Log home & log wall insulating properties: This article describes the insulating and heating properties of log homes, comparing solid log structures, slab-sided log homes, and conventionally framed homes. This series of articles provides information on the inspection and diagnosis of damage to new and older log homes and includes description of log house and log siding insulation values and alternatives, and also a description of the characteristics of slab-sided log homes as well as all other types of log home construction. We include illustrations of log structures from several very different areas and climates in both the United States and Norway. Our page top photo shows a modern kit log home constructed in New York State.
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The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Question and Answer: Comparison of Energy Efficiency of Log Homes with Wood Framed Homes
Question: Log Homes, All Bark?
We are planning to build a new home in several years and want our project to be totally successful and energy efficient. We have always had leanings towards rustic structures and have almost settled on a log building. All the manufacturers of log buildings stress their tremendous energy efficiency.
Confused about log home energy efficiency would be describing our state lightly. Have you ever done a study of the energy efficiency of log structures or compared a log home's energy costs with a conventional, highly-insulated structure?
Although log home manufacturers would like the public to believe that log homes are highly energy-efficient, they have not yet impressed us. While any home can be made energy efficient with enough insulation and tightening up the building envelope, log houses have some built-in energy inefficiencies.
Questionable Log Wall R-Values
First, wood by itself is a poor insulator, at about R-8 for a 6-inch-thick (average) cedar log wall. [Have you noticed that the thickness of a curved round-log wall or a half-curved D-log wall is not uniform in thickness? A nominal 8-inch solid log wall made of rounded logs has an average 6-inch thickness.] Insulation must be added to such a solid log wall even to bring it up to the R-11 insulation value of a standard 2x4 wood framed stud wall insulated with fiberglass batts.
Of course you can't add insulation to a solid log home without diminishing some of the log house's original rustic appeal on the inside or outside. Also, adding insulation inside will lose the comfort benefit of thermal mass of the logs. We discuss these factors in detail at LOG HOME WALL INSULATION VALUES.
Log Home Wall Air Leaks
Second, log houses invite air infiltration because they have many yards of between-log gap. It is true that log home manufacturers have come up with ingenious log wall gasketing that should stop air infiltration leaks between logs, but if you are looking for energy-efficiency, why not choose a design that does not have such a large air infiltration problem to be solved in the first place.
[DJF Note: our experience with both building and inspecting/diagnosing log homes indicates that too often, especially with owner-built kit log homes, errors and omissions in the gasketing system are responsible for serious air and sometimes water leaks in the log home's walls. Similar problems occur around windows if they are not properly installed and sealed. See Leak Diagnosis & Cure for Log Houses for details. If your home, log or otherwise, is drafty, see: AIR BYPASS LEAKS, AIR LEAK MINIMIZATION, and AIR SEALING STRATEGIES.]
Log Homes Have Thermal Mass
Solid log homes are more massive than lightweight wood-frame insulated structures, but a National Bureau of Standards study found that the energy that a log home saves in the swing seasons (spring and fall) through added mass (and comfort for occupants by heating or cooling systems needing to cycle on or off less often) does not amount to much on an annual basis.
A slab-log sided home (see our photographs just below) looks like a log home on its exterior, but is built with conventional wood framing that permits high wall insulation values; this design also avoids the log home wall air leak problem. This highly-insulated log home alternative gives up the interior beauty of solid log walls, gives up the comfort of thermal mass, but gains high energy-efficiency and low heating costs. See Slab Log Cabin Siding for details.
The above question-and-answer article about the energy efficiency and comparative heating and cooling cost of log homes compared with conventional wood frame structures, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
Overcoming drafts and un-wanted air leaks is the first priority for making a building comfortable and for reducing heating or cooling costs in cold climates. INSULATION R-VALUES & PROPERTIES provides detailed estimates of the insulating values and properties of various insulating materials.
Readers should see R-VALUES & THERMAL MASS in LOG HOMES, and see LOG HOME WALL INSULATION VALUES where we compare the typical insulation values of a log home with a conventional wood framed structure, and where we include a discussion of the effects of thermal mass of log homes, providing also typical solid log wall home R-values.
That article also explains the insulation and energy efficiency character of log-slab-sided conventional wood-framed homes. Readers whose homes are drafty, leaky, or otherwise too cold and who have high heating bills should also see these air leak articles: AIR BYPASS LEAKS, AIR LEAK DETECTION TOOLS, AIR LEAK MINIMIZATION, and AIR SEALING STRATEGIES.
The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article.
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