Building a sustainable home
Building a new home can be a stressful and confusing process. There are many builders, home designs and locations to choose from and ensuring your home is energy efficient is something that is often overlooked. If you spend the time to choose a home design and features that will reduce your heating and cooling costs, you will buffer yourself from rising energy prices in the future and enjoy a lifetime of comfort in your new home.
Familiarise yourself with the following information and take our building a sustainable home checklist with you when you are talking to builders. This will ensure you don’t get bamboozled and that you get the sustainable home of your dreams.
1. Designing for comfort
Energy, in the form of heat, moves into, around and through your home in three ways – conduction, convection and radiation. Heat transfer will have a big impact on how often you need to cool your home in summer and heat your home winter.
Thermal mass is the ability of a material to absorb and hold onto heat energy. Building products that have a high density, such as bricks and tiles, have a higher thermal mass than materials with a low density, such as timber. A brick wall will take longer to heat up than a timber wall, but it also takes longer to cool down once it is warm. Appropriate use of thermal mass can help reduce temperature fluctuations in your home and moderate temperatures throughout the seasons.
Warm in winter and cool in summer
The angle of the sun, in relation to the Earth’s surface, changes as the Earth moves around the sun throughout the year. In Perth, the angle of the sun is lower during mid winter (about 35° at noon) compared to mid summer (about 82° at noon).
Maximise energy efficiency by orienting your home with living and entertaining areas to the north and minimal windows on the east and west sides.
Smart shading techniques block heat from entering your home in summer, while allowing the sun’s warmth to enter your home during winter.
Shade sails, adjustable louvres and deciduous vegetation can be used to block summer sun and then can be removed in winter to invite warmth into your home.
Much of the heat energy that enters your home through windows is reflected heat from hard surfaces such as paving. Eaves and overhangs generally don’t extend out far enough to block the heat that is bouncing in from hard surfaces surrounding the house, so shade structures should extend three metres from windows on the northern side of your home for maximum effectiveness.
During summer, heat enters your home through walls, floors and from reflected sunlight transferred through glass surfaces. Your appliances and lighting also create heat within your home.
Hot air can be removed from your home by opening windows and doors during cooler evenings. Homes with open plan living spaces, security and fly screens allow for greater natural ventilation.
2. Sustainable building features
Insulation in walls, ceilings and lining underneath roofing material will help keep warmth in during winter and the sun’s radiant heat out during summer. Wall insulation is a great option for the standard double brick home. Fibreglass batts and blow-in insulation will deteriorate and sag over time so are not a good option for wall cavities, instead choose a foil backed insulation blanket. The reflective foil layer will hold the insulation in place and prevent sagging.
Tip: Take a look in your roof cavity and check that insulation has been installed correctly. We have heard many stories of people discovering that the insulation they paid for had never actually been installed!
In general, a dark coloured roof absorbs more heat than a light coloured roof, this heat is transmitted into your house through convection and conduction which reduces the energy efficiency of your home in summer. This is especially relevant for concrete and terracotta tiles, which have a high thermal mass . Tiles continue to emit heat after the sun goes down, keeping your home hot through the night.
Doors and windows
Orient doors and windows so that prevailing cool breezes are able to enter the home and flush out warm air before exiting on the opposite side. Openings should be larger at the exit point to ensure good ventilation. Sliding, louvre or casement windows offer far greater ventilation capacity than awning type windows. Security screens or fly screens installed in doorways and windows are important considerations to facilitate natural ventilation in the evenings and nights during summer.
Curtains and pelmets
Heavy, multilayered fabric curtains block summer heat convection. Maximise their effectiveness by ensuring they are snug fitting to prevent air from leaking out the sides. Pelmets trap an air layer between the curtain and window. Curtains can be opened to allow sunlight and warmth into the house during cool weather.
Awning blinds and roller shutters
Awning blinds and roller shutters on the eastern and western sides of your house can block heat in summer and be opened at night to allow ventilation. Blinds and shutters can be left open in winter to allow heat to enter through windows.
Trees, shrubs and groundcovers can improve the thermal performance of your home, create an appealing aesthetic, provide habitat for wildlife and can have positive mental health impacts.
- Deciduous trees and vines on the northern, eastern and western aspects of your home can be an effective way to block summer heat. Deciduous species lose their leaves before winter, allowing the sun through.
- Thick shrubs and trees on the side of your home can form a windbreak from hot dry summer winds. Vegetation can also channel the prevailing cool summer breezes and dampen strong winds during storms.
- Gardens also act like air conditioners, providing shade and cooling the environment. The soft, green surfaces don’t hold onto heat like bare sand or hard built surfaces. Vegetation can shield and cool walls, outdoor living spaces and windows.
4. Smart living in your sustainable home
By taking control of your home’s climate control features, you can drastically reduce energy use, saving money as well as reducing the environmental impacts of your lifestyle. Some of the sustainable building and landscaping features outlined above require ongoing active management in order for them to function effectively and reduce your energy needs.
- Install 3 metre shade sails on northern aspect during summer, remove around April, once weather has cooled.
- Open curtains to allow winter warmth in, closing curtains to block summer heat.
- Open windows in the evening to allow natural ventilation to cool the house and clear stale air during periods of hot weather.
- Adjust louvres to maximise shading in summer and to allow light and warmth through in winter.
- Regular pruning and maintenance of shade and wind break vegetation.
5. Sustainable appliances and technology
Heating and cooling the home is the single biggest energy consumer in Australian households, accounting for about 40 percent of energy used. Ceiling fans work very effectively in Perth’s hot weather and reversible ceiling fans can also cycle warm air from the ceiling down during winter. Compared to an air conditioner, the energy use from a ceiling fan is negligible.
Solar hot water systems and heat pumps
Heating water uses on average 21 percent of total household energy, making it the second biggest consumer of energy within Australian households.
Solar hot water systems are a great idea for any sustainable home in Perth. These systems absorb the suns warmth to directly heat water through a panel or series of tubes before it is stored in an insulated tank for later use. The systems are generally fitted with a booster that can heat water when there is insufficient sunlight.
Heat pumps use electricity to move heat from one place to another instead of generating heat directly. Quality heat pumps are extremely energy efficient; they work like a refrigerator, but use the heat rather than expel it. Heat pumps can be combined with photovoltaic systems to create a highly cost effective water heating solution.
Solar roof ventilator
Roof ventilators move hot air out of the roof cavity to reduce the amount of trapped heat while the sun is shining. Generally they require wind to drive the process.
Solar roof ventilators use inbuilt solar panels to power a fan that operates throughout the day, without wind. A mains power connection can allow the last hot air to be removed after the sun has gone down and a thermostat can prevent warm air being removed during cold weather.
Photovoltaic energy system
Perth receives an abundant supply of sunlight throughout the year. A photovoltaic system (solar panels) will allow you to take greater control over your energy consumption. Solar panels provide cheap, renewable energy by converting sunlight into electricity. Battery storage technology allows even greater control, by supplying power after the sun has gone down.
Sealing your home against air leakage with weather strips is one of the simplest upgrades you can undertake to increase comfort while reducing your energy use. Air leakage accounts for 15−25% of winter heat loss in buildings and can contribute to a significant loss of coolness in during summer when air conditioners are used. There are many products on the market which can be used to close small gaps around doors, windows and other unwanted spaces. However, your home should not be airtight as this can also create problems with condensation and indoor air quality.
You can reuse the waste greywater from sinks, showers and washing machines on your garden. A simple reed bed treatment system can improve the quality of waste greywater before it is used more widely on the garden. A small scale treatment system can enable you to reuse treated greywater for toilet flushing and washing clothes.
Capturing and storing rainwater from your roof is a great way to reduce your use of treated scheme water. To determine the size of rainwater tank you will install, consider how much you will use the rainwater, how much space you have for a tank and how much rainwater you are likely to capture (Tankulator is a great online tool). If using rainwater for drinking, install a mesh filter to prevent leaves and large particles entering, as well as first flush system to reduce the risk of harmful bacteria, toxins and organic material entering your storage tank. Checkout our Rewards for Residents for discounts on rain water tanks and other sustainable products
6. Other Resources
In depth information about home design and sustainability features for home builders in Australia.
Six sustainable eco homes designed for the City of Cockburn, each responding to a different lot orientation.
A sustainable living demonstration home and education centre in Bayswater.
Josh's House is an online project and web video series that sets out to prove that high performance energy efficient homes are affordable and achievable.
Leading building company crafting quality, functional homes with a focus on sustainability and the environment.