My Latest Project - Walk-in Cooler - Page 3

**Ize** · 07-26-2006, 06:20 AM

John,

That's freaking AMAZING.

I have a totally raw 30+ year old garage and you have given me a crapload of ideas for sealing that sucker AND making it brew friendly. Keep posting, I can't wait to see how it shakes out...

Ize

Todd · 07-26-2006, 03:16 PM

does that insulation maintain its R30 rating when placed in a 2x4 wall? Just curious, I thought it needed a certain amount of expansion room.

**the_bird** · 07-26-2006, 03:25 PM

Yeah, if you compressed that insulation, you lose a LOT of the insulating value. Your R30 is probably half that, at most, if you compressed that into a 2x4 wall. Stuff that thick is designed to either sit on TOP of rafters or go into 2x10 framing between rafters. Remember, it's the air pockets within the fibers that provide the insulation, NOT the fibers themselves.

**John Beere** · 07-26-2006, 03:53 PM

Live and learn... I just figured the heavier, the better - but your point makes sense about the air space. I noticed last night that the framing isn't all that square - maybe I'll leave a small amount (inch or so) of deadspace behind the foam board to both square the area up and allow the insulation to better expand.

I'll do the math here in a bit, but even if I lose 1/2 of the insulation power of the R30 - with all the other insulation I think I'm still only around 1,000~ 1,500 BTU heat loss per hour maximum.

Todd · 07-26-2006, 03:59 PM

Quote:

Originally Posted by John Beere

Live and learn... I just figured the heavier, the better - but your point makes sense about the air space. I noticed last night that the framing isn't all that square - maybe I'll leave a small amount (inch or so) of deadspace behind the foam board to both square the area up and allow the insulation to better expand.

I'll do the math here in a bit, but even if I lose 1/2 of the insulation power of the R30 - with all the other insulation I think I'm still only around 1,000~ 1,500 BTU heat loss per hour maximum.

I don't know how much it might help but you could always at a 2x2 on the framing to give a bit more room for expansion.

Like you said you're still going to have good insulation.

**the_bird** · 07-26-2006, 04:03 PM

I made the same mistake when I insulated my attic, although not to the same extent. The floor framing is 2x4, I bought insulation that was 6 inches think and compressed it (slightly) into place. Learned after the fact that my effective R value is the same as if I had just installed the (cheaper) insulation designed for the 2x4 space.

What I'm concerned about, though, is that you may have compressed it SO much that you've lost even more insulating value (I'm guessing about the 50%). Do some googling, talk to someone at the home center, if your effective insulating value is now less than what you would get with the right sized insulation, you may be better off ripping it out and replacing it with the right stuff (you might be able to re-use this stuff in your attic or something). But, get a good answer to that question, what IS the effective R value of 10 inch insulation compressed into a 4 inch space, comp that to what you would get with the right insulation, before you go any further.

**the_bird** · 07-26-2006, 04:04 PM

Todd has a good idea as well. That's a damn good idea. You'd want to take the insulation out and re-install it after adding the 2x2, and you might think about peeling off an inch or two from the bottom so it doesn't compress so much when you re-install it.

**John Beere** · 07-26-2006, 04:09 PM

Quote:

Originally Posted by Todd

I don't know how much it might help but you could always at a 2x2 on the framing to give a bit more room for expansion.

Like you said you're still going to have good insulation.

I was just thinking thinking about that... at least on the two exterior walls.

Here is the heat loss formula from: http://franklinbrew.org/members/sj/walkin.html

"First I calculated the peak heat loss using the following formula:
Heat Loss(BTU/Hr) = surface area X ΔTR Value and came up with less than 1000 BTU / hr with a 4' X 8' X 6' size, R10 insulation value, and 40°F temperature differential. The result is that even the smallest AC unit should be more than enough for this size unit."

This guy only had an overall R-value of R10 and still only needed 1000 BTU's to create a 40 degree differential. I'm guessing I need up to a 70 degree differential maximum but already have way more than an R10 value. Should be adding another R15 or so with the two layers of foam board.

**John Beere** · 07-26-2006, 04:12 PM

Quote:

Originally Posted by the_bird

Todd has a good idea as well. That's a damn good idea. You'd want to take the insulation out and re-install it after adding the 2x2, and you might think about peeling off an inch or two from the bottom so it doesn't compress so much when you re-install it.

Yeah, that seals the deal... I'll add at least another two inches to the studs on the exterior walls. I'll see about peeling a little insulation off the back of the insulation as well. For the interior walls, which I haven't done yet, I'll just peel some of the insulation away before installing.

Thank you guys for the input... keep it coming!

**the_bird** · 07-26-2006, 04:13 PM

What are the interior walls going to be covered in? I'm a little concerned about condensation, although I can never get straight in my head where you should have the vapor barrier. How are you handling the moisture issue?