According to Bruce Kerswill, executive chairman of the Green Building Council of South Africa, the sustainable elements of their “green” north-facing family home with its striking Table Mountain views have performed very well. They moved in just as the 2011 winter started.
Sustainability drove every aspect of the process of creating this Cape Town residence. Engineer-architect and sustainability consultant Vernon Collis said that often people who want to introduce green elements in their properties, “think of water and energy and that is where it stops.” He believes one has to look at things strategically and consider a house’s
relationship with its environment “in every sense, including insulation, shading, solar orientation, appropriate materials, life cycle analysis, appropriate building technologies, maintenance strategies, recycling of existing materials and much more.”
Project architect Rohan Young told how he and Kerswill held a series of workshops with Collis even before starting to demolish the old house that had been on the site: there was a rigorous strategy around every material, considering reuse and recycling – and each material was tested to ensure that it could still perform structurally as it was supposed to. In total about 80% of the materials from the old house was reused. In addition, the house was built using sustainable building practices that were labour intensive, with minimal use of power tools. “If we could do it by hand, that is what we did,” says building contractor Malcolm Grant.
The first level of achieving energy savings was passive design, which “does not cost you any more, but you can achieve a lot just by starting there. The plan was to get as much light and heat as possible into the house during winter, while cutting out the heat in summer,” explained Kerswill. For instance, the large windows and correct orientation of the home, have meant that the light inside has been good throughout the winter months.
In terms of heating, the deck with its glass windows on the outside functions, as planned, as a heat trap to distribute heat into the rest of the house and in general the house performed well thermally during the winter. Kerswill says the heat differentials in South Africa are not as severe as in countries such as Canada, where the passive house concept also demands a complete seal of the house. Our weather does not really warrant a complete seal.”
The renewable energy sources include a biodigester, a solar water heating system and 16 photovoltaic panels generating 200 watt each, totalling a capacity of 3.2 kW and the installation of a rainwater collection system. The biodigester has started functioning and is delivering enough gas for 10–15 minutes’ use a day. It is hoped that it will deliver more gas during the summer months.
The rainwater tank system is working well and the tanks were kept full by the winter rains.
The natural pool is still establishing itself. A current growth of algae is seen as normal and is expected to die back in the months to follow.
The integrated thinking is illustrated by elements such as the following:
- A careful choice of wood (ordinary local pine and FSC-certified hardwood).
- The use of LED lights throughout the house, using a new type that is expected to last for 30 years.
- The bamboo finishes used in the kitchen is sustainable. A reconstituted stone product was used for the kitchen tops.
- Valuable trees that were superfluous for the new garden, were taken out by nurseries for use elsewhere. Smaller existing plants were kept for reuse. Everything that could not be used from the old garden, became mulch for the new garden.
- A small green roof area over the garage.
The full project feature appears in the August-September 2011 issue on p40 . Images: Danie Nel (http://danienel.co.za)