Research Report on Energy Efficiency of Log Home Buildings Credit: Bitterroot Valley Log & Timber 2036 US Hwy 93 N. - Victor, MT 59875 (406) 642-3091
Margaret Lowe, in her article entitled "Myths and Truths of Log Home Ownership" addresses the efficiency of Log Homes. She wrote: "Myth #1: Log homes are not energy-efficient: FALSE, in capital letters. Early in this decade, the nation's model energy code finally recognized what the log home industry had claimed for 20 years -- that a log wall's thermal mass makes it as energy-efficient as a well-insulated wall. This claim wasn't acknowledged during all those years because thermal mass is difficult to quantify. Log home owners had the heating bills to prove it was true. but the Department of Energy and national code officials needed more than empirical evidence. So for 13 years the Log Homes Council ( a division of the National Association of Home Builders in Washington, DC) gathered scientific statistics from independent research projects to substantiate its claim. "At the heart of the debate were R-Values, the measure of heat transfer through materials. When the energy crisis struck in the mid 1970's, state and federal governments had to quickly develop new energy-performance standards for residential construction and all the building materials used in that construction. Since the situation was a crisis, and the R-value methodology already existed, it became the standard, no questions asked. "R-value measures a material's resistance of heat from one side to another. Log's have a relatively low resistance to heat transfer. In fact, they actually absorb and store heat in their cellular structure. This puts them at a serious disadvantage in the cold weather states. Producers had to overbuild their houses in order to meet total R-value requirements. This not only drove up construction costs, it also created a lot of confusion. "The opposite of R-value, thermal mass, measures a material's capacity to absorb, store, and slowly release heat over time when temperatures drop. Logs do this very well because of their cellular structure, bulk, and thickness. The problem, was proving it. "An early breakthrough came in studies conducted by the National Institute of Standards for HUD in 1981-82. The studies proved thermal mass does significantly reduce heating and cooling loads in moderate climates. however, energy experts continued to question the value of thermal mass during the winter months in northern climates where heat is a constant need (or during summer months in southern climates where cooling is in need) and thermostat settings are opposite outdoor temperatures. "Two more recent studies, both conducted in cold climate states, proved the log home industry was right. "In 1990, an independent testing agency, Advanced Certified Thermography, conducted a study for the Energy Division of the Minnesota Department of Public Service. Its focus was heat loss through air leakage, which was assumed to be a special problem with log homes because of their many joints. The study found the industry's improved joint construction and its use of expanded foam sealants and gaskets at joints and corner intersections had substantially reduced air-infiltration rates. The study concluded air leakage in a well-built, modern log home is not due to its log walls. In fact, in the 23 homes studied, it found air leakage occurs in the same places it occurs in conventional frame homes: at the top of cathedral ceilings, around window and door frames, and along the tops of walls where they join the roof. "A second study, conducted in 1991 for the Log Homes Council by the National Association of Home Builders (NAHB) National Research Center, discovered the thermal mass of log walls does significantly reduce energy use for heating in cold climates. It based its conclusions on a comparison of actual energy use in eight log homes to the actual energy use of eight well-insulated frame houses during one winter. The 16 homes were evenly divided between upstate New York and Montana. The study also compared the homes' actual energy use to their predicted energy consumption. The results led to the conclusion that log homes were as energy-efficient as well-insulated frame houses. What is especially significant about this study is that the average R-value of the log walls was 44 percent lower than the average R-value of the frame walls. Obviously, the thermal mass performance of log walls is an advantage to log home owners." According to an article by Peter M Hart of New England Log Homes: "the oft-cited R-value (resistance) factor is meant to be a measure of heating efficiency but actually, that concept is both inaccurate and misleading. As an example, an illusion is created to convey to the homebuyer that if three inches of fiberglass is good, then six inches is twice as good and naturally, 12 inches is four times better. "NOT SO! After a certain amount of insulation has reached optimum, the overage of insulation is waste and does not justify the additional cost. "To arrive at the R-value of a particular type of insulation, heat is passed through the material by conduction, under fixed temperatures and only when the material is completely dry. No consideration is given to convection, radiation loss, solar input, heat and storage capabilities and the influence of moisture. "For instance, a test of fiberglass sample rated R-13 when dry is reduced to R-8.3 when conditions reach a moisture content of 1.5% -- a loss of 40% insulation efficiency." These R-value standards were determined under unrealistic conditions due to the fact that we all live in a humidity laden atmosphere. This humidity level is compounded in the home environment.
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Spring Inspection & Maintenance Checklist
Creasey Log Homes
With the advent of warmer weather, Spring is probably the single best time to get out and inspect and preserve your log home. And, if problem areas are discovered, the upcoming Summer months are the optimal season for maintenance work. After decades of restoration work we have seen recurring themes that, if only they were systematically addressed, would minimize expenses for repair. The following are some of our strongest recommendations for caring for your log home:
#1 Wash Your Logs
Over time, your home's logs will see a build-up of dust, pollen, and good old-fashioned grime that can set into your log finish and actually develop damaging mildew. One of the best recommendations for prolonging the life of your log home finish is to annually wash it with an ecologically-sound cleaning solution and mild scrubbing tools. Pressurized washing equipment is not required but, if you opt to use it, make sure the pressure is light enough to not remove or weaken any of the finish. If you choose to stay up on this process yearly, the effort will not be too difficult and the benefits will be significant.
#2 Inspect Your Logs
During the process of cleaning, or at a separate time, you can give some closer examination to potential problem areas needing attention. The following are some of the more likely suspects that may need inspection:
- Railing Systems & Porch Posts
Log rails, though sometimes protected by porch roofs above, are often directly exposed to the elements. At least wall logs will typically have some measure of roof protection overhead. With such constant pounding from ultra-violet rays and, in Western Washington, high precipitation, railings are often one of the first components of a log home to begin to fail. Watch for up-facing checks and consider having them sealed to prevent water intrusion.
As well, the horizontally-cut tops of rail posts have three critical faults and deserve special attention. First, they consist of porous end grain that seeks to absorb moisture more than any other part of the log. Second, tangential shrinkage causes checks to open up which can funnel water deep into the log where it is difficult for the moisture to evaporate. Third, it goes almost without saying that the horizontal surface itself lacks the ability to shed water complicating the first two issues. If it appears that the weather is winning out over your posts consider having Creasey Log Homes install protective, malleable sheet metal caps to seal off any water penetration before it can cause further damage.
Likewise, the base of porch posts can often see a greater weather exposure than other elements of the home. The reason is simple: rain and UV rays seldom fall in an exclusively vertical manner and down low the posts are less protected from the roofline above. Although wall logs theoretically experience this same phenomenon, they are most often elevated above the ground. Posts are regularly mounted directly to a hard surface such as deck or patio material and its the resulting water splash that, over time, can create a potentially troubling situation. Be sure to inspect these areas carefully for possible development of rot and create a more aggressive plan for maintaining the protective finish.
- Extended Logs
Any time a log extends out of a wall the possibilities for an undesirable issue increase. Examples of extended logs are corner tails, log joist tails at an upper floor level, balcony joists, or purlins that extend beyond the roofline (in fact, a purlin can be susceptible to danger even if it does not extend beyond the line of the roof if the fascia does not adequately cover it). These elements realize an increased exposure to the elements and have horizontally-aligned surfaces that can be slow to shed water and may even accumulate it if there are open checks. Should rot begin to develop it is easy for it to begin to spread within the log and to the interior of the wall. With joist ends and balcony logs that are contiguous with the upper level floor framing, this can spell real danger. If you suspect that your balcony log joists may be suffering damage, consider having Creasey Log Homes apply a protective covering to alleviate any long-term effects.
- Lower Wall Logs
The lower log courses of your walls can experience greater weather exposure and the effects of vegetation. Pay special attention here and review the following comments about plants and shrubs.
#3 Cut Back Shrubbery
One of the most easily fixable, yet potentially damaging, concerns is centered around landscaping that is too close to the home. Vegetation limits air circulation and tends to shade and trap moisture in an area where you don't want it. Use common sense here; the more you can trim it back, the better.
#4 Inspect Your Sealants
In addition to log material itself, review any applied sealants including caulking and chinking. Make sure that no new significant skyward-facing checks have appeared or that previous applications have torn or pulled away from their bonding surfaces.
#5 Check Your Gutters
Some of the most detrimental damage that we have seen involves gutters and downspouts that are not working properly. Clogged gutters, improperly sealed connections, or gutters that do not extend far enough to capture all cascading rainfall from the roof, will concentrate water exposure and limit the ability of your logs to dry out. If not immediately addressed, such long term exposure will be quite negative in its effects.
These recommendations are within the ability of most homeowners to adopt. With regular attention many of the potential problems that could be experienced by your log home can be alleviated. However, should you require an application of a new finish or other protective materials, please do not hesitate to schedule an inspection and obtain a free quote for services.