By Tracey Hordern
Today, the most exciting and important development in contemporary home design is the heightened awareness of the environment. Architects, builders and engineers are now increasingly employing sensitive designs and building techniques that work with, rather than against, nature.
The built environment has a huge impact on the environment, accounting for approximately one-sixth of our freshwater usage, a quarter of all wood harvested and two-fifths of the total material and energy flows of the planet. Sustainably designed and constructed buildings aim to lessen their impact on the environment through energy and resource efficiency. Strategies include minimising non-renewable resource consumption, while at the same time eliminating or minimising the use of toxins and reducing waste.
Those buildings that have minimum adverse impacts on the natural environment, as well as the built environment, can be defined as “sustainable building”. This impact is measured in terms of the buildings themselves, their immediate surroundings and the broader regional and global setting. To qualify, building procedures and strategies should include rational use of natural resources to contribute to saving scarce resources, reducing energy consumption and improving environmental quality.
True sustainable building involves considering the entire life cycle of the building. In most countries, attention used to be focused primarily on the size of the building and quality issues hardly played a significant role. Today, however, in strict quantity terms, the building and housing market is now saturated in most countries and the demand for quality is growing in importance.
Most importantly, it is imperative to construct buildings that last. Longevity depends as much on finishes and the method of assembly employed as it does on the material used. It is important to avoid using materials from non-renewable sources or materials that cannot be reused or recycled, especially in structures that have a short life.
Sustainable building practices include:
- Demolishing and rebuilding only when it is not economical or practicable to reuse
- Adapting or extending an existing structure
- Tightly controlling all processes to reduce noise, dust, vibration, pollution and waste
- Making the most of the site, eg by observing the sun’s positions throughout the day, prevailing winds and weather patterns for the region
- Designing the building to minimise the cost of ownership and its impact on the environment over its lifespan by making it easily maintainable and by incorporating techniques and technologies for conserving energy and water and reducing emissions to land, water and air
- Wherever feasible, using the construction techniques that are indigenous to the area, learning from local traditions in materials and design
- Putting the function of the building and the comfort of its occupants well before any statement it is intended to make about the owner or its designer.
Increasingly, architects today are aligning themselves and their firms with sustainable principles and the clients are following. As the director for Allen Jack+Cottier’s urban design section, sustainable building practices are Peter Stronach’s passion. “As a firm and as a practising architect, my concern for environmental issues is paramount. I have been responding to that concern for more than 20 years now. My work has evolved over the past few years in that whenever there is the opportunity to use sustainable practices, I do. I push as far as our clients will let me.” Peter Stronach is not the only one.
There is a wave of talent in Australia that is pushing environmental sustainable practices into mainstream, such as Sean Godsell and James Russell, the latest RAIA recipients for residential design. Both architects are passionately pursuing new directions and solutions in sustainable designs.
Then there’s Tone Wheeler, principal architect from Environa Studio, whose beautiful houses featuring large verandahs, shading devices and roofs that pitch up to the sun are clear evidence of sustainability within the design. Caroline Pidcock, the principal of Caroline Pidcock Architects, specialises in environmentally-friendly design for both residential and commercial projects. Pidcock believes that “One of the big things becoming more obvious today is that people need to be designing energy-efficient buildings. This is a tidal wave; you are either going to catch it or be dumped by it.” Following are some definitions and practical strategies to help you understand and if you’re building, create an environmentally sustainable home.
The embodied energy factor:
Embodied energy is the energy consumed by all of the processes associated with the production of a building, from the acquisition of natural resources to product delivery. This includes the mining and manufacturing of materials and equipment, the transport of the materials and the administrative functions. Embodied energy is a significant component of the lifecycle impact of a home.
Every building is a complex combination of many processed materials, each of which contributes to the building’s total embodied energy. Renovation and maintenance also add to the embodied energy over a building’s life. It is now understood that the embodied energy content of a building can be the equivalent of many years of operational energy. The single most important factor in reducing the impact of embodied energy is to design long-life, durable and adaptable buildings.
Go Eco: An energy and resource efficient home:
An energy and resource efficient home is one that incorporates common-sense design principles and thoughtful resource usage strategies. It is entirely possible to make your home efficient in terms of reducing the need for expensive heating and cooling appliances, while at the same time reducing energy-related greenhouse gas emissions. This can be achieved without compromising lifestyle and comfort. In reality, with the correct intent and planning, an energy-efficient home is generally more comfortable, easier to maintain and costs no more to build than a conventional home.
For a house to be really energy efficient and sustainable, these elements need to be considered and optimised:
- Orientation, siting and layout
- Home insulation
- Ventilation and draught proofing
- Thermal mass
- Landscaping design
- Energy-efficient appliances
Orienting, siting and layout:
If you are building your home, by carefully considering the position of your house on your block of land you can maximise the passive solar design advantages that can make your home more comfortable all year round. The following points should be considered when selecting a block of land:
- Size and orientation of the block
- Solar access to the north side of the house
- The angle and slope of the block (to enable sun entry)
- Tree coverage and height (to avoid too much shading)
- Height and proximity of surrounding buildings (to avoid overshadowing)
The orientation and sitting of your home can also make a huge difference to your energy bills throughout the year. The ‘ideal’ home in the southern hemisphere is sited with the daytime living areas facing north, with the long axis of the house running east-west. If this is not possible, variations on the orientation can be made up to 30 degrees to the east and 20 degrees to the west of true north, with no major effects on the solar advantage.
Large windows on the north side of the house will also let in the sunshine during winter, but can be easily shaded from the summer sun. This will make the house warmer in winter and cooler in summer. If your house is closely bordered, to prevent overshading allow a setback of at least six metres from a single-storey house to the north, and at least 11 metres from a double-storey house. If this is not possible, you might be able to use a clear storey window to allow adequate sunlight into the home. Note that this window will require sufficient shading for summer comfort.
Ideally, have your daytime living areas facing north and have northfacing windows to optimise capturing the winter sun. Following an open-plan style of home will also help. Not only does it make the best use of all available space, it should allow light to penetrate easily and air to circulate freely around the home. Another good idea is to design open areas so they can be reduced in size by closing doors, thus minimising the areas needing heating and cooling at any one time. To make your house energy efficient, the single most important measure is the addition of insulation to the walls and ceilings.
It is with insulation material that you can slow down heat transfer through the external surfaces of your home. It can make your home up to 10 degrees Celsius cooler in summer and 5 degrees Celsius warmer in winter. In an uninsulated house, approximately 40 per cent of heat loss takes place through the roof and ceiling, while around 35 per cent of heat is lost through the walls and floors.
The rating performance of bulk insulation materials is specified with an R-value. The greater the R-value, the more effective the insulation is at resisting heat flow into your house in summer, and out of it in winter. There is a wide range of bulk insulation materials that come in two forms: either in long rolls called blankets, which need to be cut to fit the length of space; or the other type of insulation material with pre-cut lengths known as batts.
There is also loose fill insulation; this has no backing and is supplied loose and can be easily poured or pumped into a wall cavity or roof space. Rigid insulation comes in pre-cut boards that are used primarily in new home construction and are ideal for insulating areas such as raked ceilings, solid-brick external walls, under wooden floors and around concrete slabs. Reflective foil insulation works by reflecting large amounts of heat from its highly polished metallic surface, and transmitting very little heat due to the emissivity of the product. Due to these characteristics it is more effective in summer than winter.
Ventilation and drought proofing:
A really well-designed house, for the most part, will not require air-conditioning in summer or heating in winter. In summer, a cool breeze flowing through the house helps cool down the house. The house does not need to face directly into the prevailing summer breeze, but can be offset at an angle of up to 45 degrees either way. While adequate controllable ventilation is essential to provide fresh air, prevent condensation and help cool a house on summer nights, draughts can create discomfort and lead to energy losses in both summer and winter. In winter, draughts can account for up to 25 per cent of heat loss.
Reducing these draughts can be a cheap and cost-effective way of reducing heating and cooling costs. New houses should be built to minimise draughts by avoiding gaps at construction joints between different wall materials, and where walls join or meet the ceiling and the floor and by ensuring that doors and windows fit snugly in their frames.
Draughts can be further reduced by:
- Draught-proofing doors and windows
- Sealing up cracks and gaps
- Sealing unnecessary vents
- Sealing exhaust fans and outlet grills
- Sealing unused fireplaces
- Sealing vented skylights
- Covering ceiling evaporative ducts during the colder months
The ability of building materials to store heat is referred to as thermal mass. Building materials that have a high thermal mass, such as internal bricks and masonry and a concrete slab with hard floor coverings, can store large amounts of heat without a large temperature change. In places where the difference between day and night temperatures is eight degrees or more, there are benefits in using high levels of thermal mass inside north-living zones to stabilise internal temperatures in both summer and winter.
The correct use of thermal mass inside a house can significantly improve both thermal comfort and energy efficiency. A balance, however, needs to be achieved between the thermal mass, window areas and insulation levels to suit the climatic conditions. This can be done now efficiently with the new-generation rating tools, about to be introduced across Australia.
Energy-efficient homes make good use of concrete, tiled or slate floors because apart from being easy to clean they play a big role in absorbing heat in winter. The floor must be able to absorb as much heat as possible during the day and then release the stored heat into the room at night. Carpets and rugs act as insulators, so the slab floor can’t absorb as much heat. Tiles, slate or any other heat-absorbing hard surfaces are ideal and work well when situated in rooms that have north-facing windows.
With normal windows, the sun’s rays can easily penetrate and heat your house. This can provide welcome warmth in the cooler months but can lead to overheating in summer, as the heating power of sunlight shining directly on east- and west-facing windows is around 1000 watts per square metre, equivalent to the heat generated by a one-bar heater. Double-glazed windows, while good at reducing conducted heat transfer, need to be used with effective external shading in summer. Ideally, all north-facing windows should be full length so when the winter sun is low in the sky, the heat will penetrate well into your home.
Use minimum or zero glass on the east and west sides, and small glass areas on the south side of the house. The total window area should be less than 25 per cent of the total floor area of the house (these proportions are a guide only, as new energy-rating software for houses considers this and a range of design features when assessing the overall rating of the house). If windows are made too large, they can make the house uncomfortably hot in summer and hard to keep warm on cloudy winter days and nights.
Shading the sun is vital to keep your house cool in summer. Well-designed shading greatly reduces heat entry, adding significantly to summer comfort in the home. It can also significantly reduce the need for, and running costs out of the house is to use adequate external shading. North-facing windows can be easily shaded with fixed shading devices, such as an eaves overhang, horizontal shade or awning, and pergolas. These shading devices must be designed so they allow sun entry in winter and totally shade the windows in summer.
In Adelaide, to achieve this, the width of the fixed shading on the north side should be 0.5 times the vertical height of the window (at the top of the window). Attention should be paid to adequately shading east- and westfacing windows, while south-facing windows generally do not need shading. While important, internal shading such as curtains and blinds will never be as effective as external shading because the radiant heat from the sun has already passed through the glass. To get the best performance from curtains and blinds, you need to ensure they are opaque and of light colour, to maximise the reflection of sunlight. Pelmets are a good way to reduce heat loss. Tinted or reflective glass should be used where it is not desirable to obstruct the view, internal shades with a reflective backing should be used where it is not possible to install external shading devices.
Landscaping can enhance your property and provide benefits to you in maintaining more comfortable conditions in your home. By carefully planning the landscaping around your home, you can control the entry of heat as well as the quality and direction of the breezes you allow to blow through it. Breezes entering your house will be cooler if they have passed through gardens or courtyards that have shade, pools or shrubs and lawns. The layout of your garden can also be used to screen or direct breezes.
We all know this is the most important resource we have — water. There is now a plethora of water-saving options available for the home: using grey water, storing rain water, water tanks, water bladders and water recycling. Here are some specific water conservation methods:
- Low-flush toilets
- Dual-flush toilets (three/six litres)
- Vacuum or compressed air toilets
- Cistern displacement devices
- Waterless toilets
- Composting toilets (heated or unheated)
- Incinerating toilets
- Urinals: Urinal controls (infrared, radar, auto flush) and waterless urinals
Wash hand basins:
- Push taps
- Flow control, self-closing taps
- Tap flow regulators
- Shower mixers
- Water-saving showerheads
- Self-closing shower system
- Water-saving washers
- Control and usage
- Auto shut off and pressure regulators
- Water bladders installed rainwater and grey water systems
- Rainwater recycling systems
- Grey water recycling systems
It is currently mandatory for all the following electrical products offered for sale in Australia to carry an approved energy label:
- Clothes dryers
- Clothes washing machines
- Refrigerators and freezers
For further information and updates regarding energy-efficient appliances visit www.energyrating.gov.au