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12" width batt insulation

5K views 38 replies 16 participants last post by  eat.sleep.wheel 
#1 ·
My shop was built with a 4/12 pitch and the architect specified the 2x6 rafters be 12" on center due to the high collar tie. Blown in insulation is impractical and spray foam is cost prohibitive.

I have been looking, but can't find anyone that sells a batt or roll insulation that will fit the 11" spacing. Sure, I can get 23" wide and cut it in half, but I'd rather not if 11" wide is readily available and affordable.

Anyone know who makes or sells such and animal in the contiguous USA?
 
#6 ·
Um, not pertinent, but I have baffles plus soffit/ridge vents.

blow in cellulose and be done with it
smh.

I got 24" OC roxul to fill my 12" OC spaced stud wall. (Yes, cutting every batt.) I may even cut the other way for smaller chunks because I have considerable obstacles and mess to work around. :homer:
I've thought of this as well. I can easily weld up a rig to squash the insulation enough to make it easy to cut.

Got this idea the other day for an attached lean-to-shed area I have to enclose.... how about foam board screwed over the rafters? It would preserve the roof venting, and you can seal the seams with tape or spray foam.
It would have to be too thick to provide the R value I need/want. I'd lose 4" of headroom.

I considered foam board, for about a minute. It's at least 3 times more expensive for the same R value. Which is the same reason I discounted spray foam.

Oh well, I guess I'm going to just have to cut some 24" or 23" batts/rools in half. No big deal. Was hoping to avoid that.
 
#4 ·
I got 24" OC roxul to fill my 12" OC spaced stud wall. (Yes, cutting every batt.) I may even cut the other way for smaller chunks because I have considerable obstacles and mess to work around. :homer:

Got this idea the other day for an attached lean-to-shed area I have to enclose.... how about foam board screwed over the rafters? It would preserve the roof venting, and you can seal the seams with tape or spray foam.
 
#7 ·
Job site we’re working now... the guy has a wet crawl space and can’t get the floors to dry out for hardwood install... he’s basically forced to use the spray foam!!!! It’s 3 x the cost of normal fiberglass insulation!!!! But anyone who’s been in a crawl space with years old fiberglass insulation knows how fkd that shut can be!!!! Falling down from rodents using it as housing.... then it gets wet... not fun to clean out!!!! I wonder if rodents like the spray foam for residency?????


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#12 · (Edited)
I don't disagree. I already had someone look at this. Blown in CAN be done, it's just not worth the hassle of trying to get it into all the tight spots.



There's only about 6 inches between the collar tie and the ridge beam. The rafters are about 4 feet to the top of the wall. Beyond the wall is a 2' overhang/soffit.

I'd have to modify that gap to accept the vent baffle, and to ensure that it's not going to let the blown in stuff past. That insulation that's stuffed in there is just there to keep the heat from a propane heater while the concrete floor was curing.

Just too much going on there to make it worthwhile, since I wouldn't get any additional R value.

Spray foam could give me a LOT more R value, but at a huge increase in cost. It's a hobby shop, I don't need it to be a sauna. LOL.

I have had contractors come over and look it over. As I already said, blown in is not practical. Spray foam would be great, just too expensive.

Time vs return...
Cost vs labor...
Or
Time is money.
Your call.
Get it done.
A well known tip for cutting glass batts..
Get a 12+ " serated kitchen knife, place 2x4 across batt where you want to cut and press down on 2x saw along the edge paper up!
My labor is free. Unless I hire someone else. Time is something of which I have plenty.

I'll be cutting batts unless someone wants to make a sizable donation to the spray foam effort. ;)
 
#11 · (Edited)
I considered foam board, for about a minute. It's at least 3 times more expensive for the same R value. Which is the same reason I discounted spray foam.

Oh well, I guess I'm going to just have to cut some 24" or 23" batts/rools in half. No big deal. Was hoping to avoid that.[/QUOTE]

Time vs return...
Cost vs labor...
Or
Time is money.
Your call.
Get it done.
A well known tip for cutting glass batts..
Get a 12+ " serated kitchen knife, place 2x4 across batt where you want to cut and press down on 2x saw along the edge paper up!
 
#22 ·
Matches the house and garage. Since the shop roof ties into the garage, the pitch needed to match (ish).

What are you being quoted for spray foam?

Worst case, you just do the bats cut in half.


You do need some sort of venting though.
$1880 was the quote I got last year. But I don't recall the R value for that. If it was full thickness, I may have to go back and ask the contractor. But I doubt it. Not for 600 square feet of roof.

I plan on cutting batts in half. It's not that big of a deal, figured I would ask.

Soffit vents and ridge vent are already in place. Baffles will go under the sheathing before the insulation is placed.

How old is this roof system?

You should have just bought scissor trusses. 2' on center, and enough room for venting
A year. Scissor trusses were not practical. This is attached to the back of an existing garage with the same pitch roof. Plus the 2 foot overhang. I would have had to order trusses that exactly matched all of that, and quite frankly, I wasn't going to bother. It was cheaper to buy 2x6's and build it.

Are you due for new shingles?

If so, then strip old shingles, lay rigid on top of old sheathing, add another layer of sheathing screwed through to the rafters and re-shingle.

It's called a hot roof and doesn't requite venting.
Nope. Brand new addition.


----


Although I appreciate all the commentary on how I should have built my shop ;) - it has absolutely nothing to do with finding 12" wide batts. :laughing:

The shop was built to look like it had always been there. I still have a few details to finish the inside namely a few more circuits in the panel, lighting, insulation, plywood for the walls, and the ceiling - I'm leaning towards interior barn siding, 3' wide with 9" spaced ribs. I think it would look cool and would reflect a lot of light.

Some of you seem to be interested, so here it is from the outside:





 
#18 ·
Spray foam is going to be a PITA to deal with when its time to redo the roof and the OSB is shot.

4" thick batts between the 2x6's would leave a vent space. Add say 1.5"-2" foam board on the face of the angled area before interior sheathing
 
#20 ·
We had a whole building worth of 12" wide insulation a while back. Came out of a commercial building that was re-reroofed. They had money to waste so tore out all the insulation. Was all 4ft long for some reason.

I'd assume it was purchased like that, but maybe they had a couple laborers making it that size.
 
#21 ·
Are you due for new shingles?

If so, then strip old shingles, lay rigid on top of old sheathing, add another layer of sheathing screwed through to the rafters and re-shingle.

It's called a hot roof and doesn't requite venting.
 
#27 ·
It looks badass. It fits the house. Its built into the house. Its a sneaky way of having a cool little shop out back while keeping some curb appeal.

Not everybody is in a situation to have the giant 2600ft metal pirate abomination looming over the lower roof 1700ft home. :laughing:
 
#33 ·
Cut the 24s in half, it won't take that long.

setup a table with a stop, put the batt against the stop, use a carpenters knife, with the blade all the way out, drag it down, you'll have two batts ready to go.

Do the whole lot as an assembly line, I bet it takes less then an hour.
 
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