20 September 2011
Sweden aims to reduce building-related energy use by 50 % until 2050. The main savings have to be in existing buildings and in this respect heat pumps have a strong position in Sweden. This paper describes a retrofit solution that can be used also in newer, heat efficient single-family houses. The presented heat pump system design was first evaluated by simulations based on laboratory-tested capacity data for the heat pump. Simulations were made for various levels of upgrades of a standard installation. The heat pump was installed in a single-family house with direct-acting electric heating and the various upgrades were
made one after the other. Measured values agreed well with the predicted results and, compared to a standard installation, the new system raised SPF from 2.7 for heating-only to 3.7
for heating and hot water. Specific energy use for heating and hot water in this house from 1977 is now on a par with future requirements in Sweden for new housing with electric heating
(30 kWh/m2/year) and less than that of current passive houses.