Now that we’ve gotten our wall and roof assemblies together and insulated them, it’s time to seal the home and apply the air and vapor retarders. Air and vapor retarders are sometimes referred to as air and vapor “barriers”. This can be a misleading term as they do not block air or moisture 100%.
There are two types of air flow in a home, controlled and uncontrolled. Controlled air flow is that which is created by ventilation and/or a mechanical device (i.e. furnace, air conditioner), and is designed to be in the home. Uncontrolled air flow is that which makes its way into the home via gaps and openings. Every structure will always have uncontrolled air flow, but this is the type of air flow, or air infiltration that we strive to minimize.
In a full log structure, the easiest place for air infiltration to occur is between the courses of log. Our full log system at Expedition requires the installation of a foam gasket, set into a routed channel, in two locations between the courses of log, and at the butt joints of adjacent logs.
We also specify for the installation of “Stacker” sealant on the inside and outside of every course, as well as the butt joints of every log. This, done along with the standard caulking or chinking is a great way to minimize the air infiltration in a full log wall system.
In a half log system, we compensate for air infiltration in walls by using products such as Tyvek or Typar, as well as caulking between every log course.
The other major area of air infiltration is through the ceilings. One of the methods used to insulate a roof or ceiling, still requires the use of ventilation. If steps are not taken to attempt to keep that ventilation within the rafter cavity, a vast amount of air leakage can occur, especially through knotty pine ceiling boards. This air leakage can cause condensation in areas where there are great temperature differences between the indoor and outdoor air.
We recommend the installation or 5/8” sheetrock to the underside of the ceiling, before any knotty pine boards are installed. This is a practice that is standard in the commercial end of the building industry, and it can greatly reduce the amount of air infiltration into a ceiling.
These practices, used in accordance with a good HVAC design, quality mechanical equipment, and proper ventilation will ensure the long and “dry” life for your log home.