Energy Efficient Design and Usage

The Shire encourages the integration of environmentally sustainable design principles into the siting, design and construction of both new and redeveloped residential, commercial and mixed-use buildings.

Any style of building can be designed for energy efficiency, to ensure savings on future energy costs, and to assist the environment. The main features of energy efficient buildings relate to building orientation, internal room layout, window placement, sizing and shading, use of insulation, ventilation, landscaping, and certain materials and colours.

When preparing a development or building permit application, regard should be given to (where applicable) the following:

Re-use and Adaptation of Existing Buildings

The Shire encourages the retention of existing buildings capable of reasonable adaptation and re-use, in view of the significant reduction of waste that results from re-using a building.

The adaptability in the design and construction to ensure the continuation of the building is encouraged by the Shire.

Passive Solar

To the maximum extent possible, the Shire recommends that buildings should:

  • be oriented;
  • incorporate appropriate features (for example, shading for north-facing windows, wide eaves, and roof ventilation); and
  • use appropriate building materials

to maximise the benefit from the winter sun, minimise the impact of the summer sun, and make use of prevailing breezes with the result of reducing the need for energy-consuming artificial heating and cooling.

The sun passes overhead at different angles in different seasons. In winter the sun is lower in the sky. You can naturally heat living areas in winter by letting sunlight into the northern side of the house. Avoid putting garages, carports or verandas on the northern side of the house that block the winter sun and keep the house colder and darker.

The Shire recommends a shade cut-off angle of 65 degrees for eaves on the north side of a house, to provide the best balance between winter sunlight and summer shade.

Use the 65-degree diagonal fold line and instructions provided in the Passive Solar Building Design brochure to check the shade from northern eaves onto the window or door on a section drawing.

Eaves and verandas on the east, west and south will shade the walls and windows early and late on hot summer days.

For residential development, it is recommended that land which permits the living areas of the dwelling to face north, be free of obstructions such as buildings or evergreen trees on this side of the home.

Orientation is the key factor in achieving energy efficient design. While items such as pergolas, shutters and insulation can often be retro-fitted at a relatively low cost, the orientation of a building is often set in `concrete’ and if poorly orientated it is virtually impossible to correct.

Indoor living and entertaining areas should be oriented on the north side of the home where possible, with other rooms to the south. This will create warm and bright living areas in winter since north facing windows and walls receive maximum winter sun.

Energy Use

Buildings shall be designed with the intention of maximising the use of renewable energy (for example, through the use of solar panels) and minimising the use of non-renewable energy.

Water Use for Buildings

Buildings are encouraged to be designed to minimise the use of water, including by locating hot water systems close to those areas that will use hot water.

The installation and use of rainwater tanks and/or wastewater reuse systems is encouraged as they result in more efficient use of water resources. There are various types of rainwater storage systems commercially available:

• Above Ground Tanks - are common, and slimline style tanks will take up less room next to your house.
• Bladder Tanks - have soft sides, and can be installed under the house floor or under a deck, and save space.
• Underground Systems - include heavy duty tanks built to withstand the pressure of the surrounding soil in which they are buried. It is generally more costly to install underground systems in the hills due to rocky soils; the sandy soils of foothills in the Swan Coastal Plain are easier to excavate.

Check with the Shire’s Planning and Building departments whether approval is required prior to installing. 

Construction Materials

Buildings should be designed to maximise the use of locally sourced, recycled, recyclable and rapidly renewable materials in their construction, however where necessary will still be required to comply with AS3959 (Construction of Buildings in Bushfire Prone Areas).

Light external colours are encouraged as they tend to reflect the sun’s heat while darker colours absorb it. You can take advantage of this fact when selecting the colour of your roof and wall materials. In summer, lighter coloured materials will help to keep your home cooler by reflecting heat from the sun.

Insulation

High levels of insulation is a good investment. A well-insulated house will be more comfortable throughout the year and dramatically reduce heating and cooling costs.

Under a metal roof you should use 50mm insulated foil sarking blanket, commonly known as Anticon. This stops heat transfer into the roof spaces. Anticon continued over roof ridges and under valley trays can also help keep out burning embers for houses in bushfire prone areas.

Wall and ceiling insulation bats comes in different ‘R’ values and the higher the R value, the better the performance (provided it’s installed properly). Use thicker and higher R rated ceiling insulation. For walls and cathedral ceilings, the thickness will be limited by space – squashed insulation bats don’t work well.

Thermal Mass

Thermal mass in sustainable building design means careful use of high-density building materials (including concrete and masonry) to help moderate temperature cycles inside a building.

Internal thermal mass can smooth temperature extremes and limit heating and cooling costs. For example, a tiled concrete floor in a north facing living area will naturally warm up during a winter day. Then at night when the temperature drops, the thermal mass of the floor is gradually releasing some heat to keep the room comfortable. If correctly angled eaves provide shade from the summer sun, the slab will also stay cool and help keep the house comfortable in hot weather.

A negative effect of thermal mass can be external brick walls and tiled roofs that heat up in summer, and then radiate unwanted heat into the internal areas of the house overnight. The best approach is to build a highly insulated exterior for the building combined with good levels of internal thermal mass internally and avoid tiled roofs.

Landscaping

Plant Selection

Plant selection should adhere to water wise gardening principals to minimise water usage. Plants recommended by the Shire can be found the Landscape and Revegetation Guidelines.

Location

Extensive areas of unshaded paving to the east and west of your home should be avoided as it can cause heat to be reflected into windows during summer. Lawns and other ground covers will help reduce this problem.

Landscape Protection

In addition to the Residential Design Codes requirements for tree planting, the retention of existing trees and planting/maintenance of new trees is strongly encouraged, particularly in locations where they shall not compromise a dwelling’s access to winter sun but instead provide cooling afternoon shade to the dwelling and/or outdoor living areas in summer.

Vegetation of significance (e.g. habitat trees) should be identified early on to ensure that it will not be impacted by any proposed development. The Shire's Environmental Team offers a site inspection service to residents to identify environmental assets on a property.

Referred to as an Environmental Asset Inspection, we have made this service available so that a Shire Environmental Officer can provide residents with site-specific advice regarding environmental assets and issues. This information can then be taken into account in the design stages, rather than causing problems and delays during the planning application process.

Hydro Zoning

Group plants together in your garden by their water needs. Plants that need very little water can be grouped together and higher water using plants can be placed in a separate area. This makes for much more efficient watering and reduces water use.

Soil Protection

A 5−10cm layer of mulch over the soil will allow water to drain into the soil and prevent evaporation. Waterwise mulch should be of a chunky consistency rather than fine so it will soak up the water, compact and prevent water filtering through to the plant’s roots.

Mulch also helps suppress weeds, which reduces maintenance. Top up mulch each year to maintain the appropriate level but do not place mulch so that it contacts the stems of the plant as this can cause the plant to rot. Mulch should be well composted to prevent the spread of disease and weeds.

Be aware that adding mulch can cause nitrogen drawdown. This is when micro-organisms such as fungi and bacteria start to compost the woody materials on the soil surface. To do this they need to draw nutrients out of the soil. Nitrogen drawdown results in the competition for nutrients between the plant roots and the mulch on the surface being broken down. To combat this first place a 1−2cm layer of well-rotted cow manure or compost on the soil around your plant, then the woody mulch layer on top of this. The manure will directly provide nutrients for the plants and creates a ‘buffer’ so the mulch sitting on top won’t compete and draw nutrients out of the soil away from the roots.

Fertilisers

Fertilisers are high in nutrients, such as phosphorus and nitrogen. These can wash down stormwater drains and enter our waterways, ending up in the Swan-Canning River system and the ocean. Phosphorus and nitrogen can be responsible for toxic algal blooms in our waterways, resulting in fish deaths. Phosphorus can also seep into our groundwater systems which forms much of Perth’s drinking water supplies, which is a problem. Ways to reduce your household’s fertilisers entering our waterways include:

• Grow local native plants instead of exotics as natives require less fertiliser and water
• Apply fertiliser sparingly in Spring or early Autumn, as these are the optimum times for absorption of the fertiliser by plants
• Use natural alternatives instead of chemical fertilisers such as compost, soil improvers and worm castings.

Efficient Irrigation Systems

Irrigation is most efficient when water is applied to the root area of the plants rather than spraying the leaves. For this reason, drip irrigation systems are highly efficient and are a cheap option for your garden. A drip irrigation system prevents loss of water through surface evaporation, especially if it is installed under a good layer of mulch. Watering early in the morning before 9:00am or in the evening after 6:00pm will help to avoid evaporative loss.

Sustainability tips

• Choose durable, low maintenance building materials
• Avoid tiled and dark coloured roofs, lighter roofs are cooler
• Water heating can be a large part of gas or electricity bills – look at a solar hot water system with a booster on a timer
• LED lights use less electricity and tend to last longer
• Check the star ratings - energy efficient appliances may be more expensive to buy but cost you less in lifetime running costs
• Plan for comfortable outdoor living areas and include herbs, edible plants or wildflower gardens in waterwise landscaping
• Don’t build more than you need – you may end up compromising on quality and larger homes cost more to furnish, heat, cool, clean, maintain and insure.

Contact Information

For more information please contact our Planning, Building or Environment departments on (08) 9290 6666 or via shire@mundaring.wa.gov.au

Useful Links

Environment and Sustainability

Passive Solar Building Design Brochure