LOG HOME and CABIN EDUCATION INFORMATION
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LOG HOME and CABIN EDUCATION INFORMATION
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R-Values or Thermal-mass in log homes In 1982 the North American Log Homes Council, part of the National Association of Log Home Builders preformed a study on “Energy Efficiency of log buildings”. The National Bureau of Standards technicians conducting this test built 2 structures 20’ x 20’, one out of 7” log and the second conventionally framed with 2” x 4” with roof, windows, doors and ceiling insulation being the same on both to compare wall R-values. The 7” logs was rated with nominal R-10 value and the 2”x 4” framed structure with 3 ½” of insulation rated nominal R-12 giving the 2”x4” structure the advantage of 17% higher R-value. During the entire 28 week three season test cycle both structures used virtually identical amounts of energy to conclude that the “Thermal-mass” of log walls is an energy-conserving feature in residential construction. The National Bureau of Standards research team found that heavyweight walls (framed, concrete and logs) did exhibit a thermal mass effect saving significant amounts of energy both in summer cooling seasons and intermediate heating seasons representative to Fall or Spring in the Washington, D.C. area where tests were conducted. During the 11 week summer cooling season the log building used 24% less cooling energy than the 2”x4” framed building with 17% higher R-value. In the 14 week winter season the log structure used almost the same amount of heating energy as the 2”x4” framed building with the higher R-value. R-value in logs depending on species can be calculated at an approximate 1.45 R-value per inch of log diameter. To review this report and learn more about “Thermal-mass” and benefits log on to www.ornl.gov/sci/roofstwalls/AWT/Publications/index.htm The Log Home Council in cooperation with the Buildings Technical Center will be performing a “Thermal Performance of log walls” beginning in Fall 2005. These tests will reflect dynamic thermal-mass benefits on nine basic species used by members of the Log Home Council. Two samples of Chinking will also be tested.
Species tested: - Lodge Pole Pine, Engleman Spruce - Red Oak - Southern Yellow Pine - Douglas Fir-Larch - Hemlock, mountain and Western - Red Pine, Bald Cypress - Hem-Fir, Ponderosa Pine, Sitka Spruce - Eastern softwoods, Eastern Pine, Western Red-Cedar, Western woods - Cedar, Northern-White
All manufacturers that are current members of the Log Home Council were invited to participate in this 24 month study, but only a few stepped up providing funding and materials to finally evaluate different species used in log homes and to set the standard proving that one species is better than others. You will see the final results from this test to discredit the old saying “one species is not better than another”. Manufacturers that have been in the industry for over 28 years or longer harvest their own logs from the forests and have a fully functioning mill operation here in the United States can now, with this independent study prove their knowledge that “one species is better than another”. Foresters know the science of logs and have been discredited for too many years. Time will set the record straight. You as a consumer need to do your home work and ask questions that any log home manufacturer should answer. We hope to help you in developing questions that could save you lots of money in the long-run. |
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