Hi,

We’re planning a sealed crawlspace in our upcoming house, for several reasons, not the least of which is the excellent science and articles about crawl spaces, on this site. It’s my understanding that to meet the code for sealed crawl spaces, one must either;  provide a continuously operated exhaust fan which draws air out of the crawl space at a rate of 1 CFM for every 50 square feet of crawl space floor – would be 26 CFM for our 1296 SF floor area – or; provide a heating duct blowing into the crawl space from a central ducted heating system. As we won’t have a central ducted heating system, I think the first option is our only option. There will need to be an opening in the floor connecting the crawl space to the first floor, naturally.

I’ve also just learned that we are required to have a whole house ventilation system, which also draws air out, and continuous operation is much preferred, for several reasons. For our size home and number of bedrooms, it looks like we need 60 CFM of continuous exhaust.

So my question is this. Can these two continuous exhaust fans be the same unit? So in other words, is there any reason we couldn’t simply have one fan of approximately 85 CFM, in the crawl space?

The few diagrams I’ve seen for the simple exhaust system tend to show the exhaust fan and duct on the top of a second floor house, exhausting high out the gable end, soffit, or roof. However, I couldn’t find anything in the actual WA VIAQ code which specifically says exhaust has to be in those locations. But then, very few people in WA use sealed crawl spaces….