Strategic design of wall envelopes for the enhancement of building thermal performance at reduced air-conditioning costs

A strategy is proposed for the design of wall envelopes to improve unsteady thermal performance in non -airconditioned buildings and to reduce energy costs in air-conditioned buildings. The thermophysical properties of building materials (e.g., burnt bricks, mud bricks, laterite stone, cinder concrete, and expanded polystyrene) were measured experimentally using a thermal analyzer. A total of 28 combinations for composite walls were designed with expanded polystyrene as an insulation material based on seven criteria and were subjected to 8 different external surface heat transfer coefficients, which were tested for unsteady thermal performance parameters and air-conditioning cost-saving potential. In this paper, unsteady thermal transmittance obtained from admittance method has been employed to compute cost saving potential of air-conditioning for the various wall envelopes. The use of C-H-5 design at a 2 m/s wind speed was found to increase the decrement lag of burnt brick, mud brick, laterite stone, and cinder concrete composite wall envelopes by 48.1%, 49.0%, 59.5%, and 47.0%, respectively, relative to the common wall design (C-H1) in non-air-conditioned buildings. The laterite with a C-H-5 design offers the highest annual energy cost savings (1.71 $/m(2) at 2 m/s), the highest life cycle cost savings (18.32 $/m(2) at 2 m/s), and the lowest payback period (4.03 yrs at 2 m/s) in all tested building materials for airconditioned buildings. The overall results of this study are expected to open new paths to deliver simple design strategies for energy-efficient buildings.

Automated summary

This study presents a design strategy for wall envelopes to improve thermal performance in non-airconditioned buildings and reduce energy costs in air-conditioned buildings. Experimental measurements of building materials were used to optimize composite wall designs, resulting in substantial energy cost savings and enhanced thermal performance, particularly for laterite stone. The findings demonstrate the potential for simple design strategies to promote energy efficiency in buildings.