Thermal Bridging Explained
How it works: Learn how to improve the effectiveness of insulation.
In the article, “The Passive House: Green Without Gizmos“, Jefferson Kolle takes an in-depth look at the Passive House standard. Houses certified by the Passive House Institute are so tight and so well insulated that they use 90% less energy than code-built homes. Many design practices must be included when building such a high-performance home. One requirement is significantly reducing thermal bridging, which is a major cause of heat loss. Before you reduce thermal bridging, though, you need to understand it. Here’s how it works.
In a typical stick-frame house, lumber occupies 27% of the wall area, leaving little room for insulation. Since the insulating value of softwood lumber (R-1.25 per in.) is less than that of fiberglass or cellulose insulation (R-3.6 per in.), each stick of wood lowers the wall’s overall R-value. Each piece of framing lumber acts as a thermal bridge, a conduit for heat to leak through…