Sustainable Houses

Passive design

The sun, wind and shade are free natural resources that can be used to light, heat and cool spaces. Passive design utilises these resources by working with the specific conditions and climate of a site.

Houses are purposefully oriented for the movement of the sun and wind, and the building envelope (walls, floor, roof and windows) is carefully designed to control where and when the sun, breeze and shade enter the house throughout the day and seasons. Depending on its location and site, a house using good passive design can be thermally comfortable all year round, without the need for additional heating and cooling.

Energy efficiency

Heating and cooling are the largest consumers of energy in a home. By reducing the need for heating and cooling, the energy consumption and therefore ongoing carbon emissions of a home can be reduced. Passive design principles provide the foundation for creating such an energy-efficient home: high-quality materials, products and construction ensure that it is well ventilated, insulated and airtight.

The energy efficiency of a building can be measured to determine how much or little energy it consumes. In Australia, we use the Nationwide House Energy Rating Scheme (NatHERS) to measure the thermal performance of a building. Based on architectural drawings and a sustainability assessment using computer modelling, it is possible to generate an energy-efficiency star rating out of 10. The higher the rating, the less energy needed to heat and cool the home. Architects should set ambitious NatHERS targets when designing a new building.

Life cycle carbon footprint

The goal of sustainable architecture is to create buildings that have a low carbon or carbon neutral footprint throughout their life cycle — from construction to operation and maintenance. A life cycle assessment (LCA) is one metric for measuring and assessing the carbon footprint and environmental impact of a building.

An LCA considers the embodied and operational carbon of a building over the course of its life. Embodied carbon refers to the emissions associated with the production, transport and installation of materials. Operational carbon is the emissions associated with operating a building, such as energy for heating, cooling, cooking and domestic hot water. To achieve a carbon neutral footprint, a building must be carbon neutral in both embodied and operational carbon.

(With currently available technologies and due to the complexity of supply chains, the embodied carbon of many materials can currently only be ‘neutralised’ through the purchase of carbon offsets.)

The unadorned concrete stairs leading into the courtyard of Double Life House.

Reductionism

Reductionism is one way to reduce the carbon footprint of a building. Every square metre of house has environmental and financial consequences; therefore, the need and necessity of every space, material and product is questioned and considered. Through a reductionist approach, redundancies are taken out to reduce the carbon footprint, energy consumption and cost of a house. By building less but building well, a house can be simpler and cheaper to build and run, and as energy efficient and carbon neutral as possible.

Material impact and waste

Every material used contributes significantly to a building’s embodied carbon footprint, as the manufacturing, transport and installation of that material produces greenhouse gas emissions. There is also waste associated with the use and installation of new materials, as well as those discarded through demolition and renovation.

Sustainable architecture minimises the environmental impact and waste of materials through considered selection and use: by prioritising recycled and recyclable materials; minimising demolition, construction, and unnecessary material consumption; choosing locally sourced materials; and incorporating construction techniques that make a building easier to adapt, reuse and eventually dismantle.

Local environment

Respect for the environment is the overriding principle of sustainable architecture. Sustainable houses minimise their impact on nature and resources, and make a positive contribution to a neighbourhood and the local environment.

By valuing the outdoors as much as the indoors, smaller sustainable houses enjoy the benefits of more landscaped area: stormwater can be absorbed on site; vegetation can be preserved or planted; and the heat island effect can be mitigated. A smaller building is also more sensitive to neighbours and the streetscape, and lower energy demand puts less stress on resources.

The bathroom at Edgars Creek House uses robust, simple materials.

Longevity

Buildings should inarguably be designed and built to last. Investing in sustainable architecture is an investment in the longevity of a house. Quality construction, durable materials and versatile design not only reduce the cost of a building over time, they also help ensure that it ages well. Making maintenance and repairs uncomplicated and worth doing will extend the building’s life. And an adaptable design will enable the house to respond to changing needs of its inhabitants without costly or substantial alterations.

Budgeting and affordability

A sustainable house doesn’t need to be an expensive house (although there is lots of valuable technology that presents an upfront investment). Prioritising sustainability in the budget will result in a better, more economical and energy efficient house that yields greater savings over time.

A house with good passive design and a well-insulated and air-tight envelope is cheaper to operate and will rationalise the ongoing cost for the building’s life. A smaller, smarter floor plan reduces material and construction costs, and can offset higher upfront investments, such as double glazing, solar PV arrays and durable materials that require less maintenance and repair.

Health and wellbeing

A sustainable home is also a healthy home, with spaces that nurture and support our physical and mental wellbeing. Through the nature of its design, sustainable architecture promotes certain intangible qualities that humans innately enjoy: thermal comfort, natural light and ventilation, good air quality, outdoor views and a connection to nature.

Good sustainable architecture further emphasises these qualities through its holistic approach that extends to using natural and non-toxic materials, integrating landscaping into buildings and framing views of greenery. It’s architecture that not only looks and feels good, but actively contributes to our wellbeing.