h a l f b a k e r yPoof of concept
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Inside this house you would see the roof joists. Depending on the way this was engineered, there might or might not be any "ceiling beams", to which a ceiling is normally attached. But there is NO ordinary ceiling in this house.
Attached to the roof joists only, on the inside, are panels of clear
plastic sheet. There has to be a prettier way than staples to attach this, perhaps glue. Or perhaps the staples can be painted into inconspicuousness.
Before I get to the rest, let me point out that clear plastic sheeting is often used outdoors, and doesn't last because of "ultraviolet decomposition" caused by sunlight. That should not happen in this particular usage, however; the sheeting should last for many years.
Next, we fill the space between the roof joists with aerogel, the ordinary/original stuff, not the fancy new clear stuff. Since it weighs very little, it will place almost no stress on the clear plastic sheeting. Then we use acrylic/plexiglas plates (or equivalent thereof) to cover the rafters and form the outer roof surface. Used for decades as a replacement for window glass, we know this stuff can withstand prolonged exposure to sunlight.
What the aerogel does, in this Idea, is fivefold. First, it is excellent thermal insulation. Second, it is excellent noise insulation, Third, it blocks ultraviolet light, to protect the inner layer of plastic sheeting. Fourth, it allows daylight to saturate all rooms of the house, saving on daytime lighting/electricity costs. And fifth, it blurs all light passing through it, so that nobody looking through the roof can see what you are doing inside your house.
UV blockage by aerogel
http://p25ext.lanl....nix/aerogel/talk_1/
The thicker the aerogel, the more it can block UV. See the curve for a 10cm thickness (a little more than the typical insulation thickness between roof joists made of (English units) 2x4s. [Vernon, Nov 01 2007]
Aerogels can be tailored
http://books.google...0LVFxSFFnaWpVDtONuU
The document at this link describes tailoring aerogel to increase its ability to absorb/block infrared. [Vernon, Nov 01 2007]
[link]
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It sounds awesome and functional. (+) from my dark old house. |
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Why the plastic wrap on the inside? Just texture/dye the aerogel into pretty patterns or something. |
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[GutPunchLullibies], I'm assuming the aerogel has to be supported. It weighs very little, but it still needs to be held in place, up there. |
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Can't we bond it to the outer layer or the joists? It should be able to support it's own weight, and is extremely rigid. |
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I live in Oklahoma and I'm thinking "hail". While golfball and larger sized hail isn't a lot of fun on a regular roof, it'd kill plastic sheeting, aerogel and plexiglass. Unless you're going to use some kind of bullet-proof type stuff. |
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[GutPunchLullibies], the way aerogel is made (think "gel") may require some initial support. |
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[Noexit], plexiglas is available in different thicknesses, so I would assume that if the climate in a certain place requires a thicker layer, then in that place you would use a thicker layer. But what you wrote about hail breaking the clear plastic sheet is silly, unless the outer roof is already broken through. I clearly stated that the sheeting was on the INSIDE of the house. |
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It's just that the main draw of this is seeing that aerogel floating up above you looking like a indistinctly-edged, brightly glowing cloud (especially during a full moon). It seems so tacky to throw saran wrap on top. |
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One could do this idea much more cheaply by swapping in bubblewrap for aerogel. |
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Summer sun, transparent roof, Wien's displacement law, extreme airconditioning expenditure. Bad idea in my book. |
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re. what [Texticle] said, I think this might be a better idea in cold climates. I'm guessing that the thermal insulation might be good in winter for keeping heat *in* the house (by blocking convection and conduction), but not so good in summer for keeping *radiant* heat *out* of the house. In other words, I might live under one of these in Scotland, but not in Australia. |
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[GutPunchLullibies], there is an additional reason to seal the aerogel between layers of plastic (sheet and roof). Many aerogels don't get along well with water vapor. |
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[MaxwellBuchanan], I admit I'm guessing about aerogel blocking UV, but it is an educated guess; the solid part of an aerogel is silicon dioxide basically, and that stuff CAN block UV in quantity (ordinary window glass does it quite well). |
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[Texticle], your point depends on how much infrared gets through. Since original/ordinary aerogel is blue-ish, it follows that the lower red and possibly also the infrared frequencies are mostly getting blocked. |
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It would be nice to find some links going into more detail on those points, of course. |
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//ordinary window glass does it quite well// |
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The same kind that's used in greenhouses? |
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I would prefer shrinkwrap. |
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Why not use clear polycarbonate roofing - I think this is fine with UV. |
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[pertinax], ordinary window glass is not pure silicon dioxide (neither is aerogel). I think I once read somewhere that really pure SiO2 (like in fused quartz) is able to transmit UV. I don't know what if any special glass greenhouses use, but I do know that plants get almost all of their photosynthesis energy from ordinary visible light, so it doesn't matter if greenhouses block UV. |
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[hippo], I have no objection to polycarbonate (except maybe it's more expensive than acrylic?). Note the paragraph in the main Idea that specifies acrylic also says (or equivalent thereof). One clear plastic is equivalent to another, if clearness is the main thing desired. |
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/[Texticle], your point depends on how much infrared gets through/ |
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No it doesn't. I dropped a pretty big hint with the Wein's displacement law thing. |
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//plants get almost all of their photosynthesis energy from ordinary visible light// |
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My point was that the function of a greenhouse is to trap heat. |
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One of the things I've learned on the half-bakery is that IR frequencies are not the only form of radiant heat, but that the visible frequencies of sunlight are also 'hot'. I think that may be what [Texticle] is getting at. Would anyone like to confirm or dispute that? |
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[pertinax], I can dispute that to some extent. Have you put you hand on a 60-watt-bulb equivalent-light-output fluorescent bulb, and then on a regular 60-watt incandescent bulb? IR heats mostly because it is strongly absorbed. Visible light is often cool because it is easily reflected. |
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The fluorescent bulb is less hot because it is more efficient. More energy is coming out in the visible range, with less radiant output for the same amount of visible brightness. |
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Any radiant energy not reflected or refracted will warm things up. |
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[gutPunchLullibies], yes, absorbed radiant energy becomes heat. A clear roof, however, can at least let reflected light get out. Since a significant percentage of sunlight is infrared, however, and is strongly absorbed, it follows that that is the cause of most of the warming in a greenhouse. And any place that has had a partial-silvering-coating added to its windows knows how much less the warming effect is, if infrared is blocked. In this case, then, if the aerogel is not good enough for blocking infrared, then the clear plastic sheets could instead be partially silvered sheets. |
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I had a habbit of not sleeping untill I saw a shooting star in the night sky. When I get considerably wealthy some day I will buy this product and have it custom tailored, I won't need much more than a nice bed to stargaze before sleep. |
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