Thermal comfort in a two-storey malaysian terrace house: Are passive cooling methods sufficient in present and future climates?

Rising temperatures due to climate change will impact both the indoor thermal comfort of naturally-ventilated housing and the cooling energy needs of air-conditioned housing in tropical regions. This study aims to evaluate the impact of rising temperatures based on the IPCC A2 scenario on indoor thermal comfort and cooling energy in a typical Malaysian terrace house. It addresses three key questions: 1) Can passive cooling (PC) achieve future thermally acceptable conditions? 2) How will PC impact cooling energy with air conditioning (AC)? 3) What is the effectiveness of various PC methods, individually and combined, in controlling indoor climate and saving energy under present and future conditions? We evaluated the effectiveness of eight PC measures—including shading, insulation, solar reflectivity, and nighttime natural ventilation—using EnergyPlus simulations. Results indicate that without PC and AC, indoor temperatures range from 26 to 31 °C, rising to 29–36 °C by the 2050s, often exceeding ASHRAE 55 standards. Currently, combined PC and nighttime ventilation can improve thermal comfort time fraction by up to 87 %. However, by the 2050s, this drops to 38 %, indicating PC alone will be insufficient, and AC systems will be essential. Additionally, in an AC scenario, PC measures reduce cooling energy by 6 % compared to the baseline under future conditions, yet demand is 67 % higher than current conditions. These findings underscore the need for integrating both PC measures and efficient AC systems to mitigate future greenhouse gas emissions from residential sectors in Malaysia and other developing hot climate regions.