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

Abstract

The aim of this study was to evaluate the life-cycle costs (LCC) and energy performance of different heating and ventilation systems (HVAC) in deep-energy renovation of Norwegian detached houses. Eight different HVAC combinations based on heat pumps are compared using two case buildings, with different performance levels for the building envelope. The case buildings are small wooden dwellings without a hydronic heating system, which is representative of existing Norwegian detached houses. The insulation level had only a limited effect on the relative performance of the various HVAC combinations. Many solutions with medium and higher investments have a payback time close to the technical lifetime. Uncertainty regarding investment costs is important and affects the relative performance between HVAC combinations. Electricity prices also have a decisive influence on the relative performance. Solutions with lower investment costs often lead to low total costs but higher energy use. However, solutions with medium investment cost lead to a significant reduction in energy use and only a minor increase in total costs. Improving the cost-effectiveness of these technologies (reduced investment costs, grants, increased electricity price) would unlock large energy-saving potential. The lack of hydronic distribution systems in existing Norwegian buildings is a barrier to implementing air-to-water and ground-source heat pumps. For the investigated cases, the current government subsidies in Norway do not seem large enough to make investments in deep-energy renovation profitable.