Extending Horizons

Samantha Dunn

It’s common for a family to outgrow their house. Though buying elsewhere is one solution, many choose to avoid uprooting by simply extending their own residence. In building these additions, sustainable features are often neglected in order to reduce cost. Simone Schenkel of Gruen Eco Design, who specialises in affordable sustainable houses, knows this doesn’t have to be the case. For a budget of only $300,000, her project the ‘Box Hill South Residence’ achieved an energy efficiency rating of 8.1 stars and was a finalist in the 2015 Sustainability Awards. 

This excellent result was a collaborative effort. The clients were highly informed and engaged with the project from the beginning. Wanting to recycle as much as possible, they ensured that many materials were reused from the existing house or sourced second hand from elsewhere. This not only cut costs, but also the project’s carbon footprint. Some reused items included:

» Floor boards and bricks

» Tapware, fixtures and fittings

» Cabinets, benchtops and appliances 

» Existing hot water system

Simone worked with the clients to design a building that was simple but thermally well-performing. Central to her design philosophy was the concept of quality over quantity; a compact but well-planned house was important to both maximise energy efficiency and reduce costs. The clients were consulted to tailor the restricted space to their needs and created a sense of spaciousness by including slightly raised ceilings, open-plan living spaces and avoiding corridors. 

Standard, low-cost construction methods were used creatively to fulfil their sustainable potential. The critical features for thermal efficiency are the windows and insulation, particularly because they are difficult to alter once the building is complete. Standard-sized double glazed windows were carefully placed to allow cross-ventilation and natural light, and the new walls were built more thickly than usual to fit extra insulation. The existing house’s formerly external brick wall was enclosed within the extension and left exposed for additional thermal mass. 

Other features that contribute to the extension’s fantastic energy rating include:

» No downlights to avoid losses in ceiling insulation

» A fridge and pantry fitted with exhaust fans to control temperature and function efficiently 

» A concrete floor for thermal mass

One of the project’s major difficulties was finding a suitable builder, with the search lasting six months. Some quotes were rejected for breaching the budget; other builders were unwilling to take on such engaged clients and the design’s more unusual construction techniques. But the arduous search eventually paid off, says Simone. A competent builder and tradies are vital to the success of a project, as they’re the ones who make the clients’ dream a reality. 

Some additional sustainable elements of the extension include:

» Two rainwater tanks (combined capacity 15,000L)

» LED and fluorescent lights instead of halogens

» Water feature outside lowlight windows to cool air in summer

» Slow combustion wood heater 

» Veggie patch 

This extension doesn’t contain any fashionable expensive features, such as retractable flyscreens, bi-fold doors and full-length windows. Nevertheless, Gruen Eco Design has enabled their clients to expand their home into a cosy and liveable dwelling that leaves minimal impact on the environment and the clients’ bank balance. If you look beyond your horizons you’ll see that affordable sustainable architecture is thriving.