I am finally building my own personal home later this year. Portland Oregon, three story home 3200 sq feet with 3,400 sq feet of walls. House will have a WaterFurnace 7 Series ground source heat pump system for heating and cooling. I have performed a Manual J on the home and its a 27K BTU heat loss just being built to code.
I have looked at 1" of spray foam and then a batt for what they call a flash and batt option at about $1.50 per sq foot
I have also been told about wet/damp applied cellulose which I heard Portland likes for its moisture barrier and sound deadening as an added benefit which is about $1.40 per sq foot.

What are your thoughts on these options. I do not want standard insulation but am I missing any options and if this was your home what would you do?
I was also going to have the builder quote out 8" walls instead of 6" but was thinking 1-2" of rigid foam on the outside might be a better way to go?

Rigid foam on the exterior of 2x6 walls is definitely better than 2x8 walls from a thermal heat gain/loss standpoint. We've discussed this many times on here.

Do you plan on doing all of the work yourself, part of the work, or hiring all of it out?

IMO, 4 or 6" stud walls filled with sprayed cellulose and covered with 1.5" or more of rigid foam is very hard to beat.

It would be a good idea to caulk or otherwise seal each stud bay where it meets the sheathing, top, bottom, sides, and any penetrations before insulating. Then the wet sprayed cellulose is an excellent way to insulate the stud bays, with rigid foam on the outside to minimize thermal bridging. The wet sprayed cellulose helps reduce air infiltration, and buffers moisture. As Dana1 points out, the production of EPS or polyisocyanurate rigid foams have much lower global warming potential than XPS.

All the work will be hired out. While I own a heating company I know my speciality and why people hire me to do it so I will keep that same though process in my home. The city I am building in is VERY picky when it comes to code and there is no way I could build it myself, plus I just don't have time to take away from the company.
I did try searching for 2 hours last night but the serach feature kept giving me errors so I finally just posted even though I knew the topic must have been covered.
I do have to go with 6" studs but I like the rigid foam on the outside walls, I just didn't know if that was better than a thicker wall but it sounds like its not. Thanks for the info so far. I know a lot about HVAC and a decent amount about performance but hate that I am still fairly undeducated when getting to the nuts and bolts of insulating/windows etc for the home, I just know the basics.

When I asked about building it yourself or hiring it out, or doing part of the work yourself, I was trying to get a feel for air sealing. The spray foam provides a great air seal, but at a great cost as well (~$5000 in your example). If air sealing is something you would consider DIY, then for the cost of a couple of cases of canned spray foam and caulk, you could do this for less than one tenth the cost of your spray foam quote.

The search function on this site is all but non-functional. In the future, just use google to search this site. As an example, search google using the following in the search box: site: greenbuildingtalk.com exterior foam

I would put an air barrier on the inside (like taped, not stapled MemBrain) AND tape up the foam on the outside.

you could do this for less than one tenth the cost of your spray foam quote.

Over the course of my build, I would estimate that I spent at least three to four weeks of full-time work on sealing. It is substantially mindless, so 2 hours at a time is most comfortable, although I did spend 7 8-hr days in a row at one stretch. No matter how you value it, there is a cost for that time.

Also, unless you are full-time on the build you can't always be there when it "needs" to be done and I've noticed that tradesmen aren't too bothered bypassing opportunities like that.

Doing the spray foam is a much more effective way of getting a good air seal.

tradesmen aren't too bothered bypassing opportunities like that.

Maybe if you tell them that they get to rip it apart and redo it without pay if it doesn't pass a blower door test.

Oh, we did that, but here are the barriers;

1) Even if they agree whole-heartedly, self-motivation is hard to come by.
2) There is always the possibility it will pass even if you do nothing towards it.
3) You can "argue" about whether it passed or what is really causing the problem.
4) Good luck getting them to come back.
5) Good luck making them come back.
6) How long will that delay the build progress?

With all this talk of sealing I thought damp applied cellulose sealed the same as spray foam or am I missing something here?

Cellulose helps some but is much more air permeable.

Posted By Lee Dodge on 20 Apr 2013 10:12 AM
It would be a good idea to caulk or otherwise seal each stud bay where it meets the sheathing, top, bottom, sides, and any penetrations before insulating. Then the wet sprayed cellulose is an excellent way to insulate the stud bays, with rigid foam on the outside to minimize thermal bridging. The wet sprayed cellulose helps reduce air infiltration, and buffers moisture. As Dana1 points out, the production of EPS or polyisocyanurate rigid foams have much lower global warming potential than XPS.

Is there a prefered type of caulking for this?  Regular silicone okay; or does it have to be something like OSI Quad (poly) sealant?  Starting a garage/shop build in the not-to-distant future; and at this time am planning on wet-blown cellulose for the walls.

Posted By strawmyers on 22 Apr 2013 12:48 PM
Is there a prefered type of caulking for this?  Regular silicone okay; or does it have to be something like OSI Quad (poly) sealant?  Starting a garage/shop build in the not-to-distant future; and at this time am planning on wet-blown cellulose for the walls.

I am not a good person to answer this question. They use expanding foam for sealing penetrations. For caulking the stud boxes, you might try a search of this forum using Google with greenbuildingtalk.com caulk, etc., as it has been discussed previously.

Posted By Lee Dodge on 22 Apr 2013 02:21 PM

Posted By strawmyers on 22 Apr 2013 12:48 PM
Is there a prefered type of caulking for this?  Regular silicone okay; or does it have to be something like OSI Quad (poly) sealant?  Starting a garage/shop build in the not-to-distant future; and at this time am planning on wet-blown cellulose for the walls.

I am not a good person to answer this question. They use expanding foam for sealing penetrations. For caulking the stud boxes, you might try a search of this forum using Google with greenbuildingtalk.com caulk, etc., as it has been discussed previously.

Found different opinions in different threads.  One said acoustic sealant, one said construction adhesive, and another said mastic... so what I'm talking from that is that it probably doesn't matter what is used as long as it seals the opening.  I would think something that stays somewhat flexible over time would be best since the studs/sheathing will change size with temperature fluctuations.  These were about the two cheapest acoustic sealants I found (both 28/29oz tubes):

http://www.amazon.com/Insulation-SC-175-DRAFT-ACOUSTICAL-SOUND/dp/B0047ZYFMI/ref=sr_1_4?ie=UTF8&qid=1366726780&sr=8-4&keywords=acoustical+sealant

http://www.amazon.com/Franklin-International-Sealant-2892-Adhesive/dp/B00171JEC6/ref=sr_1_1?ie=UTF8&qid=1366726780&sr=8-1&keywords=acoustical+sealant

Whenever I have agreed to use "mastic', it has been pretty odious stuff. In my opinion, not something that should appear in green building and a definite no-no in areas exposed to the inside of a residence.
Construction adhesive cures pretty hard and while it might be a bit flexible in tight-fitting situations like subflooring, I can imagine how it might not be so good in a gap-filling situation.
My choice would be the acoustic sealant, primarily because it has been developed to seal gaps and stay flexible over time. I wish I had used that.
Instead, I used a lot of "Acrylic Latex Plus Silicone" on the theory that it is a bit more flexible than straight painter's caulk. Now, a year later, I can still inspect many of those joints after a season of curing and movement and it appears to be doing the job in all ways. I just don't know about 5 years and 10 years down the line.....

We use mastic on ductwork all the time that is water based and seals very well while being flexible on metal ductwork, I have not had odors come from it and have never tested for VOC levels before and after installation but have not had any issues. I have also only used mastic for sealing ductwork, i have never had my employees use it on a home before.
OK so I thought cellulose when damp applied sealed but as you all are saying it does not so I should still do as much sealing as possible as well as taped rigid foam on the outside and damp cellulose inside.
I will reiterate at this point that I do have a 155 CFM ECM HRV system that will be installed in the home for fresh air exchange.

Dense packed cellulose seals a lot better than simply damp-sprayed, and it's pretty good. Damp sprayed is literally spraying the slightly damp adhesive-loaded goods against the wall and seeing what sticks, then scrubbing/scraping the excess flush with the studs. There is nothing forcing the fiber into seams/cracks/holes, and while it's very air-retardent compared to other fiber insulation, it's still air-permeable.

By contrast dense packing is done by inserting a hose into the cavity (or behind netting) and blowing at high pressure until the blower stalls, backing it out a few inches to get it flowing again, wait for it to stall, repeat. When installing blown fiber this way it forces fiber into every exfiltration path, crack & seam under signficant pressure (orders of magnitude more pressure than any wind loading would achieve even during a hurricant)- like stuffing micro-corks into micro bottle necks to plug the air leaks.

Open cell foam seals stud bays somewhat better than dense-packed cellulose when properly applied, but it's somewhat academic. In measured test assemblies it seals better than closed cell foam, probably due to the much higher expansion ratio forcing it into the same cracks/paths that would be plugged only slightly-less effectively using dense-packed cellulose.

But air sealing a wall is more than sealing the wall cavity. The seams between doubled-up top plates, between the bottom plate & subfloor, etc all add up to a lot larger hole than most people would believe before seeing a blower door test with theatrical smoke for indentifying the leak paths. Acoustic sealant caulk is the gold-standard for sealing those leaks as you go, but there is some benefit to using construction adhesive instead (particularly on the sheathing/stud interfaces) in hurricane prone areas.

Acoustic sealant in the fatter cartridges and a powered caulking gun makes hitting every stud-cavity seam pretty quick & easy, and shouldn't be a big cost-adder for the contractor. If they're doing it with the simpler manual caulking guns it's literally 2-3x the labor, (and the guys doing it will hate it, which is always great for getting the job done to near perfection.) If you go that route there's no reason a "stand back and blast it" damp spray approach can't be as tight as open cell foam. Knauf and Owens Corning both have their special-goo for doing this, but acoustic sealant has a good track record in this type of app. (Air sealing isn't rocket science- it's goop science.)

What others said about 2x8 vs. 2x6 + foam. Typical framing fractions come in around 25% of the total area, and putting 2" of foam over the 2x6 raises the R-value of that 25% from about R6 (assuming doug-fir framing + half-inch sheathing) to over R14, whereas going with deeper studs the R of the framing fraction only increases to R7.5-ish. The net effect on whole-wall R is only about R4 with the deeper 2x8 studs, but a minimum of R8 (if EPS) or as much as R13 (if polyiso) if going with 2x6 + 2" foam. Would you prefer R19 whole-wall performance (2x8), or would you prefer R27 (2x6 + 2" iso), at a comparable wall thickness?

If R20+ whole-wall is good enough, you can hit that performance point with 2x4 16" o.c. framing and 2" of exterior iso.

Thank you Dana, that is exactly the answer I was looking for! I guess my next question is, should I look into ICF or are my floor plans not conducive being a 3 story home?

Air sealing isn't rocket science- it's goop science

I'd like to see more comments/data on taped films/foams (no staples) vs caulks.