Sustainable House Prototype

This sustainable house prototype was designed by Trevor Scott, architect, for his GreenEarth Shelter architectural practice.

Sustainable house design features

Orientation

A plan of rectangular shape with sides in the ratio of around 2/1 is an ideal shape to take advantage of winter warming from the sun’s rays, providing the long side of the rectangle is facing due north.It is also good for minimising summer warming because of the angle of the sun’s rays at midday in summer, combined with the eave overhang.

 

Glass

The sustainable house has double glazing for all windows and glazed doors facing east, west and south.

Thermal mass and insulation

Thermal mass materials, ie brick walls and concrete floor slab, collect heat from the sun and store it in the structure. This helps with winter warming, and delays warming up in summer. Reverse brick-veneer walls (ie brick on the inside and timber frame wall on the outside) are a good example of thermal mass and insulation working together for the best benefit. The lightweight wall crammed with insulation and a layer of aluminium foil under the external cladding shields the internal, thermal mass wall from changes in temperature that are taking place externally due to seasonal changes in the weather.

Storm water

The butterfly roof collects all the storm water falling on the roof. The central box gutter channels the water to the west end where it is collected in the large water tank. Water stored on site is available for the house (clothes washing, toilet, cisterns), garden and for fire fighting if necessary. The tank shown will contain approximately 40,000 litres of water.

Solar

Solar panels on the roof, tilted at the optimum angle (ie around 37 degrees for Melbourne), collect energy from the sun for water heating and electricity production. The hot water produced – gas boosted when necessary – is stored for use in the house; and the electricity produced is converted to AC and fed back into the grid, reducing the cost of electricity used and minimising reliance on mains power.

Energy use and sustainability

Heating is by the controlled combustion fire in the living area. Heat is stored in thermal mass walls and trapped inside by insulation and double glazed/well-sealed windows and external doors. In a similar way the house is designed to resist summer warming, and to make use of summer breezes, with cross ventilation for cooling. Use of ceiling fans alone will be sufficient to keep the sustainable house comfortably cool.

Energy efficient lights and appliances will be implemented, so energy demands for the sustainable house will be minimal. It is possible for rural and more remote locations, by use of a more sophisticated solar-electric system that includes an inverter and battery storage, that the sustainable house will not need to be connected to mains electricity or gas.

By use of a grey water system connected to the garden and an on-site sewerage disposal system there will be no need for the house to be connected to a municipal sewerage or storm water disposal system.

Planning

1. Living areas and bedroom 1 have a northern aspect, which provides sunlight and warmth in winter.
2. The car port at the east end and the water tank at the west help to shield the house from extreme summer heat. Windows facing east and west have been minimised for the same reason.
3. The large deck on the north side provides additional living space outside. A pergola with deciduous creeper growing on it means that the deck is usable all year round.
4. To minimise winter heat loss and summer heat gain, an entry/air lock is located at the eastern end of the house. This entry provides for both siting options: house south facing to street or house north facing to street.
5. Bedrooms are large enough (3.6 X 3.6 metres) to accommodate either a double bed or two singles.
6. Storage: the kitchen is provided with a generous walk-in pantry. A store for bicycles and tools is adjacent to the entry/air lock. Both linen store and drying cupboard have been provided in the passage. In the laundry is a cupboard for the equipment needed for solar-voltaic and solar hot water systems.
7. A separate toilet provides extra flexibility for washing/bathing in the bathroom.
8. The western window in the bathroom provides a view of the “waterfall” of stormwater into the tank.

Shading and screening

Summer heat gains have largely been eliminated by the eave overhang, which screens out most of the summer sun. As mentioned, a pergola shades the deck with a deciduous creeper. This allows for full sun penetration in winter and maximum shade in summer. To prevent heat gains through south facing windows in summer, retractable external awnings have been added. Inside, to prevent winter heat loss, particularly at night, heavy drapes with pelmets to all windows and external doors have been installed.

Site Planning

The long side of the house (ie the windows and external doors of the living areas) must face north for all locations in Victoria. Where the block faces north to the street, an external door to the kitchen is an option. Trees for summer shade and shelter from the wind should be planted where required. For maximum exposure to winter sun, trees to the north should be avoided. However, if they are needed here for shelter, they should be deciduous species.

Versatility

1. The plan can be mirror reversed in the east-west direction, providing for two possible variations.
2. The tank to the west can be smaller or relocated to the back or front side of the house for narrower block sizes.
3. A three bedroom “L” shaped version of the plan is possible for narrow blocks, which in turn also has two possible variations.
4. With a re-plan of the curved, eastern end and provision for fire separation, a lobby/stair can be incorporated, allowing for two sustainable units, one above the other.

Energy rating

If the sustainable house is oriented to true north and built strictly to the design shown, it is anticipated that it can achieve an 9 star energy rating, based on thermal performance alone. However, it should be noted that energy star ratings are only an indication of a building’s potential to conserve energy; the occupants need to help.

For example, for energy use to be minimised, it is essential for:

1. Heavy  drapes to be closed at times of extreme hot or cold temperature, ie especially at night during winter.
2. Awnings to be pulled down at times of extreme temperature, ie especially in the day time during summer.
3. Windows on opposite sides of the house and also internal doors to be opened  in summer to take advantage of cooling breezes.
4. Energy efficient and water saving fittings and appliances should be installed (eg water saving shower heads, compact fluorescent light globes and appliances with at least a 5 star energy/water rating.