Abstract
In this paper, the thermal performance of residential building envelopes including thermal bridges (TBs) in a hot climate, using four different exterior wall types, is modelled and assessed. TBs at the junctions between columns and walls and between walls and slabs of the ground floor, roof, and intermediate floors are considered. The tested wall types are classical (two layers of cement blocks with insulation in between), autoclaved aerated concrete bearing (AAC-B), AAC column and beam (AAC-CB), and exterior insulation and finish system (EIFS). The results indicated that thermal bridges have a considerable effect and determine the best external wall type which was the EIFS that has a continuous exterior insulation. EIFS proved to reduce the heat transmission with the outdoor environment for residential buildings by 101.8, 51.2, and 13.9% than the AAC-CB, AAC-B, and classical walls, respectively. Thermal bridges effect on the building envelope using the EIFS is insignificant as the thermal resistance of the envelope and wall differs by less than 1% for small areas. The overall heat transfer coefficients for small buildings are larger than those for large buildings by 8–26%. As the number of intermediate floors increases from 1 to 50, the envelope overall heat transfer coefficient increases by 4.5% for the EIFS, 14.1% for classical, and 19.5% for AAC-CB walls. The AAC-CB, as the common practice wall structure in many hot climate countries, has the lowest performance among the tested wall types.
Highlights
Buildings contribute to environmental pollution substantially as they are responsible for about 36% of worldwide primary energy consumption and 39% of CO2 emissions [1]
This paper investigates the effects of four different wall structures on the thermal bridges and the building envelope performance, in a hot climate, using two-dimensional mathematical models
As the area of the thermal bridge may be as large as 50–80% [6] of the external walls, it has a substantial effect on the various types of external walls used in hot climates
Summary
Buildings contribute to environmental pollution substantially as they are responsible for about 36% of worldwide primary energy consumption and 39% of CO2 emissions [1]. Other studies have investigated the insulation type [10–12], thickness [10,13–15], and location [16] Those studies did not consider the effect of thermal bridges on the building envelope performance and energy consumption. The previous work lacks the accurate effect of different external wall structures on the thermal bridges and envelope performance, in hot climates. It makes it difficult to select the suitable wall type that has the best thermal performance of the building envelope. The novelty of this work is identifying the best wall structure type by the comparison of the four wall construction envelopes regarding the overall thermal performance of the building envelopes including the thermal bridges on the four different locations, using two-dimensional heat transfer models
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