Sips Panel Timberframe
Bob Stanell’s house in Cashiers, NC 28717
My apologies to all.
I had no idea it had been so long since I put up a post. Some things fell through that I was hoping to cover. Like I was hoping to visit the SIP Village at the International Builders Conference but I never made it down there. Also I wanted to get some information in from the World of Concrete Expo that I visited in Las Vegas.
But all that fun I was having was in between working on this:
This is all SIPs.
I finally turned in the article and it will be published in the next issue (FHB #188). There will be information on the SIP Schools as well as my trips to Boston and Vermont. Now that the pressure is off a little I hope to get back to putting up some posts as they come in. In the meantime you can visit Fine Homebuilding’s new Web-site and see what we’ve been up to. If you look you can find a free video of me mixing concrete in a wheelbarrow.
SIPs are certainly designed to reduce the amount of energy a house consumes, but does that make them green?
To find the answer to this, I called David Johnston who is a green building consultant and author of Green Remodeling. David is pleasant and easy to talk with but when you bring up SIPs he can get excited. I asked him about the argument that SIPs are not green because they consume petrochemical products.
“This whole idea that plastic can’t be green is silly,” he said. “When plastic is used inside the wall, it’s a lot more green than driving your pickup truck to the lumber yard.”
The reasoning is that once the EPS is expanded it becomes inert and no longer reacts with the environment (there are disposal issues that I won’t go into now). If the house just sits there, the material used will not be contributing to global warming.
So this EPS house is pretty benign as long as it gets recycled.
Urethane and XPS panels are a little more complicated because they do discharge HCFCs into the environment during manufacture and for a short while after construction. As far as the OSB that is used for most SIPs skins, according to Johnston, there are two good qualities of OSB. First, the wood pulp used is from fast growing softwood trees that are a renewable resource (typical cycle is 35-45 years). Second, the glue is a phenolic resin that does not emit substantially more formaldehyde than the wood itself.
So I’m going to go out on a limb and say that SIPs are green. Are they perfect? Nope. Is anything perfect?
This might come pretty close.
I am traveling deep into the heart of SIP country, to the New Englandshire of Brattleboro Vermont. It’s cold, it’s snowing, 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 are 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.
Of course change is good. Otherwise we would still be building like this.
There are three basic materials used as the foam core of Structural Insulated Panels. Each of the three core materials have different advantages.
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. Effectively 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 says 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, 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 sight and most sip installers have experience dealing with EPS. It’s also the least expensive option in terms of 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.
Expanded 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 requests 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.
As always I invite you to post a comment with your thoughts and insights about SIPs.
Better yet, go to the link at the top right of this page and Post Your SIP House.
Pictures from today
I’ve still got some questions about plumbing.
I have asked several different SIP installers and manufactures about how to deal with the issue of plumbing and the standard response is; don’t put plumbing in exterior walls. That is 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 is planning. I called my local plumbing source, Ed Cunha, who lives on the Cape. He said that if I’m not a…, um 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 vertical. 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 will use copper to dress it up a bit.
On another note, some people have asked me what it is really like to work at FHB. Short answer: Great!
And as far as all the free stuff floating around, take a look at these shwag stacks.
Free shwag: All you can take
Not-free shwag: Testers only then this stuff goes back
My thanks to the SIP School Team.
As much as I’d like to, the demands of my job don’t allow me to attend SIP school every week so I won’t be able to post every day. But that doesn’t mean the site has to suffer.
Go to the link at the top right of this page and it explains how to post your own house on this site.
If nothing else, it might serve as a collection of SIP houses that anyone can look at.
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 install.
At the school we had the advantage of extra bodies. More people than you would ever need.
We also got certified to use a Class 1 forklift.
Cobb took this picture of me after I completed my certification test.
Do you need to get a crane like this?
Or will a fork lift 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 undersized, it’s less versatile during staging and preassembly, and ultimately the install 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 that like 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.
I felt pretty comfortable sitting in the driver’s seat of the big crane
There are a few ways to attach the panels.
One way is to simply wrap the strap around the panel. This is used to get stacks of panels off the truck but won’t work for install 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.
Hooks are the other way to fly.
And they are fast. Just stab them in…
Not exactly. Cobb makes his own hooks and also sells them at $500 for a set a four with straps. Each panel gets four hooks, two long and two short, oriented towards the center. When the crane lifts them up they bite in and are secure.
Later he goes back and foams the hole when he foams the seams.
How hard was the certification test?
Disodium octaborate tetrahydrate. This was an answer that I got right. This is also called a borate and is used to discourage insects from using the EPS foam as a house. It’s pretty harmless stuff that is also used in talcum and baby diapers.
Pentane gas. I couldn’t remember this one. It’s the expanding agent used in the manufacture of EPS SIPs.
Back to work.