What type of insulation should I put under my wooden floor in my basement.?

Question

I would like to take up the old wooden floor in my basement (20ft x 16ft) and put insulation under it. the floor sits about 1 1/2 in above the concret and is probably sitting on 2 x 4's. I don't know what type of insulation to buy or what type of wood to put back down. I am looking for good material but not...

Answer 1

The easiest way to insulate between the 2x4 sleepers would be to buy sheets of 1-1/2" extruded polystyrene board, such as Styrofoam, rip it into pieces to fit between the 2x4's, and then cover with OSB. If you are looking to replace the sleepers, use pressure treated 2x4's. You may want to consider renting a Hilti gun. It uses a .27 caliber shell to set a 2-1/2" hardened nail through the sleeper into the concrete. Hope this helps.

Answer 2

USA First, when considering insulation, consider R Value first, then type of material. In the northern half of the country, a minimum R30 would be required at the floor. If using fiberglass with a facer, or any insulation that has a vapor barrier, place the vapor barrier up against the floor. For better results, also install a vapor barrier on the ground in the crawl space. A heavy (10 mil thick) plastic, completely sealing the area wall to wall will do fine. The building codes all refer to R Value, no matter what type insulation. However, any insulation is better than none at all. 2" thick 4' x 8' sheets of extruded (not expanded) polystyrene or, better yet, polyisocyanurate nailed to the bottom of the house with no gaps at all will help, even though the R Value is only about 10. Do not listen to anybody who does not talk in terms of R Value and vapor barriers.

Answer 3

Without knowing why you have a floating floor in a basement, I suspect you have a reason. I might disagree that a basement is warm in Winter, most especially if one does not have a furnace in the basement, and/or winters are extremely cold, anyway, and given the fact that most basements set at least 5 ft. below ground level, surrounded by soil.

First of all, even to lose some space I might intall the 2 x 4's side up, as opposed to face up. I'd use Pressure treated lumber in any case. I'd probably use construction grade foam insulation sheets cut to fit, and I'd floor it with 3/4 inch plywood. I might even do as is done in dance floor installations and attach rubber shims to the underside of the 2 x stock. The 2 x 4 issue of course depends on ceiling height currently. Supplies would depend on your choice of how you install

If you intend any kind of finish over the substrate, then you need not buy top of the line substrate.

I will assume you do not have water or moisture issues.

Steven Wolf
Just my two "sense"

Answer 4

As my ANSWER, consider not insulating that basement floor. It is thermally locked to underground temperature which is cool in the summer and warm in the winter. People spend scads of money to create what that basement floor of yours has naturally. Regards, Larry.

Answer 5

This is one method, easier to link you to the site than explain.

http://www.diynetwork.com/diy/hi_family_...