Styrofoam construction question

- P
- Paul Ciszek
  
  Contact options for registered users
posted
16 years ago

Mon, Jul 2, 2007 5:29 PM

Has anyone here worked with styrofoam, cutting and glueing it? I have an object about 8"x8"x4" that I want to surround on all but one side with a foot or more of styrofoam. i.e., I want to embed it in a huge slab of styrofoam with one flush surface exposed.

I can buy the stuff in blocks up to 4'x8'x41" as needed. So, one approach could be to cut a 4'x4'x2' solid block, and try to dig a hole

8"x8"x4" in one side. I would want this depression to be pretty close to right-angled, flat-bottomed, etc. I don't know how difficult that would be.

Another approach would be to cut the aforementioned block in half, cut a 4"x4"x8" notch in each half with a "hot knife", and stick them back together with this stuff that acts like caulk for styrofoam. That would create the same shape as digging a hole in one side, but with a seam running down the middle of the entire block. I would want to make sure I had blocked any possible path for heat leakage as I stuck the two halves back together.

I am also looking for a good insulating fluff or "batting" to cram around the edges of the object. Fiberglass is prefered in buildings because it is fireproof, rot-proof, etc., but it is not the most insulating fluff out there. What would be good for packing the cracks in my styrofoam structure?

Is there a newsgroup that would be more on-topic for styrofoam?

- P
- Phil Hobbs
  
  Contact options for registered users
Vote on answer
posted
16 years ago

Sat, Jul 21, 2007 1:07 AM

This reply is of course almost three weeks late, but oh well.

Good styrofoam (the kind that squeaks when you rub it hard with your finger) has almost the same thermal conductivity as air, about 0.026 W/m/K at room temperature. (There's a good reason for that, of course.)

The seam you're talking about is made from some sort of plastic goop, which (assuming it doesn't dissolve polystyrene) will result in a very thin bond line whose thermal conductivity will be around 0.1 W/m/K in rough figures. (Glasses are around 1 W/m/K.)

The thermal conductivity of the glue will be something like four times higher than that of the same area of styrofoam, but that area will be probably 1 part in 10**5 of the whole--you won't even notice a difference. I'd definitely go with the cutting solution.

Cheers,

Phil Hobbs

- M
- mr_wizard2
  
  Contact options for registered users
Vote on answer
posted
16 years ago

Wed, Jul 25, 2007 8:03 PM

I'm not sure how insulating it is, but there is a product out there marketed under the name "Great Stuff" it's a yellow foam which expands by several hundred %. Depends on how insulating you need, and what kind of volume you're talking about. My thought here is that you out the item in the bottom of a container ~ 1ft. larger than the object you want to surround with the exposed side down, and then add the foam until it has filled the container. This should eliminate the need for "stuffing" material.