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

Investigators noted that the SIP is a good product, but needs to be properly installed. The
detailing associated with SIPs must be installed right particularly in a climate like Juneau,
Alaska with 90 inches (2300 mm) of annual rain and 9000 heating degree F days.
Thermal performance in laboratory studies: Laboratory tests suggested that a 100 mm
(4 in.) thick SIP wall rated RSI-2.6 (R-15) outperformed a 150 mm (6 in.) thick wood
frame wall insulated with fibreglass and rated RSI-3.3 (R-19) (EDU, 2001). The results
were based on whole-wall R-value, which is considered to be more representative to field
performance than the wall’s rated value. The whole-wall R-value accounts for the
thermal losses associated with framing (studs, headers, plates, etc.), which account for
about 15% to 25% of the wall area. Thermal bridging accounts for about 13% loss in the
whole-wall R-value of a 150 mm (6 in.) thick SIP wall compared to about 28% loss in the
whole-wall R-value of a 150 mm (6 in.) thick wood frame wall. Table 2 compares the
whole-wall R-value for a SIP wall and two wood frame walls.
Table 2. Rated and Whole-Wall RSI (R) Values of SIP and Wood Frame Walls
Wall Type Rated Whole Wall
100 mm (4 in.) thick SIP wall 2.6 (15) 2.5 (14)
38 x 139 mm (2 x 6) wood
stud, fibreglass
38 x 89 mm (2 x 4) wood
stud, fibreglass
Source: EDU (2001).
3.3 (19) 2.4 (13.7)
1.9 (11) 1.7 (9.8)
Based on whole-wall R-values, the R-value for a 100 mm (4 in.) thick SIP wall (R-14) is
slightly higher than R-value (R-13.7) for a 38 x 139 mm (2 x 6) wood stud with fibreglass
insulation. The study results suggest that upgrading to 100 mm (4 in.) thick SIP walls
would be economically better than upgrading wall framing from 38 x 89 mm (2 x 4)
construction to 38 x 139 mm (2 x 6).
Energy Efficient Houses, Northern Canada
Keewatin District Energy Efficient Housing Project
Seven high energy-efficient houses were built in Keewatin District, Northwest
Territories, in 1980 and 1981 (CMHC, 1994-2). Design heat loss was 14% less than
conventional housing, and air tightness was twice that of conventional construction. The
ceiling, floor, and walls were heavily insulated: ceiling RSI-10.5 (R-60), floor RSI-8.8
(R-50), and walls RSI-7 (R-40). Thick walls, 27.9 cm (11 in.) were designed to
accommodate the insulation. The thick walls also facilitated the construction of rigid and
airtight joints at the floor and the ceiling. The foundation is a continuous-span laminated
beam system that rests on a gravel pad. Several lessons were learned from the Keewatin
District project.
• Inefficiencies in the space heating system detracted from the projected performance.
PERD-079: Task 2 - <strong>Literature</strong> <strong>Review</strong> 28