Passive house renovation of Swedish single-family houses from the 1960s and 1970s : Evaluation of cost-effective renovation packages

Sammanfattning: Single-family houses (SFHs) constructed between 1961 and 1980 account for approximately one-third of the total energy use, 31 TWh, for space heating and domestic hot water in Swedish SFHs. These are responsible for about 40 percent of the total energy use in all buildings. There are roughly 715,000 houses from this period and they are largely homogeneous in technical terms, with low levels of thermal insulation, and ventilation with heat recovery is rare. The average energy use for houses from this period is about 40 percent higher than SFHsconstructed between 2011 and 2013.The BETSI study showed an extensive need for renovation in the SFH building stock. About 70 percent of the evaluated SFHs had some damage – found in all parts of the houses – although most damage was not categorized as severe. The fact that many of these houses need to be renovated provides an excellent opportunity to incorporate energy efficiency measures to reduce both operational cost and greenhouse gas emissions related to energy use.The aim of this project was to evaluate the possibility for cost-effective renovations of SFHs to Passive House level, while improving the indoor climate. Included in the assessments are thermal comfort and moisture safety, and the alternative of installing local renewable energy production and energy storage. The approach involved theoretically applying the energy efficiency measures to two case study buildings. These reference houses were based on typologies determined from the initial literature review.The research project began with identifying pilot renovation projects aimed at drastically reducing the energy demand of existing SFHs. Based on the renovation measures used in these projects, possible energy efficiency measures were identified and evaluated to find the energy savings potential from this type of extensive energy renovation. The results showed great potential, and such renovations could reduce the final energy use by over 65 percent.This was followed by a sensitivity analysis to determine the impact of different input parameters and building properties of the reference houses used in the energy simulations. These results showed a significant dependence on location of the reference houses if the Passive House requirements were to be fulfilled. The results were also used to limit the number of alternative energy efficiency measures used in the subsequent LCC analysis.A LCC analysis was carried out to determine cost-effective renovation packages to Passive House level. This built on the previous energy simulations by including the energy costs of adding and evaluating different types of heat generation and distribution systems. This was done to determine the operational costs of the houses and investment cost of implementing the energy efficiency measures. Also included was the alternative of implementing renewable energy production.The results show that Passive House renovations can be cost-effective, but this is largely dependent on the type of heat generation used in the houses – based both on the difference in operational costs and on the requirements for Passive House. The most cost-effective individual renovation measure was installing an exhaust air heat pump and the least cost-effective was installing new windows. In houses using direct electric heating, the Passive House renovation package was the most cost-effective alternative.