Performance of curtain walls for pre-heating air.

For state of the art buildings ventilation heat loss can exceed 50 percent of the total heat loss of the building. Balanced ventilation systems with heat recovery from the exhaust air lead to bjg costs for ducts. Alternatively, the incoming air of exhaust ventilation systems can be pre-heated by curtain wall facades. A newly developed simulation program for transient analysis of curtain wall systems is validated by measurements. Parameter studies for pre-heating air with curtain walls are presented. Location, orientation, construction, and geometry are considered. The calculations show that the heat demand for ventilation can be reduced by 50 percent. Efficient systems have a translucent curtain wall and are attached to a thermally insulated wall facing south. Special advice regarding optimal construction is derived from the hydrodynamics of the systems compared. The depth of the air gap can be optimised to values of 2 to 24 mm. The performance of curtain walls for pre-heating incoming air can be estimated over a wide range of parameters.