The Effect of Balcony Thermal Breaks on Building Thermal and Energy Performance: Field Experiments and Energy Simulations in Chicago, IL

Abstract

A common envelope performance problem in buildings is thermal bridging through balcony slab connections, which can be improved with the use of commercially available thermal break products. Several prior studies have used simulation-based and/or hot box test apparatus approaches to quantify the likely effect of balcony thermal breaks on effective thermal resistance of building enclosures. However, in-situ measurements of thermal performance in real buildings remain limited to date. This study uses a combination of field measurements and models to investigate the effects of installing balcony thermal breaks on the interior surface temperatures, effective thermal resistance, and annual building energy consumption. For the field experiment, yearlong measurements were conducted on the 13th floor of a 14-story multi-family building in Chicago, IL, in which thermocouple sensors were embedded into eight balconies and their adjacent interior floor slabs just before concrete was poured to complete the construction. The eight balconies included four control balconies without thermal breaks and four thermally-broken balconies with a commercially available thermal break product installed. The experimental data were then combined with 2-D heat transfer modeling and whole building energy simulations to investigate the impacts of the thermal break product installation on the envelope thermal resistance and overall energy use in the case study building as well as in several more generic building designs with simpler geometries. The results demonstrate that although the balcony thermal breaks helped regulate interior slab temperatures and improved the effective thermal resistance of the curtain wall enclosure assembly by an estimated ~14% in the case study building, the predicted effect on annual energy consumption in all modeled building types was small (i.e., less than 2%). The results also highlight the importance of paying careful attention to envelope design details when using thermal break products and considering the use of thermal break products in combination with other energy efficiency strategies to achieve high performance enclosures.

Efficiency of Different Balcony Slab Modernization Method in Retrofitted Multi-Family Buildings

“…The impact on the overall U-value of the building envelopes can be improved from 9-18% and the space heating energy consumption may be reduced from 5-13%. The results of research by Susorow et al [26] showed a similar level of improvement in the effective thermal resistance of the curtain wall cladding assembly in a multi-family building in Chicago (by approximately 14%). However, the predicted effect of the use of thermal breaks on the annual energy consumption was significantly lower than in [25].…”

“…However, the predicted effect of the use of thermal breaks on the annual energy consumption was significantly lower than in [25]. In several more generic building designs with simpler geometries, it was less than 2% [26]. The authors suggested the need to consider the use of thermal break products in combination with other energy efficiency strategies to achieve high performance enclosures.…”

Influence of Balcony Thermal Bridges on Energy Efficiency of Dwellings in a Warm Semi-Arid Dry Mediterranean Climate

“…These con-struction solutions can reduce the linear thermal transmittance of thermal bridges by more than 60% [38] and decrease heating consumption by 5% to 13% and cooling consumption by 1% [39]. However, other research limits the impact of thermal break disruptions in balconies on the overall thermal and energy performance of the building, demonstrating that their effect on annual energy consumption is relatively small [40].…”

Thermal bridges in building envelopes – An overview of impacts and solutions

“…A fi eld study [28] evaluated the infl uence of thermal break in the balcony construction on the thermal performance and energy saving of high-rise multi-unit residential buildings located in Chicago, IL, USA. The study was done by installing thermocouples on both the slab board of a thermally broken balcony and the conventional balcony slab (non-thermally broken balcony) to measure the temperature gradient.…”