Q: With all the severe weather and natural disasters recently, I want to build a house that is both superstrong and energy efficient. What do you recommend?
A: Rectangular, stick-built, wood-framed walls are inherently weak. With heavier lumber and fasteners, they can be made stronger at a higher cost, but there are better construction options if strength and energy efficiency are your primary concerns.
It does not take an engineer to determine the most storm-resistant and efficient house design. Just look at nature and see what shape animals use most often for their own homes. It is a sphere or a domed-shaped structure, such as a bird's nest, a beehive, a bear's den, etc.
There are several reasons a dome house is the most energy-efficient and the strongest design. The amount of heat a house loses during winter (or gains during summer) is directly related to the amount of surface area of the walls and roof. A dome-shaped house has the least amount of surface area. A long, rectangular house of the same interior space can have as much as twice the surface area. (A good Web site for basic information is www.monolithicdome.com.)
Winds pass smoothly over a dome house with minimum forces and pressure differences from side to side. With less pressure differences across the house, there is less outdoor air infiltration into the house. This is also why dome houses often are the only ones still standing after tornado- or hurricane-force winds.
The basic circular design of a dome house is ideal for efficient open floor plans. This design provides for better natural circulation of air throughout the house and for better ventilation. With a venting cupola at the peak of the dome, hot, stale air naturally vents out during the summer.
There are several construction methods for dome houses. The strongest and most efficient ones are made from concrete and super-insulating foam. One design uses large, thick, triangular foam panels with a thick layer of reinforced concrete on the exterior and drywall on the interior. A channel in the edge of each panel is filled with concrete and steel mesh to connect them.
Other non-concrete designs use metal hubs and wood struts that are bolted together to create the dome frame. The structure is enclosed with sheathing, and insulation is placed in the walls, similar to typical wall construction. Another design uses prefabricated insulated wood panels that are bolted together.
James Dulley is a mechanical engineer and do-it-yourselfer. Send questions to James Dulley, The Sensible Home, St. Petersburg Times, 6906 Royalgreen Drive, Cincinnati, OH 45244. Go to his Web site at www.dulley.com to tour his energy-efficient home, post questions for other readers and find other information.