Articles_and_InformationGlu-Lam-Log Notes, Log Home News Articles and InformationSun, 05 Apr 2009 14:19:08 GMTCopyright 2012. All rights reserved.Pyron Technologies SuiteFin CMSSun, 05 Apr 2009 13:34:32 GMT We have all seen the checking that occurs in round logs, heavy timbers, utility poles, and round-wood rustic furniture. Checking is a natural occurrence in wood components that contain the pith, or center of a tree. But what is the cause? As was pointed out in the previous article, wood shrinks twice as much in the tangential direction as it does in the radial direction. This can be observed in the amount of shrinkage that occurs in individual pieces of wood cut from trees. But, whenever concentric circles (continuous growth rings) occur in wood, the circumference of those circles (tangential orientation) shrinks twice as much as does the diameter (radial direction). Since the circumference is shrinking at twice the rate as the diameter, something has to give.       The outside circumference of a log (tangential direction) shrinks at almost twice the rate of the diameter of the log (radial direction). Stresses build up and in effect, the outside circumference pulls apart, causing a check.  At the time of milling, these logs were lightly checked and had a moisture content of 15% measured one and a half inches into the wood. The outside of the wood continued to dry at a faster rate than the inside, opening the check to the point where the top log no longer rests evenly on the log below it. One way to visualize how the difference between tangential and radial shrinkage causes checking in logs is to consider the concentric growth rings. The line formed by each growth ring is basically a series of tangent lines, or, one continuous tangent line (in a manner of speaking). As a log dries, the length of each growth ring will shorten by a proportionate amount (tangential shrinkage). But even though the growth rings are shortening, the overall log diameter shrinks at a lesser rate (radial shrinkage). Stresses build up, and checks occur. How big will the checks become? It depends on the location within the log. The larger diameter outer rings shrink more than the inner rings, since they all lose a percentage of their overall length. Thus, the checks in smaller logs are narrower than the checks in larger diameter logs, just as checks are narrower the closer one gets to the pith. Checking can be avoided entirely by avoiding what is referred to as “heart-centered” wood, which is wood that contains the pith. Whenever continuous growth rings exist, the tangential versus radial shrinkage stresses will cause checking. Can checking be prevented in round wood? Not really. Some log home manufactures saw a kerf along one edge of a green log before they allow it to dry. This acts as a stress release slot, forcing the check to occur along the saw kerf and preventing additional checks from occurring at random on the rest of the log.Since individual boards cut from logs usually do not contain the pith, these boards will not check during drying. Those boards that do contain the pith will typically check only on one side. So, laminated logs avoid the problem of surface checking.Besides the appearance of checks, which is objectionable to some people, checks serve as water- entry locations for wind-driven rain, causing checked logs to become wetter than those without checks. This may lead to decay problems. Also, checked logs have been found to allow air- infiltration to occur at wall corners, when one end of a check is exposed outdoors and the other end is exposed indoors. These checks should be caulked to improve the energy-efficiency of the home. AUTHOR BIO: Dr. Tom Gorman, P.E., is an associate professor at the University of Idaho in Moscow. He teaches courses in wood properties and timber design, and teaches “Understanding Wood” seminars at the Willow Creek Wood Productivity Training Center in Willow Creek, Montana. His research has included log home energy performance and strength properties of logs. He is a licensed professional engineer in Idaho and Washington states. His e-mail address is tgorman@uidaho.edu http://www.glulamlog.com/Articles_and_Information?id=2Sun, 05 Apr 2009 13:49:00 GMT "Sometimes in our zeal to protect nature, we can, in fact, create a more hazardous situation for our own existence within it."Building in a fire-prone area is not much different than building in a flood-prone area or an earthquake, hurricane or tornado zone. The possibilities for a disaster have to be considered and recommendations by knowledgeable professionals need to be followed. One of the factors cited in most of the literature describing the problems of wildfire threats to homes is the increasing human development of remote areas. There is no doubt that human incursion into once natural landscapes are on the increase throughout the country. Many homeowners, seeking solitude and natural settings, now have the resources to extend roads, power lines, and other infrastructure to allow very comfortable living in areas that were once thought of as only suitable for grazing or logging. It is important to recognize that humans are a part of the landscape. We have the ability to change the landscape and profoundly alter it. This not only occurs with residential development, but also with our utilization of the natural resources. Sometimes in our zeal to protect nature, we can, in fact, create a more hazardous situation for our own existence within it.   In an emergency, police and fire vehicles would have no access to a house at the end of this driveway.Fire in the landscape is something we are beginning to come to terms with. We are starting to recognize its natural role and see that it can never, nor really should, be eliminated entirely. Years of conventional wisdom taught us that fire was always bad and must be suppressed vigorously. Now, in many places, near total fire suppression has resulted in a buildup of fuels that can result in uncontrolably large and devastatingly destructive wildfires. In most of the areas we are now developing, the historic role of fire was a cycle of low-intensity burns that cleansed and renewed the landscape every few years, but didn’t kill the majority of trees. Fire was one of several agents of change that worked to make the forest what it was when the European settlers first came here. We can not rely on our ability to forever suppress this natural force, but we can learn to possibly withstand it.How does this perspective affect plans to build in the residential/wildland interface? An awareness of all the aspects of the proposed homesite should be factored into the plans. Learn all you can about the forest. Slope, geographic orientation, and vegetation are all important considerations. Aesthetic and other values, whether they are wildlife, seclusion, clean water, or economic resources should be balanced with the realities of the environment. This includes fire. The fact that there is risk does not rule out any development, nor can all risks be eliminated, but awareness and foresight can help prevent your dream from turning to a tragedy. When choosing a site for your home, do not forget to consider that, in the event of a crisis, emergency vehicles need to be able to get to you. This requires wide, well-constructed roads with sufficient turnarounds to prevent getting stuck off the road, and to allow simultaneous access by emergency vehicles and escape by local residents. Turns must be designed and hill grades established with truck traffic in mind. Narrow, private roads, while picturesque and inexpensive to build, reduce access and limit the ability of emergency vehicles to respond quickly. All developments should have more than one access route and emergency vehicles must be able to drive close to residences. Lastly, be sure to mark all roads and property with clearly visible reflective signs and numbers. Whether you’re building a new home or retrofitting an existing one, you can work with building contractors, your architect, and fire protection agencies to create a design that is both aesthetically pleasing and fire safe. Some things to keep in mind are:Undereave vents should be located near the roof line rather than near the wall to prevent wildfire heat or flames from becoming entrapped. For the same reason, the eaves themselves should be boxed or designed with minimal overhang.Attic openings, soffit vents, foundation louvers, or other direct openings in outside walls, overhangs, or roofs should be no greater than 144 sq. in.Where practical, build all roofs with the minimum of a 4 in 12 pitch and avoid horizontal roofs.Minimize the size and number of windows especially on the downhill facing side. Also, windows should not face trees or shrubs that are closer that 30 feet away.   Wind-blown sparks can be a serious fire hazard. Always use non-combustible materials on your roof.Just as important as design and construction is the material used during the building process. The number one cause of home losses in wildland areas is wind blown sparks that land on untreated wood shake roofs. For your homes safety, never use untreated wood shakes or shingles, but instead use noncombustible or fire resistant materials. Some people think that roof sprinklers could prevent a wood shake roof from burning, but they are living under a false sense of security. Often water pressure is at its lowest during the fire season and large volumes of water are needed for sprinklers to work their best. The electricity needed to pump the water may also fail during a fire crisis. Also, the high winds which often accompany wildland fires can divert the sprinkler spray away from the roof. Other precautions are:Protect all exposed underside of all eaves, balconies and unenclosed roofs, decks, and floors with one hour fire-resistant materials. Protect all supporting beams and posts with one hour fire-resistant materials Cover all openings in outside walls, overhangs, or roofs with a 1/4-inch noncombustible, corrosion resistant metal mesh Screen chimneys, stovepipe or vents of any heater, stove, or fireplace with noncombustible wire mesh, Sparks can melt through plastic or nylon screening. Build outside walls out of one hour fire-resistant materials. Thick tempered safety glass for windows is the safest choice and the possibility of protecting windows and sliding glass doors with nonflammable shutters, balconies, or decks should be considered. Fire resistant drapes add extra protection inside.    This house is a fire waiting to happen: The chimney has no spark arrester; Brush has not been cleared around the structure; Trees are too close to the house; No screens are around the porch; The porch is on the downhill side of the home; The roof is covered with debris.The next area of concern is the surrounding property and landscape of your home. The fire safety goal of landscaping and maintenance is very simple. Reduce the amount of fuel immediately surrounding your home. However, this doesn’t mean your landscape has to be barren. Some plants are more fire resistive than others. One of the most important things any wildland homeowner can do is to create a safety zone or fire break around the house using these fire resistive plants. Your safety zone can consist of numerous varieties of plants, including grasses, border plantings, flowers and vegetables. In most areas, a safety zone should be cleared away from your home for a distance of at least 30 feet. As the slope of the lot increases, additional clearance as far out as 100 feet may be necessary. Clearance also depends on vegetative conditions that provide ladder fuels enabling fire to climb into trees. Trees and shrubs are fine, as long as dead or low-hanging branches are removed and the height of ground vegetation is controlled. Beyond 100 feet from the house, dead wood and older trees should be removed or thinned. Be sure to remove all tree limbs around your chimney, as well as any dead branches that may hang over the roof. Accumulated leaves, needles, and other dead vegetation should also be removed. Keep an eye on any limbs that may come in contact with power lines. If you’re not equipped to trim them yourself, call the power company or a tree service company for assistance. The reduction of flammable vegetation and other hazards around buildings provides a “defensible space” for firefighters and residents. Other defensive measures suggested are: Attempt to space buildings at least 60 feet apart and at least 30 feet from the property line. Never build structures in forest fuels where the slope is greater than 30%, at a canyon mouth, on a ridge saddle, or in other areas of extreme fire hazard. Remember to sweep your gutters, eaves, and roof on a regular basis, especially during the hot, dry weather of the fire season. Tinder, dry needles and leaves are a fire waiting to happen. Stack your fire wood well away from anything that’s combustible, including fences, outbuildings and your home. Install as many smoke detectors as local regulations require and ask your fire officials to help you plan and rehearse a home fire escape drill. Have at least two ground level doors as safety exits in case of fire, and each room should have least two means of escape, including a door and a window, leading to the outside. This is especially true in bedrooms.    Open landscaping, cleared of debris, can reduce the fire load around the home.If you do all these things, especially clearing the safety zone around your house and building a fire safe roof, you have an excellent chance of protecting your home and family against wild fire. This is a beautiful country. It’s a privilege and a pleasure to live here. And with that comes the responsibility not only to protect your own property and the safety of your neighbors, but to preserve the resources, wildlife, and natural beauty that belong to everyone. If you have any questions, contact your local fire department, wildland fire agency, or state forester. If you live in an interface area, it’s not a question of IF, but WHEN a wildfire will threaten your home. The best defense is the work that has been done beforehand. Complacency is the biggest danger. It is much better to be prepared today, and enjoy your home in the future, than to ignore the possibility of wildfire and have to recover from a disaster later. Individuals and their neighbors have to make their own best decisions in weighing the tradeoffs between safety and other values. Your efforts DO make a difference.AUTHOR BIO: Tony Swallow has worked in forestry, fire prevention and fire fighting for over 20 years. In 1989 while working for the U.S. Forest Service in Montana, he took leadership in developing a program of public information and cooperation in what is known as the residential/wildland interface in the Bitterroot Valley. Recognized as one of the fastest growing counties in Montana, the Bitterroot Valley is experiencing an explosion of new development, much of it adjacent to vast public wildlands. Tony is now Project Manager for the Ravalli County Residential/Wildland Interface Fire Task Force, a group comprised of local, state, and federal agencies and private interests addressing concerns surrounding these issues. http://www.glulamlog.com/Articles_and_Information?id=3Thu, 05 Mar 2009 02:57:43 GMT Wood shrinks as it loses moisture. This simple fact is the cause for a wide range of potential problems for wood users, including warping and splitting in lumber, squeaking wood floors, and checking and “settling” in house logs. On the other hand, an understanding of wood moisture relations is the key to preventing nearly all problems related to shrinkage. This article explains the relationship between moisture changes and dimensional changes in wood, and shows how those who manufacture wood products can minimize shrinkage-related problems in their products. Shrinkage in Wood To understand how wood shrinks, we need to understand its structure. At the microscopic level, wood has the appearance of bundles of soda straws, in which the fibers (usually referred to as wood cells) are long, hollow, and oriented along the direction of the trunk. In the living tree, these hollow cells are filled with liquid water. The walls of the cells also contain water, though that water is bound molecularly to the cellulose molecules that make up the cell wall material. Whenever liquid water is present in the hollow cells, the cell walls are also saturated with water Shown enlarged several hundred times, wood is made up of hollow cells that are oriented along the longitudinal axis of the tree. These hollow cells are like bundles of straw filled with water. As wood dries, these "straws" eventually shrink, causing the wood to also shrink. Shrinkage in the tangential direction is significantly greater than shrinkage in the radial direction. there is very little shrinkage in the longitudinal direction. After a tree dies or is harvested, the liquid water in the hollow portion of the cells is slowly lost to evaporation. The point at which all liquid water has evaporated, but the fiber walls are still fully-swollen and saturated with water, is called the fiber saturation point. This is an important condition, because even though a significant amount of moisture has been lost, no shrinkage has taken place, since the cell walls are still fully swollen. In most wood species, the fiber saturation point is around 28-30% moisture content. As wood continues to dry below the fiber saturation point, it begins to shrink, since moisture is being lost from the cell walls. The amount of moisture that leaves the cell walls depends on the relative humidity of the surroundings, since wood moisture content eventually reaches an equilibrium point with the relative humidity. The drier the air, the greater the moisture loss, and, consequently, the greater the shrinkage. Wood used indoors, such as in furniture, cabinets, and wood floors, eventually reaches an equilibrium moisture content around 8%. So, manufacturers of these products should make sure that the wood they use has already been dried to that level. If they do not, the products will shrink and could cause problems after they are placed in service. The face of the board on the left was cut along the radius of the original log. It will tend to shrink far less along its width than the board at the right, which was cut along a tangent of the original log.The surface of a piece of wood reaches equilibrium with its surroundings fairly quickly. The inner part of the wood takes a bit longer, since it takes a while for the moisture to migrate out of the piece. We refer to this moisture difference within a piece of wood as a moisture gradient. In extreme cases, such as when green, fully swollen wood is placed in a very dry environment, the outer shell dries quickly before the inner portion begins to dry at all, and damage can occur to the wood. In these cases, the outer shell shrinks and squeezes the wet inner wood. If the squeezing, or compression, of the inner wood becomes high enough to exceed the compression strength of the wood itself, the inner cells may collapse. Kind of like a flattened soda straw. Improper kiln drying can cause collapse of the inner wood cells, but good kiln operators are aware of this and use drying schedules that prevent this type of damage from occurring. Logs used for house logs should be dried prior to being placed in service, and a reasonable target moisture content is 15%. That way, most of the shrinkage has already taken place. Building with “green” logs, which are those harvested from living trees, will result in considerable shrinkage in walls of log homes and requires specialized construction techniques to allow for shrinking around doors, windows, interior walls, and stairs. The actual final moisture level of logs in log home walls will vary by climate zone, but a typical range is between 10 to 14% moisture content. One industry standard considers logs to be “dry” as long as the moisture content is no greater than 19% at a depth of 1 1/2 inches, but it is clear that additional drying, and therefore, shrinking of walls, should be expected in the completed home. So, pre-drying to the 15% target moisture content has some real benefits. The amount of shrinkage that takes place in wood depends on several factors, including: the amount of moisture loss; tree species, and grain orientation. We have already seen that pre-drying can limit the amount of moisture loss (and, therefore, shrinkage) that occurs after a home or piece of furniture is built. Some tree species shrink (and swell) more than others. However, as long as pre-shrinking has taken place, the individual differences become less of a consideration, unless the wood continues to dry once it is converted to the final product. An interesting phenomenon with wood, however, is that shrinkage varies according to the grain (or, fiber) orientation. Along the grain, wood typically shrinks very little, so length change in logs or lumber is quite small. Most shrinkage occurs across the width of logs or lumber, and even then, there are differences. Think back to some geometry terms. A line drawn from the center of a circle to the outside is called a radius.  Each of the boards used to make this laminated log were already kiln-dried to a moisture content of 12%, well below the equilibrium point. This log is “pre-shrunk” and will remain check free. In addition, virtually every piece of wood used in the logs are cut in the radial direction.A line drawn such that it only touches the edge of a circle is called a tangent. Boards cut from logs such that the exposed face is oriented in a tangential direction will shrink twice as much as boards cut in a radial direction. In lumber this shrinkage difference can cause distortion in the form of warping or cupping. In logs, the shrinkage difference results in checking.Pre-drying round logs can take a considerable amount of time, since they contain lots of water and their volume is large. Log home producers specializing in round logs typically must wait over a year for their logs to dry to 15% or less moisture content. Nonetheless, this drying period is essential for pre-shrinking the logs and minimizing (or eliminating) further shrinkage after the walls are built. Even “standing dead” trees can contain lots of water so drying for a period of time may still necessary. It is also important to note that even though the outside shell of a log may be dry, the interior may remain at a high moisture content, and additional shrinkage will occur. One advantage in laminating kiln-dried lumber to produce house logs is that each board has already been dried to the appropriate moisture content. That way, the laminated product has a uniform moisture content that is quite close to the final equilibrium moisture content it will achieve in the log home. Another advantage is that checking is essentially eliminated, since checking is nearly eliminated by converting logs to lumber. The result is a stable, check-free log. “Settling” of log home walls often occurs after construction. The amount of settling varies considerably from one home to another. The major causes of settling include: settling of the foundation into the soil; settling of the layers of logs, and additional shrinkage taking place. It is important that concrete foundations be poured onto undisturbed soil, or subsequent compaction will take place. If foundation settling occurs unevenly, cracks in the concrete can form and the home may tilt slightly. Good builders usually can prevent this type of settling from occurring. Log layers may compact on each other slightly, taking up the slack between logs as the weight of the building (and snow) presses down. Compression of the logs does not occur, since the strength of wood in compression far exceeds the loads involved. Additional shrinkage, on the other hand, is usually where the most “settling” takes place. A home built with “green” logs can have as much as 2 inches of shrinkage or more in an 8-foot wall! Log home builders who specialize in green log construction will allow for this shrinkage around doors and windows, so as to prevent damage. However, they must also take care in the placement of interior walls and stairs, so that the log walls can shrink around them. Building walls with logs that are pre-dried to an equilibrium moisture content of 10 to 14% will minimize the amount of shrinkage-related “settling” in walls. AUTHOR BIO: Dr. Tom Gorman, P.E., is an associate professor at the University of Idaho in Moscow. He teaches courses in wood properties and timber design, and teaches “Understanding Wood” seminars at the Willow Creek Wood Productivity Training Center in Willow Creek, Montana. His research has included log home energy performance and strength properties of logs. He is a licensed professional engineer in Idaho and Washington states. His e-mail address is tgorman@uidaho.edu http://www.glulamlog.com/Articles_and_Information?id=1Sun, 05 Apr 2009 14:15:29 GMT The energy efficiency of log homes is a perplexing issue that has not been completely resolved. One hears stories of the old-timers' trap-line cabin, always drafty and cold. Even today, building officials often rely solely on R-value comparisons as a way to evaluate construction methods, and log wall performance is expected to be less than that of a framed wall insulated with fiberglass. But when you talk to those who live in modern, well-built log homes, you consistently hear about comfortable homes, with low fuel bills. What's going on, and why can't we get our hands around this issue?   The south side of this home is protected from the high angle radiation of the sun by low E glass and a roof that provides shade.  the lower angle radiation of winter sun warms walls and penetrates the glass, adding heat to the interior of the home. I've been researching the area of log home energy efficiency for several years now! Predicting the thermal performance of a log home is a challenge because of a variety of factors, including some we can control and some we can't: floor plan, type of log and sealing methods, exposure and orientation to the sun, window location, climate, and even life style of the occupants. Though I don't have all the answers regarding energy performance, I've come to some conclusions that should be helpful to those planning their log home purchase and construction. Assuming that you are interested in building a log home that achieves its maximum thermal performance, the following topics address some of the major areas that you can usually control and will significantly impact energy efficiency. Air Infiltration (leaks)Heat loss in a "leaky" house occurs the most when the outdoor temperature is lowest. This is based on the principle of convective heat flow, or "the chimney effect", which causes heat to rise. The colder the temperature outside, the greater the tendency for this to occur. Leaks in the walls or logs will allow the heat to escape and as heated air is lost, cold replacement air enters the lower part of the house around windows, doors and any leaks in the walls, causing uncomfortable cold spots and drafts. While this seems to be a simple issue, some areas of a house do not get sealed properly. Where log walls meet roof lines is one place where major heat loss can occur, and is often overlooked during construction. Recessed lights, chimneys, stove pipes, plumbing vents, and other breaks in the ceiling should all be identified as potential leaks and the area around them sealed. The way that your logs are sealed is important, too. Air tight caulking or gaskets between logs and at the corners is effective. Checks in solid logs, which occur as the logs dry, can form a path for cold air to enter the house from the outside, especially when ends are exposed at the outside corners. The argument that a house needs to "breathe" is one I do not buy. Problems such as high humidity or inadequate fresh air can be solved with mechanical fans in bathrooms and kitchens, or mechanical fresh air inlets. Better to have control over the air flow than let the house ventilate naturally -- this only results in the biggest air exchange when it is coldest outside. Siting Hopefully, you will have a spectacular view to enjoy from your home. With luck the view will be to the south, or reasonably so. Windows on the south side can allow solar radiation to enter the house during the day and provide warmth. There's even a bonus for log homes: the high-mass log walls (and perhaps a stone fireplace) will absorb some of the sun's heat and remain warm into the evening. Large windows on the north, however, will cause considerable heat loss, even with today's high-tech windows. A well-designed roof overhang will prevent overheating from the summer's sun, but will still allow the low winter sun's rays to enter the windows. For more information on getting a home to take advantage of the sun, the wind, and the topography, see the article, "Siting a House" in the February/March 1995 issue (No. 93) of Fine Homebilding Magazine. Log Insulating ValuesNo one area regarding energy performance of log homes is less understood than that of heat transfer through log walls. Over the years, building officials have taken a simplified approach to specifying insulating values for walls. Unfortunately, the simplified approach does not apply to walls with high mass, such as logs. Most of my research with log homes has been focused on how the "mass-effect" effects energy performance. I've monitored a test house throughout a full year, conducted simulation tests with a sophisticated computer program, and read as many of other researchers' reports as I could find. High-mass materials have the ability to store heat during the day. As nighttime temperatures drop, the heat is there to reduce the need for supplemental heating. On the other hand, once high-mass walls get cold, it takes a while to heat them back up again. Still, log walls perform better overall than a light-frame wall with the same R-value. The R-value of a material is a measure of how much heat will be conducted under "steady-state" conditions, or constant indoor/outdoor conditions. Steady-state conditions rarely occur outdoors, so R-value alone is not a good measure for high-mass walls. Here in the northern U.S., many building jurisdictions require R-19 insulation levels in the walls. Typically, 5 1/2-inches of fiberglass is used to achieve this. But does it? Tests have shown that the overall performance of a wall insulated with fiberglass falls short of its rated value, for a variety of reasons. Still, this seems to be the measure by which log walls are compared. The R-value of dry wood is about l 1/2 per inch of thickness, so a 6 inch log wall has an R-value of about 9. This is why log walls are often penalized when R-19 walls are required by the building code. Though the mass effect does exist with log walls, it only adds the equivalent of R-1 to R-5 to a wall, depending on siting, climate, wall thickness, and wood species. Consequently, the mass effect does not fully explain the low fuel bills enjoyed by so many log home owners. I suspect that the high-mass interiors, coupled with good solar gain, is adding more to these homes than many realize. Other Insulation IssuesThough it is difficult to achieve high R-value walls when building with logs, other insulation strategies can be brought in to create a house that is very energy efficient. A study conducted in Idaho a few years ago demonstrated that log homes in cold climates can perform as well as stick-built homes with R-19 walls when various combinations of "upgrades" are incorporated. For example, by reducing air infiltration to below standard levels in R-19 stick-built homes, overall heat loss is comparable. Likewise, upgrades in floor or ceiling insulation, improved windows, or siting to take advantage of solar gain can also have similar results. There are no simplified guidelines, however. Each home must be assessed to determine the best strategy to follow. The best solution may not add prohibitively high, or any, cost at all to the home. Code RequirementsOftentimes local building regulations dictate minimum R-values for walls. When log walls are desired by a prospective homeowner, this can create a difficult situation. However, most codes allow an alternative method for demonstrating that a home will meet overall energy performance criteria. Rather than the "component performance" approach, which spells out the insulation value for each component in a home, a "system performance" approach may be the most appropriate method for log homes. That is what was done in the Idaho study mentioned in the previous section. Many states recognize this approach, though it often takes a computer program to conduct the analysis. Those states that take energy performance seriously will often assist with the system performance computer analysis of a home. Unfortunately, the mass-effect is usually not considered in the simplified software they commonly use. While this may not present any problems, some marginal house designs may not be approved if the mass effect credits are not incorporated. The computer program that I have used in my research is particularly appropriate, since it models energy loss for the complete home and incorporates the mass effect for walls. If you are dealing with a building jurisdiction that dictates a specific R-value for the exterior walls, ask if your design can be analyzed as a system. The analysis may be provided by the state's energy office. This could help you develop a strategy that allows you build, despite the apparent code barrier. Should that approach fail, an energy consultant's analysis of your design may be necessary to gain code approval. When building any home, one should hire a competent builder, use a good design, and ensure that quality materials are used. By following these rules during the construction of your log home, you can expect good performance in the final product. A well-built log home should be comfortable, with low fuel bills . The success stories are easily found. Find out what was done right and use them as a guide for your own home. http://www.glulamlog.com/Articles_and_Information?id=4