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Posted by on June 19, 2005, 1:30 pm
>Move to South Carolina and try your idea here.
No thanks. Altho houses in western NC seem cheap. BTW, this scheme might work
in a reasonably airtight house that can store some dryth in Charleston, with
w = 0.0166 on an average July day and w < 0.0100 from October through April.
I could determine that with a little TMY2 simulation. You probably couldn't.
>It does not matter what the RH differaece is unless the temperature is
>the same when you ventilate.
I'm not sure what you are saying or why you are saying it, but it seems
to me that you are wrong. For instance, if a basement is 50 F at 70% RH
and outdoor air is 40 F at 50%, it's time to ventilate. Perhaps you would
like to clarify your claim. I also suggested a way to make a bit of indoor
and outdoor the same temp so we could simply compare RHs as a measure of
the humidity ratios. Sounds like you didn't understand that. You may be
over your head and mired in old cut-and-dried HVAC techniques in this case.
>If the humidity ratio(in grains of water per pound of dry air) is higher
>outside than it is inside, you DO NOT want to ventillate!
That's what I said (with one L :-)
>If the humidity ratio is lower outside than inside, then ventilating MAY
>do the trick.
It will. The question is how often that happens and for how long, compared
to how fast the house collects moisture and how much it can store. Looks like
it works fine in Phila, with a max 75 wet hours in a row in a typical year.
>Either way, you MUST be sure that the surface temperatures in the basement
>are ABOVE the dew point of the air present.
Now think hard: if we ventilate when the weight of water in a pound of
basement air is more than the weight of water in a pound of outdoor air,
we are removing water from the basement. If you think we are adding water,
where do you think it comes from?
>If the air outside is dryer than the air inside, but the wall temperatures
>in the basement is still below the outside air dew point, ventillation
>WILL NOT HELP!!!!!!!!!
I disagree (with one L and an "are" vs "is" :-)
>Using fans with an improper control system can rot the walls out!!!
I suggest using fans with a proper control system.
>In order to determine the proper fix for the OP problem, I would want
>to check the weathe data for his area, measure the wall temperatures
>over time with data loggers and measure the humidity inside and outside
>over time with data loggers.
That might see you into retirement.
>Using your RH sensor scheme may destroy his house!!!
Nope. The patent described a technique for drying out flood-damaged houses.
>I can't see how you can recommend such an option without measuring the
>conditions inside and outside his house with data loggers and his wood
>moisture in the basement walls using a wood moisture meter.
I know... Pity.
>Here in the "land of the midnight fungus", recommending ventillation
>to solve such a problem is downright irresponsible!
Recommending dehumidifiers to solve such a problem is downright irresponsible!
>Please remember Nick, most people with mosture problems do not live in
>dry climates! Therefore dehumidifiers are usually a better solution to
>high humidity than exhaust fans.
I disagree (about moIsture :-)
>Please start recommending practical solutions that are climate specific...
Unlike you, I've been doing so all along, with detailed weather data.
Nick
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