[Greenbuilding] Humidity between multiple windows
nick at early.com
Wed May 11 06:13:22 PDT 2011
Bob Klahn <Home-NRG at dnaco.net> wrote:
>If you have access to a blower door, you could build a frame that would
>just enclose the window, seal a cap on it with a hose barb for the pressure
>gauge hose. Pressurize the house, with relation to the outside air
>pressure, to a benchmark... Measure the pressure difference between the
>house pressure and the pressure within your enclosure.
It seems simpler to drill a small hole in the storm window frame and push a
manometer tube into the hole, then measure the pressure in the
window-to-storm-window cavity. If it's 0 Pa outdoors and -10 Pa in the
cavity and -50 Pa inside the house, we might say "the innermost window is
five times tighter than the outer."
But is -10 Pa the right number above? How high can we make this number, and
still avoid condensation on the inside of a 4'-tall U1 storm window over a
U0.5 house window, if the house is 70 F at 50% RH and the outdoor temp is 30
F with a 0.0025 humidity ratio on an average January day in Phila?
In a 2-story house, I guess this only applies to upstairs windows with
outward air leakage, vs downstairs windows with inward air leakage.
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