[Greenbuilding] Glass overhead doors for passive solar application?

[Keith Winston]

Uh, an R-17 window? I don't think you'll find that.

The very best glass I know of is Superglass 88 or whatever it's called, 
which has a center-of-glass value of about R-10. When you count in 
spacers and frames, you might end up with an R-6 in a decent 
application. And an overhead door would almost certainly NOT meet the 
criteria of a decent application. Getting tightly fitting seals would be 
next to impossible. There are wall systems sort of like what you're 
talking about, for commercial applications (restaurants on boardwalks, 
those kinds of things). They are pricey, not particularly tight, and not 
highly efficient, as far as I know. And I mean PRICEY! I saw one that 
was, I think, $20k for each 8' or something like that. Anyway, knock 
yourself out.

I'd love to be proven wrong, if you find anything interesting please 
report back! If you find an R-17 window, I'll use it in every single 
project from now on, I promise you!

Keith


Dan Johnson wrote:
> Working on a passively-heated garden classroom on the chilly
> California coast and looking for a manufacturer of glass sectional
> overhead doors (like garage doors but mostly glass) with good
> insulation (about R-17) and airtightness (I've seen as low as 0.1
> CFM/linear foot). These doors will be on the south for solar gain,
> and in warmer weather we'll open them up to the garden and work
> indoors-outdoors.  Anyone know of a good product? I'm having trouble
> finding something on the web.
> Regards,
> --Dan Johnson
>
>
>  
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-- 
Keith Winston
Earth Sun Energy Systems
3927 Madison St.
Hyattsville, MD 20781
301-980-6325
keith at earthsunenergy.com
www.EarthSunEnergy.com