Q&A / 

What Is SIP?

Hi, I'm Tim Carter and I'm here in New Hampshire at a frosty, residential construction site. It is winter and I want to show you this timber framed construction and you have to think about what happens with it.

This is a beautiful timber roof structure. We have Douglas fir for both the big rafters and the collar ties, which keep the roof from spreading apart. The underside of the roofing is all Eastern white pine. It's already been pre-finished. It is in beautiful shape but here's the problem.

Think about this. Here's a piece of the material that is being used for the roof structure. But look at the problem. Look how thin this piece is. So two things. If we were to nail shingles onto the top of this, you would see the nails come through. What's more, what about the insulation, since this is the inside of the roof.

On this particular job site, they are using a structural insulated panel. Or SIP for short. It is make like a sandwich. First there is a half-inch piece of OSB board, then 6 inches of closed cell foam insulation, rated at R39. Then another piece of half-inch OSB board on top to complete the panel. The way this is attached is using giant screws. The screws go all way through the SIP panels into the rafters.

Using these panels will give the house plenty of insulation from the cold. It's that simple. That's how you use structural insulated panels on a roof.


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