Effects of building thermal performance and HVAC control on indoor comfort and energy use

Thermal comfort significantly impacts indoor environmental quality, influencing occupant health, productivity, and building energy efficiency. Conventional HVAC control strategies primarily utilize dry-bulb temperature (DBT) setpoints; however, this approach often neglects radiant temperature variations, resulting in uneven thermal comfort conditions across indoor spaces. This study investigates the influence of building thermal performance on indoor thermal comfort through field measurements conducted in two office buildings characterized by differing insulation properties, window performance, and airtightness levels. Additionally, building energy simulations were performed to comparatively assess the effectiveness of operative temperature (OT) control versus DBT control. The findings reveal that inadequate thermal envelope performance leads to pronounced radiant temperature discrepancies between perimeter and interior zones, exacerbating occupant discomfort and increasing energy demand. While OT-based control strategies enhance thermal comfort by accounting for radiant temperature effects, they simultaneously elevate energy consumption, especially in buildings with inferior insulation and envelope performance. Nevertheless, improvements in envelope performance significantly reduce the energy consumption disparity between OT and DBT control methods, enabling high-performance buildings to achieve optimal thermal comfort and energy efficiency simultaneously. Considering the extensive proportion of aging building stock in South Korea characterized by suboptimal thermal envelopes, this research underscores the critical need for retrofitting strategies, including enhanced insulation, advanced glazing technologies, and improved airtightness. Ultimately, integrating advanced HVAC control approaches with robust building envelope upgrades is essential to sustainably balance indoor thermal comfort and energy efficiency. • Perimeter MRT differed by about 1.5 °C across seasons, consistent with discomfort. • OT control achieved full comfort, while DBT lagged in older perimeter zones. • OT used more energy in every case, and the penalty fell from 30% to 6%. • Heating was driven by conduction and infiltration, and cooling mainly by SHGC.