Q: We are planning a new super-efficient house and considering nontraditional construction. What are some options for a livable, budget-minded home?
A: There are many options when it comes to super-efficient construction materials and assembly techniques. There also are ways to include some of these new methods into more traditional wood-framed stick-built construction.
Methods such as staggered double-stud walls, thicker studs on wider centers and insulating sheathing are efficient.
One of the most efficient construction techniques uses foam blocks and concrete. These houses are indistinguishable from stick-built homes. Large, hollow foam blocks made for your specific house plan are stacked to create walls. The foam provides wall insulation levels as high as R-30.
Once the foundation is poured, your builder may allow you to help stack the blocks to lower labor costs. Concrete is then pumped into the openings in the top blocks. It flows throughout all the open channels to form a strong, rigid core. Interior and exterior walls can be finished with commonly used wall materials.
Circular houses are another option. This is efficient because, for a given amount of usable floor space, it has less exterior wall area than a rectangular one.
Less wall area means less heat loss—or heat gain during summer.
Cold winter winds flow smoothly around a circular house, creating less pressure gradients and less air infiltration.
One particularly efficient circular house construction technique uses self-supporting roof trusses with no interior supporting walls, providing greater interior layout flexibility and an open floor plan. This is an advantage when using solar or other alternative supplemental heating. Heavily insulated, R-30, 8-foot-long exterior wall panels create the shape.
Using foam-core wall panels is another well-insulated and airtight construction method. Structural insulated panels use thick foam sandwiched between two strong skins for up to R-45 insulation. They are designed for your specific house plan and locked together by various methods to create the walls. SIP panels are self-supporting.
If you prefer to use wall framing or like the interior appearance of timber framing, less expensive standard foam core wall panels are available. These are as efficient as SIPs construction, but require a supporting
Steel-framed wall construction can be very efficient. Although steel conducts heat, the strong, heavy red iron framing members can be spaced far apart. This reduces the uninsulated area—called thermal bridges—for better overall insulation levels up to R-40.
Steel framing is extremely strong, so the house stays airtight and never settles. This is how most commercial buildings use steel construction. Its strength also offers architectural design flexibility.
Geodesic construction is efficient because the shape is spherical, which minimizes exterior area. One unique design uses thick foam blocks—up to R-60—attached together with supporting wood framing. Concrete is poured into steel-reinforced channels. The wood framing is then disassembled and used for interior walls. These have withstood hurricanes.
Straw bale wall construction is certainly not a new method, but it’s efficient and relatively inexpensive in rural areas where straw is plentiful. The bales are stagger-stacked, similar to bricks, with a vertical steel rod through them to create the walls.
The interior and exterior are usually finished with cement, plaster or stucco to create a strong attractive house. With 2-foot-thick walls, insulation is as high as R-50. Check your local building codes for approval with any nontypical construction method.