There's a technology that was developed a number of years ago called a solar wall. It's part of the CANMET Materials Laboratory, the new one built down in Hamilton, but we've also got a demonstration piece here in Ottawa out at the Bells Corners facility.
Basically, it is an external wall that is built and creates a gap between the building exterior wall and this passive solar collector. It's semi-permeable and it's coloured the right colour so that it attracts as much heat as possible. You can then draw that warm air into the building without having to buy additional energy. So it's a solar wall, but for heating, not in the classical case of a solar panel that turns into electricity.