Impact of Roof, Wall Insulations and Double Glazing on HVAC Energy Use in Residential Buildings of Bloemfontein

T. Kumirai and T.N. Ngonda (S. Africa)


Passive, Energy efficiency, Thermal comfort, Residential buildings, modeling.


The purpose of the paper is to demonstrate that it is possible to minimize the use of active systems in providing thermal comfort in single-family detached middle to high income residential buildings of Bloemfontein. According to Mathews [1] a typical middle to high income house in Bloemfontein South Africa has a floor area of between 180 to 200 m². A house in Fauna, Bloemfontein (latitude 29.1 S, longitude 26.3 E, altitude 1353 m) was chosen as the case study house after approaching various owners of households in low to high income suburbs. The field studies were conducted from 18 to 24 May 2009. The field studies were primarily done to acquire data for calibration of the Ecotect v 5.6 model. The construction details of the case study house were input in the Ecotect™ v.5.6 program as well as a weather file for Bloemfontein. The results of fieldwork measurements were compared with thermal simulations from Ecotect™ thermal simulation tool (Ecotect™ v.5.6). Passive strategies were incorporated on the Ecotect™ model in combination, then both thermal and space load simulations were obtained and compared to simulations from the original situation (base case) for assessing improvements in terms of heating, ventilation and air conditioning (HVAC) energy consumption. Annual HVAC electricity savings of up to 55.2 % were obtained from incorporating passive strategies in combination. Incorporating passive strategies resulted in small improvements in thermal comfort.

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