I hope it's not taboo to talk prices in this forum, but I wondering if my insulation plan might have a bogus ROI.

My house is in a cold climate, two story with (hopefully) finished attic.

I've been looking at going with an unvented attic for some time, but know I don't even know if that is the way to go. Not sure what the benefits would be in my particular situation. I've received a quote to dense pack the entire house, including the cathedral attic for $5K. The company claims r-21 in the walls, and R-40 in the rafters.

I originally wanted to do a flash/batt with closed cell foam, but the cheapest price I'm getting on that is $12K, over twice as much.

I obviously want to do some air sealing. I'm wondering if maybe I could get a 600BF kit of ccSPF for $500 and do this myself.

As for the rafters, I'm not sure how that works without any foam, just dense packing. Should I then avoid doing an unvented, and install some rafter chutes?

Something tells me that paying 6K more a few inches of foam on the rafters and one inch in the walls would be a terrible return on investment.

Economics wise, there is a lot to be said for building similar to the way that the majority of other houses in your area are being built. The collective wisdom, experience and economic sense of other builders tends to be pretty good.

If you feel it , go for it and do it yourself .Its worth a try.
Good luck

Please share any info you find out. I'm in a similar boat and have many of the same questions. For going from straight batts to CC foam is about 4x the $

I have a boatload of quotes. At the end of the day, the dense pack cellulose is about 1/2 the price of doing a flash/batt or flash/dense pack. The problem with the ccSPF is the quote you get only gets you 1/2 of the way there. Doing the house with only ccSPF is about 3-4X the dense pack. So I'm asking myself what I'm gaining by essentially adding a bit of ccSPF to my assembly. Yes, the R per inch is better. You get better air sealing. You get a tighter structure. I'm not sure this is worth 6 grand. I can't imagine the ROI on that is less than 20 years.

Common around here is fiberglass bats + house wrap for the walls. 1" or 2" of rigid foam and/or cellulose are often used. Spray foam is rare. Unvented attics are rare.

Yeah, I have anywhere from .5" to .75" to 1" of foam on the outside..... (dont ask)

Posted By beckkl on 09 Jul 2010 11:37 AM
Yeah, I have anywhere from .5" to .75" to 1" of foam on the outside..... (dont ask)

Just my opinion, but I think that if you're using the foam board on the exterior, the dense pack should be fine.  Once the foam board seams are all taped, that will provide pretty significant, if not complete, air sealing.  I would go as thick on the foam board as you can - in addition to air sealing, it reduces/eliminates the thermal bridging issues.  What you're describing is pretty similar to what we just did.  With an inch of rigid foam, you end up close to R30 in your walls.

You can always add a/another layer of housewrap if you want to get tighter. It doesn't have to go on the outside.
PE (plastic) also can go on the inside, but that depends on code and your opinions about vapor barriers.

Any price, heat loss simulations or payback calculations you do would be valuable to hear about.

The difference in the cost leads me to wonder if the dense pack quote is insulation only with no air sealing. The spray foam is not inexpensive, but the batts are, so I would expect less of a difference. Is the cellulose contractor sealing the rafter bays at the top plate? If you are not venting the rafters they need to be blocked with cardboard or something solid and foam-sealed.Yes, you can do it yourself if you know what you are doing & know what & where needs to be sealed, but I suspect you may need more than one "kit". Once the house is air sealed the dense pack insulation should work fine, but if they are selling cellulose without airsealing I would be suspect. The sill/rim joist area also need to be foamed.