Expanding on Building America?s efforts to bring innovations in housing to the market, the U.S. Department of Energy (DOE) launched the Building America Solution Center in January 2013.
A new online tool, the Solution Center allows industry professionals direct and easy access to a wealth of proven innovations and best practices from the DOE. The Solution Center brings together recommendations from the country?s top building science experts?who work directly with the housing industry?to help remodelers continually improve their construction practices.
So, what?s in the Solution Center?
There are hundreds of topics accessible through the tool?s many functions, including common construction components using the Component Explorer, Energy Star specifications using the Checklist Manager, and home-performance-related topics using the Building Science Explorer.
Each topic provides a detailed description, a scope of work, and a variety of multimedia resources, such as CAD drawings, ?right and wrong? images, training materials, and compliance references.
These are just a few of the many valuable nuggets of content that you can find in the Solution Center. For more information, or to browse additional topics, visit the Solution Center (www.basc.energy.gov).
Double-wall construction is an option remodelers can incorporate to achieve higher R-value for walls.
They are relatively inexpensive to construct and use readily available materials that construction crews may be more familiar with than other high R-value options such as structural insulated panels and insulated concrete form walls. Double-wall construction consists of two stud-framed walls set up next to each other to form an extra-thick wall cavity that can be filled with insulation. Because the interior and exterior framing are separated by insulation, thermal bridging is also reduced or even eliminated.
Building Science Corporation, a Building America research partner, investigated several forms of double-wall construction including double-stud walls, truss walls, and offset frame walls in a study on high R-value walls.
Double walls are designed and specified by the architect and implemented by the framers. Site supervisors should ensure that framers and trades responsible for air sealing, insulating walls, and installing windows are knowledgeable and trained in techniques required for double-wall construction, and that skill-level expectations are included in the contracts for these trades.
Double-stud wall, cellulose insulation
One form of double-wall construction consists of an exterior 2x6 or 2x4 stud-framed structural wall and a second 2x4 nonstructural wall built to the inside with a gap in between of several inches.
If the studs in each wall are installed at the same spacing (e.g., 24-inch on-center) they can be staggered, although research has shown only minor improvement (<R-1) when staggering the studs.
Plywood boxes must be installed around the rough-in spaces for installing windows, which are typically installed flush with the exterior wall. The cladding attachment is the same as normal stud-framed construction practice.
One example uses a 2x4 exterior structural wall built at 16-inches on-center and a second 2x3 wall built at 24-inches on-center that is nonstructural but is used to support drywall and electrical services.
The two stud walls plus the gap in between provide a 9½-inch cavity for cellulose insulation, which would have a clear-wall R-value (for that section of the wall without interruptions) of R-34 or a whole-wall R-value of R-30.
In this example, a Class I vapor barrier of 6-mil polyethylene is installed on the exterior side of the interior wall to control air leakage and vapor diffusion.
A vapor barrier may be appropriate in very cold climates but is not necessary in warmer climates. If one is installed, it should be located on the exterior side of the interior wall and care should be taken to ensure that insulation on both sides of the vapor barrier is fully aligned with the barrier for the entire length of the wall.
For more information on how to construct a double-stud wall with spray foam or how to construct a truss wall, visit the resource guide on double-wall framing at tinyurl.com/m5mywr3. PR
Building Science is provided by EEBA and its National Education Partners. Building America research reports, Energy Star field guides, and a wealth of other technical content are now easily accessible via the Building America Solution Center at http://basc.pnnl.gov/. Contact Stacy Hunt at firstname.lastname@example.org.