An effective way of providing natural heating and cooling to a building is by a double envelope facade, in which a building essentially has two exterior walls.

The key to a double-envelope system is the cavity between the inner and outer walls. This cavity forms an insulating buffer between the exterior and interior temperatures.

The cavity typically extends uninterrupted from ground level to the top of the building. In cooling mode, louvers are opened at the top and bottom of this cavity, so that heat buildup is expelled at the top of the building through natural convection, as cooler air is drawn in at the bottom.

To control excessive solar gain into the interior of the building, shades can also be installed in this cavity, to block out sun before it even enters the interior of the building.

In heating mode, the louvers are shut, creating a buffering volume of air between the outdoor and indoor temperatures.

The louvers may be operated manually, mechanically by a control system, or even passively.