Thermal performance of balcony thermal bridge solutions in reinforced concrete and steel frame structures

Abstract

Thermal bridges in balconies considerably affect the overall thermal transmittance of building envelopes and are the main cause of building defects such as condensation, mold formation, and degradation of materials. The aim of this study is to conduct an evaluation of the impact of two thermal bridge solutions in common balcony connection details of residential buildings in Tehran, Iran. Through three-dimensional simulation, 33 scenarios of various balcony connection details, as well as adjacent wall assemblies are examined with and without thermal bridge solutions to evaluate the impact of these solutions on the thermal coupling coefficient of balcony connection, balcony linear thermal transmittance, and temperature factor at the internal surface. The simulation process is conducted using the heat transfer module of the three-dimensional simulation program COMSOL 5.2.an under steady-state conditions. The results demonstrate that concrete-concrete connections compared to steel-steel and concrete-steel connections are influenced more by thermal bridge solutions. Considering all scenarios, implementation of these solutions leads up to 44.5% and 75% reduction in thermal coupling coefficient and linear thermal transmittance respectively, depending on the wall and floor materials. Results obtained by examining a case study with different balcony and window options also highlight the importance of applying a thermally insulation balcony connector which reduces the normalized total heat transfer coefficient of building façade up to 12.2%. The findings of this study highlight the effectiveness of different technical solutions for reducing balcony thermal bridges in both steel and concrete structure balcony connections. Also, applying the balcony thermal bridge solutions evaluated in this research can remove the limitations against the insulation method of “very low energy” buildings based on the Code. No. 19 of Iran.