Forest Walks Lodge is a solar passive architect designed house, thermally efficient, with its own in-built electricity, clean water, heating and waste water systems. As far as possible it is built with sustainable materials. Decisions between materials durability, miles traveled, thermal efficiency, toxicity, carbon produced in production, sustainable management in the choice of timbers, time and cost, provided for many challenging decisions. Built with standard building materials, electricity is generated on site and heating is derived from the surrounding environment, including the sun. Water of the highest quality is sourced from a spring-fed creek within the property boundary.

New Building: House design

Owners and eco-tour operators, Sean Cadman and Rosemary Norwood engaged an environmental design specialist to design the house. No compromise was made on the integrity of the building shell to ensure the house would be thermally efficient. R7 insulation was installed in the ceiling and European style tilt-and-turn windows and doors with effective seals and triple-glazing, were used on the south facing wall.

The principle of using recycled materials, where possible and appropriate, was one of the building design criteria and helped to reduce cost. A wide range of feature timbers has been used throughout the house, most of it recycled. The two large pillars that support the main roof were found on the property, originally designed for another purpose. They are hand adzed. Celery top pine benches, hand crafted blackwood bench tops, a magnificent Oregon beam that had been abandoned in a timber yard as too twisted to use, are all incorporated into the house. Locally grown cedar from a small plantation was used for the reveals in the clerestory windows.

The building site

The house was sited low in the landscape, in the middle of an open area to maximise access to the sun, the site being on the south side of a mountain. Its situation should also help to protect it from wildfire. The river is below the house, the forest immediately above it and the profile of the house follows that of the mountains to the south. The design brief was to create a seamless barrier between the inside and the outside and that has been achieved very successfully.

Unique Sustainable Elements featured in this home

Solar passive design: Trombe walls along the northern corridor absorb heat from the sun through the windows in winter but are effectively shaded by the roofline in summer. These walls have been rendered in the traditional way with a sand and lime render giving a timeless finish but also adding some several tonnes of thermal mass to the house. The builders apprentice was kind enough to fill the cavities in the concrete blocks with sand, again increasing the thermal mass at little cost and with local materials. The floor was tiled in large sandstone tiles the natural stone quarried tiles being considered more sustainable than fired tiles. Clerystory windows in all the bedrooms provide winter sun and summer ventilation.

Sourcing sustainable materials: The most difficult task in building this house was sourcing timber from sustainable sources. The other was trying to find local materials to reduce carbon emissions associated with transport. Sometimes the two were mutually exclusive. Laminated beams were used for the main roof supports. These are produced using low quality timber and natural glues but come from Western Australia. It is an excellent use for wood that would otherwise be chipped. Their depth allowed two thick layers of insulation to be installed in the ceiling. The framing timber is radiata pine and the exterior cladding, substituted for the original recycled polystyrene, is baltic pine. This came all the way from plantations in Finland. Unfortunately there is no local alternative exterior timber produced sustainably.

Thermal mass: In order to meet the requirement for sufficient thermal mass for a solar passive house the owners have to confess to using a lot of concrete. A low trombe wall inside the entrance also acts to store heat, as does the rock wall that is a feature of the living room. The impact of the thermal mass is to maintain an even temperature all year round, even with traffic movement through the house, inside and outside. The walls and floor continue to give out heat overnight, and help to keep the inside temperature stable on hot summer days.

Hot water and heating: One of the main reasons for deciding on a concrete slab, apart from the requirement to maximise thermal mass, was the spaghetti of pipes that carry hot water from the woodheater in the living area, through the floor to all parts of the house to keep it warm in winter. The water for the bathrooms is heated through a solar array with an instant gas backup for times when there is no sun.

Thermal efficiency: We used plenty of insulation in the house. A double layer of wool bats in the ceiling, with an R rating of 7, insulation in all the walls and even more importantly polystyrene insulation, both around the perimeter of the slab, and under it as well. This was specified in the building design but is not commonly attempted. Many people say that underfloor heating is not very effective, however with the slab effectively insulated from the earth around it and under it, it seems to work very well.

The windows and four sets of french doors to the south are triple glazed, and the windows to the north are double glazed. The third layer of glass in the south facing windows gives an extra 25% increase in efficiency at almost no extra cost due to the depth of the window construction. The European hanging system ensures they are tightly sealed. Curtains in the bedrooms also reduce heat loss. The Paarhammer triple glazed windows along the south face of the house were made from a New Guinea hardwood, produced from an eco-forestry project, imported into Australia by the Woodage in NSW and made into windows in Balan, Victoria. An extruded polystyrene was used around all doors and windows and plenty of no-more-gas under timber trims.

Toxicity: Choosing materials with low or no toxicity is a problem in our modern world where many materials have a chemical base. Both Porters and Murabond paints were used throughout the house. These paints contain little or no volatile organic compounds, the chemicals in paints that give off fumes when first applied. Wool bats where used over other types of insulation in the ceiling and walls. Often the choice of clean/green materials involved extra cost. For example Queensland Cyprus pine was used for external partitions instead of the usual tantalised pine. It was double the price.

Lighting: Developing a low energy lighting plan, consistent throughout the house took a lot of research. LEDs are generally hailed as the low energy lighting solution of the future but they have not yet been developed to the stage where they create suitable space lighting. They are mostly directional. Cost is also a significant factor when purchasing multiple light fittings and leds are still very expensive. The compromise was hybrid fluros, from 9w to 13w per globe which is significantly less than the 50-100w incandescent globes for the same level of light. Their only downside is that they contain mercury so have to be disposed of carefully once they break down.

Power: It was not until the back up power source to the house died in April that owners Sean and Rosemary realised that they were living in an all electric house. However when things went wrong they quickly discovered they had chosen a waste water management system with two electric pumps, a heating system that relied on three electric pumps and an instant gas hot water heater that had an electric ignition source. A back up generator proved vital.

The main source of power for the house, electricity, is produced by the sun. The system is a 24V system with an inverter to convert it to 240V inside the house. Since 240V appliances are more
plentiful and more cost effective it was decided that the conversion was preferable to setting up a non standard 24V system and having to find appliances to match. The system generates approximately 2.5Kw of electricity per day on a good day and the batteries store 960 amp hours. This is not enough electricity to run a modern house in northern Tasmania in the winter when living on the south side of a mountain. Alternative energy sources will be considered before next winter.

Waste management: The waste water system is a Biolytix, which has so far proven very effective. Since the house is located in a sensitive environment, close to the water table in the upper catchment of the Meander river, it was important to install a system that would mitigate any environmental impact. The biolytix is a 2m high worm farm, installed underground, which receives all waste water, both black and grey, processes it and delivers clean water, via en electric pumping system, to a nutrient rich irrigation bed above the house. The next challenge is to turn this nutrient rich water into a sustainable food source.

Landscaping: The landscaping is a work in progress using large rocks and gravel. All vegetation close to the house will be in removable pots. A fern garden and local rainforest plants will create damp areas with local provenance shrubs and trees to add interest and variety to the plantings. Birds and wildlife all visit the surrounds and create interest, and a small excavation in the creek at the side of the house has resulted in a platypus feeding ground with a local platypus visiting irregularly during summer from the creek below. In keeping with the sustainability of the house, the property is covered by a substantial conservation covenant which protects the river flats and the threatened forest ecosystems on the property for the future.



Contact Details

Hosts: Sean Cadman and Rosemary Norwood
Address: 669 Jackeys Marsh Rd
Jackeys Marsh Tasmania 7304
PO Box 212
Deloraine Tasmania 7304