Economic and Energy Performance of Heating and Ventilation Systems in Energy Retrofitted Norwegian Detached Houses

Abstract

The aim of this study is to compare the life cycle costs (LCC) and energy performance of different heating and ventilation systems (HVAC) in deep-energy renovation of Norwegian detached houses. More specifically, the relative performance of nine different HVAC combinations based on heat pumps is compared using two case buildings with four different insulation levels for the building envelope. The case buildings are small wooden dwellings without hydronic heating system, which is representative for existing Norwegian detached houses. The energy performance was simulated using the dynamic software IDA-ICE, in compliance with Norwegian Standards. The standard NS-EN 15459 (2017) was mainly used for the cost performance assessment. HVAC combinations with low investment costs (e.g., EAHP, balanced ventilation and air-to-air heat pump) showed lowest global costs, but the highest delivered energy. Low energy consumption can be achieved with different balances between investments on energy measures for the building envelope versus HVAC systems. Heat pumps can contribute significantly to the reduction of the energy use. In many cases, the cost uncertainty within one HVAC combination is larger than the difference between the combinations. The global cost and delivered energy diagram show a Pareto front relatively flat over a long range of energy use, so that some HVAC combinations can significantly decrease the energy use for a small increase in global costs. The compact heat pump and ground source heat pump fall into this category. For the investigated cases, the current governmental subsidies in Norway do not seem large enough to make investments in deep energy renovation profitable. Finally, results show that the prebound effect should be taken into account to make a realistic analysis of the cost performance of energy retrofit.