Making Structural Insulating Panels (SIP)

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Old 07-10-06, 09:52 AM
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Question Making Structural Insulating Panels (SIP)

Has anyone made or considered making their own SIPs? I have a large amount of 2" polyisocyanurate foam and I'm attempting to research if manufacturing one's own SIPs is practical. I have a rough design for a homemade press (that can be scaled up to higher pressures) but will easily provide a pressure of 10 lbs per square inch. Is that sufficient to bond OSB to the top and bottom of two 2" foam panels and the foam together? What to use for a bonding agent?- does the bond need to cover 100% of the surfaces? Will liquid nail suffice? If there an inexpensive brush on glue that will work? My design also incorporates a form for keeping panel elements aligned during lamination. I estimate that my final cost for the panels will be a little over $1/square foot (and a bunch of my time) and will result in an R value of about 30. Thoughts?, Criticisms?, Warnings? Thanks!
 
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Old 07-10-06, 04:54 PM
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I'm not positive but I think the panels are made using the foam itself as the bonding agent. It would make sense that they simply take two pieces of OSB and squirt the unfoamed foam onto it and lay the top layer on and then control the thickness. The foam itself would adhere to the OSB with no further bonding agent.

Since these are structural units, I doubt you will get a local building inspector to accept home made SIP's. The chance of failure is too great.
 
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Old 07-10-06, 06:57 PM
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I Think There are Several Methods of Producing SIPs

And, from what I have read, injecting foam between the outside panels is one of the techniques. I have a local manufacturer of SIP's that I drive by frequently and I noticed that they have stacks of what appears to be expanded polystyrene (the old fashioned bead board). I called them after posting today to ask what they charged for an R30 panel and what they used. Their panels are expanded polystyrene bonded to 2 layers of OSB or, alternatively bonded to one layer of OSB and one layer of gypsum board. The cost per square foot for an R30 expanded styrene panel consisting of the foam between 2 1/2" OSB's is about $3.50.

From what I have read, polyisocyanurate foam is commonly used to reduce the thickness of the panel required for a given R value, but increases the cost of the panel.

Ed
 
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Old 07-10-06, 07:55 PM
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Making Structural Insulating Panels (SIP)

There is a little more to SIPs than a sandwich of wood and foam.

A manufacturing method is not difficult to come up with as you have discovered. Making is reliable and usable is a much bigger challenge.

From a practical standpoint, you will have to make the panels a usable thickness and not let the 2" or 4" of foam dictate the panel thickness unless you want to enter the world of everything non-standard.

If it is structural, you will need back-up or proof of the strength of the panel AND the strength onf the wall after constructed. Since this is a system and not individual products,it depends on the type of foam, thickness, adhesive, the exterior materials AND how they are put together.

Fire resistance can be an even bigger problem and cost. It is not just like going to 5/8" drywall on a garage wall insulated with fiber glass.

Another very important is the way you propose to handle the utilities. This is a major item in the success of any building system.

When you go to get a permit, the approval contemplates that someone else will eventually buy and live in the structure. therefore it must meet or probably exceed current standards, since it may be considered "experimental".

Even if you don't need a permit, you may wish you had one when you go to sell the structure.

You can expect complaints from existing SIP producers that have invested in developing their systems and have done all the testing to get it accepted. They do not people competing after they have made an investment. Building code approvals for systems are not easy and do not come cheap even though you are using some familiar materials.

You are facing a big challenge that could be fun, but it definitely will not be simple to get approved. - Good luck!

Dick
 
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Old 07-10-06, 08:01 PM
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Well I don't know what they would use for bonding EPS to the boards. That stuff doesn't really stick to anything unless it has been melted. Even the bonds to itself aren't that strong.

and again, along with concretemasonry, restress the possible problems with building department approval.

In my area, unless you could get an engineer to put his stamp on it, they would not let me build with it. That is part of that $3.50/sq. ft. cost.
 
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Old 04-03-11, 08:50 PM
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Go for it!

So many SIP outfits have come on to the seen recently... it can't be rocket science. I'm sure everybody is right about resale trouble and building code compliance, but those are not factors for everybody. I'm also looking into manufacturing my own sips for a small house boat I'd like to build. I can't get cheap foam like you can and I'm also nervous about the quality of adhesion. I discovered a company in FL making sips with urethane (2 part pourable) foam instead of pre-fab sheets. They use steel studs with metal fasteners instead of glue. They claim a very high R value so they must not think the galvanized studs contribute to thermal bridging (I'm not so convinced -- would love to hear other opinions about it). That may be of no help to you since you already have the press and full size sheets of foam, but it is interesting I think to know there is no single receipt for a good sip. Despite the fact that 90% of what you see on the market all looks the same. The above mentioned FL company does another thing; no OSB, no wood at all. Termites can still work over the wood so they use fiberglass on both sides. I'm concerned with OSB in the wet wet climate of the big blue. So as a do it your self project, you wouldn't need to limit yourself to the standard sheathing materials. Currently I'm considering a composite like fiberglass exterior and medium density overlay interior. No drywall and no OSB. My point is, you have flexibility to fit a niche. Makes the idea of home-aid sips very exciting to me. Best of luck. Dave
 

Last edited by the_tow_guy; 11-01-11 at 11:01 AM.
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Old 04-03-11, 09:09 PM
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As far as using steel studs,for added strength, steel studs are worst material you can use when it come to "thermal short circuiting".

All to often people just look at the fictitious (short term lab test) "R-value" of the insulation as a measure of the wall R-value. R-values are just for a single material and not for a wall. A 6" steel stud wall with R-19 insulation has a real wall R-value as low and R-10 or so depending on the stud spacing. Wood is better and a continuous layer of XPS is always better.

Dick
 
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