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monkeyboy
Trying to warm my floors
monkeyboy

I live in Los Angeles, so we don't get very cold winters, though it will get down to freezing on occasion at night. We have a 1954 home with original hardwood floors. There is a crawlspace under the house, maybe 24" high, from dirt to the underside of my floor. The foundation walls have vents, open year round. In the Wintertime, the floor gets very cold. We dealt with it the last few years but now we have a baby crawling around and I'd like to solve the problem. I've been reading ****** about all sorts of options, but I suspect a lot of them vary depending on the climate you live in. I've read that insulating the underside of the floor will work, others say no. Some people say you can seal up the vents to the outside and install a crawlspace heater. I've read that sealing up the vents can cause mold issues. I've even read that hanging a few 100 watt bulbs in the crawlspace can make a noticeable difference.

The house is only 950 sq feet, so there's not a whole lot of crawlspace to heat. I've even considered trying to redirect some of the heat gathering at the ceiling, down into the crawlspace. Seems like it would do more good trickling up through my floor than collecting at the ceiling.

keith3267
Re: Trying to warm my floors
keith3267

Warm air will rise up. In theory, heat, which unlike warm air radiates uniformly in all directions will radiate into the crawl space, warm up some air which will then rise up and get trapped under the floor. This is not happening in your case.

Around the edge of your floors, sitting on the concrete blocks is the rim joist. Air leaking between rim joist and the floor and between the rim joist and the sill plate on top of the blocks is blowing away the warm air. Start by sealing the rim joist and adding insulation to it. This should help a great deal with allowing the air under the house to stratify with the warm air at the top.

Closing the vents on the north side of the foundation will help too. The coldest winds come out of the north. Close the vents on the east and west side except the one closest to the south wall and leave the ones on the south wall open.

You may also be getting a lot of infiltration from the bottom plate of the wall and the floor. Take up the baseboards and caulk this seam. The cold air coming in at this seam stays right on the floor, making it very cold.

monkeyboy
Re: Trying to warm my floors
monkeyboy

Thanks for replying. The outside of my house is Stucco, from the ground, up to the roof. Could there be air leaking through the rim joist if the entire outside is stucco?

Fencepost
Re: Trying to warm my floors
Fencepost

Just install fiberglass batt insulation between the floor joists. This will give you the warmest floors and greatest energy savings. Anything else is a half-hearted effort that will end up being a waste of time and money and not make much difference; putting heat in the crawlspace will increase your energy bill.

Better yet, hire a contractor to install it; the price difference is very likely to be minimal, and you don't have to mess with it. Installing insulation is an unpleasant experience; it's usually worth it to pay someone else to deal with it. 950 square feet should not be terribly expensive, and your energy utility (electric if you have electric heat; gas if you have gas heat) may even have incentives that will pay for a large part of the bill.

If you don't have a vapor barrier on the ground in the crawlspace, (have the insulation contractor) install one. It's just heavy plastic sheeting ("Visqeen") that covers from wall to wall. That will help prevent moisture damage and reduce humidity in your home.

With insulation between the joists, you can leave the crawlspace vents open, which further helps to reduce moisture problems and, if you have radon issues where you live, helps prevent radon exposure in your home.

If you choose to install insulation yourself, it needs to be in contact with the floor. Don't leave a gap between the insulation and the floor. If you use faced batts, the facing material is a vapor barrier that must be toward the indoor space (in other words, put it "up") to prevent interior moisture/humidity from entering the insulation and reducing its effectiveness. Before installing the insulation, seal any penetrations (where pipes & wires go up through the floor, and other holes) with caulking or expanding foam.

keith3267
Re: Trying to warm my floors
keith3267
monkeyboy wrote:

Thanks for replying. The outside of my house is Stucco, from the ground, up to the roof. Could there be air leaking through the rim joist if the entire outside is stucco?

Would have been nice to have this info from the start. But you do have vents so there is air circulation under the floors. You should still insulate the rim joist first. You can still close the vents on the north side of the house in winter. You can get vents that close up completely at 40F and open completely at 70F. I use these and my floors stay warm in winter, and my winters are colder than yours. Before I got them, I just closed the vents on the north side and most of the east and west sides every winter. That worked too.

I don't have insulation in my joists and my rim joists are triple 2x10 so the extra wood is my rim insulation.

hollasboy
Re: Trying to warm my floors
hollasboy

I had my crawlspace sealed off and lined, and the temperature and humidity sensor down there never shows more than a 5 degree difference between down there and the conditioned living space right above. Once I stopped the air movement, all my temperature and draft woes stopped. There was another post here a while back covering crawl space lining - I commented in that one too. I'd recommend considering that as an option.

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