Balancing home efficiency with comfort
By James Dulley
The channels along the edges of the panels are interconnected with reinforced steel for extreme strength. Photo by American Ingenuity.
This efficient house construction method uses many insulated wall panels and self-supporting roof trusses. Photo by Deltec Homes.
Dear Jim: I am planning to build a new house. I want one which is very energy efficient, but still livable. I know that standard stick-built is not the most efficient. What construction methods do you recommend? - Pete S.
Dear Pete: You are wise to think about the livability of a house in addition to efficiency measures. While building a small, simple house with thick insulation and very few windows would save energy, it likely would not suit most typical American families. You should balance a home’s energy efficient aspects with comfort and convenience. Often, by making minor lifestyle changes, your family can dramatically reduce utility bills even in a less efficient house.
The typical “to-code” stick-built house—a home constructed entirely or largely on-site—is not very energy efficient, but this does not necessarily mean all stick-built homes are inefficient. With adequate (more than to-code) insulation, high-quality windows and doors, and attention to construction details, a typical lumber-framed house can be very efficient. Attention to detail, such as sealing all the vapor/air barriers, is particularly important as it relates to the airtightness of a house.
Several new construction methods are inherently much more efficient than a rectangular lumber stick-built house. These methods include round panelized, geodesic dome, steel-framing, foam block/concrete, structural insulated panels (SIPS), and post-and-beam houses.
A round house is particularly energy efficient for several reasons. A circle provides the greatest amount of indoor floor space with the least amount of exterior wall surface area. Since heat loss (or gain) from a house is directly related to wall surface area, less wall area results in less potential loss. Also, wind tends to flow smoothly over the exterior resulting in fewer air leaks into and out of a house.
A circular panelized house, such as ones made by Deltec Homes (www.deltechomes.com), uses a series of eight-foot wide flat panels to create the round house. These panels are made specifically to your house plans and are delivered to your building site ready to assemble. A combination of insulation inside the hollow panels and thick foam sheathing on the exterior results in a high level of insulation. Being manufactured in the controlled factory environment, the panels fit perfectly together for an airtight house.
The roof is self-supporting using trusses. This provides the opportunity to have a open floor plan which is an efficiency advantage with solar or other alternative heating methods. Many house manufacturers have energy efficiency experts on staff, such as Deltec’s “Green Team,” to help you design a super-efficient round house. These companies also offer predesigned green home packages and super-insulated wall designs.
Geodesic dome houses are the ultimate in circular design for the least overall exterior surface area, but the interior living space is quite different from a typical house. The most efficient and strongest ones are made of a combination of triangular foam pieces covered with concrete. Because of their shape, both circular panelized and dome houses are inherently resistant to damage from severe weather such as hurricanes.
Although it seems counterintuitive because metal conducts heat, steel-framed houses provided by folks like Kodiak Steel Homes (www.kodiaksteelhomes.com) are very energy efficient. Since the steel members replace the lumber in the walls, these houses can look identical to a standard stick-built lumber house. The only difference is the walls may look thicker, only noticeable at the window and door openings.
The most efficient steel-framed houses use large steel-framing members (called red iron) spaced very far apart. This greatly reduces the amount of thermal bridges (no insulation at studs) inside the walls. The steel members are very strong and stable, so the house stays airtight without the settling typical with lumber framing.
Foam block houses are assembled somewhat similar to hollow Legos. The lightweight foam blocks are stacked on top of one another to create the walls. When stacked together, open channels are created throughout the blocks. A concrete truck pumps concrete into the top of the wall and it flows throughout the wall. When it sets up, the wall is extremely strong. The foam blocks provide superhigh insulation levels. This construction method offers much architectural design flexibility and the homeowner can easily help with the basic construction.
SIPS are very strong panels with thick insulating foam in the center. They are also called stress skin panels because the interior and exterior skins provide the structural strength for the house. These long panels are factory-crafted to fit your house plans. With the high insulation level and few joints needed between the panels, these houses are efficient.
Standard form core wall panels are similar except the skins are not strong enough to be self-supporting. These panels are often attached over attractive post-and-beam framing which supports the house.
Have a question for Jim? Send inquiries to James Dulley, Illinois Country Living, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com.