Composite thermal walls for low energy Brazilian homes

Abstract

The objective of this study is to investigate the behavior of thermal walls as elements in low energy consumption buildings and residences. The problem is formulated based on one dimensional model and solved numerically by finite difference technique. Numerical tests were realized to optimize the numerical grid. Two wall arrangements were investigated; simple wall with incorporation of external surface colour, bio mass additives to construction slabs, and double wall with and without spacing filled with stagnant air. The influence of these variations on the maximum internal ambient temperature and the corresponding time lag with respect to the maximum external surface temperature were calculated for each case. Results indicated that increasing wall thickness reduces the internal peak temperature and delays its occurrence. Light colour paints and wall planted vegetation have similar effects as increasing wall thickness. Low thermal conductivity material and use of surface finishing mortar mixed with dry biomass helps reducing the solar heat gain, internal ambient temperature and increasing the time lag. The spacing between the walls can reduce significantly the heat transferred to internal living space and increases both the thermal comfort and the temperature time lag.