SA Affordable Housing January / February 2017 // Issue: 62 - Page 16

COVER STORY GRAPHS FOR ANNUAL ENERGY USE OF THE DIFFERENT TYPES OF MATERIALS 280mm cavity clay brick + insulation 3500 270mm cavity clay brick 3087 220mm clay brick 3000 140mm hollow concrete block Light steel frame (SABS 517) 2500 2428 Timber frame (SABS 10 082) 2164 2000 1904 2054 1953 1623 1505 1500 1464 1282 1055 1000 749 827 10821066 1009 1012 887 853 734 725 590 496 479 454 500 945 868 862 786 1244 1135 1079 379 296 218 2 0 2 40m2 House KZN 2 40 m2 House GT 2 40m2 House WC 2 40m2 House FS 2 40m2 House LM 2 40m2 House NC The study found that high density walling systems (clay brick) consistently result in lower annual energy use even without additional insulation. WALL TYPES Six wall types were analysed 1. Double (internal and external) clay brick solid wall (nominally 220 thick, plastered). 2. Double clay brick cavity wall with air cavity (nominally 270mm thick with an uninsulated 50mm air cavity). 3. Insulated double clay brick wall (nominally 280mm thick, with 30mm extruded polystyrene insulation in the 50mm cavity). 4. 140mm hollow core concrete block (150mm thick with a single external layer of plaster and bagged internally). 5. Light steel frame, externally clad with 9mm fibre cement board to SANS 517 (nominally 145mm thick with 0.2mm polymer vapour membrane, 20mm orientated strand board and 0.8mm steel studs. Internal wall of 15mm gypsum board with 75/100mm fibre sound insulation). 6. Timber frame to SANS 10 082 clad with external shiplapped tiles or weatherboard (nominally 145mm thick with 20mm orientated strand board and internal cladding of 15mm gypsum plasterboard). A wall lifespan of 40 years was estimated, although not all the walling types have been shown to have this lifespan. US housing lifespan is taken at 32 years and influenced by the use of timber frame and lightweight construction systems in the American housing market. CLIMATE ZONES South Africa has six major climate zones. Energy use varies depending on the location of the building – warm climate zones use more air-conditioning and ventilation, cold climate zones need heating. 14 JANUARY - FEBRUARY 2017 AFFORDABLE SA HOUSING High rainfall areas need to deal with humidity and condensation. Lighting requirements have seasonal variations. Temperatures and other parameters used in the study are acknowledged averages for that zone. The measurements were based on the residents living in reasonable ‘thermal comfort’ which is between 19 and 25˚C. ANALYSIS OF THE RESULTS The low density walling systems (timber and steel frame) show a trend towards higher annual energy use even when they have low U-values. High density walling systems (clay brick) consistently result in lower annual energy use even without additional insulation. The results showing the variation of heating and cooling energy modelled for the three building typologies, can be summarised as follows: BEST (LOWEST) ENERGY USE • Residential buildings (all climate zones, all sizes): thermally insulated 280mm clay brick cavity walling • Non-residential building (climate zone 1): 140mm hollow concrete block walling • Non-residential building (climate zones 2-6): 220mm solid clay brick walling WORST (HIGHEST) ENERGY USE • Residential buildings (all climate zones, all sizes): 140mm hollow concrete block walling • Non-residential building (climate zone 1): timber frame walling • Non-residential building (climate zones 2-6): light steel frame walling