, Interesting)

      by WOV ( 652967 ) on Tuesday August 10, 2004 @12:57PM (#9931747)

      It's too darn hard. I just came off of reading NREL's annual report on the research they're doing to bring down the costs on existing PV materials (silicon, CIGS, TIO2, etc.,) and it's more than enough to make me not want to "reinvent the wheel" on another niche PV compound.

      Better to take existing PV and incorporate it into a window made of something else if you want to do some active cooling. In fact, I wish I could find a good link, but I know that Audi does this with the sunroof on their "warm weather package" models - thin-film PV in the glass of the roof powers fresh air fans behind the headliner when the car is parked, so that you don't have to get into such a heinously hot car when it's been outside for a while. (or burn the gas to run your AC at "Max" for 15 minutes.)

  • Well... (Score:3, Informative)

    by iamdrscience ( 541136 ) on Tuesday August 10, 2004 @12:37PM (#9931451) Homepage
    My AC comes on way before 84F.
    Yes, but the surface of your glass is hotter than the air in your house/apartment, so 84 degrees might not be that far off.
    • I'm sure they studied what target temparture was desired, I imagine they could go lower if needed. I doubt that 84 just happened to be the lowest temp they could get with the tungsten technique.

  • solution (Score:3, Interesting)

    by jeffy124 ( 453342 ) on Tuesday August 10, 2004 @12:37PM (#9931456) Homepage Journal
    three panes of glass, separated by a short distance each. pump warm air into the two gaps. The middle glass is this infrared blocker dealy.

    Or, if only one side needed to be warmed, use two panes instead of three with a small gap. The exterior pane is the infrared blocker. When it's cool outside or the window is shaded, pump warm air into the gap between panes.

    IANACE

    • Re:solution (Score:4, Informative)

      by redJag ( 662818 ) on Tuesday August 10, 2004 @01:01PM (#9931790)
      No, the point of activating it only when it's hot is for cold weather times. When it's cold outside, letting solar energy IN saves money; when it's hot outside, keeping it out saves money. Pumping in hot air would be a waste in three ways (heating the air, pumping the air, and negating the entire point of the treated glass).
    • No, typically you want it on the #2 surface. If you want to get technical, argon is the high performance gas of choice for filling the gap in an insulated unit. The two lites are separated by as little as 1/4 inch up to 3/4 inch. The size of the unit will dictate the minimum required.

      Using a polysilicone sealant is also a bonus for prevention of heat transfer as is using an extruded insulating frame as opposed to aluminum.

      There are already [cardinalcorp.com] many [guardian.com] companies [sunmanagement.com] that already produce low emission glass [glasslinks.com].

      Look

  • combination (Score:2, Interesting)

    by www.sorehands.com ( 142825 )
    An interesting combination would be to incorporate it into a photosentive dye (photogrey?) like sunglasses. When it gets brighter, it gets darker. It would be useful in keeping rooms or cars from getting too bright.
  • Simply sandwidtch between panes of glass and seal- that way there's no place for the shield to go, and therefore, it stays put.

  • Why Block When you can consume (Score:3, Insightful)

    by grunt107 ( 739510 ) on Tuesday August 10, 2004 @12:39PM (#9931482)
    While the lowering of heat-causing agents is noble, the better scientific path (IMO) is to grab this energy and use it to power the home (solar).
    Spend time and effort developing more efficient, resilient, and less-expensive tech on solar energy and every new house could be roofed with 100% solar tiles. These homes could even GENERATE enough exess energy to sell back to the grid, which would help every income level.
    'Zero' dependence on energy businesses could be a very real thing for homes (oh the humanity)...
    • We want to block because we're talking about windows. We want light and sight but not heat.
    • Imagine living in Nevada, where you get sun for more than 300 days a year, and most of those days are high quality 90F or higher sun.

      A solar home can only use so much.
      A trombe wall can only absorb so much.
      Even the new 10% transparent solar collectors can only do so much.

      What do you do with the excess heat?
      You run evaporative coolers and AC.

      The only other way to shed the excess heat is to absorb it (ala these panes or burying the house underground) or redirect it, with things like geothermal heat pumps.
      • But why can't the consumptive tech be improved so solar collectors/transformers DO use ALL the heat (or the amount above xx Celsius)? Is this some law of nature where thermal can be blocked but not utilized?
        This is not my area of knowledge but it would seem to me that efficient solar/thermal conversion is as possible as the tech described here.

        • Nature says you can't (Score:4, Insightful)

          by Engineer-Poet ( 795260 ) on Tuesday August 10, 2004 @03:25PM (#9933522) Homepage Journal
          But why can't the consumptive tech be improved so solar collectors/transformers DO use ALL the heat (or the amount above xx Celsius)? Is this some law of nature where thermal can be blocked but not utilized?
          Yes. It's called the second law of thermodynamics. You can't convert heat to more-useful forms without a heat "sink" at a lower temperature, and when your house is the thing at the lowest temperature and you want to cool it this is problematic. Just keeping the heat out is the easiest and most economical thing to do; heat that doesn't get in doesn't have to be pumped out again.
      • A solar home can only use so much.

        Homes can be fitted with "reverse meters" that allow you to sell power back to the power company (sample /. mention [slashdot.org]). So, collect all the solar energy you can--collect the entire set!

  • Buildings as giant heat syncs (Score:4, Interesting)

    by Anztac ( 322182 ) <theAnztac@hotmai l . com> on Tuesday August 10, 2004 @12:39PM (#9931489)
    This is wonderful, and a step in the right direction to be sure. I was actually just pondering if this kind of thing was possible the other day. Unfortunatly, buildings are still made like huge heat syncs. This is because a flat surface has a very poor surface area to volume ratio, other sky scraper shapes, such as cylinders, are even worse. R. Buckminster Fuller explains this in his Critical Path. What really elucidates this is he says if we theoretically covered all the buildings from 20th to 80th St, I think it was, in Manhatten with one large dome we would decrease the surface area exposed to the elements by a factor of 84. Consequently, it would take 1/84th of the energy to heat and cool the environment.

    • Re:Buildings as giant heat syncs (Score:4, Funny)

      by soulsteal ( 104635 ) <soulstealNO@SPAM3l337.org> on Tuesday August 10, 2004 @01:00PM (#9931776) Homepage
      Sure you could make the environemental control costs lower, but then Snake Plissken would have to save the President from the King of New York.

      It's just not worth it.

    • Re:Buildings as giant heat syncs (Score:4, Interesting)

      by paulthomas ( 685756 ) on Tuesday August 10, 2004 @01:02PM (#9931803) Journal
      You're right on as far as domes being the way to go. Case in point: The German parliament building.

      The Reichstag in Berlin was recently renovated to put a huge glass dome on top of the existing structure. The dome doesn't cover it but merely sits on top. Running from the very top of the dome to the parliament floor is a funnel which is optimized to move hot air out via convection.

      You can actually go to the top of the dome and stand at the opening to the funnel and feel all the warmth. This is combined with traditionally cooling for a very economic effect.

      It's also a really cool looking building and a must see if you ever find yourself in Germany.

  • How useful is that? (Score:3, Interesting)

    by grahamlee ( 522375 ) <graham.iamleeg@com> on Tuesday August 10, 2004 @12:45PM (#9931562) Homepage Journal
    Most of the heat that comes into your house will do so by conduction from the air by the window to the glass to the air by the window, then get carried around by convection. It won't get in by radiation, so IR-proof glass will have only a small effect. If you have double glazing then you have a hefty heat buffer between your house and your environment anyway, and the buffering effect is large enough to render any conduction heat exchange negligible. What it *might* do, however, is stop your neighbours from changing the channel on your TV.
    • I think you overestimate the conduction by air, it is a good insulator. If air conduction was so great, a house would cool really fast at night and I guarantee this is not true with my 1920's plaster. The sun is the major factor.

      Think about why you stand in the shade when it's really sunny out.

    • Re:How useful is that? (Score:3, Informative)

      by dbrower ( 114953 )
      Most of the heat that comes into your house will do so by conduction from the air by the window to the glass to the air by the window, then get carried around by convection. It won't get in by radiation,

      Wrong. Solar gain from radiation is a significant factor in design. See for instance this, [cityu.edu.hk] or this, [lbl.gov] or this, [energy.gov] or this [ucf.edu].

      Convection/Conduction are certainly at issue when there isn't sun (say, Seattle or Syracuse), but when there is, the radiation transmission is a major factor. This new technology

    • Do you have any proof for this? Then why does my room stay cooler when I close my window blinds?
      Get a clue... windows are usually sealed very well any more, and convection is a very poor means of transfering a large amount of heat. Air is actually a very good insulator.
      IR is one of the main ways that homes heat up through windows, by the light/IR coming in, and then being unable to escape because it's shifted to a lower wavelength upon reflections from inside surfaces.
  • Is this correct? The greenhouse effect happens precisely because the atmosphere absorbs infrared but transmits visible light - light heats the earth, the heat is re-radiated in IR, but is trapped here by the atmosphere. To cool down you want to radiate IR, not trap it?

    I presume these people know what they're doing, but its sounds to me like the future holds unformfortably sticky leopardskin seats in our flying cars.
  • Since most windows these days use dual-paned glass for its insulating properties, presumably only the outer pane would be made of this stuff. It then shouldn't matter if the room interior is a bit less than 84 F.
  • Imagine that you accidently leave the heat on too long, or that you have a fire in your house. Now the air inside is hot enough to cause the coating to phase change, and all the heat gets reflected back INTO your house, causing it to get even hotter!

  • Hooray for grandma! (Score:3, Funny)

    by Proc6 ( 518858 ) on Tuesday August 10, 2004 @12:50PM (#9931640)
    Sweet, now I won't feel so bad when I leave Grandma in the car on a hot day with the windows rolled up.
  • I was under the impression that glass already relfected a substantial amount of infrared light - isn't that how greenhouses work? Visible light passes through the glass, is absorbed by things inside the greenhouse and re-emitted as infrared, which is reflected by the glass and thus trapped inside the greenhouse.

    Obviously I've misunderstood, otherwise this breakthrough wouldn't be worth writing about, so can someone please explain to me how greenhouses actually work, and why glass that reflects infrared wo

    • Nope, greenhouses work by allowing the infrared light in which hits the material in the greenhouse which in turn conducts the heat to the air. This air is small in volume and thus is easily heated by the relativly high energy per volume from the solar energy. For more info see this [howstuffworks.com] article at howstuffworks.

  • Trouble (Score:5, Insightful)

    by dr_dank ( 472072 ) on Tuesday August 10, 2004 @12:55PM (#9931702) Homepage Journal
    Won't this interfere with the thermal imaging cameras fire departments use to find people in fires?
  • A better smart glass would not just block that extra thermal energy. It would find a way to convert that energy into a useable form or direct it to a useful purpose.

    END COMMUNICATION

  • Ok, cool... but (Score:2, Interesting)

    by petra13 ( 785564 )
    It seems to me that it would make more sense to come up with a roofing material that blocked infrared above a certain temperature. For example, I'm sure that my house gains far more heat from having the dark roof sitting out in the hot sun all day than it does from the windows. It would be *really* cool if someone set something up that would absorb IR in the winter (like a dark roof) but not in the summer (light roof). Still, I guess windows are better than nothing.

    • Re:Ok, cool... but (Score:3, Informative)

      by pclminion ( 145572 )
      It would be *really* cool if someone set something up that would absorb IR in the winter (like a dark roof) but not in the summer (light roof).

      No, you actually still want a light roof in winter. A black roof is a good absorber and a good radiator as well. In the winter, a black roof will radiate the heat out of your house more rapidly than it can heat up from the sun (since the radiant intensity is generally much lower in winter). You still want a light-colored, insulating roof, even in winter.

      In areas

    • Re:Ok, cool... but (Score:3, Informative)

      by ad0gg ( 594412 )
      Thats why there are vents on the top of your roof and the bottom of the roof. When your roof gets hot, there's nice airflow going on as the colder air is sucked through the bottom vents and exits through the top. If you house is getting hot because of the roof. Your vents could be blocked.

      In cold weather, it still wouldn't make sense since it would require you to remove the insulation layer which in turn would cause heat to escape from the house. Only solution I could think of is skylights but unless t

  • In double glazed or triple glazed windows (with air space between the glass layers) I think you'd treat the outside surface of innermost pane not the outermost pane. The innermost pane has the coolest inside surface and the air spaces between panes are always hot.

  • Conservation of energy (Score:3, Interesting)

    by Asprin ( 545477 ) <gsarnoldNO@SPAMyahoo.com> on Tuesday August 10, 2004 @01:00PM (#9931780) Homepage Journal

    What happens to all that infrared energy that isn't being absorbed by the interior of the building anymore? Is it absorbed by the glass/film iteself and then dissapated by conduction or convection with other nearby materials like air, glass and steel or is it reflected back outside to make other buildings and surfaces and stuff even hotter?
    • It'll be bounced outside to be absorbed by the rest of the environment. Pretend the building isn't there - the sun is going to hit anyway, so it's not much different unless you have a convex building with a focus.

      If the film is on the inside pane to prevent it from environmental damage, then there will be two passes through the outer pane, which can warm up the gas between the panes, leading ultimately to convection/conduction gain. Coating the outside would be most effective, if it weren't fragile.

      -

  • The glass is coated the chemical vanadium dioxide. This material transmits both visible and infrared wavelengths of light, and normally undergoes a change at about 70C.
    Above this transition temperature, the electrons in the material alter their arrangement. This turns it from a semiconductor into a metal, and makes it block infrared light.

    And you thought it was just in the movies!

  • This is odd (Score:3, Informative)

    by GCP ( 122438 ) on Tuesday August 10, 2004 @01:25PM (#9932110)
    One of the reasons rooms get so hot is that ordinary glass is already blocking a lot of infrared--from getting out. Non-infrared (ordinary visible) light comes through easily and strikes whatever is inside. In doing so, it heats it, so a portion of the visible light is converted to infrared. But, since the glass isn't very permeable to infrared, it can't get out, so the inside space heats up.

    This innovation will make it even harder for infrared to get out, but it also reduces the infrared that gets in. So the question is whether the inside heats up more with visible light converted to infrared that can't get out at all, or visible plus some infrared converted to even more infrared that can get out a little bit.

    I suppose they've done the experiment, but it's not obvious to me which one would be superior or by how much.

  • It should work (Score:5, Interesting)

    by DarthTeufel ( 751532 ) on Tuesday August 10, 2004 @01:27PM (#9932126)
    I've worked in the glass industry for over three years, acutally for one of the direct competitors of the people (Pilkington) who came up with this. Coating glass almost always (90% of the time) requires an insulated (two lites of glass) unit. The coating goes on the inner surface because it is easy to scratch the coating off, and since its a near vaccum inside insulated units they don't have to worry about what ambient conditions will do to the coating. Now the yellow tint will be a non-issue come production time. It realy will be either applying it to glass that is already tinted to cancel out the yellow or they'll modify the formula to get it to appear clear. And the fact that it eventually wears out will either be adjusted for in the R&D process (not likely, too expensive), or offering some kind of warranty on it. It is cheaper to re-produce because of the scale of glass plants, than it would be for the R&D to get another year or two of useful life. The process of coating itself is very very interesting. They pretty much ionize particles to bond at a molecular level to the glass. It's a niche field, but one that is very lucrative because there are not that many people in it. And as far as costs are concerned, it should be rather cheap. Glass itself costs around 1-5 cents (US) per squarefoot. A float glass plant produces around 650 tons of glass a day. The process is really really efficient.

  • block by reflecting or absorbing? (Score:3, Interesting)

    by nicknicknick ( 648150 ) on Tuesday August 10, 2004 @01:41PM (#9932302)
    The article just says "blocks" If the glass blocks by absorbing IR then this would be a problem in double pane windows. The outer pane (or is it lite?) would become dramatically hotter and would expand more than inner one. This could break the seal between the two sheets and release any enclosed gas (argon fill is commonly used to reduce convective currents that transfer heat) as well as allow moisture in causing fogging. This was apparently a problem with some do it some do-it-yourself window tints. I don't know much chemistry but they say it's metal-like above transition temp so maybe that means it reflects. BTW I have now idea why Argon would reduce convective currents. Anyone know? I just know that lower convection is a property of heavy gasses

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