Insulating a crawl space


Old 02-07-04, 06:08 AM
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Insulating a crawl space

Our family bought a house in 1995 that was built in 1900. We know we have to add additional insulation in the attic and I have read some other forums about insulating an attic over old blown in insulation and I am planning on adding an unfaced attic blanket R-25 over the existing insulation. My real problem though is in the crawl space. Our floors, especially the kitchen, are very cold and we would like to insulate the floor joists in the crawl space. I have been told by a few people to be very cautious about this project because of moisture problems they have experienced with their crawl spaces that were insulated, one gentlemen told me about one of his in-laws homes that the entire floor rotted out due to moisture being trapped in the insulation in the crawl space. To complicate matters I have a 6 foot wide by 6 foot deep water cistern in my crawl space which consistently holds 8-12 inches of water. The foundation, as you probably guessed, is rock and mortor. How can I insulate the floor and avoid the problems I have been warned about?
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Old 02-07-04, 08:34 AM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389
Lightbulb crawl way

YOU DONT. You dont want to put insulation in the joist there at all.
This cistern??? fill it in are put a sump pump in it. You have to put 4 or 6 mil poly down on the ground and then 2" or 3" insulation on the wall and in the joist just there on the sill plate.


Old 02-07-04, 02:07 PM
Dave_D1945's Avatar
Join Date: Dec 2003
Location: Bay Area, CA
Posts: 1,178
I would focus on attic and wall insulation and elimation of drafts around windows and doors before I got into insulating the floor. You'll get way more bang for your buck by working from the top down.
Old 02-07-04, 04:14 PM
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Thank you both very much for your replies. I will concentrate on the outer walls of the crawl space and filling in the cistern. The attic is a lock for more insulation, but I have had a proffessional tell me that the walls have enough. Again thank you.

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