High-Performance Walls: Page 3 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

Structural Insulated Panels
Fast Assembly, Tight Construction

Structural insulated panels (SIPs) are sandwiches of insulating foam faced on both sides with a thin skin, often oriented strand board. They combine the framing, insulation, and sheathing in a single package. SIP houses can be built much faster than conventionally framed homes.

Panels can be up to 8 feet wide by 24 feet tall, with standard thicknesses ranging from 4 1/2 to 12 1/4 inches, according to the Structural Insulated Panel Association. Small panels can be moved around and set by hand. Large wall panels and roof panels require a crane to help set them in place.

R-values vary considerably, depending on how thick the panel is and what type of foam is used. For example, a 4 1/2-inch EPS panel has an R-value of 14, while a 10 1/4-inch XPS panel has an R-value of 48. Today, the most common core by far is expanded polystyrene (EPS). Less frequently, panels are made with extruded polystyrene (XPS) or urethane foam. Both of those alternatives have higher R-values than EPS, but they also have a few drawbacks, such as higher cost; a higher melting point, which makes field alterations with heated cutting tools more difficult; and, in the case of XPS, limitations in panel thickness.

For those who are concerned about using plastic foam, Agriboard Industries makes a panel with a core of compressed wheat straw. Tests at the Oak Ridge National Laboratory found the R-value of a 7 7/8-inch-thick panel was 16.47, although the manufacturer has claimed higher effective R-values because of the wall’s mass (see the discussion on thermal mass and R-values in the “Insulated Concrete Forms” section).

SIP manufacturers can take construction drawings and turn them into precut panels with door and window openings already cut. There is a learning curve to assembly, but seasoned carpentry crews should be able to pick up what they need to know fairly quickly, and some manufacturers offer job site assistance.

Speed of assembly, low rates of air infiltration, and dramatically reduced thermal bridging all are energy-saving advantages with SIPs. Although material costs are higher than for conventional frame construction, costs usually even out when lower labor costs for SIP assembly and less job site waste are taken into account. In addition, improved energy performance may allow the installation of smaller, less-expensive heating and cooling equipment.

Straw Bales
Simple Techniques & Materials

Straw bale construction in the United States dates to the late 19th century in a part of Nebraska where trees were few and far between. Some of those straw bale houses are still standing.

Advocates point to a long list of advantages of straw bale construction, including durability, fire- and insect-resistance, the renewable nature of the building material, low material cost, high R-values, and relative ease of construction, making houses well suited for owner-builders on a tight budget.

Straw (not to be confused with hay) is an abundant resource—it is what’s left after the harvest of grain crops such as rice, wheat, oats, barley, or rye. Bales can be two-string, which weigh about 50 pounds each and are up to 40 inches long, and three-string, which may weigh 100 pounds and measure up to 47 inches long. Straw bale houses can be planned around these dimensions to make construction simpler, just as a conventionally framed house can be planned around the 4-foot increments that panel products come in. According to one online calculator, it takes 240 bales to make a 30-by-40-foot one-story house (see ironstraw.org).

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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