The Energy Efficiency of Log Homes
June 1999
Over the years through my involvement in home building, there are two truths I have come to learn:
- People who own log homes love them, and do not complain about energy efficiency problems.
- People who live in conventional frame housing wish they owned a log home.
With this discussion, I wish to put to rest the many myths about energy problems in log homes.
Stone Mountain Safaris Lodge - Fort Nelson, B. C.
An 8700 square foot masterpiece heated comfortably in the winter with only two wood stoves.
Comparing Heating Performance between Conventional Frame and Log Homes
The big question asked by log home consumers is "How Energy Efficient are Log Homes?" In 1991, the Research Centre at the North American Home Builders' Association, conducted a study on the energy efficiency of log homes entitled Evaluation of Log Homes ' Heating Performance in Northern Climates. For their study, they examined the heating performance of conventional frame homes with R-19 batts in New York State, to homes with 4-inch western red cedar walls in the same region.
The study showed that the two wall systems provided the same benefits of energy efficiency. A number of companies have built similar western red cedar homes in Northern British Columbia, Saskatchewan and Alaska with similar results.
R-factor is not the only issue
The amount of energy used to heat any home involves more than just the R-value of the wall system. It also involves:
- the tightness of fit and dryness of insulation in the wall cavity.
- the ability of the wall to block air transfer from inside to out.
- the ability of the wall system to store heat and radiate it back later.
Log Walls are Tight Insulators
Wood is an insulator. In each log wall, there are millions of tiny air pockets which insulate home owners from the elements. As an insulation system, log walls can be far more effective at blocking heat transfer for the following reasons:
The effectiveness of insulation depends on how well it fits the cavity. Batt insulation will sag over time, creating cold air paths for heat transfer. Insulation can also be damaged by interior condensation penetrating ineffective or damaged vapour barriers, or by failure of external water screens. In either case, the effective R-value of the wall cavity will diminish over time. These problems do not occur in log walls.
Air barriers play an important role in keeping heated air inside the house. If constructed properly, log wall systems are more effective air barriers than the polyethylene sheeting found in conventional housing. Air tightness tests on Canadian rectangular-milled log homes have out-performed conventional housing for years.
All solid objects have the ability to retain heat and radiate it at a later time. This thermal mass property will reduce utility bills, and is one of the reasons why many log home owners have experienced lower heating bills with their new home.
For log home energy efficiency, your best choice is western red cedar. Based on thermal efficiency standards listed in ASHRAE handbooks, it has the highest R-value per inch.
Thicker Wall Systems Are Not Worth Their Investment
As part of developing a national energy code for Canada in 1995, the Canada Codes Centre of the National Research Council sponsored a study on log home energy efficiency entitled: Construction Report for Solid Wood Walls in Houses - Final Report. This study reviewed the cost of building a variety of round and profiled log wall systems in every Canadian province. The results of this study showed that for the coldest Canadian region and the most expensive heating fuel, a four-inch thick wall system was the most energy efficient log wall system. There is no energy pay back in going to a thicker wall system.
In 1996, I studied this issue for the North American Home Builders' Log Homes Council. For an average 1,600 square-foot home with pine logs, it would cost about $4,700 to go from 6-inch to 8-inch thick logs. (Note: In 1999 dollars, no less than $US 6500.) If you built with western red cedar or oak, the cost would be higher. No matter where you built this home in North America, you would not save enough energy to get your money back—even if you owned this home for 30 years!
As a homeowner, you have to make a very serious decision about how to spend money wisely. It is not wise to spend $6500 on something with no payback. You would be better off to take the money and spend it on maintenance-free materials (metal roof, metal clad windows, tile floor upgrade in high traffic areas, etc), or on features that will enhance the market value of your house (more or bigger windows, Jacuzzis, higher quality kitchen cabinets, landscaping, etc.)
If you choose a thicker wall, do so because you like the look. Not because it's a wise investment in energy.
Are You Worried About Freezing to Death In Your Log Home?
Ironically, most people in the U. S. are more concerned about heating and cooling problems than folks in Canada. Hard to understand why? The bigger problems should occur in northern climates where the heating needs of a structure will be the greatest. But they don't - not even with a western red cedar wall system.
Below is a table showing a variety of heating degree day (HDD) readings across North America. HDD readings are used by weather services to determine how often you will heat your home. The higher the HDD, the more often you will have to turn on the heat to keep warm.
Ft. Nelson, B. C. is the home of the lodge for Stone Mountain Safaris. An 8700 square foot hunting lodge heated primarily by two wood stoves and a backup propane furnace. The tight lock between logs and the thermal mass of wood keep people warm even on the coldest days.
Canadian Cedar Log should know. We have built thousands of structures in Northern Climates.
| Location | Heating Degree Days (HDD) |
| Ft. Nelson, B. C. (Stone Mountain Safaris) | 10874 |
| Anchorage, Alaska | 10860 |
| Burlington, Vermont | 8030 |
| Calgary, Alberta | 9703 |
| Denver, Co. | 6150 |
| Fargo, North Dakota | 9250 |
| International Falls, Minnesota | 10600 |
| Kalispell, Montana | 8150 |
| Logan, Utah | 6750 |
| Marquette, Mi. | 8390 |
| Saskatoon, Saskatchewan | 10856 |
| Rock Springs, Wyoming | 8430 |
| Wausau, Wisconsin | 8490 |
Heating Problems in Log Homes
If there are heating problems in log homes, they are no different than the problems found in conventional housing. These problems have nothing to do with the wall system, but with the design or installation of the heating system. If the heating system is undersized, improperly installed, or the thermostat is not effective, there will be heating problems and potentially high heating bills. Many heating contractors have not been formally trained to do their work. The heating system in any new home should be designed and installed by certified contractors (ACCA contractors in the U. S. - HRAI contractors in Canada).
Bill Kolida is a North American log home regulatory specialist. In 1995, he represented the log home industry in Canada on the National Energy Code. He has been responsible for developing the insulation performance standard for two provincial building codes in Canada. He has also written a paper for the National Assn. of Home Builders - Log Homes Council on log home energy efficiency issues. In the past, he has worked for BC Hydro both as a program manager and consultant on new home energy efficiency issues. He is also a certified heating and ventilation system design specialist in Canada. Currently, he sits on a standards development committee in Canada.