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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.
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: 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.
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.
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.
Readers whose homes are drafty, leaky, or otherwise too cold and who have high heating bills should also see these air leak articles:
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.
The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article.
Continue reading at INSULATION R-VALUE, SOLID LOG WALL or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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(Feb 20, 2013) Matt Davidson said:
hi i am a handcrafter of log homes. ok,i admit log homes are not built to r 2000 standards, nor will they ever be. they are getting better though. The industry knows what people demand. the industry is getting better all the time.
as a builder, i do not try to sell our handcrafted product as the most energy efficient building money can buy.
they are very comfortable though when built correctly, and we do. it seams to me you are painting us all with the same brush, professionals and do it your selfers alike. your pictures are bias to prove your point. what you dont mention about the shack in the top picture is that this happens to framed buildings as well. that picture is not an example of poor log construction as much as it is a fine example of poor roof insulation,vapour barier and air ventilation. editor, i dont know if you noticed but the roof in your picture is not made of logs!
i dont see icicles coming our of the log wall! a little honesty would be nice. how about the fact that wood has the highest r value of any natural product, the fact that a log home sequesters carbon, and that a properly built log home(not like the drafty shacks you show) can last for 800 years(as they have in Europe)! they are built form a sustainable renewable resource. that is good for the environment period. put fiberglass up against that track record.
i do not dispute the fact that log r values are lower per inch than foam, mineral wool,or fiberglass, but even these insulation products fail miserable when installed wrong (as your picture proves). i resent the fact that you speak about a construction industry you obviously know nothing about.
Davidson Log & Timber Artisans Inc.
Mr. Davidson is a log home builder in Ontario, Canada. He can be contacted at - [Ed.]
Davidson Log & Timber Artisans, Inc.
54 Rama-Dalton Boundry Rd.
Washago, ON L0K 2B0
We appreciate hearing your opinion; we also welcome critique, content suggestions, citations and references, and objective data that makes all of use smarter.
It is useful to separate aesthetics, perceived comfort, actual energy costs, durability, and other factors for log homes as well as other types of construction, and at least as important to separate opinion from objective data or facts. Certainly taking an experienced look at a building after it has been in service for a decade can give us a dose of "real world" data.
Both the original author, Steve Bliss, and I (InspectApedia editor) have constructed log homes, and in my case, inspected hundreds of them in various parts of the U.S., Canada, The U.K., Norway, Spain and Germany.
I have sene a wide range of experience and expertise among log home builders, with a concomitant variation in energy efficiency, comfort, leaks, operating and maintenance cost, durability, and yes, even rot.
At a ten year old log home I foundleaks at every window and predicted future rot: none of the windowshad been properly installed, all using makeshift inserted frames, no splines, no sealant. The builder, who was at the inspection, was surprised at my concern. He had been building log homes for a decade and "... had never seen any rot"
"Where is the first log home you built?" I asked. [Note: this builder was a New York log home builder, he was NOT Mr. Davidson who commented above - Ed.]
"Nearby, I live in it. Let's go over there" he suggested.
The home was beautiful, in a shady wooded glen in a country setting. Together we walked around to the rear of the home, a shady spot where I suspected a low roof eave might also suffer from overspilling gutters, rain splash, or other worries. I could see water stains and punky looking wood at the builder's log home bedroom window. Using just my bare hand, I reached out and grabbed a handfull of rotted log at the lower corner of the window. I could stick my fist into the wall.
The builder, like so many in our field, had good intentions, was a great craftsman on some topics and not so expert on others, and like many of us, didn't make those distinctions. The builder, whos opinions were as vehement as Matt's (above), had never actually gone back to his homes a few years later to see how they were doing.
Matt this article may be of interest to you: LEAK DIAGNOSIS & CURE in LOG HOMES
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