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too-cold 11-08-2012 12:53 PM

Crawl Space Insulation in NWT Canada
I have a question about insulating a crawl space. I live in Northern Canada in a mobile home. The home is on engineered wood blocks that set on a gravel pad and perimeter is Pressure treated plywood skirting with 2x4 studs. The house is heated with forced air Oil furnace. The height of the crawl is about 4’ in the front and 3’ in the back. The crawl space is dirt floor with a under “belly blanket” insulating the floor joists, plumbing, duct work etc. This blanket has fiber glass insulation between joists and another fiberglass batt blanket over that that is sealed with a tarp like material with cardboard backing.

The place was built in 1984 so the belly has sagged over time and in the past few years I have had the occasional pipe freeze. Also smell was pretty musty with the gravel floor and vents in the skirting. This summer past I decided to do something about it so I researched online and found many articles saying that sealing or encapsulating the crawl space is the best bet and placing a few heat registers in the space.
So in August I insulated all wall stud cavities with 2” ridged foam boards and sealed every seam with spray foam. I laid a 10 mil poly vapor barrier on the ground and sealed it too the bottom of the skirting with acoustic caulk and screwed strips to it keeping it in place. Within a week I must say the smell is virtually gone and air quality is way better. I cut three holes in the belly and reversed 3 heat registers into the space. Because the furnace doesn’t have a cold air trunk return I left the 3 registers in the house open so air can pass freely. That was the summer. Now it’s November and -20 Celsius outside. The air temp in the crawl is about a steady plus 10 Celsius. However in the house above I started seeing condensation on the bottoms on my windows. Hmm I thought, That didn’t happen last year. I picked up a humidity sensor and the indoor humidity is 40% which is too much with -20 outside… Is this because of my changes in the crawl space?

Should I have removed the under belly? Sorry for the long post, but I am concerned because winter is here and if I need to fix this it has to be soon. It will only get colder. Also if I reseal the belly with the sealed crawl space with that sealed space be a dangerous dead air space then…?

too-cold 11-09-2012 03:59 PM

no replies?? I think I am going to just place registers back the way they were and reseal the under belly and see how that goes.

Windows on Wash 11-10-2012 07:14 AM

Tough to say where the additional moisture is coming from.

Were you very detailed in putting down that vapor barrier and was it sealed to the wall or to the foam board.

If it was sealed to the foam board and not the wall, you might have moisture coming up between that connection and getting upstairs.

creeper 11-10-2012 02:11 PM

Doesn't everybody have extra moisture in the house at this time of year. Its a misconception to say that Spring is the wettest. Outside maybe but not in.

I think you will find less condensation in a few more weeks, especially with forced air. It is very drying.

I'm also finding extra condensation on the bottom of my new windows and well sealed home. I believe this is normal and will run its course soon

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