With a hurricane proof WRB/AB details, and the benefits of a continuous mineral-wool- insulation-thermal barrier, these assemblies are projected to meet the needs of the high performance build community for decades to come.
The wall assembly will contain a continuous 6″ layer of Roxul ComfortBoard IS on the exterior side of the sheathing in a manner free from thermal interruptions to all but eliminate thermal bridging through the wall assembly. The predominately 2×4 stud bay structure will also be in-filled with Roxul ComfortBatt to top-up the assembly to a total effective R40.
The roof assembly will employ parallel chord roof trusses with extended 2×6 top chords to support roof overhangs. 18″ trusses at 24″ spacing will allow 18″ of ROXUL comfort bat and result in a R60 effective assembly.
The foundation assembly will comprise of a 6.5″ concrete core in a Durisol 10″ foamless ICF blocks. The R8 assembly will be boosted to an effective R20 with the addition of a continuous 2.38″ ROXUL DrainBoard outboard of the ICF and the infill of a 2×4 services raceway with ROXUL ComfortBatt
Air and Water Control Layer
SENWiEco are proponents of an air control layer (AB) that is separated in function and location from the vapour control layer. In the BC construction region, Poly is typically used on the walls interior surface, beneath the drywall, as both a vapour control layer AND an air control barrier. While the poly performs flawlessly as a vapour barrier, the difficulty in sealing the poly around numerous penetrations has led to its absolute failure as an air barrier in all observed cases. We instead promote an exterior air control layer that is combined with the Water Resistant Barrier (WRB) and detailed outboard of the main sheathing. There are significantly fewer penetrations to address at this location and those penetrations are typically straight sided and easily detailed. By sandwiching the AB/WRB between the rigid sheathing and exterior continuous insulation, you also end up with a barrier that is well supported in both positive and negative pressures, is protected from UV and mechanical damage, and will provide decades of trouble free performance. This location also allows for the AB/WRB to be installed (as soon as all windows and doors are installed) and tested early in the construction cycle allowing for easy and cheap repairs if inconsistencies are found.
This build will utilize a AB/WRB consisting of Tyvek sheathing paper in the field of the wall with all penetrations detailed using the Prosoco three (3) part RGuard air barrier system. This combination provides the strengths of sheathing membrane, including its high permeance, low cost and ease of application, combined with RGuard’s hurricane proof water and air detailing system.
SENWiEco tested the RGuard system up to – 4500 Pa in a mock-up wall assembly including a Cascadia window, parapet wall, electrical and water penetration, and a vent termination. The system was easy to apply and performed flawlessly.