All Nick is saying is that a south facing window with an R factor of 2
or more, gains more BTU during thef day from the sun then it looses
at night , i.e. there is a net heat gain over 24 hours.

Seems hard to beleive at first but when you look at the numbers it
appears to be true.

I pointed out that he did not include radiation losses and wind chill,
but I think these factors are small and do not change the overall
result that much.

If you disagree with the conclusion, please find the flaw in the
analysis.

Mark