[GBlist] Glazing

["John Daglish" <john.daglish@vnumail.com>]

Dear listmembers

A few years ago there was an discussion regarding glazing

"Each gas has an "optimal" cavity spacing,
(approx. air 12.7mm, argon  9.52mm and for krypton  6.35mm)
beyond which the primary heat
transfer mechanism switches from conduction to convection. However,  the
TOTAL R-value remains constant beyond the "optimal" spacing, as the
increased heat losses from convection are offset by decreased heat losses
from conduction. "

I presume the above was for double glazing only?
What is the situation with extra clear (low iron) glass and/or low
emmissitivite coated glass?

What is the situation with triple glazing ? For example some data from
manufacturers where the spacing increases :

Triple glazed krypton gas filled, low e coat on suface 2 et 5 calculated
DIN 52619 (German standard)
4/8/4/8/4 mm      0.7 W/m2K u value
4/10/4/10/4 mm   0.6 W/m2K u value
4/12/4/12/4 mm   0.5 W/m2K u value

Are there any detailed technical papers on this subject available via the
internet?

What are the pros and cons of using a plastic film eg Heat Mirror? What
life expectancy can be anticipated?

When will partial vacume aerogel (transparent insulation) filled double
glazing or vacume glazing (Nippon Glass??)be commercially available with
its superior u values in Europe or the US ?

We are looking for comparable glazing data for high performance low energy
building in a cool temperate climate (European) which maximises light
transmission and solar heat gain, and minimises heat loss.

Thanks for your comments

John DAGLISH, B.Arch
eco-tecture, baubiologie & permaculture

4, rue des Coteaux
91370 Verrieres le Buisson, FRANCE
Tel / Fax : +33.(0)1.60 11 12 10
Email : john.daglish@vnumail.com
Web:  http://johndaglish.free.fr

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