01.04.2011

The House With No Bills

Tim Adams achieved the ‘House with no Bills’ where water is free and passive thermal building conditioning is embedded in the design.

The current anxiety caused by the prospect of costing carbon and the associated political argy bargy would be largely inconsequential for many if greater numbers of the community used building design solutions to arrive at carbon neutral nil cost housing solutions.

The 6 star workshop program presented by BDAV in early 2011 – with the assistance of grant funding by Sustainability Victoria – endeavoured to demystify the issues of delivering cost effective if not cost neutral ways of meeting the new regulatory standards as well as community expectations.

Part of the narrative to illustrate possible solutions by way of example included a summary of the sustainability outcomes achieved in my own house. It was suggested by one of the workshop participants that a brief summary of the project in BDAV News would be of interest to those who have been unable to attend the workshops.

The house in Gherang, after two years of occupation, has now delivered on the goals that were set for it to be ‘A house with no Bills’ (1) and to have a zero carbon footprint.

While only achieving an energy rating of around 7 Stars because of the modest specification and double-glazing only in the south windows, an emphasis was placed on summer performance to ensure that air- conditioning would not be needed. A major decision to this effect was to use a concrete slab on ground without under slab insulation. The coupling of the slab to the ground under the slab gives the best outcome for using the stored coolth of both bodies of thermal mass to assist in passive summer comfort. Careful attention to summer shading, cross ventilation, ceiling sweep fans and night purge cooling assisted by an evaporative water feature help to give total confidence that mechanical air-conditioning would not be part of the capital budget or ongoing running costs.

Another key decision was to settle on all electric appliances, understanding that it would be easy to balance the demand using on-site renewable generation with a grid-connected photovoltaic system. Bottled gas was deemed to add an unnecessary level of complication to the initial services installation and ongoing management of energy supply.

Artificial lighting is provided predominantly by compact fluorescent up lights and pendants with some LED fittings. Cooking appliances include a full suite of everyday gadgets with kettle, toaster, microwave, espresso coffee maker topped off with 800mm oven and 4-plate induction cook top. Other major electrical appliances are a 500L two-door fridge, full size dishwasher, front-loading clothes washer and an assortment of entertainment electronics. There is no clothes dryer or separate freezer. A cool cupboard with natural convection airflow helps to reduce the capacity needed from mechanical refrigeration.

Pumping power is higher than standard suburban loads due to the need for a domestic water supply pressure pump, black- water treatment system, solar hot water circulation, hydronic slab heating circulation and wood fired backup boiler circulation.

Prior to installing the PV system, the power use through a full year of seasonal variation came out at an average daily use of 9.25 kW hrs. Accordingly it was decided to install
12 x 190w PV panels with a 3 kW inverter. Given average sunlight data, this system should deliver enough to match demand with scope to add a further 40% panel capacity if required in the future.

The first electricity account for a full three-month period with the smart meter in place has delivered a $205 total credit, including all consumption and service charges. This has been achieved even though the average daily sunshine this summer was 1.5 hours below average. Current tariffs are $0.2145 for supply and $0.66 feed in. If, as anticipated, the cost of electricity increases significantly, the purchase price will get closer to or even overtake the enhanced feed-in tariff. This will reduce the potential for credits but will also multiply the savings.

Saving the $950 cost of power bills in the previous 12 months combined with an anticipated annual credit of approximately $800 will result in a return on investment of around 18% for the $9,300 cost of the PV installation.

Our water costs are zero, given that around 400sqm of roof on three buildings is drained to 120,000L of tank capacity, storing more than enough for domestic consumption and garden watering. We even play under the sprinkler in summer.

60 evacuated tubes provide solar heating of domestic hot water and primary input to the slab hydronic heating system. Backup to the solar heating comes from an Italian boiler with high efficiency heat exchanger system, which runs at 70-75% efficiency. A reforestation program on the property will provide a totally self-sufficient fuel supply on site and sequester more carbon in the trees than will ever be released by the fire in the boiler. There will be some minor costs associated with chainsaw operation and maintenance.

Black-water treatment is achieved with a worm-based system which has an annual service fee of around $350. The treated output can be used for sub surface irrigation.

In summary we have achieved the ‘House with no Bills’ where water is free, passive thermal building conditioning is embedded in the design, wood fuel is grown on site and credits from the electricity feed in tariff (contracted for 15 years) will easily offset black-water treatment system maintenance fee and chainsaw costs.

Not all projects and all sites will offer the combination of opportunities available in this case, but a combination of most of the parts will regularly be possible and to ignore them will deny the potential for good cheap sustainable solutions.

Instead of giving your investment dollars to shiny shoed suits in the city to bet on the stock and bond markets you should consider redeploying the hard earned towards building designers who can make an environmental difference and reduce the cost of living at the same time.

(1) Term coined by Robert and Brenda Vale for their own home as set out in The New Autonomous House – Thames and Hudson – 1990.

Tim Adams is a Fellow and Past President of the BDAV. He has more than 40 years of building design experience and is as a leader in the field of energy efficient house design. He runs F2 Design, which is dedicated to ensuring that high performance houses and integrated sustainability responses are delivered with no impact on housing affordability.

He created and lives in ‘The House With No Bills’, which received considerable media coverage. To read one such feature, CLICK HERE.