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Hawss Drew 01-08-2010 07:51 AM

Would it benefit me to insulate my basement floor?
To be as simple as possible, I'll put it like this: I have a ~1900 sq ft bi level home, with 2 car garage. The finished lower level is basically a large family room/rec room, being about 24x13 in size. There is also a laundry room and a half bath down there.

Now, I know that a lower level will always be cooler than the upper level. Right now, as far as I can tell, the only thing between our feet and the bare concrete floor is some laminate flooring. The house was built in 1986, so I doubt there is any insulation foam board underneath the foundation.

Would it benefit me to insulate the floor? 2x4 sleepers with 1.5" rigid foam board (XPS), and then .5" OSB on top? I think I have the room for it, height wise. My question is would it benefit me to do so? Feet are always cold down there, and we will probably be carpeting it in the next few months, I'm just curious if it will make a substantial difference to insulate.


Bob Mariani 01-08-2010 08:40 AM

not likely. We insulate the basement floors only when floor heating is used. Insulation will help but not cost effective. The perimeter however should be insulated at the floor at least 24" into the room.

Hawss Drew 01-08-2010 08:44 AM

so 2 feet of the floor all the way around should be insulated?

Bob Mariani 01-08-2010 08:51 AM

it should have been done under the concrete. Use a themo scan laser to see where the heat loss is. Placing it as a retro fit over the concrete may cause more problems than benefits. If you do insulate you will need to seal it completely and use 5/8" plywood over the 3/4" foam board before installing a new floor.

Hawss Drew 01-08-2010 10:08 AM

What should I do to prep for carpet? Take up the laminate and lay down some OSB? Leave the laminate there?

Bob Mariani 01-08-2010 11:23 AM

for carpet I would use a double layer quality padding, leave the laminate.

HautingLu 01-08-2010 11:53 AM

What about if the living space is a above an uninsulated garage? Flooring is hardwood. Both are really cold. Which of these, if any, get me the most bang for the buck? This is what I've come up with for next Spring:

In the garage:
-Insulated garage door
-New door leading outside
-Insulate and drywall garage ceiling
-New windows

Living area:
-New windows

beerdog 01-08-2010 07:24 PM

the carpet and padding will make a huge difference. I saw this at a store. Never used it but it woould probably work well for what you want.

Bob Mariani 01-08-2010 08:15 PM


Insulate and drywall garage ceiling
this one will be most beneficial to fix the living space heating above the garage. But PEX radiant heat -> closed-cell spray foam - 6 mil poly air barrier then tow layers of 5/8" sheet rock will give you a system that I would use if it were mine. And new windows above.

Gary in WA 01-08-2010 11:13 PM

Option "B', and cover with drywall:

Be safe, Gary

HautingLu 01-09-2010 10:40 AM

Bob - thanks for the info, and GBR thanks for the link.

Sheila4467 01-11-2010 04:55 AM

I had the same problem in our split foyer years ago. Family room, about the same size as yours, and it was concrete with no flooring. I purchased the BEST PADDING I COULD FIND, and used IT, and even downgrade the carpet just a little bit, so I could buy the best padding, but IT WORKED GREAT.

I also used a tip from another DIYer friend, you may want to try it.
Take a candle, a short one, in a dish with no sides, and slide it along the floor to find out just where any leaks, or drafts may be. When you plug them, your carpet will do the job a lot better too.

Turned out that my worst problem was the electrical plugs! They literly blew in cold air, and I never even knew it. Once sealed up, the room was warm as toast.

Make sure you check the windows too, cold air sinks to the floor, so any drafts may play a bigger roll than you think. It sure did in my family room.

Good Luck, and let me know how it went when you done OK?

You will LOVE your room when it's finished.

Hawss Drew 01-14-2010 08:08 PM

thanks for the ideas guys. I actually have new windows (triple paned gilkey) throughout the house already and a new HVAC system. I do have quite the caulking project for the spring coming up, though.

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