Insulation Choices
Last Post 10 Sep 2015 06:41 PM by Dana1. 19 Replies.
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RGatesUser is Offline
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25 Aug 2015 08:17 PM
Currently debating the choices for the insulation on my new home. I am in zone 4A.  I am interested in building an efficient, not just to meet code home. It has to make sense and provide a reasonable ROI.

The build up, from the outside, is as follows:

Stone + 1" air space + insul out (2" thick) + 3/4" plywood + 2x4 framing + insul in (3 1/2") + 1/2" drywall + latex paint

insul out choices are:                  

1) 2" XPS reclaimed
2) 2" CCSF
3) 1" XPS reclaimed + 1" CCSF on top
4) 2" ISO reclaimed
5.) 2" of Roxul
6.) 2" EPS

Each have their issues. The 2" XPS, 2" EPS and 2" ISO  require taping (not confident in the tapes) and detailing for water, vapor, thermal and air control. The 2" Roxul would require the same detailing minus the tape.
The CCSF will handle all of the preceding controls with one product. When I consider the installation of the initial 1" of XPS (labor, fasteners, etc.) then 1" of CCSF I am back to the 2" CCSF.

insul in choices are:

1.) Unlimited. I am kicking that bucket down the road for now. LOL

In an effort to avoid redundant debates. I am aware of and respect the following issues as they relate to insulation:

1.) blowing agent debates
2.) ISO performance at lower temperatures and how to combat it with EPS
3.) possible off gasing of the CCSF  

Any input, positive or negative, would be appreciated.

Respectfully,

Ron




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25 Aug 2015 09:53 PM
I'd suggest the recycled insulation; first the polyiso; 2nd choice the 2" recycled xps. I've had bad luck with tapes also; then I discovered SIGA. Buy a roll online & try it; not cheap, but worth the cost. Acrylic, non toxic, an amazing adhesive, flexible & tough. Tape the insulation; air sealing is critical so seal everything in sight.
Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant
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25 Aug 2015 10:08 PM
Bob, thanks for your input. I am indeed familiar with Siga. I just can not help to believe that all the tape,caulk,membranes, etc. will be able to compete with the performance of the 2" CCSF.  Besides the cost I can not see any negatives. Its just one and done. Tighter than a frog's *ss!

Ron

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25 Aug 2015 11:02 PM
it's not competing; it's enhancing. keep cold air out of your assembly.
Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant
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25 Aug 2015 11:31 PM
Whats your plans for the wall ties for the stone RGates?
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26 Aug 2015 01:14 PM
Not Roxul for cost, air and water vapor reasons. Then look at total cost (labor, tape, etc) vs actual R value for the others.
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26 Aug 2015 01:49 PM
Exterior insulation:

In a zone 4 climate the average wintertime performance of polyiso on the exterior of the sheathing would equal or exceed that of XPS of similar thickness, even though it would under perform at the extreme cold temps. During the shoulder seasons it would outperform 2" of XPS by quite a bit, since it's performance peaks when the average temp through the foam is is between 55-60F, outperforming it's labeled R. Reclaimed XPS does not perform as high as the labeling on virgin-stock due to the slow blowing agent release. After 50 years it's roughly the same performance of EPS of equal density. From a design point of view don't count on anything more than R4.5 per inch.

.In the event of a fire XPS would melt into a flaming puddle at the bottom, whereas polyiso would char in place. When all else is equal, go with 2" polyiso (any density or facer type) rather than 2" XPS. The 2" ccSPF would also char in place, but without facers it would ignite sooner.

Your primary moisture concern in a zone-4 climate is interior side moisture drives, not the moisture drive off the back-ventilated stone veneer, and 2" of ANY foam (taped or not) is sufficient protection from your exterior moisture drives due to it's vapor redardency, and huge dew-point margin from interior vapor drive point of view.

Roxul would be slightly riskier from a moisture point of view, unless you installed a vapor retarder between the Roxul & wood sheathing. Non-perforated 1/4" fan-fold XPS taped with Wigluv or 3M All Weather Flashing tape between the Roxul and the plywood would be more than adequate for protection from exterior drives, and would still offer some drying capacity for the plywood to dry into the veneer cavity. It comes in 4' x 50' sheets, so the number of seams to seal would be small, and it can be made VERY air tight. But it's more expensive and more complicated than a rigid-foam solution. But Roxul is completely fireproof- if the fan-fold XPS layer ever reached melting or kindling temp it means the house is already gone.

Taping the seams of the wood sheathing under either fan-fold or rigid foam goes a long way toward making the combined taped-foam + taped-plywood extremely air tight, especially when the seams of the two layers are staggered by a foot or more.

Cavity insulation:

Using ocSPF is a better air-sealant than 1-2" ccSPF, is cheaper per R, and a heluva lot greener than any rigid foam (including EPS & polyiso). As a cavity fill it might be the right way to go, as long as the installer is competent. (Off mixture-ratio or off temperature installation risks long term outgassing of polyols.) That would further tighten the wall structure from an air leakage point of view.

Caulking the framing to the sheathing in every stud bay with the appropriate caulk (ProPink, et al) is every bit as tight as ocSPF, and would let you use R15 batts (rock wool preferred to fiberglass, due to less friable airborne fiber and much higher fire resistance), to equal or exceed that of ocSPF, provided it's installed as perfectly as possible.

Air sealing detail:

No matter what you do for exterior or cavity fill installation (even the 2" ccSPF + 3.5" ocSPF) you'll still need to lay a bead of caulk under the bottom plate of the studwall and between doubled-up top plates to make the wall truly air-tight. This includes caulking the subfloor to the band joist, and the band joist to the foundation sill, as well as a hiqh quality sill gasket (EPDM is good) or expanding foam between a good capillary break and the foundation sill to prevent moisture migration from the foundation to the sill.
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26 Aug 2015 09:16 PM
Ricky, There are a lot of choices for wall ties, it depends on what exterior insulation system I go with.


Ron
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26 Aug 2015 09:27 PM
Bob, bad choice of words on my part. Should of used compare not compete.
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26 Aug 2015 09:48 PM
Dana, thanks for the input. Could you please explain your statement about OCSPF being a better air sealant than CCSPF.
My thoughts are by going with 2" of CCSPF on the exterior would give an ~ r6.5 per inch and be the best air and vapor barrier choice. The CCSPF will lap down on the foundation and connect with the exterior foundation insulation. With the contiguous foam the caulk, tape and other membranes along with cavity detailing would be alleviated. Obviously I would detail the interior insulation to allow drying to the inside. If I am missing something here please let me know.

Ron
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27 Aug 2015 10:19 AM
I think you are right that CCSPF would give you the best air sealing and r-value per inch. But you also started out saying you wanted a reasonable ROI. That would make reclaimed or EPS much more attractive. And if you want to go beyond the R-value that provides, why not simply move up to 3" thick? That's still much cheaper the CCSPF.

You also started out saying you are aware of "blowing agent debates". There's no debate. The blowing agent in standard CCSPF, HFC 245fa, is a potent greenhouse gas.
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27 Aug 2015 08:09 PM
Chris

 There are numerous CCSPF that use other blowing agents such as Solstice and even water which are magnitudes more environmentally sensitive. This is why I posted in the general forum to avoid this discussion in regards to the blowing agent debate (maybe should of used discussion in place of debate). A 3" thick foam is not an option due to space limitations. Obviously, ROI depends on the cost of the initial installation along with the quality and longevity of the installation. Costing is made up of materials, labor and time with time and labor being driven by the complexity of the install. The monetary side of ROI is then a math calculation. The quality of the finished product becomes a more complicated factor.  Balancing the quality of the finished product with the initial costing.This is where I am at, thus the post.
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01 Sep 2015 07:39 PM
Forgot about the roof. This is a timber frame home so when you look up at the ceiling it is 2x6 T&G. The T&G is your finish on the inside and the roof deck on the outside. Here is what I am thinking from the inside out:

Option #1

2x6 T&G +  synthetic felt + 3.5" of ISO (reclaimed) + 2" CCSF + 1 1/2" airspace + 3/4" Plywood + synthetic felt + Roofing material

This option would depend on the CCSF to seal the entire roof.

Option #2

2x6 T&G +  synthetic felt + 3.5" of ISO (reclaimed) + 3.5" of ISO (reclaimed)+ 1 1/2" airspace + 3/4" Plywood + synthetic felt + Roofing material

Option #2 would involve staggering the layers and sealing the joints.


OPtion # 3

2x6 T&G +  synthetic felt + 3.5" of ISO (reclaimed) + 2" of XPS (reclaimed)+ 1 1/2" airspace + 3/4" Plywood + synthetic felt + Roofing material

Option #4

2x6 T&G +  synthetic felt + 3.5" of ISO (reclaimed) + 2" of EPS (reclaimed)+ 1 1/2" airspace + 3/4" Plywood + synthetic felt + Roofing material

In option 3 and 4 I would be using the top foam layer (EPS or XPS) to help the ISO along in the cold temps.

Any thoughts on the above would be appreciated.

I am trying to utilize the 3.5" ISO to offset some of the CCSF costs. The ISO has a glass fiber facer on it. I have access to a huge amount at an extremely good price. If any one is interested in any of the ISO let me know. It looks brand new and does not even have any screw holes in it.

Ron
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02 Sep 2015 08:06 AM
One minor thing to check: we've seen several ceiling/roof assemblies with T&G where the T&G extends to the outside of the structure & provides lots of air channels for infiltration & exfiltration. This can be caulked from the inside if necessary, and/or tapes and covered on the exterior to stop air flow.
Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant
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07 Sep 2015 08:23 PM

Hope everyone is recovering from the long weekend. I have a few questions in regards to my roof build up and would appreciate any input. I am leaning toward one of the following:

Option #1

2x6 T&G +  synthetic felt + 3.5" of ISO (reclaimed) + 2" CCSF + 1 1/2" airspace + 3/4" Plywood + synthetic felt + Roofing material

This option would depend on the CCSF to seal the entire roof.


Option #2

2x6 T&G +  synthetic felt + 3.5" of ISO (reclaimed) + 3.5" of ISO (reclaimed)+ 1 1/2" airspace + 3/4" Plywood + synthetic felt + Roofing material

Option #2 would involve staggering the layers and sealing the joints.


Questions:

1.) If I use option # 1 would the synthetic felt, below the ISO, and the CCSF create a moisture issue?
2.) In option #1 & #2 what would my finished R-value be when it was cold out?
3.) Would it be worthwhile to add a third layer of foam above option #2 to help the ISO when it was cold?
4.) Does anyone have any better suggestions?

Thanks
Ron
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07 Sep 2015 09:21 PM
1. Make certain the product is breathable
2. I'll let the scientists answer that one, but there are excellent reasons for using the two layers of 3-1/2", include keeping unneeded chemicals out of the atmosphere, and providing an excellent re use for materials manufactured for that purpose.
3. I think people are getting way too hung up on some of the details of this stuff. With another 1-1/2" of foam, you are isolating yourself further from ambient; 3.5 seems to be the low end of the R value scale; so maybe it loses R3 at low temperatures and it goes up as it warms. How much will you save on an annual basis with the difference? Probably pennies in a good house.
Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant
Dana1User is Offline
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09 Sep 2015 05:09 PM
Posted By chrs on 27 Aug 2015 10:19 AM
I think you are right that CCSPF would give you the best air sealing and r-value per inch. But you also started out saying you wanted a reasonable ROI. That would make reclaimed or EPS much more attractive. And if you want to go beyond the R-value that provides, why not simply move up to 3" thick? That's still much cheaper the CCSPF.

You also started out saying you are aware of "blowing agent debates". There's no debate. The blowing agent in standard CCSPF, HFC 245fa, is a potent greenhouse gas.

ccSPF has a lower expansion ratio during cure, and doesn't seal quite as well as ocSPF. This has been experimentally demonstrated in test wall assemblies at the Building Science Corporation.  The difference is subtle, but real:

http://www.greenbuildingadvisor.com/sites/default/files/images/Thermal%20metric%20testing%20-%20Image%204.preview.jpg

Wall 5 leaks ever so slightly more air than wall 6 under exfiltration pressure, but quite a bit less on infiltration pressure.

The rest of that is generally true. 2lb foam uses ~2x the amount of polymer per R as half-pound foam, and uses a far less benign blowing agent.
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09 Sep 2015 05:30 PM
In zone 4a & 4b you don't need or want any sort of vapor barrier in your assemblies. In zone 4C a smart vapor retarder on the interior side can be useful.

With an all-foam roof-R solution, a membrane type roof WRB between the T & G and the foam would do a better job of air sealing than a crude closed cell foam spray-job over the top of it. Grace Ice & Water the deck plus a slip-surface material for the roofing foam should do it, at a far lower cost than an inch of closed cell polyurethane.

Option 2 is the real deal. Tape the seams on all layers of foam, fill any broken off corner chunks with can-foam as you go.

Polyiso blown with CHFCs prior to the Montreal Protocol does not have the wierd temperature derating issues that the more recent pentane + "magical proprietary mouse-milk" blown polyiso seems to have. So if the foam is old enough it could even outperform new stuff.

As long as you're not sandwiching moisture-susceptible materials between the vapor-tight materials, it creates no moisture issues. Polyiso is mildly hygroscopic, but air-impermeable. It takes chronic bulk-water leakage to load up polyiso with enough water to be an issue, and even then it's a localized performance issue, not an "Aw hell, my place is rotting from the inside out!!" kind of problem.

A mere 7" of polyiso doesn't quite meet code for roofs in zone 5 on an R-value basis, but it would make it on a U-factor basis. IRC specifies U0.026 max for zone 5, which is ~R38.5 whole-wall. Even derated to R5/inch you have R35 of foam, another ~R2 of T&G, ~R1 of nailer deck, and ~R1 of air films in the gap. At a more realistic R5.5/inch average performance the foam hit's R38.5 all by itself. But another 3.5" never hurts, eh? And with reclaimed foam that can be cheaper than 2" of ccSPF.
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09 Sep 2015 11:16 PM
Dana, thanks for your response.

 I am in zone 4A. We are about done the roof T&G so its time to make a roof insulation decision. I have a synthetic felt over the 2x6 T&G now. We use super tack synthetic felt, it is a class I vapor retarder at .06 perms.

The roof is extremely complex with hips, valleys, octagons, crickets and dormers. Cutting, taping and fitting the foam will be a challenge to say the least. This was the reason for considering the 2" of CCSF over the ISO. We would cut and fit as best we can and then let the foam guys seal the deal.

With Option #2,  synthetic felt & 2 layers of 3.5" ISO & air space to the 3/4" plywood & synthetic felt & roofing wont the air space above  the ISO and under the plywood.alleviate any of the hygroscopic issues by allowing the foam to dry or will the moist air in the cavity introduce moisture into the ISO?  I do not know how well tape will stick to the ISO facer. What are you referring to when you say a slip surface for the foam?

The ISO has the typical fiber faced backer on both sides. It is approximately 10 years old and is in outstanding shape. The foam was loose layed and the roof was not mechanically fastened so there are no screw holes in 90% of the sheets. I have
~ 800 sheets. Obviously I will be selling the excess if you know anyone who needs foam.

I also have Option 2A. I have access to 3" XPS reclaimed. I thought about putting one layer of the ISO down and then covering it with the XPS. I know tape will stick to the XPS.






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10 Sep 2015 06:41 PM
The SuperTack felt on the T & G would be your primary air barrier. If you tape all the seam on the rigid foam, or using can-foam to fill in gaps that are too awkward to tape works fine (either a 1-part can foam like Great Stuff, or maybe a 2-part foam like FrothPak, which is 1.75lb closed cell polyurethane would be fine.)

If the polyiso is only 10 years old it has the temperature derating issue. Most fiber-faced roofing foam is 2lbs density and about R5.5/inch (prior to derating.) If you have enough 3" reclaimed XPS for the top layer, go for it. But don't sweat it if you come up short and have to use polyiso for part of the exterior layer. In climate zone 4 the derating factor is pretty small, and most of the season 3" of 2lb polyiso would outperform 3" of XPS, just not at the temperature extremes.

What "moist air" is going to get to the polyiso? If you make the underlayment air tigth there's no vapor diffusion or air-transported interior moisture drive, and in the summer most of the roof will average well above the outdoor dew points, so even if there is minor air leakage to the exterior there is no condensate/adsorb accumulation, even if you're air conditioning the place down to 70F or something.

How well the tape sticks to the intermediate layers doesn't really matter- the pressure of the layer above keeps in in place even if the adhesive itself wouldn't hold very well. Using a temperature rated purpose-made tape for the outer layer of XPS would be prudent though.
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