Thin Space to Insulate

[Bull]

I have one exterior wall in a bathroom that I need to insulate. Sadly, it was framed out with narrow lumber back in the 1930s, and I have about 2.5 to maybe 2.75" inches of depth for insulation.

The local stores don't seem to carry anything lower than R-13 for 2x4 walls. I know I will lose some effectiveness by squishing the insulation, but will it be enough to matter? Or, should I go through the trouble to find R-11?

 

[Striker]

Your situation would be perfect for closed cell insulation. However, it might be tough finding someone to setup to spray just one wall unless it was really long. I'd call around and find someone reputable. A lot of contractors are hurting for money right now. Good luck!

 

[sstruckguy]

Since there is a 1/2 inch staple edge on paper backed insulation, the only real squishing is 1/4 to 3/4 of an inch.

Personally, I would rather have the slightly squished R-13, rather than a poofy R-11

 

[Torque1st]

Just use some styrofoam or XPS insulation and use a can of foam to seal the edges. Various thicknesses are available. If I remember right the XPS is about R-6 per inch but check that figure yourself.

 

[Busted_Knuckles]

Fiberglass insulation works on the principle that the air that is in between the fibers is your insulator, to smash the bats, would be to reduce its qualities. Also keep in mind, if the wall is drafty, fiberglass does little to prevent movement of air, and your R-value can drop to ZERO. Also if it gets damp/wet, zero. Thats where you vapor barrier comes in. Bull, I think from a previous conversation we had, I'm under the impression that your home is older ? That's usually a problem with older homes, they breathe to easy.

If you really want to pack some punch, you can put isocyanurate rigid board in there, you would need to rip the sheet down to your stud bay width, and you could spray foam the edges for a sealed cavity. I cant recall the R-Value of the board, but I think its around 13 for a 2" sheet, but is expensive. Anyhow, the nice part is, when your done, you dont have air blowing through. What most guys dont understand about insulation is the air pressure factor, a house always has negative or positive air pressure, even when the wind is not blowing, because of heating and cooling, air is always on the move trying to go somewhere. When R-Values are figured, its for static air, so some materials do very well with air penetration, some are extremely poor, FWIW....

 

[Busted_Knuckles]

Just use some styrofoam or XPS insulation and use a can of foam to seal the edges. Various thicknesses are available. If I remember right the XPS is about R-6 per inch but check that figure yourself.

Hey, great timing, we dispensed the same advice, and you beat me to it. I like your signature, and I read the book "How to make friends and influence people" apparently not much of it took....!

 

[walrus]

I have one exterior wall in a bathroom that I need to insulate. Sadly, it was framed out with narrow lumber back in the 1930s, and I have about 2.5 to maybe 2.75" inches of depth for insulation.

The local stores don't seem to carry anything lower than R-13 for 2x4 walls. I know I will lose some effectiveness by squishing the insulation, but will it be enough to matter? Or, should I go through the trouble to find R-11?

Cut and fit urethane foam, foam and/or caulk the cracks.

 

[Cryptic1911]

have a company do that blown in insulation in there.. i think its like ~R7 per inch?

 

[metal1313]

how many square feet? there are do it yourself spray foam kits, they are not cheap though, last i saw they were several hundred. i would prob just do ridgid foam and spray cans to seal it, a 4x8 sheet is maybe 15, so its more than batts but less than spray foam

 

[Daniel Dudley]

Your situation would be perfect for closed cell insulation. However, it might be tough finding someone to setup to spray just one wall unless it was really long. I'd call around and find someone reputable. A lot of contractors are hurting for money right now. Good luck!

Spray foam kits are available. Tiger Foam is one brand.

 

[Stuart in MN]

I agree that rigid foam board is the way to go, if the wall cavity can't be made larger, but have you looked at furring out the wall to get a larger cavity for the insulation? I'm guessing there's a window in the wall which will make it more difficult, but it can still be done - you have to widen the window jambs to match up with the thicker wall.

 

[rsanter]

use rigid foam

bob

 

[drmoonshine]

You could try the spray insulation.

 

[ixlr8]

The cost no object best way to insulate that space would be to use spray in closed cell foam, R7/inch. But if it is just one wall of a small bathroom, it would be cost prohibitive to have a pro come in and do it. Any that I have spoken with want several hundred dollars just to show up and setup, then it is so much per board-foot/inch. Depending on the size of the wall, DIY spray kits would be the next best... but still on the expensive side. From a cost/performance perspective... as others have suggested, get some 1" isocyanurate rigid board, it is almost R7/inch, cut it to fit and seal it in with minimal expanding foam in a can. Put in two layers, you now have R14, you can get to R17/19 if you want to add another 1/2" or 3/4" board as well. I believe XPS foam is only about R3/inch.