Numerical Investigation of the impact of longitudinal thermal bridging on energy efficient buildings under humid continental climate conditions: The Case of Lithuania

Abstract

Thermal bridges play a major role in the thermal losses of the building shell and should be avoided, especially under winter dominant conditions and for high cooling degree days regions in Europe and worldwide. Since 2016 the requirement for all new buildings to achieve energy-efficiency class “A” came into force in Lithuania. One of the requirements to meet this class are detailed calculations of the thermal transmittance values of the longitudinal thermal bridges. The same requirement is also requested for higher energy-efficiency buildings that are qualified as “A+” (obligatory since 2018) and “A++” (obligatory from 2021 onwards) class buildings.The purpose of this study is the numerical investigation of the impact of thermal bridges on energy efficient buildings under humid continental climate conditions. For the purpose of the study, the energy performance of the thermal bridges of a class A building, situated in Lithuania, were analyzed, using the tool Therm of LBNL a two-dimensional conduction heat-transfer analysis, based on the finite-element method. The calculations of the thermal transmittance values of the longitudinal thermal bridges were implemented in accordance with the requirements of EN ISO 10211:2008 standard. Alternative construction designs, with the aim to minimize the thermal losses of the building shell are also presented and discussed in this study. This study showed that detailed calculation of the losses through thermal bridges may have a significant importance to avoid dew points and mold in sensitive parts of the building shell, but they have a minor influence for the energy certification criteria. The findings of this study are anticipated to provide useful feedback for the future development of the construction regulations in the Baltic countries, as well as in countries with humid continental climate conditions.