High-Performance Walls: Page 5 of 6

For Energy-Efficient Building
Beginner

Inside this Article

Walls using structural insulated panels (SIPs).
The walls of this home, which are constructed with structural insulated panels (SIPs), combine the framing, insulation, and sheathing into one unit, providing faster assembly and a thermally efficient envelope.
Traditional framing
Traditional framing often results in thermal bridging and excess wood use.
Raised heel roof trusses
Raised heel roof trusses allow more attic insulation in the space between the wall top plate and roof.
I-Joist wall construction before insulation
Klingenberg’s I-joist solution, before wrapping with rigid foam insulation.
I-Joist wall construction after insulation
Klingenberg’s I-joist solution, after wrapping with rigid foam insulation. Furring strips screwed to the I-joist flanges through the foam provided a vented rain screen and a place to attach the siding.
Structural Insulated Panels (SIPs)
SIPs are custom-fabricated in a factory and then shipped via truck to the building site. There, panels are typically set in place by a boom truck.
Structural Insulated Panels (SIPs)
Panels arrive on the job site ready to assemble, allowing faster construction times than are possible with conventional framing.
Trimming straw bales
A bale knife can be used to trim straw bales for windows and doors, or to aesthetically round wall corners.
Applying the stucco
Applying the protective stucco outer coat. The wire mesh keeps the stucco from breaking away from the wall.
Bales used as infill walls
Lengths of rebar help keep bales aligned. These bales are infill walls, with the load-bearing structure already in place.
Window framing in a double-stud wall
Door and window framing in a double-stud wall is more complex compared to standard framing.
Double-stud walls: aligned studs
One approach to double-stud walls: Separated by a gap that will be filled with insulation, aligned studs help minimize thermal bridging.
Double-stud walls: staggered studs
Another approaches to double-stud walls: Separated by a gap that will be filled with insulation, staggered studs help minimize thermal bridging.
Durisol Insulated Concrete Forms (ICFs)
Durisol ICFs, ready to receive concrete.
Rastra ICF panels
Larger Rastra ICF panels require heavy equipment to lift.
ICFs rest on continuous poured-concrete footings.
Like many other wall systems, ICFs rest on continuous poured-concrete footings.
ICFs consist of two outer layers of rigid foam insulation separated by metal or plastic webbing
ICFs consist of two outer layers of rigid foam insulation separated by metal or plastic webbing. After reinforcing steel is added, the forms are filled with concrete.
Residential exterior membrane outside-insulation technique (REMOTE
The REMOTE building technique being applied. Note the waterproof barrier under the layers of rigid foam.
Walls using structural insulated panels (SIPs).
Traditional framing
Raised heel roof trusses
I-Joist wall construction before insulation
I-Joist wall construction after insulation
Structural Insulated Panels (SIPs)
Structural Insulated Panels (SIPs)
Trimming straw bales
Applying the stucco
Bales used as infill walls
Window framing in a double-stud wall
Double-stud walls: aligned studs
Double-stud walls: staggered studs
Durisol Insulated Concrete Forms (ICFs)
Rastra ICF panels
ICFs rest on continuous poured-concrete footings.
ICFs consist of two outer layers of rigid foam insulation separated by metal or plastic webbing
Residential exterior membrane outside-insulation technique (REMOTE

Insulated Concrete Forms
Combining Insulation & Structure

Insulated concrete forms (ICFs) are made from a variety of materials, including rigid plastic foam, composites of wood chips with cement, and recycled polystyrene with cement. But they all work in basically the same way: Units are assembled to form walls, reinforced with steel, and filled with concrete. Forms are later covered with finish materials—stucco or conventional siding on the outside; drywall or plaster on the inside.

ICFs are most often used to build foundation walls, but they also can be used above grade, and some brands are marketed with this in mind. Building with ICFs is more expensive than conventional wood-framed walls, but manufacturers list a number of advantages, including lower rates of air infiltration, high strength, excellent sound deadening and wind resistance, and high thermal mass. EPS Industry Alliance, a trade group for the ICF industry, says using ICFs add between 0.5% and 4% to construction costs, when the house is built by experienced contractors. Higher costs are somewhat offset by the ability to use smaller heating and cooling equipment. Relative costs are affected by a number of variables, including local labor rates, the design of the house, and the type of ICF the builder or designer has chosen.

ICFs come as blocks, panels, or planks. The shape of interior cavities varies, too, so the concrete might be a flat wall of uniform thickness; a waffle grid; or a “screen grid” layout, with both horizontal and vertical columns of concrete. Crews accustomed to conventional wood-frame construction should expect a learning curve when they start building with ICFs. Detailing for windows and doors, stacking walls so they’re plumb and straight, bracing walls adequately for placing concrete, consolidating the concrete to eliminate voids, and running interior wiring all are a little different and take time and practice to master. Durisol, a Canadian ICF manufacturer, recommends builders take a one-day training session, and also offers on-site training.

Houses made with ICFs don’t have as much potential for air leakage as conventional wood-framed houses, and may use less energy for heating and cooling, depending on where you build. In one side-by-side test in Knoxville, Tennessee, the Oak Ridge National Laboratory found that an ICF house used 7.5% less energy than the otherwise identical wood-framed house.

Cement-polystyrene composites. Rastra is a well-known brand of this type, with a composition of 15% cement and 85% recycled expanded polystyrene, a composite the manufacturer calls Thastyron. Blocks, which can be cut with ordinary woodworking tools, are up to 10 feet long, 15 or 30 inches high, and available in thicknesses of 8 1/2, 10, 12, and 14 inches. A 10-inch-thick by 10-foot-long panel 15 inches high weighs 158 pounds—light enough to be handled without a mechanical lift or crane.

Because it’s relatively soft, Rastra panels also can be shaped to make curves or gently rounded shapes. According to the company’s website, building with Rastra adds about $5 per square foot to construction costs over a conventional home built with wood.

Wood chip-cement composites. Durisol and Faswall are two brands of ICFs made with cement-bonded wood fiber. Among the advantages cited by Durisol are no plastics, no volatile organic compounds, no off-gassing, and the capacity to absorb water vapor, which helps maintain healthy indoor humidity levels. Durisol walls won’t burn or melt and have a four-hour minimum fire rating.

Faswall blocks are made from 85% mineralized wood chips and 15% cement. Reported R-values for 12-inch Faswall blocks range from R-21 with a mineral wool insert to R-26 with polyisocyanurate insulation. Durisol blocks come in several thicknesses. With an insert of mineral fiber insulation, the company claims R-14 for a 10-inch wall, up to 21 for a 12-inch wall, and up to 28 for a 14-inch wall. The company says the block material has an R-value of 1.75 per inch, as measured by the National Research Council of Canada. A mineral fiber insulation insert adds another R-4.2 per inch. With these known values, whole-wall R-values can be estimated.

Comments (3)

Fred Golden's picture

I think that SIPS are the way to go. From poured concrete foundation to enclosed roof in one week! That is pretty good, and almost a requirement in the northwest where rain is frequent, and dry construction timing is short and in-frequent.

zap101's picture

Great article! Double stud walls but no mention of making the inner non load baring wall out of steel studs Why?

lavardera's picture

No discussion of high-performance walls is complete without considering scandinavian building practices. They build stud framed houses just like we do, and achieve very high performance levels using simple techniques that any American builder can follow. No special materials, no special skills, predictable cost and labor time. We've posted detailed information for builders. There is a video series that gives a brief overview:
http://www.youtube.com/watch?v=yZ0W...

And a detailed description of wall types is offered here:
http://blog.lamidesign.com/p/usa-ne...

But its not all about the wall assembly. The framing method is just as important, and in Sweden they have modified the western platform frame for better performance. Much more effective than so called "advanced framing", Swedish Platform Framing fixes the all the weak performance of the platform framing method.
http://blog.lamidesign.com/p/swedis...

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