Low Crawlspace Underfloor Heating?

[Diggin It]

Is there such a thing?

This house is going on 70 years old. Concrete block walls that I've added insulation to inside and out. Interior floor is wood frame above a low crawlspace. Maybe 12-18" clearance at most between bottom of floor joists and ground. No way to get under any portion. The only venting is four concrete blocks turned sideways on each side of the house, no access to any of it from inside the house. No chance at all of running any kind of piping or tubing for heated liquid.

But I keep wondering about forced air heat under there. On days like this where the is temperature is in the teens and there is a strong wind, the whole floor feels cold, tile, wood and carpeted/rugged areas. Any warm air down there should help, but I don't want to introduce moisture either.

 

[KennyG]

If I understand, you are talking about using the underfloor area as a plenum and heating the whole thing. It would probably work, but be very expensive. If you heat outside air, moisture shouldn't be a problem. Relative humidity would be much lower when the temperature is raised a little.

When I worked in HVAC, I once added hot water heat to a house with almost no clearance under the floor joists. I had to tunnel under the joists and then crawl between them. The worst job I ever did but it got done. It sounds like you really need to find a way to insulate the floor.

What kind of heat do you have now?

 

[MossRoad]

Is the crawl space under the house dirt? If so, pushing warm air into that area will be futile. So much of it will be cooled by the dirt, or escape through the 4 block vents you mention, that it would take huge amounts of hot air to warm the wood floors, costing you a small fortune.

 

[Diggin It]

Can't tunnel. No way under without cutting out a section of block from the outside or floor from the inside. Neither would allow for dirt removal.

Current is a combination of gas forced air, gas radiant (infrared wall mount) and wood stove that I'm looking to eliminate.


Yes, dirt. Vents would have to be blocked in Winter and opened in Summer. Trying to evaluate if it makes sense.

 

[RalphVa]

We've our crawl space sealed off with encapsulation but still have moisture problems. So, we went with a commercial dehumidifier. It warms up the crawl space from its normal 55ish earth temp to mid 60s, which is warmer than we keep the family room on the other side of the wood flooring above it.

Ralph

 

[MossRoad]

Even if you put heated air into that space, the floor will never feel warm to the touch. Think about it. You heat the air until it's 70 in your house, for example. The wood floors, walls, ceiling, furniture, etc... all get to 70ish degrees. Yet you put your feet on them, and they don't feel warm, because they are 70 and your skin is 95ish. That's a 25 degree difference.

The only ways to make your floors feel warm is putting in radiant floor heat, or carpet. Carpet makes a huge difference in how a house feels. But you can't (or at least shouldn't) carpet areas like kitchens and bathrooms.

You could dig out the crawlspace enough to make a workable space to install radiant floor heat under the floors between the joists. That's a big job, but very doable.

 

[chim]

Is Radon an issue in your area? If so, you may not want to have any positive pressure in the crawlspace and push the Radon into the living space.

Another story, but way way back a buddy and I were assigned the task of stapling insulation in a similar space at an old farmhouse. The space was a bit less than a cubit in spots, preventing the use of the staple gun unless the forearm was at an angle.

 

[MossRoad]

Can't tunnel. No way under without cutting out a section of block from the outside or floor from the inside. Neither would allow for dirt removal.

Current is a combination of gas forced air, gas radiant (infrared wall mount) and wood stove that I'm looking to eliminate.


Yes, dirt. Vents would have to be blocked in Winter and opened in Summer. Trying to evaluate if it makes sense.

I worked with a woman whose husband made a career out of digging out crawl spaces for repairs or installing basements under houses that only had crawl spaces. It's not as hard as it sounds. Just time consuming.

He'd bust out a few blocks and start digging, hauling the dirt out in buckets. When he got a space big enough for his body to fit, he'd insert a conveyor into the hole trough the busted out blocks. Then he'd start scooping the dirt onto the conveyor, which would haul it outside for him and right into his small dump truck. Then it was just a matter of getting a hole deep enough for him to move around comfortably and off he'd go. It helped that he was only about 5' tall.

 

[ededic]

Before building a new shop with living quarters above, I considered putting infloor heat into our cottage. It was just like you describe only there was not even 6" of clearance for the majority of the crawlspace. I painstakingly fished pipes and wires to modernize the cottage. One thing I looked into than you may consider is a vacuum truck service. They use these trucks to do delicate work in cities to evaluate around wires, pipes and underground service. They also use them for this type of work and just need a place to dump the wet dirt from the water injected into the suction process.

Something to consider that without a bunch of research and driving through a construction zone in the city did I know was possible.

 

[Dougeye]

I worked with a woman whose husband made a career out of digging out crawl spaces for repairs or installing basements under houses that only had crawl spaces. It's not as hard as it sounds. Just time consuming.

He'd bust out a few blocks and start digging, hauling the dirt out in buckets. When he got a space big enough for his body to fit, he'd insert a conveyor into the hole trough the busted out blocks. Then he'd start scooping the dirt onto the conveyor, which would haul it outside for him and right into his small dump truck. Then it was just a matter of getting a hole deep enough for him to move around comfortably and off he'd go. It helped that he was only about 5' tall.

Geez. A tough way to make a living, gotta have a lot of respect for a guy like that.