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LOG HOME BASICS |
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Log homes may be site-built or pre-cut
in a factory for delivery to the site. Some log home manufacturers
can also customize their designs. Before designing or purchasing a
manufactured log
home, you need to consider the following for energy efficiency:The R-Value of Wood In a log home, the wood helps provide some insulation. Wood's thermal resistance or resistance to heat flow is measured by its R-value. The higher the R-value, the more thermal resistance. The R-value for wood ranges between 1.41 per inch (2.54 cm) for most softwoods and 0.71 for most hardwoods. Ignoring the benefits of the thermal mass, a 6-inch (15.24 cm) thick log wall would have a clear-wall (a wall without windows or doors) R-value of just over 8.
Compared to a conventional wood stud
wall [31 D2 inches (8.89 cm) insulation, sheathing, wallboard, a
total of about R-14] the log wall is apparently a far inferior
insulation system. Based only on this, log walls do not satisfy most
building code energy standards. However, to what extent a log
building interacts with its surroundings depends greatly on the
climate. Because of the log's heat storage capability, its large
mass may cause the walls to behave considerably better in some
climates than in others. Logs act like "thermal batteries"
and can, under the right circumstances, store heat during the day
and gradually release it at night. This generally increases the
apparent R-value of a log by 0.1 per inch of thickness in mild,
sunny climates that have a substantial temperature swing from day to
night. Such climates generally exist in the Earth's temperate zones
between the 15th and 40th parallels.
Minimizing Air Leakage in Log Homes Log homes are susceptible to developing air leaks. Air-dried logs are still about 15–20% water when the house is assembled or constructed. As the logs dry over the next few years, the logs shrink. The contraction and expansion of the logs open gaps between the logs, creating air leaks, which cause drafts and high heating requirements. To minimize air leakage, logs should be seasoned (dried in a protected space) for at least six months before construction begins. These are the best woods to use to avoid this problem, in order of effectiveness:
Controlling Moisture in Log Homes Since trees absorb large amounts of water as they grow, the tree cells are also able to absorb water very readily after the wood has dried. For this reason, a log home is very hydroscopic—it can absorb water quickly. This promotes wood rot and insect infestation. It is strongly recommended that you protect the logs from any contact with any water or moisture. One moisture control method is to use only waterproofed and insecticide-treated logs. Reapply these treatments every few years for the life of the house. Generous roof overhangs, properly sized gutters and downspouts, and drainage plains around the house are also critical for moisture control. |
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