Hot Topics: Should Crawl Spaces Be Warm or Cold?

crawl space area

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When you've got a home with an unfinished crawl space, what do you do? Well, that all depends on your climate and intent. See what these fellow homeowners and DIYers have to say about finishing a crawl space in colder climates.

Original Post: Should Crawl Space Be Warmed Space or Cold?

Mustard Tiger Member

I bought a cheap house as a practice fixer upper, and I am wondering what to do with the crawl space. I'm in eastern New Brunswick, and like a lot of the houses in the area, there's a 5-6-foot crawl space with a dirt/gravel floor, and absolutely no insulation at all. Obviously it has the usual moisture problems, and I need to replace a few posts as a result. So, after that is done, I want to seal the vent and close up the outside access and vapor barrier the whole thing.

The question is, do I insulate the walls (and floor?) and make the crawl space part of the heated part of the house? It is useless space, so I really don't want to heat it, but I see a lot of people recommending this online. Or should I insulate the ceiling (main level floor) and leave the crawl space cold? I see a few recommendations for this, but a lot of people saying not to do that without saying why not. Ideally, I'd like to wall off a corner of the crawl space to use as a root cellar, so at least that part would need to stay cold space.

Also, I checked the sticky since it seems like it would tell me all about this, but the links have been broken at some point and now just redirect to a general page. If anyone knows where the updated urls for those links are that would be awesome too.

Highlights from the Thread

XSleeper Member

That's a tough one. Not knowing anything about your climate or building practices or the quality of the house makes it hard to know if its worth it. If you were going to put 2" styrofoam on the floor and pour cement to use the area as storage, I would say yes, insulate and condition the space. But if you don't intend to use it for anything other than a root cellar, I would insulate the floor. Get an estimate on having it professionally spray foamed... that would be best.

joecaption Member

Going to get a lot of different opinions on this one. No one can see what your dealing with without pictures. People here could be any place on the planet and there's a wold of difference from Alabama to AZ and Canada.

Rule #1 is prevent moisture ever becoming an issue under the house by having proper grading away from the foundation. Foundation needed to be water proofed before it was ever back filled. If there are gutters, they need to have down spouts leading away from the foundation. No mulch piled up against the foundation. No flower beds forming ponds.

Always should be a vapor barrier on the ground in a crawl space (6 mil. plastic will work).

Bud9051 Member

Hi MT and welcome to the forum.

Eastern New Brunswick may be a bit milder close to the ocean, but fairly similar to central Maine. I'll repeat some of the previous comments, but I would resolve any water issues as mentioned and then install a good vapor barrier and add 2" of rigid foam to the walls. Not familiar with your codes, but 2" should be close. Check to see if they require a thermal ignition barrier over the rigid in a crawlspace.

The advantage of insulating the walls is you can also air seal house to foundation and avoid having to air seal and insulate the floor. You can isolate an area for your cold storage, but it will still need the VB on the ground.

Once closed off, then you supply heating and cooling just as the house. Instead of having to exchange air with the outside (the insulated floor approach) you now exchange air with the house, and if well insulated, it presents a minimal load on the heating system.

stickshift Group Moderator

Two options: Seal to the outside and open the space to the conditioned air of the house. In this case, you insulate the walls. Other option is to close the space off to the house air and open it to the outside, in which case you insulate the ceiling.

Either way, you need a vapor barrier on the floor. Generally speaking, the first option is more common in norther climates, the latter in southern. Hence, if I were you, I would lay a vapor barrier, close off the vents to the outside, insulate the walls and open the space to the house air. Not necessarily an inexpensive endeavor.

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