Finally Ready to insulate New Construction
Last Post 24 Aug 2014 01:22 PM by greentree. 25 Replies.
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Dana1User is Offline
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29 Jul 2014 05:38 PM
Installed at the right mix, the right temperature, and and in 2" lifts (maximum) per pass, closed cell polyurethane foam doesn't have shrinkage & cracking problems. But it's up to the installer to get it right.

There is no simple answer to whether something is "...BETTER against moisture...". Better than what, and in what stack-up? Like 2" XPS, closed cell foam at 2" is a class-II vapor retarder- the rim joist can dry through it, but moisture passes in either direction at only a very slow rate. Unlike cut'n'cobbled foam, there is very little risk of air moving between the foam & the band joist in the event that it isn't exactly perfectly air tight, since the foam is fairly continuously adhered to the joist. With board stock foam the flatness of the foam may be nearly perfect, but the rim joist may not be, and may warp over time. In this regard sprayed closed cell foam is superior to cut'n'cobbled XPS.
easyrider470User is Offline
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29 Jul 2014 08:33 PM
So assuming the average foam installer in southern indiana doesn't have the install down to a science.....that and the two i have talked too want to use open cell foam what are my best options.

I am a fan of the eco seal product and like what I have seen on the internet about the people that have used it. Haven't seen any real numbers from a blower door test comparison BUT i assume it's as effective if not more effective at getting things AIRTIGHT as the foam. I also like that the cellulose provides a better R-value per inch at a better price.

With my stack up.....2x6 wall, 1//2 inch sheathing, tyvek, 1 1/2 inch poly-iso rigid foam with taped seams and 3/4 furring for the vinyl siding, I think i am set up for success either way.
easyrider470User is Offline
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29 Jul 2014 08:34 PM
real question is......does closed cel perform better in the rim joist areas over open cell.....will there be a moisture problem with the stack up above in climate zone 4 marginal 5 in the 47460 area.
Bob IUser is Offline
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29 Jul 2014 10:04 PM
"what are my best options?"
now is the perfect time for a blower door test! If you have succeeded in building a tight house, you can use something other than foam without worrying, and save money. If the house is still somewhat leaky, look and see if they are in areas you can fix - which many will be - and tighten it up quickly. Make sure the person doing the test stays for a couple of hours + to asses the repairs, if necessary.


"does closed cel perform better in the rim joist areas over open cell"
Yes.
Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant
easyrider470User is Offline
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06 Aug 2014 12:38 PM
ok, so I have decided that the ecoseal product is to costly and labor consuming for me to take on so I am narrowing the decisions to the following options.

1" closed cell foam in the stud voids then complete fill with wet sprayed cellulose ( price would be 1.85 per sq ft)

or

Open cell spray foam 4" deep in the stud voids ( 1.35 per sq ft)


My concerns are in relation to what I hear about the closed cell flash and batt type system....I hear that there is some concern about the foam cracking or seperating from the structure when the house settles??? I have also heard that the 1" thickness is so inconsistant that there could be limited effectivness in terms of actual R value added if it's not super uniform spray...I am also concerned that the low R value of OPEN CELL in this area is really not a lot of R value for the dollor i am spending.

Can you shed some light on these two options? Thanks and keep in mind my wall stack up is 2x6 framing with 1/2 inch shething and tyvek. 1.5 inches of rigid polyiso foam (taped seams) on the exterior of the sheathing and vinyl siding

greentreeUser is Offline
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24 Aug 2014 01:22 PM
My method is to picture frame stud bays and dense pack, bibs exterior walls. Cellulose attic r50, right at the max of drywall capacity.
I wouldnt cut n cobble foam in the rims because of the air gap between foam and rim. I spray a light coat closed cell in the rims then come back with a filler. I spray closed cell out of 600 board ft tanks with tank and line warmers. In my climate, the foam is fairly finicky with larger temp differentials. Without the skim coat in colder temps we get more shrinkage towards the end of the spray as the tanks rapidly cool down. The foam will also cup off the rim as well leaving a gap just like cut n cobble.
I have found this same issue with the local spray rig guys. Looks normal from the outside but cut out a sample and the sins are exposed.
Our two pass method, which you really need to do to get the right depth anyways solves our earlier problems.
I don't see a problem with exterior plane air sealed bays with high density batts either, as long as exterior air isn't circulating in the bays your good.

As an experiment we've also sealed exterior plane, batted every standard size bay, dense packed odd sizes and foamed small bays and tight corners. Cold weather IR testing under pressure has indicated good performance with any of these methods.
Also..we seal every bay to bay electrical hole, easy to do and keeps any errors from spreading throughout the wall. Blower door numbers come out fantastic.
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