Use of passive cooling techniques and super cool materials to minimize cooling energy and improve thermal comfort in Brazilian schools

Abstract

Standardized replicable buildings can cause discomfort and increased air conditioning usage. Besides, super cool coatings are effective passive solutions. Therefore, this study evaluates thermal comfort in a standardized Brazilian public school in 8 climates, verifies suitable super cool coatings and identifies optimal additional passive techniques to meet regulatory requirements without active air conditioning, a topic worthy of investigation. Methods include pilot simulations with DesignBuilder, thermal comfort analysis considering ASHRAE 55 adaptive model; JEA Algorithm optimization simulations; identification of most influential passive strategies by sensitivity analyses; and evaluation of the ideal opaque envelope through heat balance. Results showed that current model do not meet the Brazilian normative. Thus, different super cool coatings are recommended: thermochromic for heating-dominated; spectrally selective for cooling-dominated dry and high broadband emissivity for extreme-cooling-dominated humid zones. Regarding opaque envelope, thermal mass flat roofs and insulated walls are advised. In 7 of 8 climates, super cool roof was most effective followed by natural ventilation. Optimal combinations include super cool envelope, window shading and natural ventilation 24 hours 7 days a week with 95 % of free-aperture for extreme-cooling-dominated zones; super cool roofs, medium reflectivity walls and 5 % of free-aperture for cooling-dominated; thermochromic roof and dark walls with natural ventilation during occupancy with 5 % of free-aperture for heating-dominated.