Insulating Floors?

The joists must have been wet when the foam was applied. How would the moisture get to the joists through the barrier provided by the foam?

Everyone I have talked to tells me that the sprayed in foam is the absolute best way to insulate a floor over a crawl space IF you are not going to heat/condition the crawl space.

Unfortunately it is also the most expensive. I'm priced it out at about 1200.00 to 1500.00 do the 24x24 section that I need to do. This is doing it myself using the kit's you can find.

NW Vermont is the climate I'm dealing with.

Re: the spray foam onto the joists----- what happens if you have a pipe burst upstairs and all that water seeps down into the joists and the foam holds it there? Wouldn't that be a "black mold heaven"?

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Yes - Heartstrings - that is what I want to know too. What do you do about water pipes and electric lines? How do you know where they are and how to get to them if they are all covered up with foam?

The spray foam is impermeable. Any moisture that comes through from above will not get past the insulation. It acts as it's own vapor barrier. You would have even bigger problems with fiberglass batts in that scenario as the moisture would render the insulation useless and create the perfect enviroment for mold and moisture loving insects.

If you have the perimeter skirting insulated with nothing in between the joists and you have the same leak then the moisture will make its way through the floor system but will just sit in the crawl space creating the same conditions for mold/insect growth. The whole idea of insulating the perimeter is to create a "conditioned crawl space". This means that seasonal changes in humidity are sealed from the crawl space and the crawl space is heated. If you add moisture to a crawl space from a leak then you have defeated the purpose of the conditioned crawl space and can have mold/insect problems.

If you insulate the floor itself you don't have to worry so much about keeping the crawl space conditions consistent. In my climate we usually shut up the crawl space in the humid months and vent it a bit in the dry months. I would have to heat over 2000 cubic ft of space I never use to adequately condition my crawl space.

The plumbing and electrical are just fastened to the bottoms of the joists.

I used those stiff wires to install fiberglass batts. After , I'd say, 15 years, I had to make a repair. An absolute disaster, about half of the insulation was on the ground, the wires had rusted basically enough to cause them to fold up. What was left was awful, mice had chewed holes (paths) thru the insulation. Totally revolting. All the while we were blissfully unaware on top of the floor. Also on foaming joists, Why? Foam the floor, the joists more or less would have the same R value as the foam.