Sustainable House Day, Blackmans Bay, Tasmania

Our design brief was to build a modern suburban Hobart home implementing sustainable and environmental design elements to minimise dependence upon supplied services such as electricity and water, and to maximise solar energy for heating and reduced living costs. Other important design considerations were to use judicious room placement to take advantage of the spectacular Derwent River views, and provide the maximum land area for productive vegetable cultivation.

Hobart Climate
“Hobart experiences cold, cloudy winters, and cool, cloudy summers. The air temperature ranges from a maximum of 22°C in January and February to a minimum of just 4°C in July. Heating is required throughout the year. Humidity remains within the comfort zone throughout the year. Winds are mainly north-westerly in the morning and southerly in the afternoon. Average annual rainfall is low at 501 mm, but it's distributed evenly throughout the seasons.”  (quote taken from designingforclimate.com)

New Build: Designed by Mike Cleaver of Clever Design to our personal needs and design brief. Mike specialises in award-winning environmental house designs. Built to exacting standards by Andrew Scott, building contractors of Kingston Tasmania.

Unique Sustainable Elements Featured in this Home

Water Harvesting

A 12,500 litre above ground potable water storage tank with first-flush diverters provides pressurised water for the vegetable garden, and a back-up source of drinking water. It is not connected to the house but could be used at a later stage to provide water for household use. Gutter guards on the Colorbond roofing also prevent debris entering the system. The water tank will allow us to avoid watering restrictions during hot, dry summers.

External Walls

Exterior walls were constructed from cement blocks for structural support in important areas, and from rendered Exin stud-walls for thermal insulation. The rendered Exin walls are painted in a two-tone “beach colours” scheme. The block wall at the front of the property has a sandy Granostone finish. Wall cavities on all exterior stud walls also have R2.0 fibreglass insulation bats. The block walls have R1.5 bats where insulation is needed.

Internal Walls and Stairs

Internal walls are plasterboard covered Tasmanian Oak stud-walls painted with Dulux Enviro2 low VOC water-based paints. The internal stairs to the second level are Tas Oak treated with a natural Orange-Tung oil finish instead of the usual high VOC polyurethane coating.

Roof

Blue Colorbond roofing with R1.5 roof blanket and R3.8 fibreglass insulation. Larger than normal eaves were designed to give more efficient summer shading but allow entry to generous amounts of sunshine during colder months of the year for passive solar heating. The roofline is divided into three sections. The front and back sections are flat with a 2.5 degree slope. The middle section is aesthetically curved to complement the stunning family room area. Rainwater from the middle and back sections is channelled into the water storage tank at the rear of the house. A skylight on the back roof section provides daylight illumination for the walk-in-robe of the master bedroom.

Floors

The house has a standard slab floor on the ground level and a 200mm thick suspended slab floor on the upper level in the main open plan living area, and for the bridge between the front and rear upstairs sections. Dark chocolate-coloured floor tiles cover the upper slab, and provide passive solar heating during winter. The main bedroom area on the upper level has carpet over particleboard. The ground level flooring consists of glazed cream-coloured tiles.

Window Treatments

All windows are double-glazed with white powder-coated aluminium frames, except for two windows in the workshop/storage room which are single-glazed. Holland blinds are used extensively on most windows for privacy and added thermal efficiency. Windows on some of the large north-facing windows have heavy rubber backed curtains as a night-time light barrier and for greater privacy. The heavy curtains, which extend from ceiling to floor, also prevent much of the heat loss from the family room on cold winter nights. Extra large windows are situated on the north facing side of the house to take advantage of the sunshine and provide stunning views in the lounge room.

Solar Power Generation

A grid-connected solar cell system is installed on the roof.  There are two racks of six panels installed, with extra space and wiring allowed for more panels, if we wish to install them later. Total output of the existing system is 2 kW. On sunny days most of the output is fed back into the electricity grid. The roof area of the house is situated well away from other tall structures and trees, and is ideal for efficient solar power generation all year round.

Water Heating

A 30-tube solar hot water collector supplies heating for the 315-litre electric-boosted stainless steel hot water system. The solar installation is very efficient and on a sunny winter’s day can start pumping hot water into the tank as early as 9.30 in the morning.

Heating and Cooling

Sunny days provide enough passive solar heating upstairs in the main living areas during the day and well into the night. Additional heating may be needed on especially cold nights during winter when several days without sunshine cool the house substantially. There are two split system heat pumps, one for downstairs in the family room and the other for the open plan living area on the upper level. During summer strategically placed opening windows provide cross ventilation for good cooling on most hot days. The air conditioner is seldom needed and only used on the few extremely hot and humid days after Christmas.

Outside Landscaping

To supplement the sustainable house features we are cultivating most of our remaining land with a large vegetable garden and numerous fruit and nut trees. At a later stage we intend to build a chicken run and install a hot house for growing warm climate vegetables. The paling fences on the garden side of the house are made from hardwood rather than the treated pine to prevent soil contamination. The soil is a well-drained sandy loam and the veggie garden receives full sunshine during the summer months. Our building block is 860 square metres with about a half available for cultivation and outdoors entertainment. The garden area may take a year or so before it is finished to our expectations, and the outside family entertainment and recreational areas are a work in progress. Our aim it to make our suburban property as sustainable and self-sufficient as possible providing food for our family’s needs and enjoyment at digging our own plot of land.