insulating crawl space


Old 01-10-02, 04:16 PM
Mark B
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insulating crawl space

Well, I've read a number of responses to questions about insulating crawl spaces and I'm unfortunately still puzzled about my situation. I've got a 50 year old house built over a crawl space with dirt floor that I'd like to insulate better. The crawlspace currently has fiberglass batting draped along the walls, but no vapor barrier over the ground. It is ventilated and I keep the vents open due to the conflicting reports I've read about moisture build-up. The gas furnace and all heating ducts (uninsulated) are down there, as are all of the plumbing pipes, suspended below the joists.

My question is: would insulating the floor with fiberglass batting between the joists cause my pipes to freeze in the winter (I'm located north of Denver in Longmont CO)? If I insulate the heating ducts (cold air blows up into the house when the furnace first turns on), would that further jeopardize the pipes? Should I close the vents in the winter if I insulate the floor? And what's this I'm hearing about condensation with fiberglass insulation causing problems even with a vapor barrier covering the exposed ground? Thanks in advance to all of you who respond.

Mark B
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Old 01-14-02, 01:45 AM
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The moisture barrier that covers dirt floors prohibit evaporation, it works very similar to a solar cover for pools.

The vast majority of heat loss in a crawl space is due to the heat sink in it. As the term implies, it's anything that drains heat from the house ( masonry and dirt floor). The amount of heat that comes off ducts in a situatiion like yours, will have very little effect on weather your pipes freeze or not. Yet the amount of discomfort and increase energy bills will be significant. Insulate and seal all the ducts.

Crawl space ventilation applies when insulation is installed and does not apply when it is not. This is due to the heat flow characteristics with insulation.

The U.S. Dept. of Energy states that homes that experience 8,000 degree days should have the vapor barrier between the insulation and the conditioned space. In other words, if you're in the crawl space, the vapor barrier goes up first and then the insulation.

If you're worried about freezing pipes, at the bottom of this message is a little house icon with www next to it. Click on it and read topic "Water Heating". There is a name of a manufacturer and phone number. The AutoCir pump will eliminate any possibility of freezing pipes and will save you money on your energy bills. I don't know their website address, if you find out, let me know.
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