Analysis of energy economic renovation for historic wooden apartment buildings in cold climates

Buildings represent the largest sector of primary energy consumption and play a major role in saving energy and reducing greenhouse gas emissions. Our analysis of energy consumption and potential energy savings is based on field measurements, computer simulations and economic calculations. The average primary energy consumption (PE) of wooden apartment buildings was 331 kW h/(m2 a) 83% higher than the limit 180 kW h/(m2 a) set in national regulations for apartment buildings subject to major renovation. The studied buildings represent a high potential for energy savings. The renovation packages were compiled using different insulation measures, HVAC solutions and energy sources to achieve a 20-65% reduction of primary energy. For historic buildings, the renovation solutions that concentrate on the building envelope can be problematic due to the need to preserve cultural and architectural values. Our calculation results indicate that the cost optimal PE level is around 250 kW h/(m2 a) and the point at which renovation packages recover expenses is around a PE level of 170 kW h/(m2 a). In terms of the architectural appearance the point at which renovation packages recover expenses is around a PE level of 210 kW h/(m2 a). We propose to set a different PE limit for historic wooden apartment buildings with an architectural appearance worth preserving.