Tanya from Surrey, British Columbia has a very shallow, very wet, very cold crawl space under her house, and the heating bills show it. She has tried all the weather-stripping and caulking she can do up in the house. Now what to do about the crawl space?
First, despite the fact that there is almost no room to work in her crawl space, someone must crawl in there and lay down a 6 mil polyethylene sheet over the soil. This is the only way she will ever reduce the humidity that is coming into her house. A tough job because of the lack of working space, but one that costs little and is absolutely necessary.
Then I would recommend that while someone is crawling around down there, they air seal all the cracks around the top of the foundation wall and around all the ends of the floor joists. Then put foam insulation boards against the entire perimeter. Because there are no heating devices in this space, you do not need to cover the foam with fire protection. And because the foam will not take on water, you do not need to add a vapour barrier.
Stopping the moisture from evaporating up from the soil, stopping all air currents in this space during the heating season, and getting at least a little insulation around the parameter will make a big difference in the comfort and heating costs of this little house. A lot of dirty work, but not much cost.