The performance of retrofit energy conservation measures in two semi-detached houses

Two 1930s semi-detached houses were retrofitted with an extensive range of energy conservation measures including loft and solid wall insulation, draught stripping, double glazing, heating controls and heat pumps. The performance of the houses and their heating systems has been monitored and the results compared with expectations. The houses were unoccupied but heat gains equivalent to a family of four were simulated; the heating systems were in continuous operation to maintain nominally constant temperatures of 21 °C in the living rooms and 18°C in the bedrooms. The heat losses were slightly lower than predicted. Air leakage was also low. The heat pumps showed some fall-off in performance at high outdoor temperatures but generally performance was predictable from laboratory data. It is shown there may be two types of heat pump in so far as defrosting behaviour is concerned. Temperature controls on individual radiators provided little overall advantage compared with control by a single room thermostat—the difference between them is discussed.