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Originally Posted by menaus2
Hi AC,
Quick questions about your wall insulation technique of sealing rigid foam boards into walls. How much of a cost saving over 100% spay foam do you figure? Anything you learned from doing it? Would you do anything differently, or even use a different insulation approach?
Thanks,
menaus
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Well, all good questions.
You can do the materials cost comparison pretty easily, so I'll leave that one to you. But I suspect that the cost of the two methods is close, with spray foam having the higher materials cost. I'd be very interested in what you might come up with.
Regarding labor, the way I have done it is very, very labor intensive. In fact, my son has been out of work for a very long time, and my insulation project was also a way to give him some work and money. I sort of looked at it as an in-family WPA project, where projects were undertaken less to save money, but more to give people jobs.
You'd be out of your mind to just hire somebody do do this for you... So figuring labor into the two methods, spray on would come out ahead.
But you need to remember that I did put in 6" of sealed foam. I don't think there are many 6" sprayed foam walls out there.
I started out with EPS foam (the white stuff) but I have come to realize that XPS (PINK FOAM) has a higher R-value, almost the same cost (last time I checked), and does not shrink. Foaming all the edges 100% is very important. If you don't you're wasting your time and money.
Then there's this... my cash flow is pretty limited, and with my method I could do it in small increments, and as I had more money available, I could continue a little further.
The insulation has made a tremendous difference, in terms of heat retention and infiltration reduction. In fact, if you do this method or the spray on, you need to know that a heat recovery ventilator will be in your future, both for fresh air and also for humidity control. That reality really snuck right up on me, I wasn't expecting it.
Another big surprise, is that in early spring, the insulation is so effective, that my house doesn't warm up early like it used to. But I wouldn't say that it is burdensome... On the other hand, I don't turn on the heat as early in the year as winter approaches, either.
Quite often, in the summertime, people ask me if I'm running the air conditioner!
So one important thing, not immediately obvious, is that neither my method, nor spray-on foam have any appreciable humidity buffering ability. I'm looking for an HRV to help with that. I do know that dense-packed cellulose walls do have a substantial humidity buffering ability, and will take up excess humidity, and release humidity, if the inside air becomes too dry.
There was a slightly different approach that I learned about after I started the layered rigid insulation project... and that was to put in an initial sprayed foam layer of 1" to 2", depending on your location, and then dense-pack the remaining cavity. This would give near perfect wall sealing, and also give you the humidity buffering of cellulose. You would end up with a less expensive wall (with somewhat less R-value) and you would have the humidity buffer of cellulose. Sounds pretty good to me, and it would go up much faster.
But I have to say that I am amazed at the big difference this has made. I'm heating my living room, and I'm not currently heating my kitchen. In fact, I have an insulating door to keep the heat in the living room. But the interior walls in the house are imperfect, and some heat does leak into the kitchen. Most of the time it's not so bad, but there are other times when the thermometer really dips. I have found that when that happens, if I turn the kitchen oven to 'warm' the kitchen gets pretty comfortable.
There's also the angle of carbon foot print and environmental damage. Cellulose wins.
So, my whole house is an experiment in progress. And that's the result so far.
Hope this helps...
Best,
-AC