Literature Review on Building Envelope, Heating and ... - Beeshive.org

Single Stud Walls with Interior Strapping
First, 38 x 38 mm (nominal 2 x 2) or 38 x 64 mm (nominal 2 x 3) strapping is installed,
usually horizontally on the interior of the stud walls. Either membrane or rigid air barrier
system can be used. When polyethylene is used as a vapour and air barrier, it is usually
placed on the inside face of the studs before the strapping. This approach has advantages:
in addition to the RSI-3.5 (R-20) insulation in the 38 x 139 mm (2 x 6) main wall, RSI
1.4 (R-8) batt-insulation can be added in the 38 x 64 mm (nominal 2 x 3) strapped space,
which would also reduce thermal bridging.
Double Stud Walls
This system (Figure 2) consists of a load-bearing structural wall constructed with
conventional framing techniques, a lighter non-load-bearing wall that supports exterior
siding or interior drywall, and either a membrane or rigid air barrier system. The wall
thickness depends on the required R-value.
Insulation options include batt insulation. The centre cavity between the two walls,
generally 89 or 139 mm (3½ or 5½ in.), will fit RSI-2.1 or RSI-3.5 (R-12 or R-20)
insulation batts that are installed horizontally; batts are then installed vertically between
the studs. Spray-in-place insulation can also be used. This includes foam, loose fill fibre,
or cellulose insulation.
A double stud wall system provides for a flexible wall thickness to accommodate a high
level of insulation, ensures a continuous air barrier throughout the building envelope, as it
would not be penetrated by electrical or plumbing systems, allows for the use of smaller
dimensional lumber, and reduces thermal bridging. However, a double stud wall system
means higher labour and material costs. Platform framing techniques may also not be
suitable for erecting the exterior wall. Two examples of a double stud wall system
(Saskatoon House and Hanover House) are reviewed later in this section.
Standoff Walls
This system, as illustrated in Figure 3, is a variation of the double stud wall system. It
consists of:
• a load-bearing interior wall constructed with conventional stud framing techniques
(smaller dimension lumber can be used);
• sheathing on the interior of the stud wall;
• a non-load-bearing truss-stud exterior wall either site-fabricated or factory
manufactured, designed to accommodate required insulation, is placed offset relative
to the interior stud wall to cover the edge of the floor slab to minimize its thermal
bridging; and
• either a membrane or rigid air barrier system. If polyethylene is used, it should be
installed over the sheathing ensuring that there is sufficient insulation to the exterior
to maintain it above the dew point temperature.
A standoff wall system can accommodate a high insulation level, ensures good air barrier
continuity with minimum seams and penetrations, allows for the use of smaller
PERD-079: Task 2 - <strong>Literature</strong> <strong>Review</strong> 15