I'm about to start insulating my crawl space. I plan on sealing the ducts and insulating them. I plan on insulating the ceiling with R-19 Insulation. I already have a vapor burier laid on the floor. I've heard that if the crawl space walls are insulated the home's foundation could heave because of all the air trapped in the room. Is this true? Have you heard of this happening?
Answer:
I have not and I think if that is the case with a particular structure, the problems go a long way beyond insulation. My system: Crawl space is a major source of mildew but that can be corrected. First, all insulation has to be removed from the crawl space ceiling - house floor. The whole dirt floor, with all its irregularities, has then to be covered with an impermeable material (6mm polyethylene, an old swimming pool liner, etc.). This has to be firmly and permanently sealed to the existing, well applied perimeter wall vapour barrier – which should be covering insulation rated at least R-20. It also has to be taped to all perforating structural components (plumbing, support posts, etc.). That looks after the crawl space for most of the year. The vents on the walls have then to be adjusted so they can be opened and closed from the outside. This will negate the need for anyone to crawl around down there for seasonal adjustment of ventilation.
