Evaluation of thermal comfort and energy efficiency in institutional buildings

Abstract

This study investigates the thermal comfort and energy performance of C-energy conference in Ntinda, prompted by occupant discomfort and escalating energy costs. Conducted from March 13 to April 13, 2025, the research aimed to assess compliance with ASHRAE 55 and 90.1 standards and propose strategies to optimize occupant satisfaction and energy efficiency. Data were collected over 35 sessions (Wednesdays and Fridays, 1:30 PM–3:30 PM) using environmental sensors to measure air temperature, relative humidity, air velocity, CO₂ concentration, and mean radiant temperature, alongside Post-Occupancy Evaluation (POE) surveys capturing occupant thermal sensation, comfort ratings, clothing insulation, and activity levels. Energy consumption was analysed for air conditioning, lighting, and equipment loads. Results indicated that the average operative temperature (27.16°C) exceeded ASHRAE 55’s 26°C limit in 80% of intervals, with relative humidity (69.3%) often surpassing the 60% threshold. Predicted Mean Vote (PMV) values ranged from -1.08 to +2, with nearly 50% outside the ±0.5 comfort range, and Predicted Percentage of Dissatisfied (PPD) reached up to 38%, exceeding the 10% limit in over 75% of intervals. Energy Use Intensity (EUI) was 252 kWh/m²/year, within ASHRAE 90.1 benchmarks, but the HVAC Coefficient of Performance (COP) was low at 1.5, indicating system inefficiencies. Regression analysis identified temperature as the primary driver of discomfort, with air velocity and humidity as secondary factors. Recommendations include upgrading to high-efficiency HVAC systems, implementing variable air volume or zoned mini-split configurations, enhancing ventilation with demandcontrolled systems, installing ceiling fans, and adding dehumidification to reduce latent heat loads. These interventions aim to achieve ASHRAE compliance, enhance occupant comfort, and lower operational costs, contributing to sustainable building performance in educational facilities.