heating/cooling a crawl space
I have a split level with what I would call a “semi-conditioned” crawl under the kitchen/dining/living rooms which are at ground level. The crawl is 30′ x 27′ with a concrete floor about 4′ below grade. There is a 3′ x 3′ opening to the finished basement with a louvered door on the opening. Bare concrete foundation walls. No insulation in the floor joists above. Suburban Chicago.
The main duct runs along one wall and feeds across with round ducts to the rooms above. I consider it semi-conditioned because of the opening to the finished, conditioned basement and leakage from the ducts supplying the main level above. The crawl never varies by more than 10 degrees from the rest of the house, and I’d guess more like 5-6 degrees. The last owner ran a dehum in the spring when the crawl seemed damp.
We are going to be storing all kinds of things in the crawl (we are temporarily downsizing, thus all the stuff stored)/. Storage will be up 4″ from the concrete floor on plywood platforms.
I think it would be fine the way it is, but I’d like to add a little supply air from the hvac to get it closer to the temp in the rest of the house. I have no idea how to size it. Should I just pull a small, 4″ round and put a vent in the center of the crawl and adjust the output until I get a good temp? Or would I be better off with multiple outputs?