Crawl space heat??

[K31Scout]

I live in northern MI and have a 1344sq/ft ranch with a crawl space. It stays 55F all winter with the forced air furnace due to vent leakage. I just got a new wood stove for this winter and am wondering how I will keep the crawl space above freezing. All my plumbing is exposed down there so I'm a little worried. I wonder if a few vents cut in the floor would allow enough heat down there to keep things warm enough.

 

[webbie]

I live in northern MI and have a 1344sq/ft ranch with a crawl space. It stays 55F all winter with the forced air furnace due to vent leakage. I just got a new wood stove for this winter and am wondering how I will keep the crawl space above freezing. All my plumbing is exposed down there so I'm a little worried. I wonder if a few vents cut in the floor would allow enough heat down there to keep things warm enough.

Crawls will often stay above freezing just because of the wicking of ground temps upwards. Frozen pipes are often the result of drafts being allowed into the crawl or pipes being too close to the outside. Maybe you should just tighten it up for the winter and buy a cheap digital thermometer with a couple sensors to keep an eye on it. Of course, you can also insulate pipe as well as install heat tape on pipe runs that might be most subject to freeze.

 

[begreen]

Craig's suggestion is spot on. I'd insulate the crawlspace walls too and treat it as a conditioned space. Caulk all cracks to the outside and if it's a dry crawlspace, block off the vents well with foam insulation plugs for winter. Your heating system will lose less heat and your floors will be warmer. We did it this weekend as part of an overall tightening up of the house.

 

[elkimmeg]

What about boxing in around the pipes insulating the boxed area and feed a sealed boxed in area with a heat vent

Take that thought one step further, make the box enclosure out of ridged high R insulation. Caulk all seams and seal it air tight.
Add 4" heated duct to the boxed in area and a vent into the floor for its return This cycles the air flow into the box. For added protection insulate the pipes. When it gets real cold, crack the furthest fawcets so that there is a flow to the water. Moving water does not freeze as fast. Again one will have to experiment with what works.

 

[Robbie]

K31Scout, I wondered and worried about the same thing last winter. I have gas heat and it normally kept my temps in the crawl space in the mid sixties all winter.

When I got my wood stove, I put a thermometer under the house and kept an eye on it for several days. To my surprise, the temps under my house stayed easily in the 55 degree range, even on colder nights with no heat at all going into crawl space except for the apparent heat radiating down (?) from my floors from my wood heater (*with blower).

Of course the advice above is very much knowing of these things much more than me. But my crawl space has vents all the way around (closed in winter) and it was toasty all winter under my house.

I could be wrong, but I think it had to do with a couple of "gas heat" floor vents located close to my wood stove and the wood stove blower. It just makes sense that some heat would make it down these vents in a kind of reverse manner and then the heat from these pipes could help heat my crawl space.

The proof was in the pudding, 78 degrees almost constant in my house all winter, and around 55 degrees under my house, even when temps fell into the teens.

Try it, and if all else fails, kick your other heat on for about 10 minutes and it should do fine, just make sure your vents are closed under your house. Just don't go to sleep unless you check temps under your house........I made several trips in the freezing cold wearing shorts and flip flops :red: just to check my temps before bed.

Note: keep your other heat set to kick on at a lower temp like around 60 degrees just in case you damper at night and it gets colder, this will ensure you won't get frozen pipes.

Robbie.

 

[K31Scout]

Thanks guys, I'm feeling better now. My crawl is draft free and the above ground walls are insulated with 1 inch pink board. At least once a winter we get down to 20-30 below zero and with the old system it still stayed warm. I have a door to get down there in the laundry room and I suppose I could leave that hatch open with a small fan running to transfer heat. I'll make checking the temp down there a daily ritual this winter!

 

[Sandor]

Thanks guys, I'm feeling better now. My crawl is draft free and the above ground walls are insulated with 1 inch pink board. At least once a winter we get down to 20-30 below zero and with the old system it still stayed warm. I have a door to get down there in the laundry room and I suppose I could leave that hatch open with a small fan running to transfer heat. I'll make checking the temp down there a daily ritual this winter!

Just buy one of those digital mini weather stations with the remote temp probe. Keep the remote probe down there all winter, or at least during the coldest spell. It sends that temp reading to the display on the main unit. Mine was like 30 bucks at Wally Mart.

 

[wg_bent]

One thing I didn't know about crawl spaces is that they should be vented in the summer to keep condensation down due to the colder concrete floor and non-vented in the winter to keep them warmer. I read this on a website from the University of Minnesota I believe where they had done a bunch of research on basement insulation. I've been to Minnesota in January...they know cold there! and how to keep buildings warm.

 

[begreen]

Actually, they've found in humid climates that a well ventilated crawlspace in a humid climate can have the opposite effect. That is, in summer, the warm, moisture laden outside air can condense on the cooler surfaces like floor joists in the crawlspace. This happens when the crawlspace temp is lower than the dewpoint and can lead to lots of mold and mildew. www.buildingscience.com has write ups on this. I will locate a Canadian govt. site that I read the same info on (and it gets cold there too.)

However, Minn. is the land o lakes isn't it? I can understand if one is in an area with wet ground I can see where one would want to try to ventilate this space as best as possilbe.

 

[elkimmeg]

Many years half foundations crawl spaces required outside ventalation. But as Begreen pointed out that ventalation can have a negative effect. It is now recomended that it is ok to seal off the vents in the winter. Most of USA experiences colder dryer climates in the winter and having the vents opens does little to help dry an already dry season winter. The other reason is loosing heat and freezing pipes.

 

[wg_bent]

Actually, they've found in humid climates that a well ventilated crawlspace in a humid climate can have the opposite effect. That is, in summer, the warm, moisture laden outside air can condense on the cooler surfaces like floor joists in the crawlspace. This happens when the crawlspace temp is lower than the dewpoint and can lead to lots of mold and mildew. www.buildingscience.com has write ups on this. I will locate a Canadian govt. site that I read the same info on (and it gets cold there too.)

However, Minn. is the land o lakes isn't it? I can understand if one is in an area with wet ground I can see where one would want to try to ventilate this space as best as possilbe.

Hey BeGreen, Thanks for posting that site. Lots of great info there. Some of the Mold remediation info looks like the same info I found from U or Minn. Looks like a month of reading out there.

 

[Sandor]

Wet crawl spaces is a huge issue here in Eastern Va. Mold is a very big problem.

I started building with conditioned crawl spaces, as speced from Buildingscience.com.

There are no vents, and it is sealed. The outside block walls are insulated, not the house floor. A 2 inch thick concrete slab is poured in the crawl, with 6mil plastic underneath it. The leakeage from the HVAC duct system is usually enough to keep things dry, but the HVAC contractor puts a duct down there. This has solved all the problems.

For extra protection, I spray the floor joists with Boracare to inhibit any mold growth or termite munching.

 

[begreen]

However, Minn. is the land o lakes isn't it? I can understand if one is in an area with wet ground I can see where one would want to try to ventilate this space as best as possilbe.

BG, I beg to differ. In the Michigan UP, my cabin had a musty odor. So, I laid 6 mil plastic sheet over the dirt in my crawlspace, closed up all the vents and ran a dehumidifier in the crawlspace. The smell abated, and the crawlspace is noticeably drier with this arrangement.

(broken link removed to http://www.popularmechanics.com/home_improvement/home_owner_clinic/1275276.html)

You did the right thing, turned it into a conditioned space. I just meant that if you are living on really damp soil (swamp) like my in-laws, you may need to take other measures.

If building new and you can cap it like Sandor does, so much the better. For our crawlspace I am cutting in a small supply grille into the plenum to ensure conditioned air entering the space. Our soil is extremely dry so I am relying on a vapor barrier instead of a concrete cap. The plan is to have the heat pump carry the morning warmup and daytime heating load unless someone is home and a bit chilly. Otherwise, weekdays we'll start the fire about 3 -4 pm for the rest of the evening. Weekends I'll probably light up the fire in the morning while waiting for the coffee to brew.

 

[Henz]

ok..I have the same problem. but my crawl space has like a 2-3' dirt to joist clearance too with a layed up rock foundation..It doesnt ever seem to be particularly wet, but should I cover the entire area with a plastic or no? Also, I think that the best way to insulate my space is to simply use the 2" rigid foam and insulate the rock foundation from the inside..caulking and taping the seams..I would go as high as I could to basically the base of my subfloor and then dig down a couple of inches i nthe dirt and then push dirt up against the foam board..all the way around the foundation..Would I expect to see a good iomprovement with my draft problem???