The last penetration thermal bridge, shown in Figure 4.8.13, is at a roof expansion joint. In the base
case the concrete block curbs on either side of the joint are uninsulated, resulting in thermal
bridging. This is also a common situation in parapets, mechanical equipment curbs and various
other roof penetrations. In the alternate detail, insulation is installed completely around the curbs,
eliminating the thermal bridging except at the required fasteners.
Figure 4.8.13 Roof Expansion Joint
Design and Construction Issues
The design and construction of a roofing system with good thermal performance and good air and
water tightness requires the careful development of details and specifications at all penetrations.
As the construction proceeds, all work needs to be carefully inspected. Special care must be
exercised to protect work at the end of the day to prevent moisture intrusion into roofing materials.
To that end, these same materials must be protected and kept dry prior to installation to keep water
out of the roofing system at the construction stage. As good as the design and construction might
be, a good roofing inspection and maintenance program should be established to identify and repair
any problems that develop over the life of the roofing system.