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Rbartodziej 01-26-2011 03:02 PM

should I insulate the floor
I have a concrete crawl space that is a minimum of 9 feet below grade and a floor 20 inches above the crawl space floor. The walls are all insulated,and I am now doing a home reno, should I insulate the floor with 2x2 strapping and blue styro? or is it a waste of time and money Thanks in advance for your help.

kok328 01-26-2011 03:35 PM

It would be my opinion that blue styro would not provide enough R-value to make the installation worth your while.

paul52446m 01-26-2011 06:38 PM

like KoK328 said the heat loss on that floor is so small your pay back would be very slow.

joecaption 01-27-2011 05:44 AM

First you go around and seal up all the holes in the bottom plates with spray foam that wiring and plumbing were run. Make sure to wear some old gloves and an old shirt, This stuff is a pain to get off of anything. Then use fiberglass batts R19 or better and make sure the paper goes againt the subflooring. The insulation is held in place with insulation hangers, there sold often times in the same area as the joist hangers at Lowes and HD.
There was a 30% tax break on your taxes for the cost of the materails at one time and I've heard it was being extended, check it out by doing a key word search on "energy star".
You will get far more bang for your buck by replaceing old windows, resealing leaking doors and adding insulation in the attic so it's R50 then insulating a floor.

siriuschaos 04-22-2011 09:32 AM

Have you considered spray foam? Not the stuff in a can. There are kits available for the homeowner. I'm currently in a similar situation in an older home. I found an ideal product ( I think ) online. Check out These types of closed cell kits are the smaller and lighter cousins to the truck mounted set ups. Generally in the 2 lb range. Most yield an r value somewhere around 7/in. Multiple passes can easily yield an R-20 in a 2x6 up to r-40 in a 2x12! Awesome.

joecaption 04-23-2011 05:53 AM

Good luck with the DIY foam job, love to hear how that works out sirluschaos. Trying to spray foam in an over head position with little room to more around should prove interesting.
The least amount of heating and cooling lost is through the floors.
For the most bang for your buck check the insulation in the attic, old windows then get new replacement windows, check around doors for air leaks. That's were far more or your heat is lost.
Instead of foam under the floors just use R-19 fiberglass insulation held up with insulation hangers every 2'. It will give you far more R factor and cost about 75% less per ft. then blue foam.

head-first 05-08-2011 09:42 PM

By recommendation of a weatherization consultant (who is fortunately a neighbor of mine), I insulated my crawlspace this winter. The walls were done with four inches of foam sheeting Since the floor above the crawlspace is living space, I did not need to insulate the ceiling. Also, I removed the window between the crawlspace and the basement and omitted insulating that wall.

What I did NOT do was insulate the floors. I read up on it and asked my neighbor, his reply was "I wouldn't bother". I did, however, take spray foam and seal all the spaces between foam board and the floor, as well as fill in any cracks in the floor.

Like the other guys are saying here, the money would be best spent addressing the attic and all the other places where heat escapes.

Perry525 05-09-2011 11:36 AM

Let me present a different view.
Warm air rises!
As it rises it pulls cold air under the floor and through the cracks.
This makes the floor cold.
It makes your feet cold.
It wastes a lot of money, because you have to heat all that cold air that keeps coming in.

Yes the loss of heat through the floor is minimal, because the drafts keep the floor cold.

If you have baseboard heating, or any other form of heating that is close to the floor, these things emit radiant heat that goes down as well as through 360 degrees..... This heat is lost without underfloor insulation.

I am about to insulate a bathroom floor with eight inches of polyurethane foam....someone will have warm feet.

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