[Greenbuilding] Exhaust Only Passive Inlet Ventilation

[Corwyn]

On Dec 03, 2007, at 12:39, Keith Winston wrote:

> 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.

Outside air is only going to lower your humidity.  Outside temp 30ºF, 
100% humidity, inside temperature 68ºF, means that after heating up 
that incoming air, it is at 28% humidity.  Since outside humidity is 
usually less than that in the winter,  it would be even less.
>>
>> 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?

For 45% inside humidity, with outside temperatures in the teens you 
need windows at least R-2 (US units) and better (at the edge), to not 
get condensation.  Edge R-values are pretty low even for the best 
windows.

The research I have done seems to indicate that the most healthful 
humidity is in the 40-60% range.  Given that I generally put up with a 
little condensation.  I only get a very little when the house has dried 
out for the winter, (I have nice windows), but I do get some (an inch 
or two at the bottom of the south windows in the morning).

>>
>> 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.

Not sure what you are asking here, can you rephrase?

Thank You Kindly,

Corwyn


-- 
Corwyn
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corwyn at greenfret.com