In Norway, a large portion of the building stock originates from the period from 1955 to 1990. Many of these buildings fail to comply with the current building regulations regarding the energy consumption. In this study, the possibility for upgrading a hypothetical apartment building with an oil-based heating system has been investigated employing simulations from the IDA Indoor Climate and Energy software. For the construction of the original building, customs and regulations from the period 1981-90 were employed, and the building envelope was upgraded to the requirements of the Norwegian research centre on Zero Emission Buildings. Two alternative heating systems have been investigated: solar thermal collectors (i) alone and (ii) as combined with borehole thermal storage and a ground-source heat pump. For each case, the energy consumption, thermal comfort and indoor climate were studied. The simulations predict a reduction in the total annual heat demand to one third of the original with the upgrading. For the alternative heating systems, with solar collectors alone the demand for additional electric heating was still considerable, however in the combined system it was negligible. Regarding thermal comfort, in the upgraded building longer periods with elevated temperatures were observed.

Published in Journal papers


Reduced energy consumption is one of the most cost effective ways of reducing CO2 emissions for combustion of fossil fuels. Residential buildings must become more energy efficient according to the Energy Performance in Buildings Directive (EPBD). The demands for domestic hot water have become more significant. Therefore the share of domestic hot water (DHW) in high insulated houses constitutes an increasing share of total heating demand.

For DHW and space heating purpose CO2 tripartite gas cooler heat pumps are among the most efficient systems. Due to heat rejection at different temperature levels a large enthalpy difference and low compressor power input is achieved. A dynamic  model for a CO2 heat pump system combined with energy storage (by means of ice) for a zero emission building (ZEB) has been developed. The goal of the simulation is the optimization of the heat pump and of its operational modes.



Published in Conference papers

Search our website

Sort publications by:

Ascending order

Filter Publications: