r49 insulation batts in walls ?

[carsdwl11]

I have the opportunity to purchase enough r49 batts needed to insulate my shop at a deeply discounted rate (70% off) . Anyone ever put it in the walls ?
I have about 9-10 inches of wall cavity and it shows the insulation is 13" thick . I think I can squeeze it in with a little work.

Any downside or reason not to do this ?

Thanks !

 

[PCustoms]

Well compressed insulation isn't as effective. Not sure how much difference the 3" will make.

 

[carsdwl11]

I had thought about trying to split each batt into 6.5 thick sections so that it would not only be as thick but also go farther . Im not real sure if that is a valid option as I have not tried it .

 

[mike93lx]

Don't compress fiberglas insulation.

I don't think 70% off would be enough for me to justify slicing up that much insulation. Sounds like a nightmare

 

[shelteredV]

Do not stuff the insulation into a smaller cavity, nothing good can become of it. Fluffy, not stuffy is the rule.

 

[PCustoms]

Op, how does the price compare to the proper insulation?

Here's an Owens corning chart to give you an idea what it would be at with 3" compression. Doesn't list r 49 but you can take some guesses.

Contrary to my first post of this is going to be 50% of buying the proper R30 it may be worth it. My guess is your going to get down to that anyways.

 

[carsdwl11]

the correct insulation is about 1k higher by my rough calculations.

 

[mike93lx]

the correct insulation is about 1k higher by my rough calculations.

Is that worth cutting up all of the r49? If so, go for it

 

[Crazyjake8493]

I wouldn't compress it. If you have to use that, you could always peel some of the fiberglass off the back to get to the right depth and prevent compressing, that would be a lot of extra work though.

If you really want R49 in the walls, you could always fur out the studs another 3 inches and install the R49 uncompressed.

 

[PCustoms]

Here you go


13"-9.5"=3.5"

3.5"/13"=0.269, or 27% compression

.27*0.5*49=R6.6 loss

R49-R6.6=R42.4

May be some rounding issues in what I posted, but bottom line you will still be over R40 in your walls, at $1k cheaper then buying the "right" R30 material. I say go for it.

 

[DC73]

I say go for it.

Agree. There's not really a problem with compressing the insulation except for a reduction in R-value and possible bulging of drywall. The reduction in r-value is minimal in my opinion. Even at worse case, you'll still get a higher r-value than the "correct" amount of insulation. At 1K of savings, it seems like a no-brainer.


DC

 

[The Cobbler]

3 or 4 inches of compression will be difficult when installing whatever on the walls .