Evaluating energy efficient buildings : Energy- and moisture performance considering future climate chang

University dissertation from Department of Architecture and Built Environment, Lund University

Abstract: One of the greatest challenges the world is facing is climate change. The need of reduction of energy use and an increased use of renewable energy in buildings constitutes important climate change mitigation measures.The objective of this research is to investigate methodologies and performance indicators for the evaluation of energy and moisture performance of buildings, including co-benefits which may occur in “green buildings”. Furthermore, the objective is to identify a methodology for evaluation of the energy and moisture performance of buildings, including co-benefits.This work was set out with a historical review of building envelopes for residential buildings followed by a literature review and case studies to investigate how energy performance, moisture conditions and green co-benefits may be calculated. An evaluation method based on multi criteria decision analysis (MCDA) was developed and tested.The study of the existing residential building stock shows that it is not possible to analyse a single reference building that would cover a majority of the existing buildings, e.g. renovation potentials. A set of different reference buildings and constructions are needed to enable further studies, which may investigate different possibilities related to renovation.Results also show that the relative share of transmission heat transfer losses due to thermal bridges increases when the heat resistance of a building envelope is increased. Hence, thermal bridges must be given more attention in the design of buildings.The term “energy performance” of buildings is often used today, and it is generally alleged that it refers to the annual energy use per conditioned living area. However, differences exist in building regulations in different countries and in definitions of Net Zero Energy Buildings. In relation to “moisture performance”, no international or European standard or framework for assessing and presenting moisture performance has been found within this study. Quantifying and including green co-benefits may be very profitable.Common for all calculations and investigations presented—regardless if it is energy performance of building envelopes, buildings’ energy performance, hygrothermal simulations, quantification of green co-benefits or a life cycle assessment—is the need to clearly state the boundary conditions when the results are presented, as they may have a major impact on the results.A model based on MCDA was proposed and tested. The tests of the model showed that it is possible to handle a large set of criteria and to weight them into one value. Hence, it should be possible to use the model to assist with decision-making.Recommendations for future research are to further develop calculation and evaluation methods for energy and moisture performance in buildings, including co-benefits that may arise in green buildings. Finally, there is a need for an MCDA software tailored for the construction industry to facilitate more use of MCDA. The software could be based on the method presented in this thesis.