Look at energy efficiency and whole of home

While you are getting off gas, a wide range of benefits can result from also upgrading energy efficiency, including improved energy affordability, being more resilient to changing and extreme weather conditions, and mitigation of electricity peak demand, a key driver of increasing electricity prices.

The main considerations for household energy efficiency are design, insulation, draught sealing, heating, cooling, and major appliances such as heaters, washing machines, dryers, and hot water systems. Thermal efficiency (how well a building reduces unwanted heat transfer) is a way of reducing energy required for heating and cooling and is determined by the features and design of a building. Separately, the energy efficiency of appliances also has a significant impact on overall energy use.

Why building and appliance efficiency matters

In an energy-efficient home, the heating and cooling equipment is running less often, and more passive cooling and heating principles are used to maintain thermal comfort.

When measuring the efficiency of appliances, the ratio of the useful energy output of a heating or cooling system divided by the input energy is known as the ‘conversion efficiency’ or the ‘coefficient of performance’ (COP). The input, as well as the useful output may be chemical, electric power, mechanical work, light (radiation), or heat. The resulting value, η (eta), ranges between 0 and 1, or 0 – 100%. Heat pumps, though, have a conversion efficiency of 300% because they move heat rather than convert it. Standard gas tanks or boiler hot water systems, when new, have an Efficiency Factor (EF) of 0.58-0.60.

This means that while a gas heating system can produce at most 1 unit of heat for each input unit of energy (and typically between 0.6 for ducted systems and 0.95 for the most highly efficient systems), a reverse cycle air conditioner (heat pump) can provide 3 to 5 units of heat for each input unit of energy. This makes heat pump heating significantly more efficient and cost effective than gas and is a key contributor to the cost savings of all-electric homes.

Using zoning to reduce energy consumption

A simple way to reduce how much energy your heating and cooling appliances use is to create as many zones within your home as you can, and heat and cool by zone rather than the whole home. Doing so can lower your heating costs by up to 40%.

Unfortunately, ducted heating and cooling systems can be inefficient (unless they are modern, zoned units) because they are conditioning multiple areas all at once. Space heaters and coolers, specifically reverse cycle ones, used in individual zones are always more efficient that whole-of-home systems. Ducted systems can be made more efficient is they are cleaned and maintained regularly and have no damages or vents that may make them work less efficiently.

DIY zoning techniques

You can create zones in your home in the following ways:

Closing doors to rooms that are not used during the day, such as bedrooms, bathrooms, laundry, etc.

For doorways or hallways that do not have a door, consider hanging a curtain (the thicker the better, but anything will do) using an expanding curtain rod that requires no fixed installation.

Install fixed floor-to-ceiling room dividers that you can use to block off an area of your home that doesn’t require heating or cooling.

Draught sealing

Up to 25% of winter heat loss from existing houses is caused by air leakage (also known as draughts). Seal gaps around doors and windows to draught-proof your home and save energy and money.

Draught sealing is finding and fixing draughts to make your home more comfortable and energy efficient. Draughts are like ventilation, in that both let fresh air into your home. Good ventilation helps reduce condensation and damp and can help cool down a hot house. Draughts, on the other hand, are uncontrolled – they let too much cold air in and waste too much heat.

Draught proofing stops warm air from escaping your home in winter and hot air from entering in summer, saving you money and making your home more comfortable. Draughts come into your house through gaps and cracks around doors, windows, exhaust fans, fireplaces and so on. To draught-proof your home you will first need to find the draughts.

To help:
  • Look for obvious gaps;
  • Look for visible light under and around doors and windows;
  • Take time out, especially during strong winds, to listen for rattles and whistling around doors and windows;
  • Feel around doors, windows, fireplaces, air outlets, vents, stairways, floorboards, exposed rafters and beams, built-in heaters and air conditioners, architraves and skirting boards;
  • Look for movement in and around curtains, as it can be an indicator of draughts.

Insulation is the cornerstone of an energy efficient home. Insulation is also the most cost-effective way to improve the energy efficiency and comfort of your home.

A fully insulated home compared to a non-insulated home can reduce the cost of heating and cooling a home by around 40 to 50%. Adding bulk insulation, either to new or existing homes, creates a more comfortable home year-round, virtually eliminates condensation on walls and ceilings and can pay for itself in around five to six years.

An insulated house needs less heating and cooling – using insulation reduces greenhouse gas emissions. It virtually eliminates condensation on walls and ceilings. Some insulation materials can also be used for sound proofing.

All insulation materials are rated for their performance in restricting heat transfer. This is expressed as the R value or thermal resistance of a product. The R value is a guide to its performance as an insulator – the higher the R value, the greater the insulating effect. Products which have the same R value will provide the same insulating effect as each other, provided they are correctly installed.

The most important location for insulation is in the ceiling. This results in the biggest energy savings and is also usually the easiest and cheapest place to install insulation in existing homes. Wall insulation is the next most effective location, followed by underfloor insulation; these are often harder to retrofit in existing homes unless a major renovation is being undertaken.

Prevent losses through windows

A single pane of glass can lose almost ten times as much heat as the same area of insulated wall. Internal window coverings and double glazing can reduce winter heat losses by up to 70%. That means it’s worth taking some simple steps to reduce heat loss through your windows, making your home more comfortable and reducing your heating costs in the process.


The Barn by SUHO is an all-electric home that maximises energy efficiency, achieving a NatHERS rating of 9 stars. Learn more about The Barn at the Sustainable House Day website.

Using curtains

Appropriate window protection creates an insulating layer of still air on the inside of the glass. This can be achieved by the addition of thick curtains and a pelmet. A poorly fitted curtain allows heat loss to occur, while a well fitted curtain combined with a pelmet significantly reduces heat loss, so remember to:

  • Use closely woven, close fitting internal window coverings such as curtains or blinds;
  • Ensure a snug fit on both sides of the window and at the top of the curtain to stop warm air from moving down behind the curtain and cooling;
  • Install pelmets (like a scarf over the top of your curtain rod) or solid barriers above the curtain rail, or position the curtain within the window space;
  • Use curtain tracks that provide a return of curtain to the wall to create a seal;
  • Close curtains or blinds when you have the heating on, especially at night.
Using Blinds

If heavy lined curtains are not an option for you, thick, lined Roman blinds (that incorporate a pelmet or are attached to the wall or frame at the top of the window) or honeycomb blinds fitted inside the frame of the windows can be good options because they both stop air flow. Whatever you choose – ensure it is fitted in such a way that the air flow across the window is as minimal as possible.

DIY secondary glazing

Secondary glazing is when you leave the original window in place and attach a second panel or either glass or clear acrylic, leaving a gap between both panes. This creates a double-glazing effect. This is a great choice if you have timber framed windows.

Professional secondary glazing

There are numerous companies who offer secondary glazing for your windows. It costs more than the DIY option but less than replacing the entire window unit (glass and frame) with a double-glazed unit.

Thermal ratings and modelling tools

The Nationwide House Energy Rating Scheme (NatHERS) gives new homes a star rating from 0 to 10 stars that measures thermal efficiency. The scheme is the most common way for new homes to meet the minimum energy efficiency requirements of the National Construction Code (NCC). The score reflects the annual heating and cooling energy required (expressed in MJ/m2 per year) to maintain specified comfort conditions inside a house in a particular climatic location. The score is calculated using a range of technical modelling tools that consider design and thermal features. The 2022 National Construction Code sets an equivalent of 7 Stars as the minimum NatHERS rating for new homes in most locations.


Check out Renew’s Guide to Energy Efficient Home Offices.

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