Role of thermal insulation in passive designs of buildings

Abstract

The utilization of solar energy for active and passive applications in buildings requires the careful selection of materials that have, (a) high thermal storage capacity, (b) thermal insulation efficiency, and (c) a balance of the two. The choice is not easy to make notably when the building falls in a temperate climatic zone. This paper tackles the selection of materials for usage in buildings from different angles to ensure the ease of selection. First, the optimal economic thickness of an insulation material is determined very accurately using the minimum life-cycle cost method and the annual heating degree days (AHDDs) for different sites. From this, the optimal thermal transmittance (U-value) for the building structure in a given climatic zone is determined. Second, a graphic relationship between U-value vs AHDDs is established. Third, annual energy savings in kWh ton−1 of insulation material is calculated. From this, the pay-back period of energy consumed in manufacturing the installed thermal insulation material is calculated. The higher the pay-back period the less desirable is the use of thermal insulation materials and more favourable is the use of high mass materials. This approach is well reasoned to allow its extensibility to all buildings in all climatic zones. It should certainly give insight to the possible contribution of solar energy in meeting demand for active and passive heating/cooling of buildings. Results are summarized in Figs 3 and 4.