crawl space

Helping a friend who has a 1-foot hole in the plenum of her forced air heating system. I haven't been under the house, but a few estimators have for rodent invasion and crawl space cleanout/vapor barrier replacement and re-insulation (both are trashed). UPDATE -- here are two pix I was sent by...

I'm looking into getting a Takagi outdoor tankless unit and I'm thinking about installing in my crawl space. The crawl space is conditioned but the access to it is outside, so temps can get pretty cold down there. I wanted to do an outdoor unit to eliminate the existing venting up into the attic...