Cairns, Queensland

7.7 Stars

Heating: 1MJ/m²/year

Cooling: 90MJ/m²/year

Total: 91MJ/m²/year

• Passive solar design
• Wool batt and double foil-faced insulation
• Louvre and clerestory windows for passive cooling
• Renewable energy production
• Solar photovoltaic (PV) panels
• Solar hot water system
• LED lighting
• Recycled/renewable material use
• Lightweight steel-framed foundations to reduce footprint
• Lightweight timber-framing with lightweight cladding to reduce embodied energy
• Ceiling fans
• Waste reduction
• Water-efficient toilets and tapware

Building type: low density housing

NCC climate zone: 1 – high humidity summer, warm winter

Architect: POD (People Orientated Design)

Builder: Macpark Building Co

Size: 98m² internal (plus additional covered external areas of 117m²)

Size of land: 923m²

Cost: $470,000 (including design and construction, pool, and landscape design)

This 923m² suburban block is located in the northern suburbs of Cairns, Queensland. The median annual rainfall in Cairns is 1987mm, one of the highest in Australia. However, long-term data indicate that annual rainfall varies dramatically from year to year.

The longest edges of the block are the east and west boundaries, making it a challenging orientation for passive solar design. The site occupies a steep slope.

The owners approached a local architect with a view to building a 3-bedroom, 2-bathroom house that would be a sustainable investment property. They understood that investing in good design would help them realise their objectives within an efficient footprint.

The owners were concerned that it would be difficult to site the house on level ground, and that close neighbours on all 4 sides of the battleaxe block would make privacy challenging.

The key design objectives included optimising the tropical location and climate, capturing the sea views, and maintaining privacy. The owners also wanted to minimise the impact of the new building on the sloping site, including the need for costly earthworks.

The design makes the most of sea views and breezes. Good ventilation means minimal reliance on mechanical cooling.

Photo: Veronica Sagredo (© Veronica Sagredo, Blue Click Photography)

The house demonstrates that it is possible to design and build a sustainable home on a challenging site in an economical way. The single-storey house has a narrow floor plan that is flexible, modest and responsive to the climate.

The design is based on 2 pavilions connected by a covered breezeway. Large sliding doors allow the 2 parts of the house to open to each other. The covered breezeway acts as an additional outdoor room and circulation space, and helps to open up the landscaped garden, pool and entertaining area – which sit at the rear of the house – to views.

The house is elevated on a lightweight steel-framed platform. This minimised disturbance to the sloping ground below and reduced embodied energy in the construction. A small concrete slab was poured for the driveway and carport, which face the street on the southern edge of the site.

The structural design includes cantilevers to the roof and floors to create wide, protected verandahs, while complying with the National Construction Code (NCC) for C2 cyclonic regions.

The narrow plan uses prevailing sea breezes to passively cool the house. The occupants can open low-level louvre windows and high clerestory windows to purge warm air through thermal venting.

Breezeway provides indoor-outdoor living space that makes the most of sea views.

Photo: Veronica Sagredo (© Veronica Sagredo, Blue Click Photography)

Cladding

The house is constructed of a lightweight timber frame cladded with fibre cement weatherboard and 8.5mm vertical groove sheets. The roofing is lightweight steel, built in accordance with the region’s C2 cyclone regulations.

The external walls are finished with low-sheen acrylic paint.

Windows and doors

The house features louvres and aluminium-framed, multi-panel, sliding screen doors. Each of the 3 bedrooms has openings on 2 sides, with large sliding doors for ventilation and privacy. The 2 bathrooms also feature aluminium-framed, glazed, sliding door panels, which open to decks that connect with the landscaped and pool areas. A bi-fold servery window connects the kitchen and outdoor entertaining area.

High clerestory louvre window galleries (operated with a map rod) are positioned along the main spine of the building, and act as a thermal vent to expel hot air. Windows and doors on the east and west elevations provide cross-ventilation from sea breezes.

3D modelling software was used to calculate shadow movement throughout the day, and across the seasonal solstices and equinoxes. This determined the size and location of windows and doors, and of eaves and verandahs on the east and west elevations that prevent direct sunlight from entering the house. This further reduces heat build-up inside the home.

Careful design for good ventilation means minimal reliance on mechanical cooling in the tropics.

Photo: Veronica Sagredo (© Veronica Sagredo, Blue Click Photography)

Heating and cooling

Passive design features naturally cool the house and keep the sun out.

Large overhangs and pull-down operable screens provide shade from heat and glare. Sliding doors and louvre windows allow prevailing breezes to cool the house. High raked ceilings and clerestory louvre windows along the main axis of the building act as a thermal vent, expelling hot air.

The living, bedroom and breezeway areas have ceiling fans. The split system air-conditioners in the house are rarely used.

Insulation and sealing

The lightweight steel-framed roof features 75mm blanket insulation, with an upper and lower layer of reflective building wrap (R1.8). This minimises the risk of condensation in hot and humid climates.

The external walls contain reflective foil sarking and 90mm batts (R2.0).

In the living room, sliding doors open to the breezeway and verandah.

Photo: Veronica Sagredo (© Veronica Sagredo, Blue Click Photography)

Lighting

The east and west elevations of the house contain large windows and glazed doors that allow natural light into the interior spaces. During the day, electric light is unnecessary in most of the internal rooms. Deep eaves and verandahs provide shade in summer.

The house is fitted with low-energy LED downlights, which help to reduce energy consumption from lighting.

Bathrooms feature external aluminium glazed sliding doors opening out to deck, clerestory windows vent hot air.

Photo: Veronica Sagredo (© Veronica Sagredo, Blue Click Photography)

Appliances

All of the installed appliances, including the cooktop and oven, are electric. The occupants can power most of their appliances via solar power, generated on the roof during daylight hours.

There is no gas connection to the house.

Renewable energy

The house produces its own electricity using a 6kW solar system. It combines solar photovoltaic (PV) panels with micro inverters that are integrated into the panels themselves, converting DC power to AC at the source. Micro inverters were selected to help maximise the power generated by each panel.

Hot water

The house is fitted with a 325L solar hot water system with an electric boost. Having an electric boost instead of gas means that electricity produced by the onsite solar PV system can be used to run the boost. This helps decrease energy costs and greenhouse gas emissions.

Louvre windows provide ventilation throughout the home.

Photo: Veronica Sagredo (© Veronica Sagredo, Blue Click Photography)

Water

Residents have been urged to conserve water, as the region’s growing population and limited water storage capacity is putting increasing pressure on the area’s water supply, particularly toward the end of the dry season.

To reduce indoor water consumption, this house features tapware with a 5-star water efficiency rating, and toilet suites with a 4-star water efficiency rating.

Waste and embodied energy

The insulation batts in the walls are made of up to 80% recycled glass, with a sustainable, bio-based binder that contains no added formaldehyde.Efficient design of the steel footings, supporting structure and roof framing helped to minimise the embodied energy of materials needed to build on this sloping site. The house framing and walls were constructed using sheets of timber and fibre cement, selected to minimise the embodied energy in construction materials. The use of poured concrete was minimised and confined to the driveway, the slab beneath the garage, and the pool.

The wall framing is plantation pine timber, treated against termites. The floor joists, boards and decking are all renewable spotted gum. The floors throughout are polished hardwood treated with a satin water-based clear finish, which emits less volatile organic compounds than traditional oil-based products. The interior walls are painted with low-sheen acrylic paint, and trims are painted with a gloss acrylic paint.

The ceiling in the living area is radiata pine plywood (certified by the Forest Stewardship Council) treated with a timber satin finish. This was a sustainable choice by the architect as plywood is manufactured to be durable and long-lasting. It also achieved a particular aesthetic within the home.

Exterior and interior timber is treated with a mould inhibitor, recommended for use in humid, tropical, and mould susceptible areas.

Floor plan of Cairns house design. 

Plans: People Oriented Design (© People Oriented Design)

The design for this house makes the most of its steep, north–south site, taking advantage of distant sea views and its connection to the surrounding landscape.

The house allows the residents to adjust its performance to suit the climate conditions – they can open windows for cooling breezes, or use the pull-down operable screens for sun protection. Passive design features, like roof overhangs on the east and west elevations, protect the residents from the strong morning and afternoon sun.

Careful planning of the indoor-outdoor breezeway, which sits between the home’s living and bedroom pavilions, allows residents using the deck and pool at the rear to enjoy distant views towards the sea and horizon. The owner thinks these qualities are one of the home’s best features, and they consider it an improved and updated version of a traditional Queenslander with big verandahs. They feel very connected to the mountains and the water, and have a feeling of being outside even in the internal rooms.

The architect says that the home provides several key liveability advantages including:

• stable year-round indoor temperatures with minimal need for air-conditioning
• the selection and use of sustainable and low embodied energy materials
• the outlook to views and connections to landscape, which make the most of the tropical climate and location

Renew, 2020

• Next case study - Caloundra, QLD
• Read Building rating tools to see how using these tools through the design process can improve the home’s performance
• Read Design for climate to understand how to make sure your design suits the climate in your region
• Explore Materials for ideas on methods and materials for building a home in a tropical climate