Aerogel wallpaper versus air-pocketed wallpaper

[Twinbee]

I'm not usually interested in energy conversation/usage, but the space-age material called 'aerogel' seems really exciting. From what I gather it's currently around twice as good at insulation than Polyurethane and 4x better than Polystyrene (although in theory could be much better). However, apparently the price is around 2-3 times higher for the same amount of insulation.

I'm most interested for it to be used as relatively thin wallpaper. However, I have a question.

There's something I recently got for my windows that looks like cling film. You put it over the frame of the window, creating an air pocket in between, and then hairdryer it out to remove the creases. Only one layer is usually used, but I created two layers of the film (2 air pockets) and it's like having triple glazing now.

Anyway, my question:

Why can't wallpaper use this same principal, simply create many layers (say 1-2mm apart of thin plastic), and just fill it with air? Perhaps supported by tiny rods every other square cm to minimise conduction. Surely this would create better insulation than solid material alone? And yes, approximately as good as as the aerogel wallpaper as I mentioned earlier, except potentially HUNDREDS of times cheaper...

Does this idea stand up to the laws of physics?

 

[mgb_phys]

Firstly the film on your windows real value comes from stopping draughts rather than trapping a layer of air - this is also true of regular double glazing.
It's a little annoying, building standards demand higher insulation standards for the glass which makes the double glazing more expensive, which means fewer people fit it!

Anyway - insulating wall paper used to be popular, it generally used expanded foam polysterene. Being only 1mm think it isn't that effective compared to 100mm of cavity wall insulation or 300mm of loft insulation and it was a terrible fire hazard.

 

[Twinbee]

Oh, so the only advantage (say 90%?) comes from the draught exclusion alone? Do you know how much merit the pocket of air has?

About my attempt to do 'triple glazing', where the 1st layer is glass (the original glass window of course), and then there are two thin plastic films in front - each trapping a layer of air; Has that been a waste of time? Should I have just done the one plastic layer instead of two?

If that's true, then why bother with real glass triple glazing. I doubt the second air pocket stops any more than draught than one alone.

 

[mgb_phys]

The percentage depends on the windows you are replacing, if you replace leaky wooden sash windows with double glazing you get a big improvement.
Replacing double glazing with triple, or argon filled, k-float low emissivity glass is a much smaller improvement.

The reason for triple glazing? It might be worth it for an AC office building covered in glass but for a home I suspect it's manufacturers advertising.

 

[Twinbee]

Okay, so I'll probably just do the rest of the windows with a single layer of plastic film (I do have those leaky sash windows btw ;)

As an extreme example, if one were to create 15 massive layers of 1mm thin plastic, each of them with a single mm of air in between (assume perfect measurements) to total 30mm, and then put them against the wall (assume a perfectly flat wall etc.) - would this not be much of an improvement in insulation compared to just 15mm of solid plastic against that wall?

 

[mgb_phys]

There are two mechanisms. In the plastic you get conduction, between them in air you get convection.
It depends on the plastic but for a reasonably hard (not foam) plastic the conductivity is greater than air ( ie insulation is less)
So 15mm of air is better than 15mm of plastic, several layers of plastic-air-plastic would be better (the best mix depends on the plastic)

 

[Twinbee]

Okay, but I'm guessing that 10 layers of plastic-air-plastic etc. wouldn't be as good as say the equivalent thickness in aerogel.

Just to also support your point about 1 layer of shrink-plastic being good enough (instead of two). I quote from:
http://www.tca.gov.bc.ca/heritage/docs/pdf/EnergyEfficiencyWindows.pdf

1. The heat shrink film kit does not significantly improve the R-value of the existing window (R-0.81 versus R-0.79). However it does improve the air leakage around the windows

So like you say, that's the only in which it's good, to stop air leakage.

 

[LURCH]

But it should be mentioned that a thin strip of aerogel inside the walls is a vast improvement. According to the tests performed by the DOE, http://thermablok.com/" can reduce heat losses in a woodframe structure by roughly 40%.

 

[turbo]

Even in the highest-quality double-glazed windows, there will be leakage between the frames and sashes, and perhaps around the frames and trim, as well. We have some pretty nice windows, but the Duck-brand window kits make the place a lot easier to heat by reducing infiltration of outside air.