Under Floor Insulation

[duane c]

Hello, I live in Central Pennsylvania, have an old stone foudation farm house on a creek. The kitchen floor, made of 3 x 8 pine rests on 12 x 12 or so beams supported by large rocks. There is a 1 - 2 foot crawl space under the floor littered with varios boulders and material to big to easily move out. The soil is not wet under the floor. Seems pretty dry actually.

During the winter, tons of cold air comes up throught the tounge and groove floor from the crawl space. I have crawled under the floor, cut and stapled alunminized bubble wrap type insulation between the beams to the floor. Once getting stuck for a while, that was a real treat...

Is there any type of blow in or what ever insulation that I could use for insulation on the dirt and just fill up that crawl space.

Thanks for the replys.

[Amanda_931]

I had a house in Nashville like that--foundation was not nearly tall enough.  Dry rot had done a number on the floor joists in the kitchen, so the floor was on the ground.  Location had its bad points, but since it was less than a mile to work, less than a mile to the nearest big mall, and bookstores, movie theaters, restaurants, the vet, and for a while my doctor's office, I thought it was great.  The people who'd had it before me had paid to have the retrofit TVA insulation/heat pump package.  They got ripped off.  

The no-vent crawl-space will work.  Plastic film on the ground and up to the floor joists, to which it is sealed.  

Unless by foundation you mean piers.

[JRR]

You may want to consider laying rigid foam insulation atop the tongue&groove.   Then you can re-floor on top of the foam.  Foam can be purchased with compression ratings all the way up to 100 psf .... 40 psf should do for your floor.

Just a thought ...

[Bart_Cubbins]

A spray-foam insulation like icynene will stop cold air infiltration in addition to insulating. Just sealing up the air leaks will go a long way toward keeping the place warm.

http://www.icynene.com/

Generally you would hire a pro to spray it in but you can order do-it-yourself kits. The kits are expensive for large areas but can be reasonable for small areas since you're not paying an installer to come out with all their equipment.

http://www.fomofoam.com/

Bart

[Bart_Cubbins]

Some more thoughts...

If cold air is being sucked up from the crawlspace, it means that hot air is escaping out the top of the house. Just dumping insulation in the crawlspace won't help... most types of insulation offer very little resistance to air movement.

The easier solution would probably be to seal the top of the house. If hot air can't escape out the top, cold air won't get sucked in at the bottom. Get up in the attic with some spray foam and tubes of caulk and seal all the openings and cracks you can find... around plumbing vents and recessed light cans, electrical wires, etc. Use sheetmetal and mineral wool to seal around a chimney. Go to the edges of the attic and seal off the wall cavities if they are open to the attic. Then install some kind of gasket to seal the attic hatch. You could also use the same spray foam as above to completely seal the attic floor. You only need maybe an inch of the foam to seal the air leaks and then you dump cellulose or fiberglass or whatever insulation on top.

If you still feel air coming up through the floor, the next step would be to caulk and weatherstrip windows, especially on an upper floor. Also, if you have an open fireplace that you use, replace it with an insert or a woodstove. Open fireplaces tend to suck out more hot air than they produce.

Bart

[Amanda_931]

 Bart's right about general tightening and insulating being the first step.

Even if it does sound too simple.

[Jens]

Insulate the crawlspace foundation walls, and put plastic on the ground.  seal the seams between the two with duct tape, and hook up a vent from your heating system.  only let the vent be open during the coldest times.  UBC states that a crawlspace only has to be vented if unconditioned.  Such a small space shouldn't take much to heat, and most of the cold comes from the foundation walls anyway, not the ground.