The Frei house is situated in the foothills on the sunny side of a major alpine
valley, in Vorarlberg. During the monitoring season fo 1995/96 only
55 days of auxiliary heating were registered.
The house incorporates an air collector, a
rock bed and hollow core constructions for storage and distribution,
leaving a yearly requirement for only 17.6 kWh/m²a for auxiliary heat in
an average season. The system has minimum of technical equipment, simple
controls and only one fan. The back-draught dampers are self-operating.
Another attribute is the high level of thermal comfort provided by the
radiant heat from the hypocausts. A wood stove in the cellar can supply
hot air to the hypocausts if required. The larger part of the domestic hot
water is solar heated by a heat exchanger in the duct from the air
Task 19, " Solar Air Systems - Built Examples", James
& James, London, 1999, ISBN 1 873936 85 0