Where does one find this recycled polyiso? I don't think I've ever seen anything but normal polyiso.

Good question. There are insulation recycling places all over. I know of two within 100 Mi. of me but that doesn't really help you. I'm sure one of the places here could ship to you for about $500 but unless you were getting a lot it probably wouldn't be cost effective. You can often find smaller insulation recyclers on craigslist. Just search for "insulation". If you get a price break on larger orders and you have storage space it might be advisable to get as much of the stuff as you'll ever need. I'm thinking about the portions of your upstairs walls which don't meet the attic but the roof. How are you going to get those areas to R 60?

Take my basement project as an example. All the polyiso was recycled. I got the boards for about $13 a sheet for 2.25" instead of something like $37 for 2". Shipping was a couple hundred and is calculated into the total cost per sheet. I think I also got a 5% discount due to the large volume.

An other option is EPS. It is still a petrochemical but it's a lot cheaper, is much more vapor permeable, is still an air barrier and it made all over the place. And you can order it in any dimensions you want.

Me personally, I wouldn't use foam boards at all. I'd spot caulk/foam the sheathing and just dense pack. But I'm not going to do that in my house because I don't want to loose 8" at every wall so I'm going to dense pack the existing cavities after pulling the fiberglass out and then take a REMOTE like approach to outsulating.

Outsulating may be in the future, but not the near future. Especially not if this works well. :)

I'll definitely have to weigh the differences between spray foaming the cavity with a DIY kit and doing foam board. I think both are good options for sealing though.

Here is a bit more info on the office. I will get pics up yet! But, here is the layout of my house. As you can see, only one wall of the office is an exterior wall. The room isn't tiny at about 14.5' x 14'. But, this should be a relatively easy/small project to test out how I want to do all the walls upstairs.

http://ecorenovator.org/forum/attach...1&d=1312904917


The angled upstairs ceilings will definitely need some good insulation, much better than what is there now. I haven't even really thought about how I'd do those yet.

After doing a little research and pricing I think I'm leaning toward using rigid foam and great stuff. There is added work there to install it, but the price difference is pretty huge. A 200 board foot kit of spray foam would cost me $425 shipped. That would give me about 1.75" thick layer on the wall with an R value of just under 11. Alternatively, I can get 1" polyiso with an R value of 6.5 for $60 for the whole wall. Great stuff would be an additional $20 maybe? If I wanted to double up the polyiso I could easily do that and still be at half the cost of the spray foam.

As I've been fixing the basement in small pieces here and there I've used rigid and great stuff in the small cans. It lets me do it a couple of feet at a time if need be. end result may not be the best but it's a hell of a lot better then the nothing that I had before

This is the technique I have been using in my house.

At first I was cutting the foam to be a tight fit, very, very time consuming. Finally I realized that if I left about .25" all around and used Great Stuff to fill these gaps, it was both faster and more effective. Care must be taken to keep the great stuff from getting behind the foam panels, as it will push the panels forward.

-AC_Hacker

So you found a source of recycled polysio? I personally recommend polyiso for this application which is not foil faced. The foil make a complete vapor barrier which you don't need. You want the wall to be able to dry to both the outside and inside if possible. One of the great benefits of the recycled stuff is it's faced with fiberglass and paper so it is still mildly vapor permeable. And it's worlds cheaper.

I checked out craigslist and wasn't able to find anything unfortunately.

However, I was thinking about moving the polyiso layer to the inside of the wall. With a thin layer of furring strips on the outside I could utilize the foil facing as a radiant barrier in addition to the excellent conduction barrier the thicker wall will be. Since the wall's r value will be so high to begin with, do you guys think that there is any benefit to doing this?

Can you get Polyiso which isn't foil faced? I'm all for not demanding that moisture stay in one place because you can end up with problems if there is too much of it. Talk to some local green builders to see if they can point you to recycled foam boards. Call all of 'em if you have to. This is going on all over the country.

About your idea, if you later decide to outsulate you might be in a bit of a pickle. It's not advisable to have two vapor barriers in a wall. The moisture that inevitably gets trapped in there has no avenue of escape and you get rot and mold. Personally I think it's nuts that people sandwich OSB/CDX sheathing between spray foam and foil faced polyiso but there haven't been any disasters yet that I've heard of. Maybe in 30 years we'll see the truth. But none the less, putting fiber glass or cellulose between them is a no no. Also it's best to have your air barrier (polyiso and 1 part foam sealant) on the outside to minimize unconditioned air entering the cavity and convecting. All your insulation is next to useless if you have cold air cycling through there. The big advantage of the foil on polyiso sheets is that you can quite easily seal them together with foil duct work tape. Otherwise you need to seal boards together with spray foam. Some people say you can use tyvek tape but in my experience that stuff doesn't last more than a decade.

Oh, one more thought. You could put the foam boards on the inside if you air sealed the sheathing properly. This is effectively no different than putting it on the outside of the sheathing as far as moisture is concerned. You just completely eliminate the wall's ability to dry to the inside. Just don't make a vapor barrier sandwich and make sure that outside air doesn't get in. That's why I originally recomended the boards and 1 part foam. It's a relatively cheap (compared to filling the whole wall with spray foam or even filling it 1" deep) way of creating a fantastic air barrier. You kill two birds with one stone there. Oh and if you do try to dense pack the wall yourself you will have no way of knowing if you did it right. At first dense packing can be a little tricky. Even today I still am uncertain when dense packing a cavity I can't test. Well, at least I can't test it until the cold weather hits and the thermal camera shows me what a stupid job I did. :P

And your price on the spray foam looks berserk. I think that's about what I paid for the 600' kit. I think even on the Tiger Foam page they list it at $250 for the 200'' kit.

my used polyiso has some sort of paper backing that looks a lot like tar paper. I've never seen anything other then this but polyiso isn't the most common up here.