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Author Topic: Applying Polyiso or EPS Insul Panels?  (Read 5748 times)

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Offline Woodbender

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Applying Polyiso or EPS Insul Panels?
« on: March 12, 2007, 12:11:55 PM »
Hi guys.

I'm sure this may have been beat to death already. I'm wondering the feasibility of polyisocyanurate panels and EPS panels.  I have a local manufacture of SIPs who is pretty reputable but they don't provide a polyiso panel.

Polyiso's are environmentally "friendlier" than they used to be and it seems that the LTTR values are better than EPS. On the other side of that coin EPS panels are maybe less expensive and what I've seen (limited search mind you) the EPS SIPs are more prevalent.

But can I construct a built up insul system right to the Timber Frame?

If I install .5" OSB sheathing on the outside of my frame as a skin I could apply two layers of 1.75" polyisocyanurate insulation to that. Two layers allows me to stagger the joints so that no joints line up on each other. Total insulation then is 3.5" to allow for any window/door studwork. I then screw another .5" OSB through this buildup into the timberframe (basically the same screws as the SIPs would use). Tyvek (or Typar) housewrap, siding as usual.

I know this will not be a SIP as there will be very little if any adhesion of insulation to OSB.

Some speedbumps I am asking about and some problems you may see that I haven't thought about.  How will I install a vapor barrier to the warm/house side of the polyiso insulation? Glue it to the outside (cold side) of the first layer of OSB?  If I'm using polyisocyanurate will I need a vapor barrier? I don't want to create a condition where I have a "vapor barrier" both inside and outside. My wall won't breath at all if I do that.

Seems the manufacturers instructions for EPS SIPs have expanding foam for between panels and I assume that should suffice for air infiltration/ heat loss. If I'm staggering the joints of the rigid insulation I may be able to eliminate a lot of that.

Cost; is polyiso panel insulation prohibitively expensive for a 2600 sq ft Timber Frame home? The same basic insul system would be used over the roof with maybe some asthetic changes.

Am I being ridiculous and naive to even consider this as an alternative? The prebuilt EPS SIPs are attractive in that they're panelized and ready to hang. This built up polyiso option would be all manual and no cranes.

Pros?
Cons?
Nuts?

thanks guys
Tim Eastman (Woodbender)
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Offline Raphael

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Re: Applying Polyiso or EPS Insul Panels?
« Reply #1 on: March 12, 2007, 01:02:58 PM »
If you tape the seams on your polyiso it will act as a barrier for you, but your building inspector might prefer seeing a barrier directly behind the wallboard.  If XPS is available it'll give you better perfomance than EPS... not sure how it compares to Polyiso.
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Offline Don P

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Re: Applying Polyiso or EPS Insul Panels?
« Reply #2 on: March 12, 2007, 01:08:03 PM »
You will need to stay within span limits of the sheathing, it needs a "stud" or something structural at the required span intervals if not part of a third party inspected spanning "system" like a sip.
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Offline Woodbender

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Re: Applying Polyiso or EPS Insul Panels?
« Reply #3 on: March 12, 2007, 04:56:51 PM »
Oh fer cyin' out loud. Don of course you are right. Since it is not a SIP it must be supported by something else.

Okay just so the rest of these guys know - I am not dense on purpose just on Mondays. ;D

You will need to stay within span limits of the sheathing, it needs a "stud" or something structural at the required span intervals if not part of a third party inspected spanning "system" like a sip.
Tim Eastman (Woodbender)
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Offline Thehardway

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Re: Applying Polyiso or EPS Insul Panels?
« Reply #4 on: March 12, 2007, 09:13:14 PM »
Polyiso PIR panels have been largely replaced by Polyurethane (PUR) panels.  You may want to check them out.

This was due to 3 primary reasons:

 1. environmental issues with application process (CFC-11)
 2. thermal "drift"
 3. off gassing

There are also some reports of QC problems with the newer Environmentally friendly applications of PIR  (using HCFC 141b) which have caused some instability issues.

 www.nrca.net/rp/technical/techbull/may99.aspx

PUR tends to be more stable than PIR, does not offgass and is safer environmentally in application.

You can get a DIY spray kit for PUR from a number of suppliers. 

Polyiso and Polyurethane are both more $ than EPS but will perform better.  A spray in place application can give you a complete seal wheras  built up EPS will always have some air leaks.
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Offline maineframer

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Re: Applying Polyiso or EPS Insul Panels?
« Reply #5 on: March 13, 2007, 08:09:10 PM »
We build nailbase and curtain wall panels in our shop using polyiso foam adehered to 7/16 osb under pressure. We use a  hydraylic panel press for this and have had good success with it.
As far as the poly iso goes I don't think you will find a better foam out there. It provides terrific R-Value per inch making for thinner panels (read better looking building lines).
The foam we use is around R-7 per inch. You will not need a vapor barrier with this insulation. You should however exchange your air with a ventolator or other wise.
David

Offline Woodbender

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Re: Applying Polyiso or EPS Insul Panels?
« Reply #6 on: March 14, 2007, 02:52:53 PM »
David - nice work on your website - some drop dead gorgeous work you guys have done.  8)

If I can ask - what is the thickness of the polyiso panels you use in fabricating your nailbase and curtainwall panels?

Is it safe to assume the same panel thickness is used on the roof panels?

Single layer of insulation?

Do you classify the panels as true Structural Insulated Panels since they are bonded under pressure?

And lastly - who is the manufacturer of your polyiso sheets?

We build nailbase and curtain wall panels in our shop using polyiso foam adehered to 7/16 osb under pressure. We use a  hydraylic panel press for this and have had good success with it.
As far as the poly iso goes I don't think you will find a better foam out there. It provides terrific R-Value per inch making for thinner panels (read better looking building lines).
The foam we use is around R-7 per inch. You will not need a vapor barrier with this insulation. You should however exchange your air with a ventolator or other wise.
Tim Eastman (Woodbender)
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Offline maineframer

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Re: Applying Polyiso or EPS Insul Panels?
« Reply #7 on: March 17, 2007, 01:53:48 PM »
The roof panels are generally 6 inch  (51/2" Foam and 1/2" osb) . We use our panels for insulation /sheathing/interior finish only not structural. Besides that would take all the fun away from crafting frames. :)

David  
David

Offline slowzuki

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Re: Applying Polyiso or EPS Insul Panels?
« Reply #8 on: March 29, 2007, 07:11:10 PM »
I'll weigh in with my limited experience.  I was running out of time and couldn't schedule panel delivery to match my original schedule so we 2x6 framed then sheathed with 1.5" foam.  I regret this very much because the building was designed for the dead weight of EPS panels so we couldn't add layers of osb over and under the foam.

The roof purlins ate up a lot of time, the taping of the sheathing took way too long, and the edge detailing took way too long, insulating the 6" cavity with batts overhead was a nightmare and caused most of my volunteer labour to leave.  In the end we could have had the panels there and installed by the same date as the homebuilt method and it would have cost the same.

Now we are finishing we have rodent problems, they have taken to chewing through our eave venting to get into the fiberglass.  We are poisoning them at about 1 mouse a day and one red squirel a week sucess rate.  The panels would have solved this issue I feel.

Offline Thomas-in-Kentucky

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Re: Applying Polyiso or EPS Insul Panels?
« Reply #9 on: March 29, 2007, 11:25:34 PM »
Great story slowzuki.  I have "been there and done that" with my roof, although I used rigid insulation on the roof and sips on the walls.  Sort of a darned-if-you do and darned-if-you-don't.

No rodent problems (we had a few big rats last year, but they're gone now), but having the house open for so long last year let in thousands of lady bugs, which bred, and so now we have millions of lady bugs (and wasps) on the inside of the house.  The windows are literally black with lady bugs every day before I open them!  The mass exodus of lady bugs seems to be dwindling now though.

Volunteer labour?!- heck I have a hard time keeping paid labor on the job.  :)

-Thomas


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