Posted By jonr on 05 Oct 2016 11:55 AM
I'd like to see more data on ACH50 values before and after a year or two of wind induced racking, moisture/temperature changes and age related shrinkage of foam (spray or rigid).

Various people report that tape and gaskets beat sealants and spot spray foams short term - my guess is that this is even more true long term.

What do you think racking, temp, moisture and shrinkage does to tape? Honesty foam, gaskets and tape in various spots would probably be the best strategy based on location, Gaskets are great but butt joints and corners can leak if your not careful.

Posted By rgonyer on 05 Oct 2016 01:40 PM
An additional question, although I feel like I should ask this in another thread but it seems related. I'd like to have a blower door test done before insulation, but how is that achieved? Drywall obviously won't be up yet, so there will be no effective ceiling at that point.

Youd need to poly the ceiling, youll be able to get to maybe 20 Pa which would be enough to use infrared to find leaks. As you go higher youll notice the poly start to pull off the ceiling. The poly doesnt need to be perfect and can leak, you're not necessarily looking for a cfm number as much as using hand or infrared to find leaks elsewhere.

Dana,
Pex staples fine into eps. Im in the middle of my personal home so I figured Id try it and it worked just as well as xps. I used 2" type ii eps for my underslab and stapled 1800' of pex down with no issues at all. It went down tight and stayed tight during the pour.

Posted By Dana1 on 05 Oct 2016 04:29 PM
Zip code 52726 is in US climate zone 5, which need R7.5 on the exterior of 2x6 framing for dew point control on fiber cavity insulation, or R5 for 2x4 framing. An IRC 2015 code min is 2x6/R20 or 2x4/R13 + R5 continuous insulation. To go better than code-min without much learning curve you could go with Huber ZIP-R (http://www.huberwood.com/assets/pdfs/ZIP-R-Sheathing-Installation-Guide.pdf ) using the 2" ( R9.6) or 2.5" (R12.6) versions of the product. It's more expensive than foam + sheathing + housewrap, but it doesn't take a crew of rocket scientists to assemble- it's about the same as installing 1/2" CDX, but it requires some attention to fastener spacing & specifications.

Dana1 thanks for the great info. My question is this- They way most are building homes in the quad city area today is typical 2x6, blown in cellulose, OSB, and housewrap. How does this not cause moisture problems if the minimum exterior insulation needs are R7.5 for 2x6? I was actually just looking at the base ZIP product in place of OSB with the tape primer sprayed on it. I can't find anyone around here interested in building a house using exterior foam or other non standard methods (Why do you want to do all that? Gas is so cheap) and we're to the point that we need to start. My marriage may depend on it, so we're trying to tighten it up as much as possible using conventional building methods if that makes sense. I've talked to countless contractors and I get the same story every time. I wouldn't be confident that any of them would do it properly. We were actually scheduled to start building in fall of 2015 when I stopped the train to research this stuff more. This board has been a wealth of knowledge, the issue is my location. If I had time to do all the work myself, it would be a different story because I could be sure it was being done properly.

Tape - short term solution? Yes, but not with the three tapes I recommended - they're a newer formulation, acrylic & very long lasting.

Blower door before insulation - how? You're right - it can be difficult if you have an open attic to be insulated. We install a SIGA fabric - Majpell (pronounced My-pell), then strap the ceiling, then do the test, then install interior partitions. You can also get the sheetrocker to hang the ceiling early - PRIOR to building interior walls - much quicker & easier for them - and some builders use ZIP on the ceiling. PIA - yes, but it does pay benefits after. Waiting until near completion means that there is no way to repair any leaks that show up; in fact, you may not be able to even find the leaks. Easy to find and correct if the house has no insulation.

That was my thinking. If there's no issues installing the ceiling drywall first, I'll see if I can have them do that without complaining too much. Seems like a great solution.

Having said that, we were kicking around the idea of having a false ceiling 6" below the joists. The idea would be that we could have all of our can lights in that false ceiling so we wouldn't be allowing air out the can light holes. We could also run HVAC and other stuff up there as well. Thoughts? If we wind up being able to do radiant in floor heat throughout, I'd love to have the A/C fed from above as I've always disliked floor vents for AC.

LED lights that are replacing can lights are about 1"- 1-1/4" high and will fit within strapping & drywall; the old types are model T's. You can find some at HD & probably everywhere else. The 6" space would be good for running your ventilation piping, and the set lines to your mini splits. But in order for that to work, that 6" space must be airtight - so have it drywalled and "fire taped" (one coat) & build your chase underneath it.

Not sure I'm understanding the "strapping & drywall"....?

Here in New England builders install 1x3 spruce - “strapping” - on joists and rafters which receive drywall - it evens out the differences in the lumber and results in a flatter ceiling. in these high performance houses it also helps to hold up the R-60 - 18” - of cellulose which could be too heavy for drywall alone. Seems to be a New England thing for whatever reason.

Oh ok, so they basically run furring strips along each rafter, or perpendicular to the rafters? And 1.5" is enough for LED lights? If so that's pretty nice.

perpendicular to the rafters, 16" OC.

Posted By rgonyer on 06 Oct 2016 09:45 AM

Posted By Dana1 on 05 Oct 2016 04:29 PM
Zip code 52726 is in US climate zone 5, which need R7.5 on the exterior of 2x6 framing for dew point control on fiber cavity insulation, or R5 for 2x4 framing. An IRC 2015 code min is 2x6/R20 or 2x4/R13 + R5 continuous insulation. To go better than code-min without much learning curve you could go with Huber ZIP-R (http://www.huberwood.com/assets/pdfs/ZIP-R-Sheathing-Installation-Guide.pdf ) using the 2" ( R9.6) or 2.5" (R12.6) versions of the product. It's more expensive than foam + sheathing + housewrap, but it doesn't take a crew of rocket scientists to assemble- it's about the same as installing 1/2" CDX, but it requires some attention to fastener spacing & specifications.

Dana1 thanks for the great info. My question is this- They way most are building homes in the quad city area today is typical 2x6, blown in cellulose, OSB, and housewrap. How does this not cause moisture problems if the minimum exterior insulation needs are R7.5 for 2x6? I was actually just looking at the base ZIP product in place of OSB with the tape primer sprayed on it. I can't find anyone around here interested in building a house using exterior foam or other non standard methods (Why do you want to do all that? Gas is so cheap) and we're to the point that we need to start. My marriage may depend on it, so we're trying to tighten it up as much as possible using conventional building methods if that makes sense. I've talked to countless contractors and I get the same story every time. I wouldn't be confident that any of them would do it properly. We were actually scheduled to start building in fall of 2015 when I stopped the train to research this stuff more. This board has been a wealth of knowledge, the issue is my location. If I had time to do all the work myself, it would be a different story because I could be sure it was being done properly.

It depends on the density of the EPS. Think stapling coffee cups...

typical 2x6, blown in cellulose, OSB, and housewrap. How does this not cause moisture problems

That's a wall that can dry to the exterior. Quite different than foil faced rigid foam over sheathing - this can only dry to the interior. See here for discussion of the concepts.

There is a lot of evidence that some hybrids can work well by doing some of both. For example, 1" of EPS over plywood + cellulose + interior smart retarder can dry reasonably well to the exterior, very well to the interior and provides some warming of the sheathing. Would be nice to see the performance of hybrids quantified.

Posted By rgonyer on 05 Oct 2016 01:38 PM

Posted By FBBP on 05 Oct 2016 11:23 AM
At least part of the underslab foam should be over the footings to prevent thermal bridging there, so 2" under and 2" over should be good and also doable from a drainage perspective.

I'm not sure what you mean by 2" over the footings? Foam on top of the footings before pouring the foundation walls?

rgonyer - instead of placing the top of the foam at the level of the top of the footing, run 2" of foam over the footing butted against the wall.

http://www.menards.com/main/building-materials/insulation/insulation-panels/2-x-4-x-8-r-8-expanded-polystyrene-foam-insulation/p-1444435971902-c-5779.htm?tid=-465246961092941749


On sale for .31 cents, if this stuff will work I may grab it now. Opinions?

Posted By FBBP on 08 Oct 2016 01:53 PM

Posted By rgonyer on 05 Oct 2016 01:38 PM

Posted By FBBP on 05 Oct 2016 11:23 AM
At least part of the underslab foam should be over the footings to prevent thermal bridging there, so 2" under and 2" over should be good and also doable from a drainage perspective.

I'm not sure what you mean by 2" over the footings? Foam on top of the footings before pouring the foundation walls?

rgonyer - instead of placing the top of the foam at the level of the top of the footing, run 2" of foam over the footing butted against the wall.

OK that makes sense. Essentially I'll be raising the floor by 2" then correct? So I'll just need to make sure my exterior door header is a bit higher.

Posted By rgonyer on 10 Oct 2016 03:58 PM
http://www.menards.com/main/building-materials/insulation/insulation-panels/2-x-4-x-8-r-8-expanded-polystyrene-foam-insulation/p-1444435971902-c-5779.htm?tid=-465246961092941749


On sale for .31 cents, if this stuff will work I may grab it now. Opinions?

The stuff at Menards is only 1lb density "Type-I" EPS, which is pretty fragile to handle, easy to crack and dent, and has to be derated to about R2- R2.5/inch for soil contact due the higher volume of interstitial spaces that can fill with water.

As insualting sheathing for above grade walls it's fine, since it's vapor permeance is typically 4.5-5 perms @ 1", which would allow the structural sheathing sufficient drying toward the exterior even at 4".

The short-sheet spec lives here:

http://hw.menardc.com/main/items/media/INSUL004/Prod_Tech_Spec/EPSRValueFactSheet.pdf

For most construction applications you'd want to hold out for 1.5lb density "Type-II" goods, which does just fine even under slabs. If you're stapling PEX to the foam for a radiant slab you'll want to use 2lb density "Type-IX" EPS or any density of XPS for the top inch, for better staple retention.

Thank you Dana1.

https://chicago.craigslist.org/chc/mat/5821470964.html

?

That's polyiso, which is fine for above grade sheathing or the interior side of foundation walls, but not under slabs or on the exterior of foundations. The price is comparable to what I see for surplus & reclaimed iso in my area. Polyiso is mildly hygroscopic, and will load up with moisture over time in soil-contact installations, losing quite a bit to performance when saturated.

In your climate when used as exterior sheathing, derate it to R5/inch for design purposes. ( It's probably labeled R5.5- R6/inch, but for exterior sheathing it loses some performance when the average temps are below zero.)