Abstract
A primary objective with passive houses is to reduce the energy demand for heating and cooling. A well-insulated and airtight building envelope, highly efficient heat recovery within
the ventilation system, low-energy windows and doors, and thermal bridge free constructions are common characteristics for passive houses. When all these characteristics are in place, what becomes the next step? What else should one improve in order to reduce the energy use of the building?
One possible answer could be to improve the ventilation system by installing an earth-to-air heat exchanger (ETAHE). An ETAHE utilizes the thermal mass of the soil surrounding or
beneath the building in order to preheat or pre-cool incoming ventilation air. With the ground’s large thermal capacity and relatively stable temperatures, outdoor temperature
variations are dampened and ventilation heating and cooling loads are reduced.
Using the building energy simulation software TRNSYS, this report investigated the heating potential and cooling potential of an ETAHE in a mechanically ventilated passive house,
ranging in size from a detached house to a small office. Simulations of the ventilation system within a small office indicate that a parallel piped ETAHE, connected to an efficient air
handling unit, will provide energy savings ranging between 6 and 14.6 kWh/m2 floor space during a normal year with base ventilation at night and 4 air circulations per hour during day.