Photo courtesy of Natural Building Resources
Q: Severe weather is a concern in our town, where we are planning to build our dream home. What are some home-construction methods that provide efficiency, strength and ruggedness?
A: Several relatively new home-construction methods are stronger and more efficient than typical, insulated wood framing that is built to code. Some use more than double the insulation value of typical framed walls and can even withstand hurricane- and tornado-force winds.
Traditional wood-framing methods can be adapted to provide greater strength and efficiency. If you build a wood-framed house, use staggered, double-stud walls on 24-inch centers. Staggering the studs not only doubles the insulation value of walls, it also minimizes thermal bridges (the direct, non-insulated paths that allow heat to flow between indoor and outdoor walls through the wood studs).
For a wood-framed home, install rigid-foam wall sheathing on the exterior, so all of the lumber’s thermal mass will be inside the insulation envelope. This can be covered with any type of exterior finish, such as siding, brick or stucco. Building in a relatively square or circular shape helps minimize the exterior wall and roof area, which reduces heat loss through walls. Also, square- and circular-shaped homes tend to resist the forces of storm winds best.
Other home-construction methods also provide strength and efficiency.
One method, known as “stay-in-place” construction, uses concrete and rigid-foam insulation, which is efficient and strengthens the home. The insulation forms hold the wet concrete and are not removed, so they provide both insulation and a substrate surface for installing interior and exterior wall coverings. Wall insulation values are as high as R-40 when this method is used.
A similar method uses hollow foam blocks made to fit your home’s plans. The blocks are designed with an open cavity inside. Concrete is pumped into the openings at the top of the walls and flows throughout the blocks, creating a strong, efficient structure.
SIP (structural insulated panel) systems are a type of standard, foam-insulated panels, with a thick, foam core sandwiched between two rigid sheets of various materials. The standard panels are often used for exterior walls enclosing post-and-beam-framed and steel-framed homes, providing some of the highest insulation levels possible.
The rigid sheets in SIP panels are unique because they are made of OSB (oriented strand board), which creates a strong, highly insulated panel. The panel is self-supporting and does not require additional basic wall framing. Once the SIP panels are attached to the foundation and connected, they support themselves, the floors, ceiling and roof.
Steel-framed construction is an excellent construction method if strength is the goal. Steel is strong. It does not burn or change shape over time as lumber does, and each steel piece is nearly identical.
From an efficiency standpoint, steel is superior to most other framing materials. Although steel is not a good insulator, its strength allows for thinner studs and wider spacing. This leaves more room for additional insulation inside the walls and fewer thermal bridges.
Efficient straw-bale homes date back more than a century in the United States. When placed on its side, a three-string bale is about 23 inches wide. When packed to a normal density, it produces an insulation value greater than R-50. The bales are stacked and bolted to a concrete foundation with vertical, threaded rods. Properly compressed straw bales are fire resistant when the exterior is covered with materials such as concrete or stucco. Soft plaster and gypsum interior finishes are attractive and durable. When completed, other than thick openings at windows and doors, they look like any conventional framed house.
Although it may look unusual, a geodesic dome design makes for an efficient and strong home. The most efficient models are constructed with thick, foam panels. Concrete is sprayed over the exterior, completely covering the panels and filling the gaps between panels for strength. Another plus: The spherical exterior allows high storm winds to flow smoothly over it without damage.
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