In our ongoing exploration of Katahdin Cedar Log Home features, we explore the Energy Envelope System (EES). EES is the result of 41 years of working to maximize the energy efficiency of our beautiful log homes constructed from Northern White Cedar.
Do Logs Provide Enough Insulation?
To begin with, Northern White Cedar has a significantly higher insulating value than other tree species used for log homes, with an R-value of 1.41 per inch of thickness. A six-inch thick log provides about R-9. Katahdin’s interior insulation system adds to the levels of R-value already within the Northern White Cedar Logs.
The Energy Envelope System performs well in a log home because of the natural relative dryness of the Northern White Cedar. A drier log is a better log, especially when it comes to building log homes. Even when pine logs are kiln dried—necessary for killing insects—the logs themselves are still quite moist and will continue to dry and shrink until they reach equilibrium with the surrounding air. This equilibrium point is usually around an average 12% ambient humidity. Katahdin is able to ship their cedar logs at an average of 12% moisture content, which results in minimal shrinkage or settling in the constructed log home.
This provides a very stable structure and also enables us to apply the EES to the inside of the building exterior walls (or envelope) without the danger of shrinkage or settling affecting or buckling interior finished walls.
What is the Energy Envelope System?
Basically, the Energy Envelope System adds insulation to the inside face of the log walls to meet energy efficiency standards enacted in 2009 as part of the American Recovery and Investment Act. Beginning with the sealed log wall, the contractor installs foil-faced polyiso rigid insulation sheets to the inside of the log walls (see diagram at left). The thickness of this rigid insulation is dependent on the final level of R-value desired or needed to meet the energy efficiency code requirements based on the geographic location. The contractor then installs 1×3-inch strapping vertically at regular intervals along the wall. This strapping creates a ¾-inch airspace, which also acts as an insulator.
The airspace also has another feature that makes Katahdin homes easier and more cost-efficient to construct than other whole log homes. The airspace allows for plumbing and wiring to be installed easily and quickly, with minimal need to drill or mortise into the logs themselves. This has been a tremendous time- and money-saver for contractors and the interior finish work is more quickly completed. Chase work for ventilation, solar energy systems and whole house vacuum systems are also easily accommodated within the wall system.
Finally the inside finishing wall is added. For traditional log homes this is usually a beautiful tongue-and-groove cedar paneling that can be either flat or rounded profile to simulate the appearance of the log wall. For some areas of the home, other wall finishes including sheetrock, can also be utilized.
The end result is a tightly sealed, high R-value home that looks as great on the inside as it does on the outside. What isn’t sacrificed is the strength and structural integrity that whole log walls provide, over traditionally framed or hybrid “log” homes.
Continuous Insulation Benefits
Another feature of the Energy Envelope System is that it maintains the continuous insulation effect that traditionally makes log homes feel so warm and cozy. What is continuous insulation and why is it so beneficial? To understand, it helps to first take a look at traditionally framed walls. These are typically built with lumber studs like two-by-fours and -sixes, with the spaces between the studs filled by some form of insulation. The problem with these studded walls is that each stud becomes a thermal bridge, conducting heat in or out of the interior, because of the lower R-value of the stud itself. It becomes really apparent when infrared pictures of stud walls (right) versus log walls (two photos below left) are compared. The image at right shows the heat leaching out through the studs every 16 inches of every wall. Over time this adds up to a considerable amount of lost energy (and money).
With the continuous insulation of the Energy Envelope System, thermal bridging like that of a stud wall is virtually non-existent. That keeps energy dollars where they need to be inside the home.
Many of those researching log homes are told that cedar is available but for a significant extra cost. Katahdin Cedar Log Homes is the largest producer of Northern White Cedar in North America and as a result, can provide both the premium quality cedar logs, and the finely milled tongue-and-groove cedar paneling to complete the interior of the wall system at competitive prices.
In fact, Northern White Cedar forests regenerate naturally, so its cost environmentally is much lower than other species of wood. Katahdin uses every bit of the cedar log in its various manufacturing processes and even burns the sawdust and unusable scraps in its industrial biomass boiler to heat the mill buildings and finishing kilns.
Many Katahdin customers have discovered that Katahdin and its whole log Energy Envelope System construction is the best of both worlds and the right choice to save money, time, and energy.