Wright, Australian Capital Territory
New family home on a narrow block using passive solar design principles.
The house is designed with a number of flexible spaces. The carport doubles as an entertaining area.
Photo: Ben Wrigley (© Light House Architecture and Science)
NatHERS thermal comfort rating
8.2 Stars
Heating: 71.3MJ/m²/year
Cooling: 4.1MJ/m²/year
Total: 75.4MJ/m²/year
Sustainability features
- Solar passive design
- Small floor area (or footprint)
- Very airtight
- Wall and ceiling insulation
- Fan system that brings warm ceiling air into the slab for warmth
- Deciduous plants provide season-appropriate shading
- All-electric house
- Reduced embodied energy
- Recycled paper benchtop
- Recycled crushed asphalt for garden surfaces
- Durable materials extend the lifespan of the building
Project details
Building type: mixed density suburb
NCC climate zone: 7 – cool temperate
Designer: Light House Architecture and Science
Builder: 360 Building Solutions
Size: House 150m²; carport 28m²
Size of land: 405m²
Cost: $450,000
Site, block orientation, location and climate
The 405m² block is located in Wright, a relatively new Canberra suburb. Canberra is elevated so can be colder than other Australian cities in winter. Frosty nights are common, and summer can be dry and hot.
The block is narrow, with a north-facing frontage and minimal northern exposure.
Design brief
The owners wanted a 4-bedroom, 2-bathroom home with 2 offices. The house needed to be energy efficient and durable, with a modest footprint.
The owners also required several internal spaces for recreational activities, and wanted a home with a coastal feel.
There were several limitations:
- the build cost had to stay within a mid-range budget (less than $500,000)
- the orientation of the small and narrow block (with the street to the north) made it difficult to implement passive design principles.
A major goal in the design and construction was to show that highly sustainable homes are possible with a typical Australian building budget. Most materials used in construction were affordable mass-market products.
Close up of the pergola with deciduous vine plantings.
Photo: Ben Wrigley (© Light House Architecture and Science)
Design response
Solar passive and space-efficient design were applied to overcome potential challenges with floor area and aspect. Computer simulations were used to optimise the size and position of windows and shading.
A large glass sliding door and window along the northern street-facing wall uses the site’s limited northern orientation to naturally warm the concrete slab.
All but 1 bedroom extend out from the central floor plan to face the street, allowing sunlight to enter these rooms. Glazing on windows in the east and west has been kept to a minimum to prevent indoor temperatures increasing in summer from morning or evening sun.
A series of pergolas were designed to be passive-solar eaves. Deciduous vines were planted at the base of each pergola to provide shade in summer and let sunlight through in winter.
Because of size and budget limitations, the requirement for 2 office spaces was met by creating an office nook to the side of the dining area, and designing an office that doubles as a spare bedroom.
The sitting space off the kitchen can be used for social gatherings. The residents can use the shaded pergola areas connected to the home, while the carport doubles as an entertaining area. This expands the space available for the family to use.
The block and budget placed limitations on space. An office nook was created to the side of the dining area. Windows are positioned to warm the concrete slab.
Photo: Ben Wrigley (©Light House Architecture and Science)
Cladding
Some of the external walls are clad with commons bricks, a natural clay brick chosen for its affordability and aesthetic qualities. Other walls are clad with a timber hardwood product that has a natural wax added to repel water. Timber cladding was also chosen for its affordability, as well as its low environmental impact and maintenance requirements.
The steel roof was also chosen because it is low maintenance and affordable.
Windows and doors
All windows and doors are double-glazed and made from unplasticised polyvinyl chloride (uPVC). This provides high levels of insulation and durability while remaining affordable. The windows have a low-emissivity (low-e) layer that has high solar transmission, further improving thermal performance. To find out more about insulated glazing units, refer to Glazing.
A large glass sliding door facing the street makes the most of the site’s limited northern orientation to naturally warm the concrete slab.
Photo: Ben Wrigley (©Light House Architecture and Science)
Heating and cooling
After moving in, the owners wanted to test the performance of the house. No heating was installed in the combined kitchen-dining-sitting room or the central lounge room. When the overnight temperature was -8°C, the lowest temperature in the main living area was 12.5°C.
They conducted a 3-year experiment to determine how much heating the home required at different times of the year, and which method was most efficient.
In the first year they used one 600W far-infrared panel in each bathroom and an occasional 1000W portable panel heater in the study. No heating was used in the living areas. In the second year, the living areas were heated with two 900W far-infrared panels in the ceilings. In the third year, a 3.5kW split-system air conditioner was installed in the central living room for energy-efficient heating. The 900W far-infrared panels were not used.
They found that the split-system lowered the overall energy use significantly from the previous years. The infrared panels are still used in the bathrooms, providing extra heating when necessary.
All rooms except the bathrooms use ceiling fans for low-energy comfort in summer. The fans also help to disperse heat from the split-system in winter.
The house also uses a fan to move hot air from the roof space into an air void below the rear, southern-bedroom end of the slab. The system uses very little energy and provides extra heat under the floor, although it is unclear how beneficial it is. This system is currently not available commercially.
An east facing garden with advanced growth for shading. Windows and doors are double glazed for better insulation against the Canberra climate.
Photo: Ben Wrigley (©Light House Architecture and Science)
Insulation and sealing
High levels of insulation have been used. There are R6 insulation batts in the ceiling and R2.5 insulation batts in the walls. Internal walls are also insulated with R1.5 batts, which mainly provide acoustic benefits. The timber frame of the walls and roof are wrapped externally with vapour-permeable sarking, and all joints are taped to prevent air movement past the insulation. The underside and vertical edges of the slab are insulated with R1 extruded polystyrene to provide affordable thermal comfort.
Phase change materials were used in 2 of the bedrooms and all living areas, specifically in the ceiling (between the plasterboard and insulation) and in the top of the living room walls. These are plant-based materials that remain between 18°C and 23°C and function as thermal mass, absorbing heat and releasing it as the temperature decreases.
The internal envelope (the plasterboard lining) of the house is well-sealed, with an airtightness rating of 3.2 air changes per hour (ACH) at 50Pa. No internal air barrier membranes were used behind the plasterboard. There are 3 pairs of decentralised heat recovery ventilation systems, mainly used when the house is closed in winter or at the height of summer. Windows provide ventilation for most of the year.
Ceiling fans and windows have been installed and designed for ventilation.
Photo: Ben Wrigley (©Light House Architecture and Science)
Lighting
Windows have been positioned for daylighting, without compromising the thermal efficiency of the home.
All lighting is LED to minimise energy usage. Lighting design was considered from the outset, with the aim of minimising holes in the internal building envelope, especially the ceiling. This was part of the overall strategy to reduce air leakage and gaps in insulation throughout the home.
Pelmet-mounted LED strip lighting runs the length of the living area, creating a large amount of light but only needing one small hole in the plasterboard lining. In the hallway, there are 2 well-sealed, flush-mounted wall lights. Fans have integrated lights to minimise penetrations in the ceiling. Airtight LED downlights that can be covered in insulation are used sparingly in the utility areas, with the bathrooms, hallway, laundry, toilet and kitchen each only having 1 light.
Appliances
The house is all-electric with no gas connection. All appliances were selected for efficiency and affordability. The refrigerator has a 4.5-star energy rating, while the dishwasher has a 4-star energy rating and a 5-star water rating, using 11L per cycle. The kitchen uses an induction cooktop, which provides an efficient alternative to a gas stove.
The house does not have a clothes dryer, to reduce energy use.
LED strip lighting is neatly concealed in the bathroom pelmets for indirect lighting.
Photo: Ben Wrigley (©Light House Architecture and Science)
Renewable energy
The house is designed using solar passive principles, so benefits from heat produced by solar radiation in colder months.
Due to the orientation and size of the block, a large house to the east, and the angle of the roof, solar panels would not be as effective on this site as on most. Instead of installing on-site solar panels, the owners have invested in the ACT’s first community solar farm.
Water and hot water
A 5000L tank supplies water to the laundry, toilets and 2 garden taps, cutting down on overall water use. The garden is low-water, heavily mulched and supplied with drip irrigation.
Hot water is supplied by an efficient 315L heat pump, greatly reducing energy usage and emissions compared to traditional heating methods.
The floor plan has been kept as small as possible for efficiency.
Photo: Ben Wrigley (©Light House Architecture and Science)
Waste
The construction process involved less material overall than most comparable 4-bedroom family homes. The efficient use of floor space and recycled plastic dome in the slab reduced the amount of concrete used. The cost of the domes is comparable to a waffle pod concrete slab, and they can be extracted and reused at the end of the building’s life.
Embodied energy
The embodied energy in the concrete slab was reduced by using recycled plastic domes. Above the slab, materials were chosen to be lightweight, including timber frames and plasterboard lining. A smaller floor area than a typical 4-bedroom home reduced the total embodied energy.
Floor plan of Wright house design.
Plans: Light House Architecture and Science (© Light House Architecture and Science)
Evaluation
In addition to their brief about budget, lifestyle and values, the owner wanted to show that highly sustainable, efficient family homes can be produced within the brief and budget of a typical Australian household.
The total cost of designing and building this home was comparable to the more typical homes being constructed around it. However, it likely consumes far less electricity than those homes and has no gas connection. The airtight construction and passive solar design means that the occupants of this house are comfortable in the extremes of summer and winter. Although it has a smaller floor area than a typical project home, the well-designed layout makes it feel quite spacious.
The owners consider their home as a statement that sustainable construction and energy-efficient living are already achievable with typical briefs and budgets today.
The house has won several design awards, including:
- 2018 HIA Australian GreenSmart Sustainable Home of the Year
- 2017 Master Builders Association ACT Custom Built Home Less Than 150m²
- 2017 HIA ACT/Southern NSW GreenSmart Energy Efficiency Home of the Year.
Author
Renew, 2020.
Learn more
- Next case study - Dover, Tasmania
- Read Appliances and technology to find other ways to save energy in your home
- Read Passive heating and Passive cooling, for tips on how to make your home work well in winter and summer
