Increased heat loss has been measured for several insulation joint arrangements in extruded ad polystyrene placed on a 9-mm thick plywood deck. Butt joints ranging up to 25.4 mm wide, a 3-mm butt joint bevelled to 28 mm at the deck, and a 3-mm shiplap joint were used. Most. of the work was carried out with protected-membrane roof arrangements, but measurements were also made on a conventional roof arrangement with 2.5- and 12.7-mm butt joints.

Sets of two and six heat flux transducers were placed at. the underside of the deck at various locations with respect to the insulation joints . The measured heat fluxes were used to estimate heat flux as a function of distance from the joint and from this to compare heat losses with and without joints.

Units: SI