I'm facing a choice between building my new home with a 6.5" Emercor PU SIP (R44) or a stick-built home with about 6" of spray foam PU (also about a R44 or so).  Price quoted by my builder is nearly the same (few hundred $ difference).  Time to build, I'm told, is actually longer (about a month more) with the SIPs as the city of Calgary requires more review of SIPs (including extra engineering drawings) than a stick-built home. 

I had been leaning towards SIPs, but given no price difference, similar insulation value, and more time for the SIP build (due to them being "novel" in my location code-wise), I'm thinking that spray foam might make more sense.  This is for a new 2000 sq. ft. home (two-story, roughly plain rectangular) in Calgary with an R-60 attic from cellulose blown-in.

What would you recommend?  Any ideas on what criteria that would help differentiate these approaches?

Thanks in advance,
Guy

What about the 'whole wall' R value of a stick house vs. SIPs?
You will have a stud 16" or 24" on center. They certainly will not rate at R44.
This will decrease your overall R value substantially.
Check out the Oak Ridge National Labs reports on whole wall R values.

I checked with my builder and they're proposing 1.5" of EPS rigid board on the exterior of the 2x6 stick-build with spray foam.  He says this will negate the thermal bridge issue as even the SIPs will require some structural elements (posts?) within which decrease their R value at some points.

Any other thoughts? So far it sounds like both options are equally good and I should just flip a coin.

The thermal bridge for SIPs depends on the supplier. My SIP home has no studs in them. The splines are insulated, just slightly narrower than the panel itself, allowing the panels to slide together. Not trying to talk you into one way or another just wanted to point that out.

What a great thread! In my mind this is what this website is all about. Here are a few points on the side of SIPs
1. You should make up some of the time lost through the permitting process since SIPs should go up faster than a stick frame
system. No waiting for the insulation contractor to show up, no additional layer of foam sheathing to install
2. You have the advantage of the interior OSB sheathing, drywall installation is faster, easier, with less waste. Same holds true
for molding and trim with nice flat, plumb, walls. And one little bonus of being able to hang paintings, and most other wall
decorations, and cabinetry (usually with a "backer board') without worryting about hitting a stud.
3. Less overall jobsite waste which is both a "green" factor, as wsell as a reduction of the cost of this item.
4. A 2 x 6 framed wall with exterior sheathing, plus 1 1/2" to 2 " of foam board will result in a thicker wall which means wider
door and window jamb material (more cost)
5. The "stick/foam/EPS board" system will certainly result in a home that is "thermally superior" to typical stick framing but it
still won't match a properly installed SIP system, or be quite as "green".

Others may come up with additional thoughts, and suggestions, on this topic, but, in any event, good luck with whatever you decide to do.

(By the way, SIP roof? or?.........)

Why anyone would use OSB Sips is beyond good reason. Builders should check out this system and seek out the product ASAP. http://ow.ly/q34u

@Sipper: We're planning a standard attic with cellulose blown-in to R60.  Given lots of space in the attic, cellulose is significantly cheaper than roof SIPs to get a high level of insulation. (Says my builder)

@Alton: Sorry, I should have specified 1.5" XPS (R7.5) around the 2x6 stick-build with spray foam.  You're right that 2" XPS would be better, but my builder said it's not worth the extra money for 2". 

Thanks to those that replied.  Unfortunately, I'm no closer to a decision.  I tried to speak with a salesman from Emercor, but have got no response today.

guy_davis. SIPS probably make more sense for cathedral ,vaulted, ceilings and/or conditioned attic spaces than they do for flat ceiling, unconditioned attics. So as long as you minimize opening in your ceiling you will have a very energy efficient structure no matter which wall system you decide on. However, I'll stand by my previous comments that you likely won't achieve the same level of thermal efficiency with these conventional framing techniques, as you will with SIPs at a similiar cost. One caveat to that last statement, DIY'ers may realize some savings with the former, as long their labor is "free", with no value attached to it. However, I've worked with a number of DIY'ers who built their homes with SIPs, and have yet to see one who has been dissatisfied with the end result.

Again, good luck with whatever you decide to do.

Now, I don't want to hijack what had been a very constructive and civilized "discussion", until ergodesk's last post.
I do intend to challenge his contentious remarks about OSB SIPs on a new thread on this forum.

I just thought I'd give you a little more info. I'm building a Magboard SIP home in Calgary and yes they do want engineered drawings for connection details and such but it's not a big deal, I could have drawn mine myself but I didn't have the $1200 stamp. The biggest problem I ran into was using sprayfoam!!! I'm using Walltite in my ceiling, joist ends, cantelevers, etc. and he held up my permit for about a week. As far as cost, add to the rest that XPS is $25 for a 2x8' sheet, foam adhesive is $6/tube, spray foam is around $4/ square foot for R40 and now add in the other material costs. I paid about $6.75/square foot for my SIPs.

Which brings this back to where it started - how can sticks + spray = SIPs for cost? You don't seem to be reaping the cost benefit of taking so much lumber and labor out of the equation.

Hard to go with a longer building time, if I were you I would want to be in ASAP.  Not sure what the weather is like in Calgary but here in Northern Michigan a month of build time added on in the winter months could raise the price quite a bit.  Harder to get brick laid, heaters have to be added and so on.  Also I have heard that the spray insulation can settle in the walls and down the road leave you with problems.  Good luck to you!

Which brings this back to where it started - how can sticks + spray = SIPs for cost? You don't seem to be reaping the cost benefit of taking so much lumber and labor out of the equation.
[/quote]

I bet what you may save in framing is added to the electrician, mines not very excited yet but he's family. Just another point for SIPs, I was amazed at how straight and square the walls came out even for a first timer like me. Every corner is bang on 90 degrees and my longest wall, 42', is straight as an arrow. Judging by the wood I've been getting in Calgary, 2x6 may frame up nice but I bet nails will be poppin' out in no time. It's become a daily ritual to get a coffee, pick through the wood piles at Totem, HD, etc..and get it framed up before it turns into a hockey stick. We'll be starting the second floor tomorrow if you want to check it out, just pm me. Sean

Thanks to all that responded.  I've decided to stick with my original plan to use the 6.5" polyurethane SIPs instead of a stick-build with spray foam.  Hopefully that was the right choice.  Time will tell...

Well the decision's already made, but FWIW we have a SIP second story added to a stick-framed existing (2x4) structure. On the bottom we're adding 3.5" of PolyISO. That seems almost as much effort as the whole SIP structure

Foam is 4x8 sheets, the SIPs were 8x8. You have to frame around the windows since the windows are now recessed into the foam. Nothing insurmountable, but the labor/cost of stick+foam should be much more than SIPS.

There is more engineering. The local building official is asking for stamps to hang a 150lb solar air heater on the wall. Someday perhaps some sanity will return to building, but not any time soon (don't get me started on why I can hire any guy off the street to fix the brakes on my car, but I need a licensed plumber to run a sink drain).

Sean, I did my own electric. Pulling the lines we pretty easy through the chases that were there. I don't get the whining the electricians do. Seems this would break it up for them a little.

With Stud construction, about 30 pecent of the wall system is formed with low R-value wood studs, plates, headers, etc. Wood is R-1 per inch, so 30% of a 2x6 stud framed wall is roughtly R-5.5. Only the cavities betewwn studs would have spray insulation of about an R36. To find the actual WHOLE R-value, average 30% at R-5.5 and 70% at R-36. SIPs typically only have 2 to 3 precent wood, and averaged, a SIP wall is 3% at R-5.5 and the remaining 97% at the actual SIP inhsulatiuon value. SIPs are superior by far. Roe Cole, Sun Styles Timber Framing, Inc. 804-378-0501.

That would be a very sturdy 2x6 wall. For 30% studs your spacing is only about 6 inches on center. A 24" spacing is more common with 2x6 framing.

Spend a little time looking at the framing of a custom home and you'll see differently. Roe Cole did say "studs, plates, headers, etc.". By the time you add cripples, double sills and bucks, extra studs at beam pockets, intersections, and so on, there is a lot more wood than simple layout.

My point was the estimate of 30% is a bogus number. It is like stretching out your hands to tell how long the fish was. I've worked as an engineer in the construction industry over 15 years so I have been to a couple of job sites. I'm used to dealing with real numbers. There is no such thing as a 2x6 framed house with 30% of the wall consisting of framing.