Rigid foam insulation?

[joec]

I am getting geared up to install a wood floor over my concrete shop floor. The most expensive rigid foam is the foil backed 2" thick sheets. There is also the 2" Bluefoam type insulation. Anyone know the benefits etc of each one. I will be placing a vapor barrier down over the concrete so I wonder why I would need the foil backed type.

 

[steviegwood]

If you are going to put a vapor barrier down and then 2" foam insulation would 2" white rigid Styrofoam 4' x 8' sheets work? That is what I insulated the sides and roof in my metal building/shop with and it has made a gigantic difference. I can get that at $5 a sheet. Steve

 

[Teague]

The white foam boards are Molded expanded polystyrene (MEPS)...the same material from which coffee cups are made. The R-Value per inch of this material usually ranges from R-3.8 to R-4.4 per inch.

The blue foam board is extruded expanded polystyrene. The R-value per inch of this is right around R-5 per inch, so you get a little more thermal resistance per inch here over the other material.

As far as foil backed or not, in this instance I don't believe you would need the foil backing. The foil backing is very good as a radiant barrier (say in a roof deck), but in this situation, it would be a waste of money.

You want to make sure that this is installed in such a way that the foam boards are not compacted. This reduces the R-value significantly.

If you really want to make an impact on heat loss through your slab, it would involve some digging. There is more heat lost through the slab edge than there is underneath the slab. Insulating the slab edge with R-5 and not putting insulation in between the slab and wood flooring would really be the best way to go, but obviously also more expensive.

 

[joec]

My plans are to put 2/4 sleepers face down on 16" centers and then the foam insulation in between. I am going to put 1/2" ply strips on top of each 2X4 to build it up to be even with the insulation to avoid compressing it with the wood subfloor and finish floor above.

 

[Gotcha6]

Termites love polystyrene. It's the same product used in EIFS (aka fake stucco) systems. Exterminators will not treat some buildings with this product within 18" of the ground. It's not that they digest it, they just use it as a tunnel to the wood frame.
Go with the blue styrofoam. It's so stiff it could probably hold up the plywood itself without sleepers on a standard load configuration.

 

[joec]

Actually Lowes has the blue foam and Home Depot has it in a pink type color. I guess they are the same?

 

[max_in_graham]

Joe,

Just curious... are you planning to put the wood directly on the foam, or are you going to use a 2x4 (or similar "joist") to raise it up off the floor?

I would not suggest placing anything directly on the foam. It's probably not going to hold up to the direct contact pressure for more than a couple of years.

The "best" thing to do is put at least a 2x4 PT joist down (2" depth) and then add unfaced R13 between the joists... unless you can get the blue/pink rigid foam cheaper.

 

[joec]

I am planning on putting 2X4's face down with a 1/2" plywood piece on top of that to make a 2" thick board. I will put those on 16" centers and cut the 4x8 sheets of the rigid foam into strips to fill in the gaps between the 2X4's. Actually, I will place a 2X4 piece down in a line then add the foam, then another line and so on until I get a section done to the point I can start running the 3/4" ply and continue on that way.

 

[Ben325e]

Hey Joe, in your post above you say 1/2 ply but finish with 3/4" ply. For flooring I'd go with the 3/4.

 

[CrealBilly]

A wifes friend wanted a place for her daughters to be able to dance so we closed in a car port that if a tornado every came all you would need to do is lag some handles down to the floor and hold on cause that floor is not going nowhere. For insulation we glued and nailed 2x2's to the bottom of the sides of the sleepers and laid blue foam board in between the sleepers then packed in fiber glass insulation, worked like a champ and the 2x2's really stiffened up the 2x12's.

 

[joec]

Hey Joe, in your post above you say 1/2 ply but finish with 3/4" ply. For flooring I'd go with the 3/4.

The 1/2" ply is just strips that I will cut and put on top of the face down 2x4's to build them up to be 2" thick. That way they will match up with the 2" insulation. Over that will be Advanteck (sp?) 3/4" subfloor and then 3/4" hickory T&G flooring.

 

[Bill Clemmons]

Actually Lowes has the blue foam and Home Depot has it in a pink type color. I guess they are the same?

Someone asked if the blue and pink boards at Lowes and HD are the same thing. Make sure it says "extruded polystyrene", not MEPS. As Allison pointed out above, there is a difference. Bottom line: go with the highest R value you can get. You only want to do this job once.

 

[joec]

I am starting on Wed next week. One question. Should I put the "sleeper" 2X4's around the perimeter of the room, running parallel and up against the bottom plate of the stud walls? In other words, having a nailer around the entire room. I was planning on just running the 2x4's face down on 16" centers and have the ends butt up against the bottom plate. I was thinking that with the rigid foam, I would have support at the ends, between the sleepers.

 

[Bill Clemmons]

Since you're going over the face-down 2x4's w/ 3/4 ply then 3/4 hardwood, I suspect just butting the 2x4's up against the outer sole plate will be sufficient. I'm certainly not a structural engineer, but it seems to me you'll have enough support. If you think about it, you'll have the same support up against the wall as you'll have out in the middle of the floor, unless you're planning on putting cross-bracing every so often.

Bill Clemmons

 

[Gotcha6]

Just line the studs up over the sleepers. Be sure the sleepers are ACQ treated. You don't want termites. Use ACQ grade fasteners long enough to go into the 2 x4s at least 1". Screws preferred.

 

[joec]

One other question. I was planning on letting these 2X4 sleepers float (no tapcons) and then tacking a strip of 1/2 ply to the top of the 2x4 to bring it up to 2". Then I was going to screw the 3/4 Advantech subfloor down to the sleepers. The carpenter guy helping me has suggested we use an air nailer and nail the subfloor to the 2X4's. Any thoughts why this would not be ok to do rather than the screws?

 

[Bill Clemmons]

Carpenters try to do things the quickest, most time efficient way, because time is money for them. Screwing the sub-floor down is much more time consuming than nailing, unless you have one of those long handle extensions that let you walk around and screw from a standing position. I chose to screw my sub-floor down, but time was not a big issue for me, and I was doing it myself. In the long run, I think screws would hold better, but the difference may not be worth the extra time and cost. Are you putting a construction adhesive on top of the sleepers before you put the sub-floor down? And I think you said you are nailing the sleepers to the concrete floor, aren't you?

Bill Clemmons

 

[joec]

Carpenters try to do things the quickest, most time efficient way, because time is money for them. Screwing the sub-floor down is much more time consuming than nailing, unless you have one of those long handle extensions that let you walk around and screw from a standing position. I chose to screw my sub-floor down, but time was not a big issue for me, and I was doing it myself. In the long run, I think screws would hold better, but the difference may not be worth the extra time and cost. Are you putting a construction adhesive on top of the sleepers before you put the sub-floor down? And I think you said you are nailing the sleepers to the concrete floor, aren't you?

Bill Clemmons

My plan came from a another forum question I posed last winter on another forum. One guy that had done his concrete floor sought out advice from a contractor that laid gym floors for schools etc. His advice was to cut the dry PT 2X4's into 3' or shorter lengths and lay them down on the plastic sheets without anchoring them to the concrete in any way. He just said to stagger the 2X4 joints and screw the 3/4" subfloor to this "floating" sleeper system. As to the nailing or screwing issue, I would think that some construction adhesive and the nails would be good enough.

 

[steviegwood]

Just a thought but wouldn't you get some movement if you do not attach to the concrete floor in some manner? If you get movement over time I would think that nails may work loose and possibly try to work their way up into the finished flooring and cracking it and also creating a squeaky floor. Just a thought, I could be dead wrong but a thought all the same. Steve :gar-La;

 

[Dean Maiorano]

All this mention of termites, any consideration in using a borate compound as an additional insect control method? Using the ACQ and NOT using polystyrene are a must. However, you might want to supplement the pest control by doing some research on borax/boric acid/borate applications, I've seen/heard of it used in historic and residential applications. It's not meant to replace the exterminator or common sense, just augment them.