Insulation

[cabinfever]

Hi all,

I've been searching previous posts and reading everything I can about insulation - this year heat, plumbing and insulation are the focus for my 16x28 in Vermont. (Walls at 2x6 and 2x12 for the cathedral ceiling.) What I thought I understood from previous posts was that high-density cellulose was only a little more expensive than fiberglass, but better from both an air-flow and insulation perspective. Foam is better still, but much more expensive.

In talking with high-density cellulose contractors, I've got a low bid of $4,300 and a high bid at $8,300. The high number includes foam board on the cathedral as well as the cellulose for R51 vs. R41. It's also a 'wet' application.

If I do it myself with Fiberglass - R19 in the walls and R38 in the cathedral - including covering the cathedral in R7.5 1.5" foam board, I'm looking at about $1,500, including caulk and tape to seal everything up.

Not even close. I'm going to get a better R value with the cellulose, but it still seems like a pretty hefty investment. I think I'm going with Fiberglass - anyone think that's a mistake?

[dug]

I think I'm going with Fiberglass - anyone think that's a mistake?

Can't really say but I did the fiberglass for the same reason ($$$$).  I'm not worried, but it doesn't get real cold here. 

[MountainDon]

From what I've seen and read wet blown in cellulose is really superior to fiberglass batts. If I was building a new main residence that is what I'd like to have in the walls. I'm not sure what I'd do if I was sitting there with the different price quotes though. That is a substantial difference. How long will it take to pay off? Taking time and doing a careful fiberglass installation, paying special attention to areas around pipes, wires, electrical boxes etc, will no doubt result in a better R-value than the typical low wage contractor job. The cellulose gets into all those difficult spaces much better.


Just for the record, I've read that fiberglass batts were invented because contractors wanted/needed a cheap way to insulate, one that did not require measuring densities and so on. Batts are stamped from the factory as to the R factor. Any simpleton can install batts and satisfy the technical requirement of having R19 or whatever in the wall. Whether or not a proper job was done is another matter. Unless the work is real shoddy almost any inspector will pass it with a cursory look at the batts rating. Any voids in those difficult areas degrade the insulations performance. The cellulose though requires experience in getting it dense packed properly to achieve the rating desired. So the price goes up; plus there's the machine. Then it has to dry down to the manufacturers required level before the installer can sihn off. More costs in travel, etc. None of the new energy efficient builds around here use fiberglass in the walls anymore it seems. At least none I've seen.

Another factor would be how much will the cabin be used? What's the climate? Will better insulation make much difference to either heating or cooling costs? Here we have both to contend with. 

[cabinfever]

Very true, Don. In my case the place is in SE Vermont - code generally is looking for R48 in a cathedral. It's not a primary residence - although it may be someday. If that time comes, however, it is likely to be expanded significantly.

My thought is that I can spend the time to seal the potential air leaks and make sure the fiberglass is installed properly. Sure I'd prefer to have the best insulation possible, but I'm paying cash for everything I do and money is tight. I haven't closed the door on the cellulose entirely, but my wife reminded me that even carefully installed fiberglass will be far better than what we have in our primary residence...

[klorinth]

I would recommend getting the batts, but first get a DIY spray foam system. Spray a thin layer between all the rafters. This will seal the whole thing and provide some insulation. Then you can put in the batts and have the best of both worlds.

The other option is to do the reverse. Best to check for which is better for condensation/humidity.

The spray foam systems are simply 20 lbs tanks of compressed foam that gets sprayed on then expands filling everything it touches. Ideally I would be sraying the entire place(walls, ceiling, and under the decking). This will seal the place against air leaks. Once you have it sealed you can then add batts or foam boards to whatever R rating you want. Of course you would then need to make sure that you have a good fresh air system for the cabin.

Around here a small set of tanks cost just over $600, big is $900. You would need to figure out how many you would need. A big set would most likely cover the whole ceiling with no problem. Remember, I'm only talking about an inch of foam here. It doesn't take much to seal everything.

[rwanders]

How much were you quoted for closed cell foam?  I had my 2x12 cathedral ceiling (24x24 with 12/12 pitch) which was 816 sq ft filled with 11 inches of closed cell for $3600 in Alaska. I did install R21 batts in my walls and under the floor to save a bunch on those areas. If closed cell is anywhere close to the cellulose, I would go with the foam for the ceiling.

[cabinfever]

rwanders - The only place I got a closed cell foam estimate was for the crawlspace (4' high, 16x28). For that, both estimates were approximately $1,500 for 2" of foam below grade and 3" above.

I agree that the cathedral is the place to spend the money if I'm going to - I've pretty much decided that I'm doing the walls myself. For that, the first estimate was to "Install 2" Thermax on 650 sq ft ceiling - air & vapor barrier. Dense pack 10" cavity with Cel-Pack Cellulose for final R-51" for $5,337. The second was just dense-pack for $1,500. I'll get a couple more estimates for this as the variation here is pretty extreme - it's hard to believe that foam board along accounts for almost $4,000.

klorinth - I've thought about it, but I hear its a real mess and then I'm in the cost of the foam and an air-to-air heat exchanger.

What I'm stuggling with here is something like, yeah, I could spend $1,000,000 for a Buggatti, or $300,000 for a Ferrarri, but will a $20,000 Hyundai essentially meet my needs? For most of human history, people had a horse or they walked...

[klorinth]

The mess isn't all that bad. The spray is a controlled one.
The ventilation issue does not need to be complicated. You are looking at a small cabin right? No need to have any active ventilation. You just need to place a couple well thought out vents. All that you need is to ensure that there is a constant flow of air into and out of the cabin.
If you are using a wood stove then you already have one vent out of the cabin. Ensure that there is another for air to come in and as long as the fire is going the air will be circulating. Just don't use an external fresh air supply for the stove.

[KWillets]

Have you considered diy blown-in cellulose?  You can fill the cavities after drywall is up; just leave a strip open.  I'm guessing at the dimensions, but it looks like about 2000 lbs. for the roof at 12" dense-packed, about $1000 retail.  The total won't be less than fiberglass, but you might get within your comfort range.

What is the foam for?  You could possibly fur out the ceiling and fill the gap with cellulose instead. 

The wikipedia page for cellulose (http://en.wikipedia.org/wiki/Cellulose_insulation) has pros and cons that have been verified by studies.