|
|
re: solar film update 1
5 may 2005
serendipity wrote:
>energy savings are predicted at 25%.
would you have more details about that? did the film installer guarantee
that your r2 windows have become r2.5?
>...with the size of our windows, the solar gain was considerably less
>than the solar loss.
that doesn't depend on the window size. nrel says a square foot of south
wall recieves 1000 btu of sun on an average 30 f january day in phila...
800 btu might pass through an r2 double pane window, which would lose
about 24h(65-30)1ft^2/r2 = 420 btu/day, for a net gain of 800-420 = 380
btu/day. iirc, you mentioned the film would block 75% of the solar gain,
for a gain of 200 btu, with a 24h(65-30)1ft^2/r2.5 = 336 btu loss, and
a minus 136 btu/ft^2 per day net gain.
sounds like a big net energy-loser to me.
nick
|
|
