Sprayed Polyeurethane Foam vs. SIPS

I was curious if anyone had any experience with SPF, and in particular what the costs were associated with it vs. SIPS panels. SPF companies claim an R-7.3 per inch, and of course an air tight seal. Where I live, 2x6 construction is necessary (per codes) to attain the proper insulation value using fiberglass insulation. However, using SPF, I could get a better r-value with only 2x4 construction vs 2x6 stick built. So, I am trying to determine if the costs associated with SPF is worth the savings over SIPS assuming the lower cost of 2x4 construction, eliminating the vapor barrier (SPF companies claim it's not needed with their product), and lower cost (in general) of stick built framing over SIPS.

I'm not completely convinced to go with 2x6 AND SPF. I've geeked out on Fourier's steady-state heat flow equation 8)

Depending on design there are other savings to be had in shortened construction time with SIPs.

That and a 4.5 thick SIP panel will give you a better R-value than a 2x6 stick framed wall (with batt insulation). If you compare 4.5 SIP to 2x6 with Polyurethane (or soy-based) spray in foam, I think you will find the extra cost of the 2x6's and the PolyUrethane will outweigh the material cost of the SIP. 4.5 SIP vs. 2x4 w/ Polyurethane should be a very close material cost, but like I said, depending on design you could save yourself a LOT of time with SIPs. Getting an 8'x24' wall section complete with all windows and doors cut out and framed is a far cry quicker to set in place than building it out of sticks, cutting in all of the openings and making up the necessary headers, then standing up the wall, then sheathing, then insulating, etc., etc., etc.

I think it all comes down to designing with the system you will use to build with in mind. some designs it makes more sense to stick-build, some it makes sense to build with SIPs.

Mark

Here are some thoughts for the sake of argument.

SIPs look good but are pretty expensive. Also, after talking with some builders who have had bad experiences with them, I am not too convinced they always save time. IF the foundation is not perfectly level, or you have a complex design, or the SIP manufacturer makes a poor product, SIPs will cost you additional money.

An alternative would be to buy panelized/stick walls, use SPF, and add a 1 blue board panel on the exterior as a thermal break. I have been told that SPF adds about $1500 to the cost of a 2000 sq. ft. house in the Midwest over traditional insulation materials. The blue board would be in addition to that. I believe this option should be less expensive than SIPs.

I do realize that housing and labor costs in the Midwest are less than in other areas. The economics might change if building elsewhere.

I looked up the r-value that spray in foam companies claim and i see 3.7,3.6 and 4. I see how a SIP would have a higher insulation value because the blue board stuff that u can buy at home depot is R-5 for an inch. The foam could fill every gap where fiberglass may not, SIP won't have the bridging effect through studs.

Can a person get value out of using two 2-by-4 walls with fiberglass instead. These materials are friendly to me since im not up to hiring out work.

I looked up the r-value that spray in foam companies claim and i see 3.7,3.6 and 4. I see how a SIP would have a higher insulation value because the blue board stuff that u can buy at home depot is R-5 for an inch. The foam could fill every gap where fiberglass may not, SIP won't have the bridging effect through studs.

Can a person get value out of using two 2-by-4 walls with fiberglass instead. These materials are friendly to me since im not up to hiring out work.

The primary problem with batt insulation is installation. It is just very difficult to fill every nook and cranny, and block and air seal so that no air will move through the insulation. Damp-spray cellulous is great for walls, but you must do a good job of air sealing first. And it is about the same cost as fiberglass. Any of the spray foams both insulate and air seal.

sydney

Regarding the SIP as inferior or costlier...

I think one must consider:
1) SIP retailers vary quite a bit. In my neck, there are some serious SIP builders, who also sell the product. They gave up on trying to just sell, because so many builders are old school stick people, who will never like change and make every effort to complain due to lack of planning. I've found a few that I can trust and one especially that does a lot of the shop drawing work that normally the SIP factory would do.
2)One of stick's greatest PRO is the flexibility to FIX MISTAKES from various contractors. If the foundation is not level, then stick can easily accommodate. But then ask yourself WHY your foundation contractor sucks so much. Many developments today rely on pre-fab stick walls and they would, too, have the same issue of SIP IF the foundation is not level (i.e. Trimming/shimming them to fit is not that different than with SIP.).
3) In the end, not all cost can be compared by just product cost... the labor/management aspect of the builder you choose could likely be a bigger factor than the material cost comparisons (i.e. Like stick vs SIP, not all builders are created equal and sometimes you DO get what you pay for.).
4) I'm no expert, but it seems there are greater cost INSIDE the house than the shell itself (i.e. Since the shell is so massive, we tend to overlook the cost of things inside, which may make the shell cost/sf seem insignificant.).

After 10 years of designing/debating what/why/where/when/who/how I will build my home, I finally just had to say, F' it! and throw a dart... spin the wheel... so I can just DO IT.

It's important to remember that there are two types of spray foam - open-cell and closed-cell. Yes, the open-cell foams get you about an R 3.5 per inch, but the closed-cell (higher density) foams can get you R-7 or more per inch. The closed-cell foams also act as an impermeable barrier to moisture, so another vapor retarder is not necessary (actually it's discouraged). There is an article in this months Environmental Design and Construction Magazine on SPFs. With SIPS, you decrease your thermal bridging, but the cost goes way up. Consider an insulated sheeting over the studs if stick framing. Hope this helps. Thanks.

I am going through the same head scratching myself. Our project, modern homes in a beach community on the FL panhadle, began with the idea to build with CMU but obviously we ran into R value issues with the code wherein we would be forced to stucco the exterior and fur the interior - so whats the point of CMU when it as not only the structural integrity we desired but mostly the asthetics. Besides, there were major material and especially labor costs disadvantages.

So, we have been moving more toward SIPs and are in the means of revising and optimiszing our plans to accomodate these. We, like some of what you see here on LiveModern, have found that SIPs suppliers are a dime a dozen and so is the quality. BUT...we have narrowed the field by looking at 1.) only those panel mfgs that provide cement fiber panel SIPS and 2.) those in, or familiar with, Florida. With one excpeting from a builder/supplier dealer for R-Control panels (OSB). The fiber board panels, we fell, will give us resistance to the elements, asthetics, r value, and structural integrity.

Now, the builder challenge. We are looking for a builder willing to doe something different than the redneck riviera stick built mentality and have some out-of-the-box approach. Any builder, in this labor and material cost environment, should jump at the opportunity to build with these SIPs. Drying in a house in 3-7 days, more fixed material costs, minimum labor (compared to stick framing) all add up to minimizing risk - and is this not the name of the game in almost all business? A little focus on a properly poured slab, and more focus on the interiors might result in a copst effective and well planned project.

You keep me posted here at LM and I will do the same. Cheers!

I just built a structure using SIPs and I would recommend it over stick built + polyurethane. SIPs are a lot faster once you get the hang of it and the labor savings are real. There is almost no waste on site with a SIP house (if you plan it right). If you are going green on site waste is a factor to consider.

wood studs are r-1 I think.

if your foundation person is doing it with block you just go out there before the last course is up and check it with a laser level. If it's off tell the person to make it right or they don't get paid. If it's poured foundations you can check the forms before they pour. Superior walls you can check it etc. Even if it's off you can fix it though it is kind of a pain.

Why buy all those little pieces, nails, small bits of wood, some plastic, fiberglass, plywood etc. when you can buy bigger pieces?Stick framing seems way out of date. SIPs are light weight and much easier than schleping plywood and 2 x 6s everywhere. Besides the actual framing material might be one of your lowest costs.

Refreshing response. Thank you. If I might ask, were you the builder or homeowner on the recent SIPs project? Whose panels did you use? One story or two? Good information and consistant with what I have heard about getting the slab right first before panels go up. Also, did you do a SIPs roof?

I am the actual hands on builder/GC, and the homeowner. I've been a builder for about 15 years and I'm sort of tired of stick framing.

I considered both ICS-SIP out of NC and The Murus Company, in Mansfield PA. Both were east coast manufacturers of polyurethane sips. THey both seemed good. I went with Murus because it was more local (in state).

I'm building a 3 story building. The 12' high panels were a little tricky to work with. The 10' and shorter panels just flew up. You should know that there is structural framing within the SIPs that you'll have to consider for headers and such. THe SIP manufacturer will spec that out for you.

I went with a conventionally framed roof because of the very low slope. If there was a roof leak I would never know until the structural integrity of the panel was compromised. If I used a greater slope I would have gone with sips.

sipweb.com is a good resource and has a forum to ask questions.

I built a pole barn house that used SPF in the walls and floor.  Roof was staggered layers of batt insulation.  I agree one should design for technology to be used.  SPF is much more forgiving than SIPS (re leveling, gaps,) and is fast.   Most importantly for me is IT IS STRUCTURAL so I needed no plywood.  Simply put up the 1 x 8 vertical boards and sprayed.  Because of the pole barn design the horizontal nailers were 2 feet o.c. horizontal on the outside of the poles which eliminates any thermal breaks except for the poles which had an inch sprayed over the interiuor anyway because they weren't exposed finish surfaces. . .Interior walls hung off the box beam.  SPF is more flexible in insulating risers, septic pipes, and well risers if the house is on piers, which pole houses are.  Blue board invites some insects. Another house I did was conventional 2 x 6 stick with batts, then 1" high r-sheathing on inside with glued 6 mil plastic.  Then a free standing 2 x 4 2' o.c. with a 1" chase for plumbing runs on exterior walls.  (mice like it too though).  Mixed insulation systems seem to work best for me as SIPS don't work well beneath the pier construction system.  Good luck

 

We're building an off grid sips house if anyone wants to look. We're documenting in man hours, which might help you evaluate better. The project blog is here: (I am just talking in the meantime as we're waiting for the foundation to cure... the SIPs arrive Nov. 10th then you'll see a lot of change! But if you troll down the posts you can see the foundation/radiant tubing/etc.) http://www.greenmodernkits.com/casa-ti1.htm

we are in process of building our first home. went through almost year pahse of budgeting, and now we finally started. we also were considering sips at the beginning. after a time of considering pros and cons, we are not going with sips. the system we decided to go is double 2x4 staggered framed wall construction on 2x8 plates. this eliminates any thermal bridging. we will spary 2" closed cell foam for R value of 14, than for remaining cavity we will use 2 layers of 3.5 " thick bats (R 13 each layer), for total R value of wall of 40. we can still eliminate one layer of bats and get decent R27. same system for roof. believe it or not this system is going to cost much less than SIP system with lower R values and thermal britging at panel connections and at panels structural reinfocements. also installing electric, plumbing and mechanical systems is easier. 

other thing to consider with sips are perfect foundation, crane, additional lumber for connections, opening perimeters, top and bottom plates. if the price for sips was more competitive to conventional framing we would decide for sips, but there is so many things that you need to count with as an additional cost or time spent.

other good system i would recommend over sips is standard 2x4 framing (or 2x6 if structurally necessary) with 3"rigid insulation on exterior side over sheathing. this alone gives you R 18 plus no thermal bridges.  by placing additional 3.5" batts in 2x4 wall cavity you will get total R of 34. also very affordable system, besides you dont need to call specialist to spray foam, becaouse you can place rigid on exterior yourself.