A recent research project undertaken by the Built Environment division of the CSIR has confirmed that a light steel frame (LSF) dwelling, built to SANS 517, will result in significant savings of electricity used for heating and cooling of the building, compared with a conventionally built heavy masonry building. This is according to John Barnard, director of the Southern African Light Steel Frame Building Association (SASFA), a division of the Southern African Institute of Steel Construction (SAISC).
Barnard says that in order to obtain an objective prediction of the thermal performance of a light steel frame dwelling compared with a masonry building in the different South African climate zones, SASFA approached the CSIR to carry out the analysis. A typical 120 m² single storey house was used for the comparison. The LSF and the masonry houses were specified to be geometrically identical, with identical orientation. The LSF house complied in all respects to SANS 517 Light Steel Frame Building, while a typical masonry house with double-leaf external clay brick walls, without any insulation in the walls and ceilings, was used as the base case. Barnard says that the effects of adding insulation to the masonry house were also analysed, as follows: (a) 40mm insulation in the ceilings, and (b) similar ceiling insulation as used for LSF buildings (140mm) and 50mm insulation in external walls. The CSIR decided to use the Ecotect TM V 5.6 software to carry out the computer analysis. In order to eliminate the effect of user input data, which could influence the outcome, it was decided to use a passive analysis – that is, no assumptions regarding the occupancy and usage patterns of the house. The heating effect of lights and appliances was also not taken into account. The analysis, using the thermal neutrality calculation, determined the number of hours of “uncomfortably high or low temperatures” in each of the buildings and the electricity needed for heating and cooling each of the buildings to thermal comfort levels, which range from 20 to 24 o C, as recommended by SANS 204. The major differences between the two types of building are the thermal insulation and the thermal mass.