Exhaust air heat recovery in buildings

Abstract

The technique of heat recovery from ventilation air in dwellings started in Sweden in late 1979. This was due to an energy crisis and new building codes. The competing heat recovery system, air to air heat exchangers, had a firm grip on the market. Today the situation is on the contrary. Almost all new single family houses are equipped with exhaust air heat pumps. This paper describes the development of the market in Sweden and Germany and also the different techniques of supplementary heating due to national differences in electricity prices. Germany has a situation very similar to Sweden concerning new building codes concerning the allowable energy use for space heating. Starting in 1976 and continued from 1982 to 1995, the building code has prescribed tighter and more insulated houses. The new building code for the year 2000 contains requirements for well insulated and tight buildings so the energy demand for heating from ventilation air tends to reach about 60% of the total annual energy demand for the building. Under these circumstances new buildings must have ventilation systems with heat recovery. Different means of heat recovery from the ventilation system, and the benefit for the environment, by using heat pumps are described. The German market for heat recovery systems is approx. 5–10.000 units/year. Most important for the efficiency of a ventilation system is to maintain the quality criterias concerning: equipment planning, installation, taking into operation operation.VEW ENERGIE AG has accomplished a field survey of 60 units from 1994 to 1996. As the result was not statistically sufficient, the field survey is followed by an investigation into air quality and reliability.