KEC Wall Framing and Insulation

When building a net zero energy building it is important to properly insulate the building.

The energy efficiency of an entire wall assembly has been documented by Oak Ridge National Laboratory (ORNL). The testing method takes into account energy losses for the structural members, corners, joints and around windows, not just the value of the insulation. Results of these tests are shown below.  They provide R-value recommendations by zip code.  They also provide a whole wall R-Value calculator

The KEC has a doubled framed wall system.  This means the exterior wall is framed with 2x6 FSC wood studs at 16" on center.  Then an interior wall is framed with 2x4 FSC wood studs at 24" on center.  There is a 1" air gap between the interior framing and the exterior framing to prevent thermal bridging.  Some structures can get away with a 2x4 on the exterior wall, however with the long spans and the stone veneer this was not structurally possible for this project.

This double stud wall also allows a deeper cavity space for additional insulation.  Instead of standard fiberglass batts, we used a combination of open cell and closed cell spray insulation.

3" Closed cell insulation is Demelic Heatlok Soy 200 on the inside face of exterior sheathing
6" Open cell insulation is Demelic Sealection 500 was then applied.  This allowed a total insulation depth of 9" and provided an R-44 wall system.  This is nearly triple the insulation value of standard construction.

Where 3" of closed cell and 6" of open cell could not be achieved due to physical job constraints i.e. framing conditions, 6" of closed cell was used which also achieves an R-44.

The blend of open cell and closed cell is more cost effective than just 6" of closed cell.  And while the open and closed cell spray insulation is more expensive than fiberglass batt insulation, the increased energy performance reduces the energy cost to condition the interior space and makes the net-zero project goal achievable.

Interior wall and ceiling insulation is a combination of both Knauff EcoBatt and Roxul Mineral Wool depending on the location and rating requirements.