SIPs don't gulp oil

photo by debaird

In these times of decreasing oil reserves heating and cooling costs can only go up. Increasing innovation in green building is giving us new ideas about how to reduce our energy needs. One idea that is growing in popularity is structurally insulated panels, also know as SIPs.

Aiming for low energy use in a house is a noble goal. I’ve written before about one extreme target—the Passive House standard. But getting much higher insulation values and lower air leakage levels can be done in many ways. In the Bay Area two by six stud walls might be enough if, for example, dense pack cellulose insulation is used.

For colder areas more insulation is needed. One way to provide this is with SIPs. They aren’t really a new idea—they have been around since the fifties—but they are growing in popularity. And they have additional advantages.

SIPs are prefabricated panels with wood sheathing pressure-glued on each side of insulation boards. The typical materials are half inch thick OSB (oriented strand board) and expanded polystyrene (such as Styrofoam). You can order them in thicknesses from six to twelve inches depending on how cold your area is.

Each panel is cut for a specific part of a particular house design. So the architect, contractor, and SIPs supplier have to carefully coordinate their work. The most common use is for exterior walls. First floors and roofs can also be done.

There are many advantages to building a house with SIPs:

• structure and insulation in one item, one step
• quick to erect: walls, floors, and roof can be put up in a few days
• great insulation: foam is highly insulating
• fewer cold spots: only need wood posts about every four feet
• reduce heat loss through convection: panels have no air pockets
• little waste: they are made to order
• saves trees: uses about 50% less wood than conventional houses

There are a few disadvantages to using SIPs, of course, or else everyone would be doing it:

• requires a precise foundation: not really a big issue
• requires a small crane to install them: costs and know-how involved
• doesn’t allow changes to design: unless you throw whole panels away and order new ones
• uses lots of foam: a petroleum product (though smarter than burning oil)

I have mixed feelings about SIPs. They are modern and quick to assemble, and provide great insulation and strength. But they would be difficult to remodel, and the materials aren’t the most earth-friendly. There have been attempts to make a greener SIP, but they aren’t available so far.

What do you think of the idea of building a home with SIPs?

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