Crawl space

NeilTheCop · 06-21-12, 09:08 AM

I have a regular, about 24" tall crawl space under my house with no insulation.
As the joists are on 16' centers I was planning to use regular r19 batts.
My question is can I use plastic sheeting on the outside, not only to hold the batts in place but as a leak seal?
As my part of New Mexico has almost no rain and the average humidity is normally in single digits I don't think condensation is a problem.

Any input please.

herlichka · 06-23-12, 08:53 PM

That's a good question!
Here in Ontario, Canada, the building code accepts the combined qualities of your plywood sheathing, subfloor and finish floor as a "vapour barrier", as it occurs with an insulated floor over an unheated garage, or a cantilevered bay window. Given the fact that we have generous amounts of rain, snow and humidity and there is no specific requirement to add poly to the floor I would think that you would also not likely need one. I might suggest the installation of a housewrap like Typar or Tyvek. They form an air barrier to keep air from wandering into your insulation on a windy day, but allow moisture to dissipate, a handy consideration if you should ever have the misfortune of a toilet, tub or sink overflow, dishwasher leak or broken pipe.

S-F · 06-23-12, 11:13 PM

I' use reinforced poly and unfaced batts if you can't go for the poly and cellulose. And r 19 fiberglass is for 6" and your floor joists are at least 8".

NeilTheCop · 06-27-12, 08:48 AM

Quote:

Originally Posted by S-F

I' use reinforced poly and unfaced batts if you can't go for the poly and cellulose. And r 19 fiberglass is for 6" and your floor joists are at least 8".

I wanted to leave a gap for a possible underfloor heating setup later.

06-21-12, 09:08 AM	#1
NeilTheCop Helper EcoRenovator Join Date: Mar 2011 Location: Roswell NM Posts: 43 Thanks: 0 Thanked 4 Times in 4 Posts	Crawl space I have a regular, about 24" tall crawl space under my house with no insulation. As the joists are on 16' centers I was planning to use regular r19 batts. My question is can I use plastic sheeting on the outside, not only to hold the batts in place but as a leak seal? As my part of New Mexico has almost no rain and the average humidity is normally in single digits I don't think condensation is a problem. Any input please.

06-23-12, 08:53 PM	#2
herlichka Apprentice EcoRenovator Join Date: Oct 2010 Location: Simcoe County, Ontario, Canada Posts: 102 Thanks: 11 Thanked 15 Times in 10 Posts	That's a good question! Here in Ontario, Canada, the building code accepts the combined qualities of your plywood sheathing, subfloor and finish floor as a "vapour barrier", as it occurs with an insulated floor over an unheated garage, or a cantilevered bay window. Given the fact that we have generous amounts of rain, snow and humidity and there is no specific requirement to add poly to the floor I would think that you would also not likely need one. I might suggest the installation of a housewrap like Typar or Tyvek. They form an air barrier to keep air from wandering into your insulation on a windy day, but allow moisture to dissipate, a handy consideration if you should ever have the misfortune of a toilet, tub or sink overflow, dishwasher leak or broken pipe. Last edited by herlichka; 06-23-12 at 08:55 PM.. Reason: Spelling