accounting for unheated crawl space in heat loss

Boon

Is comfort above an unheated, ventilated crawl space more than simply satisfying the heat loss of the room? I have faith in my heat loss numbers because they work in every other room in my house except my sunroom, which is 10x11 above an unheated crawl space: hardwood floor; 3/4" subfloor; 2x6" joists with 6" fiberglass; 4 mil vapor barrier.

The sunroom's air temp is 74-75° but the floor has an average temp of 68°. It is very noticeable when you step in. I need better comfort in there. Even if I were to increase the size of the radiators I don't think that fixes (or does it?) the fact that my floor is a virtual radiant cold loop .

Any thoughts on how to improve the comfort? Maybe adding 2" of foam in the crawl space. Maybe lift the hardwood, install warmboard, and replace the hardwood floor - I'm not excited about the prospect of all that work. Adding another radiator is out... not sure another radiator fixes this.

Thanks

SWEI

Mean radiant temperature represents roughly two thirds of your perception of hot and cold. Radiant floor tubing will likely produce the best results, but it's not inexpensive.


Sheet foam on the bottom of the joists would add R-value, reduce convection, and dramatically lower thermal bridging via the floor joists. I would be mindful of dewpoint issues, though.

hot_rod

Any insulation will help. I rolled in some Insultarp in my crawlspace, white side up. It made it easier to roll around and work in and it also seemed to help with the cold dirt floor sucking heat.

Do you close the vents in winter time?

Gordy

Can you make the crawl space conditioned?

I have a crawl space unventilated to the exterior , but vented to the basement. foam insulation on the walls and fan fold insulation on the floor which is concrete. The floor above is insulated with r19 batts.

Even with insulation if you could condition the crawlspace it will help the foor above. Otherwise a radiant floor is the best answer. Preferably over the top.

Boon

The vents aren't operable vents so it never occurred that I should/could close them for winter. I'll close them off some and I'll try a couple inches of foam. If that doesn't help enough I'll do the radiant on top, which would fit well since the sunroom floor is about 1-1/4" lower than the rest of the first floor. It'll be fun doing the radiant loop.

Gordy

Does the crawl space have a dirt floor?

Boon

It is a dirt floor.

Gordy

Better keep it ventilated then.

hot_rod

Sealing the space would be the best. leaving the vents open in the winter will cost some, maybe a lot of energy dollars.

The under slab insulation products are really easy to install your self.

There are companies that specialize in sealing crawls.


http://www.basementsystems.com/crawl-space/crawl-space-ventilation.html