Passive solar design
The house orientation is due east-west with large north facing windows.
Solar gain is achieved from the tiled floor by northerly facing windows. Tiles in front of the kitchen units have been installed to capture the heat from the winter sun to keep us warm.
Insulation
Wall and roof insulation higher than code was installed - R2.4 in the walls and R4 in the ceiling.
As with other eco home builds, there were quality control issues with the insulation installation, perhaps an indication of the increased level of awareness and understanding of the installation requirements to ensure the benefits are not wasted through gaps being left or mismatched sizes of insulation being used.
In addition, the surfeit was sealed and insulation put in around the foundations. During an early season cold morning in April it was 3 degrees outside and 18 degrees inside the house.
Insulated concrete floor slab
Polythene was laid over the sand to provide a waterproof membrane, and then 200mm thick solid polystyrene was laid. Then 70mm polystyrene was laid on the concrete around the base to further insulate the floor slab to reduce the heat loss from the edges of the floor. Polystyrene was used for two reasons: to provide a high level of insulation and to provide filler without adding additional weight to the ground.
Cladding
The south and west facing walls have 50mm thick polystyrene sheets attached. These sheets give the walls an insulation rating of R2.55 once they have been rendered and R2.6 wall batts installed. Polystyrene cladding has high embodied energy. However, the off cuts can’t be recycled and had to be dumped. Claddings used
Light fittings and electricity
No downlights were installed to ensure there were no penetrations through ceilings which cut into ceiling and insulation, and make the insulation work less efficiently.
Energysaver CFL bulbs used. Low energy lights, compact fluro, fluro, or LEDs – standard lights in little used areas. Isolator ‘master switches’ have been installed to reduce standby power consumption.
Waste water disposal system
Reflection sewerage treatment. Total Wastewater Solutions - Reflection Treatment Systems Reed bed filtration system prior to water leaving property.
Windows
All windows are aluminium framed double glazing. When calculating the energy efficiency of the design, they could have got away with not doing double glazing. Small windows were installed to the west, to compensate for afternoon overheating.
Curtaining and shading – to do
Honeycomb blinds or heavy thermal drapes are planned for curtaining. However June is waiting to see how warm the house is during their first winter before finalizing the type of curtaining.
Passive shading includes the window orientation, eaves and a macrocarpa pergola structure which are under construction.
Ventilation
Passive ventilation is provided by the thermo siphon skylight in the centre of the house, which creates a great through-breeze. The thermo-siphon allows cool, prevailing winds to ventilate a building naturally during the warm summer months. Warm air rises up and out through windows in the tall, central monitor.
There has been discussion on setting up a system for shutting off the thermo-siphon so that heat is not lost when it is needed.
The doorway into the living area will have louvres that can be adjusted to allow either hot air escape up through the skylight in summer or closed to keep the warm air in the living rooms in winter.
Underfloor heating – to be completed
Hydronic underfloor heating is one of the oldest kinds of central heating in existence, in use since Roman times. It’s an efficient way to achieve whole-house warmth and comfort and, if an energy-efficient heating source is used, is relatively cheap to operate. A hydronic underfloor heating system delivers radiant heat that starts at ground level and slowly rises, creating a gentle, welcoming ambience. Underfloor Heating | Hydronic Floor Heating
During the construction phase, a system of pipes is embedded in the concrete floor. When hot water is circulated through the pipes from a central boiler or water heater, the concrete slab heats up and radiates a gentle, slowly rising heat.
- 100m of pipe is laid in the sand under the floor. These pipes will be used store excess solar heat under the floor during summer. The pipes are laid near the bottom of the concrete slab as they are interested in maintaining base heat rather than having rapid heating.
- Three circuits of under floor heating
- Main living area
- Master bedroom and en suite
- Back bedroom (guard against mustiness)
Hot water
The 270 litre hot water cylinder is on the roof. The optimum angle is 35 degrees, but health and safety regulations require scaffolding around the house during the build at angles greater than 30 degrees. Solar water heating panels yet to be installed
There are pipes running across the iron/purloins in the roof cavity as a low efficiency solar collection. A scavenger coil means if the hot water cylinder gets too hot, excess hot water gets pumped to floor slab instead of onto the roof.
There are short hot water pipe runs – need more pipe lagging.
The Metro woodburner has a wetback.
Water harvesting
A tank left on the property from its former quarry days have become the water tank, which is filled by water that is gravity fed from dam in the hills
This re-use of things on site also includes a concrete tank converted into a storage shed.
Paints
Low VOC paints – elected oil-based paints for doors and door/window frames. All the paint we are using is low odor and has low volatile organic content (VOC). It contains no added heavy metals (e.g. Pb, Hg, Cr) and no formaldehyde. They are benzene free and TDI content is less than 0.1% making them environmentally friendly.
Construction waste
One tonne of construction waste was generated. As well as this, June and Mark are still cleaning up the debris of the former quarry on the site – one truckload of metal has been removed.
Their experience was that trades people have little interest and incentive to be interested in waste management. Managing waste on site must be driven by those with an interest in it. They recommend putting expectations on the plan (rather than in the specs) so they are there all the time for all involved to see.
Other sustainable design features:
- Interchangeable rooms
- Bosch front loading washing machine
- Water saving loo
- Low flow showerheads
- Westinghouse fridge – 4 stars
- Smeg dishwasher
- Soap nuts – no laundry power
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