Energy Efficient Log Home
Energy efficient log homes are constructed using natural and renewable resources and are inherently more “green” and eco-friendly than stick-framed houses that use processed lumber. Logs are also typically harvested and sold in discrete regions of the country, making their delivery more fuel-efficient. Developing technology is working to make log homes even more energy efficient. We know that log homes are very durable when properly designed and constructed since some of the oldest occupied buildings in America are made of logs. Energy Efficient DesignDesigning an energy-efficient log home requires that the whole-house systems approach be taken into account. It’s important to realize that the house is a complete, linked environment and all its components interact with each other.By building smaller and smarter, small cabin plans make careful lifestyle design choices and maximize every square foot of living space. A good source for free and premium house plans using green and efficient designs is FreeGreen.com. Minimize Air InfiltrationAs logs dry they shrink and can develop cracks and gaps. Kiln-drying takes out most of the moisture and minimizes this shrinking. An energy efficient log home uses gaskets, foam or caulk ribbons between the log courses as they are laid.Carefully seal around window and door bucks with expanding foam. It’s not enough to shove some fiberglass batt insulation into these spaces as the fiberglass allows air to blow through. You may be filtering your air leaks but you’re not stopping them. Use proper log fasteners to ensure that the logs are pulled tight together and won’t shift. After 6 months or a year, go over your house and look at the cracks where logs butt together and butt into door and window bucks. See how the caulking and sealing has fared. Checks that have developed in the logs should be caulked and sealed. The energy efficiency of log homes will suffer as air infiltration rises. Cabin Orientation and Window PlacementThe long axis of the cabin should face south to absorb the heat of the sun’s rays. Keep southerly windows large and north-facing windows small to maximize passive solar energy gains.An energy efficient cabin will use long roof overhangs to keep the hot summer sun from overheating the cabin. In the winter the sun is very low in the sky so the long overhangs on your cabin roof allow the welcome winter sun to warm up the inside.
Incorporate Passive Solar DesignAn energy efficient log home will utilize five important elements of passive solar design:
Using both active and passive solar power approaches will maximize your efficiency and reduce energy costs along with helping to preserve our planet's resources. Control MoistureCheck out our page on log home landscaping for more information on water and moisture control. It’s important to keep water away from the logs as much as possible as log cabin energy efficiency decreases with higher moisture content.Wood is hygroscopic and tends to absorb moisture so be sure to keep your logs a minimum of 6” above the ground, more is better. Long roof overhangs will keep rain off the wood and reduce splashing back on to the lower logs. An energy efficient log home utilizes large overhangs to keep out the strong summer sun while still allowing in good winter sunlight to warm the cabin. Gutters are critical to keep the rain water managed and away from the logs or splashing back on the logs. Proper landscaping directs water away from the cabin and into gardens or plantings. Apply a good stain or sealer and make sure that you keep it up so that it blocks moisture from migrating into the logs. Building and Energy Code ComplianceDespite the evidence that the “thermal mass” of an energy efficient log home can provide as much as 15% better energy efficiency than stick-framed houses, some building code energy standards don’t recognize the energy efficiency of log homes.Contact local city or county building code officials to find out what the log building code standards are for your area. Some states have approved a “prescriptive approach" that allows you to make substitutions for low numerical R-values for logs so you can still build an energy efficient cabin. Building Product ChoicesChoosing appliances with the Energy Star label can save you up to 30% on your energy bills.Specify windows with a low U-factor (the inverse of R-value). Select a high solar heat gain coefficient (SHGC) if you live in colder northern climates, where you want to take advantage of the passive solar heat gain of the winter sun. If you live in the hot south, choose a low SHGC to block the summer sun, since your primary energy usage will be providing cooling. Choose your Energy Star rated windows from
this chart
which gives U-factor, Solar Heat Gain Coefficient, Visible Transmittance and Air Leakage numbers for different regions of the country from the Energy Star Efficient Windows Collaborative.
The energy efficiency of log homes is partly due to the thermal mass of the logs. Although the logs themselves may receive a lower steady-state R-value, performance adjustments or credits balance out the overall heating and cooling requirements. Studies have compared the energy use of log homes with conventionally-constructed houses (as the HUD and DOE did in the 1980s), and while log home energy use varies over the year, overall log homes used less energy than their stick-framed equivalents. The log cabin energy efficiency ranged up to 15% less energy usage. In other words an energy efficient log home may have 30%-40% lower numerical R-values, but still perform equally well to conventional construction. The exceptions are extreme climates where the benefit of thermal mass is negated. As focus shifts in the market to
building green
and optimizing energy efficiency in our homes, an energy efficient, eco-friendly log home will be increasingly recognized as a leader in the utilization of renewable, sustainable resources and environmentally-sound alternatives.
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