GREEN Topic: Log Homes
Technology Snapshot & Benefits:
Log homes are commonly associated with “The American Dream” because of their reputation of high quality and value and their classic outdoors look and feel. Log homes have been built in the U.S. for centuries, but saw a rapid boost in popularity starting in the 1960’s during the �back to the earth� movement of that era. From 1980 to 2001, the log home industry grew by over 70%, launching them into the mainstream real estate market. Currently, around 25,000 log homes are sold each year and they make up roughly 10% of the custom homebuilding market in the United States.
Log homes are a green choice for a variety of reasons. They are usually made from regionally-grown and locally-harvested materials, reducing the energy and greenhouse gas emissions associated with the transport of building materials. Processing logs utilizes far less energy than processing lumber and oftentimes logs that conventional mills cannot use can be used to build log homes. Because the logs represent the entire thickness of the wall and function as exterior and interior walls as well as insulation, no additional layers of building material are required. This reducing initial expenses and helps decrease production and manufacturing costs associated with the additional layers. Finally, the logs themselves are a renewable resource and can often be recycled and used again if a home is deconstructed.
Estimated Cost Savings:
Log homes are estimated to be 2.5-15% more energy efficient than standard homes. This can save an average of $150-$400 off of annual heating and cooling bills. Additionally, log homes have a unique, rustic look, adding significant resale value.
The R-value (measure of insulation efficiency) of log homes is typically less than standard wood-framed homes. This appears to be a disadvantage initially because higher R-values help prevent heat loss and lower heating and cooling bills. However, because there is a high thermal mass associated with thick wood, R-9 log homes are comparable to standard framed homes with R-values between 13 and 15. In other words, the R-values of log homes can be 30-40% lower than wood framed homes, but still perform the same when it comes to heat retention. Additionally, the logs themselves can provide additional insulation beyond their thermal mass benefits.
One of the main problems associated with log homes is air leakage. Air dried logs typically retain 15-20% of their original moisture which, over time, slowly dries completely. When this happens, the logs shrink, causing air gaps between them. To avoid this problem, make sure the logs your builders use are “seasoned” (dried completely in a protected space) at least six months before use. This will help ensure that they are completely dried and will not shrink after the home is built. Also, certain types of wood dry better and more thoroughly than others. Cedar, spruce, pine, fir, and larch are the most recommended species of wood when building in hopes of avoiding leakage problems. Caulk any gaps between logs to create a thorough seal of your home.
Logs are also hydroscopic meaning they absorb water quickly and easily. If uncontrolled, this can cause rot and promote insect infestation. Install large roof overhangs and proper drainage systems including sufficient number of gutters and spouts to keep water off of the log walls and away from the house. Finishing treatments are also available to help make the wood water resistant and avoid problems with mold, sapstain, and decay. Be sure to ventilate your home properly to keep moisture from building up in crawl spaces, basements, attics, etc. and compromising the strength of the walls.
Insects pose another treat to the health of log homes as they feed and/or attack the wood. To avoid insect damage, ask for logs that are pre-treated with an insecticide. Check any firewood, furniture, or other forms of wood you bring into your home for the presence of insects and store firewood as far from the walls as possible.
Because log homes have low R-values, they do not always meet building codes. However, many states (including Pennsylvania, Maine, and South Carolina) exempt log homes from having to meet all of the normal regulations since their thermal mass often compensates for the low R-value. In other states, the thermal mass can be calculated into the R-value to help create a more accurate description of the log’s insulation capacity.
Installation (Getting It Done):
When building a log home, be sure to ask your builder about the characteristics of the materials. Use wood that is treated with insecticides and finished with a water-resistant treatment.
Videos on This Topic:
Handcrafted Log Homes Video – Building a Log Home (2:38) – Precision Craft – In this video, find out the basics of how log homes are constructed and hear about a few of the benefits to choosing log over conventional building materials.
Log Homes: a Custom Home Niche Worth Exploring (2:33) – Log Homes Council – Learn about the history of log homes, what they look like, and what niche they occupy in today’s building industry.