Affordable and high performance!
We’re excited about the results from the New Zealand Housing Foundation’s HomeSmart Home. With very low energy and water use, and a fantastic healthy environment for the homeowners, it is a great example of affordability over time.
The Housing Foundation is a not-for-profit, charitable trust set up to provide affordable housing for low income households. Built in 2009, the HomeSmart Home amended a standard Housing Foundation design using Beacon’s HomeSmart Home guidelines. These guidelines have been developed out of our experience in building and monitoring the performance of two new homes, and they aim to ensure a home meets our performance benchmarks, the HSS High Standard of Sustainability®. The HomeSmart Home’s energy and water efficiency, indoor temperatures and humidity were monitored for a year with a family of 2 adults, 2 children and 2 teenagers living there.
The results were exciting. Simple but effective were improvements to the home’s passive solar design and thermal envelope. The house was oriented to the north with the garage on the south side and the majority of windows along the northern face. An overhang shaded living area windows with eaves over the upper storey windows. High levels of insulation (R4.6 ceiling insulation and R2.6 external wall insulation) were combined with U-PVC framed double glazing. The family found the house to be very warm in winter and only used the heater when they first moved in with a newborn baby. Warm winter temperatures in living and bedrooms improved the family’s health. The family reported that no-one had been sick since arriving in the house and they had not needed asthma inhalers.
Energy use in the HomeSmart Home was startlingly low coming in at 3980 kWh per year. Compare this to a recently monitored group builder house in Christchurch where year-round heat pump use resulted in 14,400 kWh per year energy use and you can see what a saving this is. In part, the great performance was due to the photovoltaic panels which generated 50% of electricity used, but even without this, the home’s design and features made it a very efficient electricity user - after all, not many affordable homes would invest in this level of kit. A combination of energy efficient appliances, lighting and hot water combined with good passive heating and thermal design significantly reduced the family’s power bills. The family praised their efficient heat pump hot water system for its contribution to their lower power bills and the warmer home meant minimal heating costs. The house also included a Centameter which enabled the family to keep an eye on their energy use. Other studies have indicated that energy monitors can reduce energy use by about 10%.
Water-wise, the HomeSmart Home also performed well. Water is metered and paid for separately in Auckland, so using less water had a direct financial benefit for the family. Water efficient appliances and fittings, a rainwater tank for the garden, and a greywater system, which reused 30% of waste water from bath, shower and laundry, reduced the family’s water use to 117 litres per person per day. This is considerably less than the average in the Waitakere area of 165 litres per person per day. Given the low cost for water efficient fittings and the ease of incorporating them into homes, they should be a top priority for affordability.