Repurposing foundation vent for ducted erv inlet and exhaust
acrobaticnurse_Eli
| Posted in General Questions on
Has anyone ever repurposed a rectangular foundation vent to use as a ducted fresh air intake/exhaust for an erv? My now encapsulated crawlspace has old 8 by 16 inch vents that are currently sealed off with rigid foam, 3m weather seal tape, and canned spray foam. It would be nice to be able to have the 6 inch inlet and exhaust ductwork for an erv go through existing holes rather than need to make new ones in a brick foundation.
I can envision rigging up my own version by making a 6 inch hole in the exterior grill and foam, maybe adding a metal vent cover to the outside to integrate the inlet into, and then sticking the inlet with a duct connector through the hole from the outside and sealing around it, but it would seem like there would be a nice readily made product available that would look better.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
If you live where snow will cover the vents, that's not a good location, and it's never ideal to draw air from close to grade where mold and fungal spores accumulate. But if the area is dry, I don't see other problems with that location.
Thank you. It's dry and 2 to 3 feet above grade. We rarely get more than a couple inches of snow. My other option is via the semi-conditoned attic. The attic would work better for running a simple, separate set of ductwork for the erv while the crawlspace provides easier access to the main ductwork.
It's far better to have the ventilation system on dedicated ductwork, so that's two reasons to use the attic. But ductwork should be inside conditioned space; what does semi-conditioned mean?
When I insulated the attic below the roof deck last year my focus had been to reduce temperature and humidity extremes but I was less focused on making it the same temperature as the rest of the house so I left the insulation on the attic floor and didn't add an HVAC register. This resulted in the humidity stabilizing in the 40s-50s vs having wild swings from the teens to 80s, and temperature gets up to about 100F in the summer vs the prior 140s. In the past week I've started removing the old insulation from the floor of the attic and I'm seeing the temperature range improve even more, staying within 5-10 degrees of the main house temperature (I'm realizing this may increase my need for an ERV with reduced stack effect). If I do add the ERV to the attic I may also add a small register up there to help cycle/condition the space in a more controlled manner. At that point I'd call it conditioned.
For now I've been keeping Acurite temperature and humidity sensors in the two attics and crawl space to see what areas need my attention based on the numbers I'm getting, balancing it with staying busy caring for a newborn and working nights as an ICU nurse. It's nice being able to see improvement in something ;-)