1 Brave Scout Trail – Thermal Bridges

Posted on Apr 19, 2018
1 Brave Scout Trail – Thermal Bridges

Paying close attention to thermal bridging in the details is something that is extremely important – as important as insulation.

Here is a Greenbuildingadvisor.com post describing what thermal bridging is and why it is so important.

According to Wikipedia, thermal bridging is “an area or component of an object which has higher thermal conductivity than the surrounding materials, creating a path of least resistance for heat transfer.”

We used THERM (available here) to model the thermal conditions at various critical construction assembly points. Our most interesting results are posted below.

Study of thermal bridging at framing corner The overall wall assembly consists of a 2x6 insulated framing cavity (R-21 dense-pack cellulose) with 4” Roxul outboard (R-16 CI). Interior there’s a 2x service cavity applied over a smart vapor retarder. Exterior there’s a vented rainscreen. Below, we explore the issue of energy loss through the heavy-duty hold-down anchor required at the corners. Study of thermal bridging at porch columns The overall wall assembly consists of a 2x6 insulated framing cavity (R-21 dense-pack cellulose) with 4” Roxul outboard (R-16 CI). Interior there’s a 2x service cavity applied over a smart vapor retarder. Exterior there’s a vented rainscreen. Below, we explore the issue of energy loss through the columns supporting the roof over the porch. (All of these are preferable to a ledger system.) Study of thermal bridging through column bases In all cases, the 4” concrete slab itself is acheiving R-2 through the use of an expanded glass bead aggregate (Poraver). The sub-slab insulation is also expanded glass beads, poured into an 8” sub-slab onsite with a binder. The r-value is expected to be R-14. Below, we explore the issue of energy loss through the higher-density, more-conductive bearing concrete underneath the columns.

We have used this and other thermal imaging modeling to inform the assembly detailing at 1 Brave Scout Trail.