Perhaps the most novel feature of the house is its Building Integrated Photovoltaic/Thermal (BIPV/T) roof, and the solar heating system based upon it. This roof has an array of polycrystalline photovoltaic panels mounted on a commercial photovoltaic framing system designed for roof installations. The peak capacity of the PV, 5.5 kWp in the first design, was increased to 7 kWp to provide energy to a plug-in hybrid vehicle. As in many roofing systems, in this framing structure each frame slightly overlaps the one located below. This is significant, as these PV panels, which occupy 55% of the total area of the roof (105 m2), are not used only for generating electric power: they also play an important role as part of the building envelope by replacing asphalt shingles. The roof has a 45° slope (roughly equal to Montreal’s latitude) and due south azimuth orientation.

An air inlet under the soffit permits the use of a variable-speed fan to draw exterior air through a gap under the PV arrays. This system allows for the recovery of useful heat from the roof and has the additional advantage of lowering the temperature of the PV panels. For a system such as that in the ANZEH, this represents additional electric power on the order of hundreds of watts, which might partially or totally offset the energy consumed by the fan. A glazing section filling the remaining area of the roof above the PV panels helps to increase the temperature of the BIPV/T air. The glass panes are mounted on the same framing system used by the PV arrays. Below the glazing section, a low-emissivity absorber surface enhances the recovery of solar thermal energy. The air temperature rise depends on several factors, the most important being solar radiation, exterior temperature, air flow rate and wind speed. For a clear sunny day during a Montreal winter and a flow rate of about 450 L/s, the air temperature rise may exceed 40 °C. As the stagnation temperatures of the BIPV/T system can be quite high during the summer (up to 100°C) a small fan will be used to remove hot air from under the roof through an opening on the east side of the roof. A manifold located at the rooftop connects the BIPV/T roof to a ducting system. The ducting system has been designed to minimize the pressure drop and therefore the power requirements of the variable-speed fan (with a maximum power of about 500 W).