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GBlist: window solar gains



We often hear of the net solar gain of south facing windows. My question is: 
Under what conditions is this referenced? Above what (overall) R-value and
air leakage standard must the window be? Are there good data for cloudy areas
such as we have here in Ithaca? Would a cloudy winter nullify the value of a
lot of south glass? Is the data assuming that there is enough thermo mass to
absorb the incoming heat? There can be days in winter in well insulated homes
where windows need to be opened to dump heat otherwise.
On another note, having the combination of concrete radiant floors with a lot
of south facing glass seems like a poor combination here in the common house
as it is difficult for the heating floor to respond quickly to the sudden
input of solar gain when the clouds suddenly appear. Mind you if you do have
a lot of cloudy weather, having the extra glass helps to input a few more
photons into your starving eyeballs.

hoping someone has an answer or two,

Rod Lambert
Ecovillage at Ithaca
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