Structural Revolution

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Follow Fine Homebuilding's John Ross on a gonzo journalism assignment (or as gonzo as we get in the annals of serious how-to) that chronicles what some are calling the next generation of residential structures.

Wiring SIPs

So you’re going to take the leap and build a SIP house. Everything is set: manufacturer, dealer, designer. Even your architect thinks it’s a good idea after you agree to supply him with a month’s worth of espresso.

You were smart and lined up the subs ahead of time. The roofing, siding, flooring, and concrete contractors all said they had been looking for the opportunity to work with SIPs. Even better, your HVAC guy has cut his teeth on three SIP structures and is fully on board.

Now all you have to do is line up an electrician.

One of the big questions with SIPs is how to make the electrical connections. Unfortunately for you, the SIP industry has a bad rap when it comes to running wire. Is this reputation deserved? If the electrician shows up on the job without a good understanding of wiring panels and/or the installers don’t help him out by communicating with him, the job is going to be a nightmare, and that electrician will blame it on SIPs instead of where the blame really belongs (frankly, that’s you). Communication is key.

The general contractor is responsible for making sure the SIP installers and the electricians communicate so that the electrician knows what tools he needs and that he has all the information necessary to do the job well.

If you build a SIP house, it’s all on you. But luckily, preparing a SIP house for wiring doesn’t take much time if you make it part of the installation. The tools you need aren’t especially expensive or hard to operate. If done right, the proper electrical preparation will save you tons of aggravation down the road.

Here’s how to do it. First, find out exactly what your SIP manufacturer will do. Most SIPs have horizontal and vertical chases, but for a nominal charge, the manufacturer might also add chases to suit your design. This will save a bunch of time later on.

Second, become familiar with a few tricks that will make the installation a breeze.

The hot ball
Buy a ball bearing from a local machine shop. EPS panels turn to vapor under high temperatures.

Heat up the ball with a torch. You want the color to be a shade just under red. At this temperature, the ball will move through the foam but not cause a flame. Drop the ball in the hole and watch it disappear. Create a funnel for it to escape. Presto! An obvious note: Don’t touch the ball!

Standard auger
For short distances, you can plunge holes with a big auger. If you’re using this hog, hold on tight.

Flex bit
A flex bit is your best friend when dealing with long runs. Clearly identify where you need to go, and angle it in.

Bingo.

This connector hole can be filled later.

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Comments (3)

8/12/08 - Guest — Built a SIP 1860 sf bungalow in 1998; ran all wiring inside the interior walls, then fed it sideways to light switches in exterior walls; wall plug wiring brought up from underneath through... Show Entire Comment
2/6/08 - Guest — I was the project manager on a sip house last fall and would not reccoment them for several reasons. the panels did not fit and go together as advertized. we had a lot of panels made wrong buy the... Show Entire Comment
1/9/08 - Guest — The big thing for SIP homes is drilling the plates and the studs for the electrical chases as the panels are being installed. Most manufacturers have some electrical chases so train the framers to... Show Entire Comment

Tue, Oct 9 2007

Lifting SIPs

Dump 'em, stage ‘em, stack ‘em. Lift, tilt, or tackle 'em. Whatever way you do it, the reality is that moving SIPs around the job site efficiently and safely is crucial to a successful installation.

At SIPs school we had the advantage of extra bodies. . .more people than you would ever need.

We also got certified to use a rough-terrain forklift.

Do you need to get a crane, or will a forklift do it? A four-wheel-drive forklift will go a long way on most job sites. But an important thing to remember is that if the lift is undersize, it’s less versatile during staging and preassembly, and ultimately, the installation might take longer. If it runs over by a day, it might have been better to spring for a bigger lift and get the job done faster.

There are a lot of site-specific variables, but basically, the professional builders at the school were in two camps: those that like to do as much preassembly as possible (and therefore had more demand for bigger equipment); and there were those who liked to put up one panel at a time and make adjustments along the way. In the end, it came down to what people felt most comfortable with.

There are a few ways to attach the panels. One is simply to wrap the strap around the panel. This method is used to get stacks of panels off the truck but won’t work for installation because the straps get in the way when it’s time to fit the panels together.

The most common method is to attach a plate to the skin. We used this method both to stand walls and to fly in roof panels.

Peter Bergford, a builder in Olympia, Wash., said he uses his CAD program to pinpoint exactly where to locate the plates so the panel hangs at the right roof pitch.

Hooks are the other way to fly, and they are fast. Just stab them in…and let ‘em rip. OK, it's not exactly like that. Al Cobb makes his own hooks and also sells them for $500 for a set of four with straps. Each panel gets four hooks: two long and two short, oriented toward the center. When the crane lifts them up, they bite in and are secure. Later, Cobb goes back and foams the hole when he foams the seams.

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Comments (3)

3/7/08 - Guest — Takes too long and if that SIP skin is wet... I use a costlier method than screws and a plate. Get used to the term 'KiloNewton' because that's what the force of gravity is measured in. 1 Kn =... Show Entire Comment
1/10/08 - Guest — I agree with Jonathan Kurz. We have been installing panels the same way and I have also seen the plates peel off if someone missed a piece of structural lumber. It takes seconds to drill a hole... Show Entire Comment
1/9/08 - Guest — I have been working with and selling SIPs for 19 years. What I use is one 1" x 6' Nylon strap (available from Northern Tool) and drill a 1-1/4" hole right through the panel. Push the strap through... Show Entire Comment

Fri, Sep 21 2007

Plumbing your SIP house

I have asked several different SIP installers and manufacturers how best to deal with the issue of plumbing, and the standard response is: Don’t put plumbing in exterior walls. That’s pretty sound advice, even if you live in the half of the country that allows it in the code.

Plan your house accordingly and you shouldn’t have any problems, right?

But what about venting?

Again, the answer lies in sound planning. I called my local plumbing source, Ed Cunha, who lives on the Cape. He said that if I’m not a…um, I better rephrase. If I’m pleasant to my building inspector, he will probably say minimum pitch is OK (2-by block on one end and half-block in the middle). That means, in the space between the floors or inside walls, I could collect all my venting into one three-inch pipe (provided I don’t have seventeen bathrooms) and then, turn it vertically. This way I’d only put one penetration through my SIP roof. If the pipe is going to be easily seen from the ground, Cunha uses copper to dress it up a bit.

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Wed, Sep 5 2007

Foam core: polyurethane, EPS, and XPS

Deep in the heart of SIP country (the New England shire of Brattleboro Vermont), it’s cold and it’s progressive. It’s the perfect storm for stress on a residential structure. Why? Because cold conditions create a large temperature difference between indoor and outdoor spaces and this is when condensation happens inside walls (read: rot). Also, when it’s snowing we're less likely to be tramping around outside checking on the condition of our houses. And finally, progress is change and change causes us to operate outside our comfort zone and knowledge base.

There are three basic materials used as the foam core of Structural Insulated Panels. Each of the three core materials has different advantages.

Polyurethane
Outside Brattleboro, Winterpanel has been making and testing polyurethane panels for over three decades. The main advantage of polyurethane (or the much harder to pronounce derivation, polyisicyanurate) is that it has the highest R-value of any SIP panel. After what’s called thermal drift, it’s about 6 to 6.8 of R-value per inch of panel.

The other advantage is that it has an extremely high melting point. If your house caught on fire, the polyurethane foam core would be one of the last things left standing.

The main detractor of urethane panels is the cost. Doug Anderson from Winterpanel told me the difference is about 40 cents a square foot of panel. The other disadvantage in terms of construction is that polyurethane has a high melting point, so hot wire burners (the primary method of modifying EPS and XPS panels on site) can’t be used. This is not insurmountable, but still something that needs to be addressed in the planning stage.

Expanded Polystyrene (EPS)
Winterpanel also makes EPS core panels. Over 80% of the SIP panels installed are EPS. EPS core material is widely available. It is easy to modify on site and most SIP installers have experience dealing with EPS. It’s also the least expensive option when it comes to material cost.

All good things come at a cost. EPS core material has the lowest R-value and has a low melting point. That means if the fire in your house is intense enough to burn past the gypsum and the OSB--POOF! The good news is that if the fire gets that hot to begin with, most likely everything else inside your house is already charcoal.

Extruded Polystyrene (XPS)
Bo Foard of Foard Panel has been in the SIP business for over twenty years. He has made and installed Polyurethane, EPS and XPS panels and is convinced an XPS core is the best option in most situations.

XPS has many of the best characteristics of both polyurethane and EPS. It has a high R-value (5 R-value per inch of panel). It is dense and stable, yet has a relatively low melting point so on-site modifications are as easy as EPS. Also, like EPS, it bonds easily to OSB and gypsum board.

Unfortunately XPS is expensive and manufactured panels are not widely available (the only manufacturer I could find that makes XPS panels as part of their regular panel line is Foard Panel; other companies like Murus will make them when customers request it). The good news is that the folks at Foard seem to really know their stuff. We sat down for a good three-hour geek-out session on building science and I get the feeling that Bo and his project engineer Paul Malko could have gone on much longer.

If you missed my recent article on SIPs, check it out; you'll find more good info there. As always, I invite you to post a comment with your thoughts and insights about SIPs.

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Comments (2)

6/30/08 - Guest — Polyurethane protects things from damages and abrasions. It is also called as Polymer, which is an essential material for almost every industry. It can be used as adhesives, building materials,... Show Entire Comment
10/24/07 - Guest — You left me when you started out talking about condensation in the walls and then mentioned the differences in Polyurethane, and EPS. You failed to mention the percolation or vapor transmission... Show Entire Comment

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