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Heating the crawl space under the house

Randy Gibson

Joined: Dec 18, 2011
Posts: 101
We have a 1600 sq ft home, and there is at least 4' of space under the house, the floors are wood, and the a/c system was also put under the house. The house is on a wall of cinder blocks with closeable vents to keep the hot air in.

In the home our ceilings are 9', and the rooms are divided by archways, which makes it very difficult to heat the house with one wood stove. (I did not design the house)

I was thinking I could put a wood stove close to the house and run the exhaust ducting under the house. Would this be a good idea, and does anyone have any better solutions?

Thank you, Randy
Randy Gibson

Joined: Dec 18, 2011
Posts: 101
More info, the home is on 40 acres, no HOA's or city matters to contend with. owned outright as well. In the boonies, with plenty of wood for fuel.
John Polk

Joined: Feb 20, 2011
Posts: 6684
Location: Currently in Seattle. Probably moving 1 hour north by end of the year.
The exhaust contains a lot of CO2. CO2 is heavier than air, and thus will settle to the bottom.

CO2 will smother a fire...and human life. If you (or a plumber) needs to go under the house, make certain to vent it well enough to get all of the CO2 out of there. If your dog/cat crawls under there, they will die. The good news is that it will probably also kill mice, ants, roaches and termites.

Also make certain that the floor is well enough sealed so that the CO2 cannot creep back into the house.

I used to live in a house where I would vent the clothes dryer into the crawl space in winter. It certainly made a difference.
Aaron Oakley

Joined: Jan 05, 2012
Posts: 18
Location: Snowmass, CO
Unless you're using the crawl space, it's much better to seal and insulate the floor than to heat the crawl space. Since you will not get a perfect seal, I highly recommend you do not pipe the exhaust from your wood stove into that space. Another good option is to use the access you have to the underside of your floor to install radiant floor heating. It's generally more efficient and comfortable than a forced air furnace or wood stove.

Check out our blog at where we discuss our experiences as we revitalize our family's ranch utilizing Permaculture principles and values.
Randy Gibson

Joined: Dec 18, 2011
Posts: 101
Thanks for the replies, I was not clear as to my plans, I reckon. I was thinking of running the exhaust pipe, if you will, the entire length of the house, and using the radiant heat off of the pipe. Maybe even run it the length of the house and back, where it would exhaust near the stove, so that I could make sure it was drawing well without alot of leg work. I do not want the smoke vented under the house for numerous reasons.

We do not use our clothes drier, and I need to do this on a "frugal" budget.
Ernie Wisner

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
dont plan to pipe your stove under the floor without sealing the pipe joints. you can do a sub-floor stove or something of the sort but i would recommend that you build the stove in the space you have and simply insulate the crawl space. straw bales are good and cheap insulation that you can just put in. Plaster the outside of the bales and chink them well and you wont get rodents. the stove can be used to make hot water for radiant floors.
you dont need to dig really deep in your pocket but you will have to dig a little.

I would recommend building a solar hot water heater and a storage tank and use that for the floors. if it is a well insulated tank and the solar heater is hooked up correctly making a heat transfer loop in the tank you can heat the house all night and all day for several days even if it gets a bit cloudy. most of this you can scrounge and not have to pay out the nose.
construction of a hot water panel is not hard to do and the components don't have to be expensive.

You dont need to use straight ethylene glycol in the panel, it can be mixed with water and do a good job until well below freezing.
4 foot would allow you to put the tank under the house and use the heat that does escape to add heat to the house.

you can also cut grate holes in the headers and put in grates at ceiling level that will allow air movement throughout the house. the grates dont have to be bought and its easy to make attractive grates at home from what most folks would call scrap (lots and lots of old pallets around and the woods they are made from are most often good hard woods). for the interim you might consider taking some aluminum foil and a staple gun under the house and put it on with the shiny side up. then go to the attic and give it the same treatment shiny side down on both the attic floor and under the roof itself. this is a really cheap way to keep some of he heat in your house.
if you have upstairs to heat Grates can be cut in the floors to allow heat to rise up to the rooms.

the stove you will have to make up your own mind on what you want.

Need more info?
Ernie and Erica
Wood burning stoves, Rocket Mass Heaters, DIY,
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Randy Gibson

Joined: Dec 18, 2011
Posts: 101
thank you, Randy
Andrew Parker

Joined: Feb 13, 2012
Posts: 380
Location: Salt Lake Valley, Utah, hardiness zone 6b/7a
I suppose you could use the RMH design and adapt it as a floor heater (floor furnace), then, rather than heating cob with the flue, insulate your crawl space and heat the mass of air under your floor. Floor heaters are very basic beasts, but worked pretty well when I lived in Texas (don't let rats or mice get into the well, the smell of burning feces and urine is pretty horrific).

Does the house sit on a slope?

You might also want to check out the designs for tobacco drying barns at
Randy Gibson

Joined: Dec 18, 2011
Posts: 101
the house is on top of a small rocky hill.
Andrew Parker

Joined: Feb 13, 2012
Posts: 380
Location: Salt Lake Valley, Utah, hardiness zone 6b/7a

I asked because, though I am intrigued with the natural draft condensing flue, I would be more comfortable if the flue gases were running downhill, away from the house. Has anyone installed a draft induction fan at the exhaust (apologies in advance if this question has been answered before)?
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