[Greenbuilding] Exhaust Only Passive Inlet Ventilation

[Keith Winston]

Sacie, you will get condensation on your windows if your interior RH is 
high relative to the temp of the window glass. Better glass, outside 
window insulation, or lower RH are the only cures. I was struck by your 
earlier comment about trying to get interior air above 50% RH. Bringing 
in outside air won't do it once it gets cold, too much energy cost for 
the associated humidity contribution.

Also, when you say "house tight", there's no telling by what standards 
you're judging that. Have you had a blower door test?

If it's tight and there's an exhaust fan, there'll be depressurization 
until it leaks enough to stabilize. So air will be coming in all the 
cracks and crevices, which even tight houses have. In principle, the 
length of time you should run that fan (assuming you're using it for 
forced mechanical ventilation) depends on the size of the fan, leakiness 
of the house, and occupants (number, activity, toxic materials 
contributed to IAQ, etc).

Keith


Sacie Lambertson wrote:
> Nick, John et al,
>
> This morning is typical.  High teens outside, RH in the 40s inside, 
> with temps in the mid to high 60s and a nice bead of water across the 
> base of every window in the house, including those that are 
> inoperable.   Simple difference between indoor and outdoor 
> temps?   Comment please?
>
> Second question: if there are no vents below or above (an open, 
> therefore multi-story house with no ability to close either up or 
> down) and a small exhaust (don't know how many cfm pulled) in the 
> main center floor, what is the effect?   House tight, but many many windows.
>
> thanks,  Sacie
>
>
>
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