Know the R-Value of Wood for Energy Efficient Log Home

Most people are attracted to wood or log home because of the warmth, beauty and cosines it inspires. When you are building a new log home, keep in mind energy efficiency besides durability and natural beauty of wood. Log homes have been around forever, which shows its staying power when constructed properly. Log homes are more environmentally efficient being made of natural and renewable wood. Homes can be built using green methods, as in logs produced locally or using wind or fire-killer timber or log manufactured using smaller wood and insulating material together. Besides the quality of log, insulation along the logs is another factor in making an energy-efficient home, which can be achieved either by building a wall on the inside of the log wall or insulating the roof with methane foam and sod.

It takes the right design; a lot of planning, construction and maintenance to make sure you are optimizing your log home for maintaining energy efficiency to the best of your ability. In log homes, the wood provides insulation, which is calculated by “R” values. This measures wood’s thermal resistance or resistance to heat flow and the higher the R-value, the better thermal resistance it provides.

How are R values calculated?

Depending on the variety of wood, generally the calculation is 1.25 inch of wood per “R”. (Depending on the wood, it may vary slightly) As in. with Pine wood if you are taking a six inch log, you must calculate using 1.35 inch per “R” and multiply that by 1.35, to get an R-8 log.

An important consideration for improving energy efficiency in log homes is the R-Value of wood, which ranges between 1.41 per inch (2.54 cm) for most softwoods and 0.71 for most hardwoods. Log homes generally have a 30%-40% lower numerical R-Value. If you overlook the benefit of thermal mass of wood, a thick log wall of about 6 inches would have a clear-wall R-value of just over 8.

Many building areas have certain building codes. Log homes do not have the insulation of a conventional wood stud wall, sheathing, wallboard (which amounts to a total of about R-14) making it a far inferior insulation system. This is the reason that log walls may not meet most building code energy standards. Several states, including Pennsylvania, Maine, and South Carolina have let off log-walled homes from normal energy compliance regulations that require prescribed insulation R-values and other states have approved certain regulatory packages for various sizes of logs, for better energy efficiency. On the other hand, the thermal mass of logs, allow it to retain and store heat better than others. You can get approval in states that follow ‘The American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) 90.2 standard code, which contains a thermal mass provision ideal for log home building. Log homes interact with its surroundings much better, as it acts almost like thermal batteries to store heat during the day and release it slowly through the night. The apparent R-value of a log rises by 0.1 per inch of thickness in sunny climates that have wild temperature swings from day to night. Using numerically lower steady state R-Values in the walls of log homes give equal performance for heating and cooling in such circumstances.

You can find out the log building code standards for your area and information on recommended energy codes by contacting your city or county building code energy office.

For designing an energy-efficient log home, you should consider the following-

  • Implement whole-house systems approach
  • Using passive solar design features
  • Logs should be cut, sanded and insulated maybe with high density polyurethane
  • Bond logs by stacking and bolting them every two feet
  • Prevent shrinkage by using Fir, Pine, Cedar, and Spruce
  • Use plastic and caulking to seal gaps in log walls
  • Install deep roof overhangs to keeps most rain from the walls of the log home

Let us at Performance Log Homes, help you meet all the building codes related to wall insulation! Get to know more about R values, the building process of log homes, by contacting us. We’d love to hear from you!