Originally Posted by Wuzzat?
I think it's more complex.
(the conditioned space has zero infiltration and
there is a big hole in the attic floor and
the attic is vented)
(most of the attic air will be pulled in from the vent and exhausted by the fan and the house air will be relatively undisturbed because there is no way the conditioned space air can be replaced).
I'm sure there is an analogy to an electrical circuit and I'm more comfortable in the electrical domain.
I guess you can temporarily put a $16 box fan in the attic with a cardboard bafflehttp://www.google.com/search?q=fan+b...03%3B449%3B522
and use smoke trails or candle flames to see what the relative contributions are.
Yes and no, Air will pull from the easiest soarce not circulate thought the attic but the shortist distance, so you are still waiting for air to warm and raise until it gets into the stream.
Warm moist air is pushing against the ceiling of the house looking for gaps and holes aound wiring , light fixtures, plumbing stacks attic access door. Yes we know this happens if there is moisture in the attic that isn't coming from a roof leak.
In the winter it might be safe to argue the air moving with the fan will be much cooler than the air leaking from the house. If the fan pulls warm moist air out, great but what if that air cools as it enters the cool stream before it leaves the house, It will leave the moisture behind, making the problem worse.http://howtohomeinsulation.com/insul...air_leaks.html