Air Handling Units? and More

[rwalter]

Ok I just got one today talking to my masonary contractor who is going to be putting in my crawl space foundation.  Looks like I probably be allowed to put in a conditioned crawl space after all. Originally the building inspector told me it must be vented but this contractor has done a lot of work with this inspector and said I should be ok with a conditioned crawl space. If I go is this route any one with a suggestion on what air handling system to use and where to buy it?  Also should I vent the exhaust out or exchange it with the living space?

[John Raabe]

In my Solar Saltbox house (http://www.jshow.com/y2k/listings/55.html) the crawlspace is insulated and a standard electric furnace with air handler pumps air into the crawlspace and standard floor vents around the perimeter bring it back up into the main floor space.

You only need to move this air occasionally. We have turned on the electric furnace only twice in 22 years when we were on long winter trips and the house might have gotten too cold. Otherwise we just use the fan switch on the thermostat to circulate the air and even things out once in awhile.

While such foundation systems as this was relatively unknown when I built mine, the crawlspace has always stayed dry and bug free.  It even stopped some mildew in its tracks that was starting to attact the framing 22 years ago when we were putting to together in a wet October.

Interesting to find that this "conditioned crawlspace" system is now the recommended practice for several climate zones in the highly respected "Houses the Work" system from Building Science Corp. http://www.buildingscience.com/housesthatwork/default.htm

[rwalter]

John,

I realize the furnace could be used to exchange air in the crawl space. What caught mr I was awhile back I saw somewhere there was a stand alone air handling unit that would monitor the temperature and humidity of the crawl space and turn it self on and off according to the fluctuations. I was interested in this but not sure if it was worth the extra money. It sounds like its probably not worth the expense.

Thanks.

[John Raabe]

As long as you have some openings and natural airflow into that space from the interior you wouldn't need powered ventilation.

Some builders do seal the crawlspace, the floor and then insulate the floor joists. In that case a controlled ventilation of the crawlspace may be useful, especially in wet soils (you would want to bring fresh air in as well as vent moist air out). This would also be a good idea if you had high radon levels in the soil.