The Influence of Thermal Bridges for Buildings Energy Consumption of “A“ Energy Efficiency Class
The Influence of Thermal Bridges for Buildings Energy Consumption of “A“ Energy Efficiency Class

Summary/Abstract: From 2016 “A” energy efficiency class buildings should be designed and built in Lithuania, as their energy consumptions are considerably less comparing with the ones that were built before. In order to meet high requirements of “A” energy efficiency class buildings should be used new energy efficient structural and insulating solutions should be made. In order to evaluate overall heat losses in these joints more exactly it is required to calculate values of heat transmission coefficients of linear thermal bridges in “A” energy class buildings.The project of semi-detached building was chosen in order to analyse influence of linear thermal bridges for building’s energy consumption as there are all kinds of linear thermal bridges which values must be calculated. Buildings energy efficiency designing program, which based on EN ISO 13790, was used to calculate building’s heat losses. Heat transmission coefficients of linear thermal bridges were calculated using program THERM. Two variations were analysed: building’s energy consumptions are close to the lowest point of A class requirements when building’s envelopes and joints of units in joint places are the same as they are in currently built houses; and effective energy solutions of building’s joints.The results of analysis showed that requirements of “A” class can be reached using ordinary solutions for building’s envelopes and joint units but if linear thermal bridges are designed like that, it makes 16 % heat losses through envelopes, and it is similar to heat losses through building’s walls (17 %), furthermore, it is about 1.5 times bigger than heat losses through roof (10 %) or floors (10 %). Specific heat losses of thermal bridges make 7.80 kWh/m² per year. The biggest overall heat losses are through walls and windows joint thermal bridges (specific heat losses make 13.55W/K). Another significant part of heat losses comes from walls and floor joints (specific heat losses make 11.88W/K).After solutions of buildings with energy effective building’s envelopes and units joints were analysed it can be stated that overall heat losses decreased about 10 kWh/m² per year, it is 20 %. Heat losses through thermal bridges make only 3 % of overall heat losses through envelopes, it is 122 kWh/m² per year.According to results of the analyse general specifications were made for designing building envelopes of “A” energy efficient class:- The building of “A” class can be designed using ordinary solutions of linear thermal bridges, bigger heat losses through thermal bridges can be covered by increasing thickness of thermal insulating layers and using windows of better thermal behaviour but as a result the costs of building house increase too.- When effective solutions of linear thermal bridges are used, the same energy efficiency of the building can be reached using less thermal insulating layers, windows and doors of less thermal behaviour if the building of better energy characteristics is designed.

• Details
• Contents