Structural Insulated Panels ?

[cbc58]

Has anyone looked into building with SIP's (Structural Insulated Panels)?   R 23  for basic panels is pretty good and could save $$ in the long run.  I think the prices have come down over the years on these.  

.... note -- sorry -- meant to put this in the general forum...

[jan nikolajsen]

Last I checked I could frame/sheath/insulate a comparable wall cheaper by myself.

On the other hand if I'd have to pay either framers or the SIPs manufacturer I would go with SIP, no question.

[MushCreek]

I've done quite a bit of research into them, and am thinking about either SIP's or ICF. I believe it is cheaper to stick-build and insulate a wall, but it has to be done right. The true yield on a 2X6 wall is pretty low unless you insulate very carefully, and add insulation outside to eliminate thermal bridging. Some SIP's (but not all) have little or no thermal bridging. SIP's can go up very fast, which may be an advantage to you. I'm looking into steel SIP's, which are laminated with steel instead of OSB. The steel is quite weather-proof, and can be left as-is without any further siding if you don't mind the 'industrial' look. Steel doesn't burn, rot, or get eaten by insects, either.

IMHO, ICF is probably the best system out there, with steel reinforced concrete walls insulated with foam inside and out. But it ain't cheap, and it's very hard to modify once the house is built. ICF can be done DIY for about $6.00 a square foot of wall area; SIP's maybe a buck less. Conventional framing is obviously a lot cheaper, although I've never attempted to get an accurate figure for a well-insulated wall.

[cbc58]

there is a SIP mfg about an hour away from where we will be building and they sell 4.5" "seconds" for about $2.50 s.f.  thought i might try it for a 12x16 shed/studio... still looking into it.  like the "fast build" part.  didn't know they made steel skined SIP's...

[MushCreek]

Wow- that's a deal! I wonder if you can use them in a house- pass inspection, and all that..... Sounds like a great way to build a shed quickly, and keep the heat and cold out, too.

[Erin]

Do you have a similar yet slightly different name on the Homesteading board?  If so, this will look familiar.  

We seriously considered it.  You're right.  They make a very convincing case!
But the DIY factor wasn't really there.  I mean, yeah, you can put them up yourself, but it's considerably more difficult.
I also don't like how much "fake" material is used.  The more time goes by, the more I come to realize that the materials that make up my human environment should be as healthy as absolutely possible.  I want "natural" wherever I possibly can.  
(Or really old so that all the off-gassing has already given someone else cancer.   )

However, I'm REALLY sold on the sealed-envelope type of insulating system that SIPs give, so this is what I found (on this board, actually) as a compromise:
FirstDay Cottages
It's a modified post and beam frame.  No composite materials except in the insulation itself.  Construction is straight-forward and very DIY-friendly and, best of all, it uses that sealed-envelope system of solid insulation with no thermal bridging (except at obvious holes like doors/windows!)
Step 1.  Erect the frame
Step 2. Sheathe the outside of the frame with the 1xT&G that'll make the interior wall surface.
Step 3.  Sheathe the outside with poly-iso insulation boards
Step 4. Sheathe one last time with the 1x that makes the exterior siding.

We're not buying their kit, but we're using the same process.

[Squirl]

The problem with SIP's is the building inspectors.  Unless they are familiar with them, they might not pass inspection.  The usually reason I read about is that the spacing of studs (4 ft for a 2x4) does not comply with most codes or stick framing.  Other than that, they seem like a great system.  If they were widely accepted I could see more houses getting built out of them.

[cbc58]

as luck would have it.. the firstday company is also about an hour from where we intend to build... so i'll have to go check them out.  seems abit pricey though when you take into consideration that all of the expensive stuff is not included.  still cheaper than some but for us truly frugal builders we can find savings here and there.

SIPS were big back in the late 80's and may make a comeback if oil shoots up and stays up.  I'm pretty sure they make some of them strong enough so that no structural framing is required.  too well insulated can also be a problem and add costs. 

[Erin]

seems abit pricey though when you take into consideration that all of the expensive stuff is not included.  still cheaper than some but for us truly frugal builders we can find savings here and there.

Which is precisely why we're not buying their kit.  (Though keep in mind, you're also buying the plans, instructions, etc.)
I sourced my lumber locally and I can easily build it the frame for half of what the kit would cost.  And that didn't even include shipping it halfway across the country...

However, I really like the method and the look. 

[waggin]

If I find some SIPS on Craigslist for an attractive price, available locally, then woohoo!  Otherwise, stick built it is.

[cbc58]

i kind of like thier saltbox...

[MushCreek]

Steel SIP's have no framing, and thus no thermal bridging. The panels fit together, and, well, that's it. The company I talked to is local in FL, but they've done projects up in SC where our property is, and they would take care of engineering and other code issues. I could have them pre-cut my entire house as a kit, if I wanted, including SIP's for the roof, and stamped steel framing for floor joists, etc. Needless to say, the cost was well over my head!

[duncanshannon]

I Just learned about SIP's today at a 'home show' (actually a cabin show). Sounds pretty interesting. I am getting kind of excited about doing the framing etc, but I want to explore the SIPs more... seems pretty interesting if I decide I dont want to frame the house myself (and i'm kinda excited about doing that work...).  Anyone have any good numbers for sort term build cost differences between SIP and stick? What about longer term savings?

How do you do the wiring/box work in these walls? 

What about framing up with sticks but using SIP only for the roof??

[Alan Gage]

There's a manufacturer less than 1/2 hour from me and I was very interested when I started planning my project (will start this spring). I got an estimate from them for a roughly 750 sq. ft. house for both the main level and full basement (they use treated for the basement). Price included panels, floor joists (i-joists), and roof trusses (just trusses, no panels). Can't remember if floor and roof sheathing were included or not. Window/door cutouts would have been framed from the factory and wiring chases would have been cut through the panels. Estimate came back at $20k.

I didn't think it was that bad but it's certainly more than stick framing. I've since decided to build on a slab so never worked up a firm estimate on stick building that design but I think it would have been close to $10k to get it to the same point (including insulation).

Alan

[rick91351]

I Just learned about SIP's today at a 'home show' (actually a cabin show). Sounds pretty interesting. I am getting kind of excited about doing the framing etc, but I want to explore the SIPs more... seems pretty interesting if I decide I dont want to frame the house myself (and i'm kinda excited about doing that work...).  Anyone have any good numbers for sort term build cost differences between SIP and stick? What about longer term savings?

How do you do the wiring/box work in these walls? 

What about framing up with sticks but using SIP only for the roof??

The local SIP manufacture here incorporates chases for the electrical.  You measure and zip saw where the chase is at according to their info.  You then have to fish tape or mule tape the wire.  Certainly not an electricians choice I would not think.  But they had a good business here with panels going all over before the bust.

They did have some video on their web site.  I have not been there in a long time do not really know what they have now.

http://www.ibpanels.com/faq.php

I really don't think I ever seen anything with just a SIP roof.

     

[MushCreek]

SIP's are well-suited for cathedral ceilings, since some of them are self-supporting over considerable distances with a ridge beam.

One way of adding a vertical hole to a SIP is to heat a ball bearing and drop it straight don, It will melt it's way down through the SIP. In other cases, shallow steel studs are added to create a wiring space, and then covered with drywall.

[keithbien]

Not much discussion about SIP's for roofing.  I am thinking of building a timber framed home and covering it with a SIP roof.  It makes for a pretty costly roof system, but a really good one, especially if I can afford a standing seam metal roof over it.  Any thoughts on doing the roof any other way?

[Don_P]

It depends on the spacing of purlins or rafters. I've used 2x6 T&G with layers of foam, 2x4 sleepers screwed down and plywood over that on several houses, "wrap and strap".

[keithbien]

Does that come out cheaper than a SIP roof?  Isn't there still thermal bridging from the sleepers, or are you laying the 2x4's on the flat and screwing THROUGH the foam?  I was planning a 5/4 decking (where you used the T&G) and the Sips on top of that.  My bents are to be spaced on 12' centers with two 8x8 common rafters between.  Appreciate your comments--K

[Don_P]

The 2x4's are laid flat over the layers of foam and screwed through the foam to the rafters and to the 2x deck (very careful screw length sizing there!)
sounds like you have a bearing every 4' so 2x decking would work. You'd have to compare and see if it is more cost effective, check the entire assembly for each. It is alot of trips over the roof but all with smaller pieces so no crane. I go back and forth on which is better.

[keithbien]

One thing that immediately stands out as an advantage of SIP's is that you can have a minimum of 4" of insulation in your roof.  I would think that it would be cumbersome to screw through that much foam in your 2x4 sandwich.  The other thing that works well with a timber framed home is the overhangs that SIP panels afford.  Most bent designs don't have rafter tails.  My bent and common rafters are already 20' long,  I think I am convincing myself to go with SIP's!  Do you have info on manufacturers?  I am in N GA.  A friend recommended Murus http://www.murus.com/  they are based in PA, but I will probably want something closer.  Thanks again for your comments--K

[Squirl]

There is an article in the recent issue of Home Power.  The author used some energy calculation software to calculate the cost/benefit of equal amounts of insulation between a 4" SIP panel and a 6" stud frame wall with standard insulation.  The energy performance was almost identical and the SIPs were much more expensive.  I assume the values he used were from the R-16 and R-19 categories not the R-26.  I would assume the R-26 is much more expensive. You can find the link to the article in one of my previous posts.  SIP's have their strengths and drawbacks.  There primary strength is labor savings and time.  You can have them up in a weekend.  Another is they usually come in a complete kit with instructions.  This can be of huge value to the first time owner builder. .I have noticed a few more drawbacks recently since this post started.  The links let me review the specifications.  First, as you have stated, they are not rated for much weight bearing capacity and they essentially become more of a sheathing.  I assume in Georgia this isn't much of an issue because of the warm climate.  The second is their energy performance.  IIRC the way they are constructed is with 2 studs on each side of the panel. This is from an older book on SIP construction I had read when I first started looking at them.  Things could be different now. So for an 8' section you have 4 2x4 studs at around an r-value of 1.2 per inch for 3.5 inches.  As opposed to a traditional framed section with 2x6 24" O/C would have 5 studs in at around an r-value of 1.2 per inch for 5.5 inches.  So performance overall is not much different.  The less expensive and easier to method to build alone is to frame and sheath it and just put four inches of solid foam on the outside.  This would give better energy performance because the foam would be a solid covering throughout.  A member here, speedfunk, has done this and posted good pictures of it. This method is more time consuming than just renting a crane and hiring some help and doing it in a weekend.

I think Georgia has a few SIP manufacturers.  It might save you on shipping.  If I can find them I will post it.

[Don_P]

The last time I did wrap and strap we had 5" of polyiso foam. 35 years ago when I was helping my Dad we used 2"... times do change. I've extended the flat 2x4 out to make the "tail", We then made plywood triangles that attached to that and were notched onto a wall ledger and accepted a subfascia. So this can be done with heavy timber... that was what we were doing.

We had Sips on a TF a few years ago. The manufacturer made some oopses and I had to modify several window openings. The voids in their blow were a real eye opener, had a couple of 3-5' areas of nothing. Murus does have a good rep.

[Erin]

Not much discussion about SIP's for roofing.  I am thinking of building a timber framed home and covering it with a SIP roof.  It makes for a pretty costly roof system, but a really good one, especially if I can afford a standing seam metal roof over it.  Any thoughts on doing the roof any other way?

Personally, I tend to think if one is going with a timber frame, SIPs might be overkill.  The "S" standing for structural, afterall, means the that the panel is designed to pretty much stand on it's own.

I'd think you can make cheaper "panels" by just putting down plywood, polyiso and more plywood.  Or, with decking and 2x's like Don suggested. 

[Don_P]

I can see either way, I'm just showing an often overlooked option.
I'm working my way up screwing in the 2x4 strapping here. I installed metal straps over the ply at the peak from 2x4 to 2x4 to make sure things didn't start to slide downhill through all the foam.


This is an interior shot, 6x16" glulam ridgeam with 4x10 dougfir rafters on 4' centers, 2x6 T&G decking;