Energy Efficient Homes

As outlined in our introduction, the UN Environment Program’s Global Status Report for Buildings and Construction identifies six main ways buildings consume energy.

• Heating

• Cooling

• Water Heating

• Lighting

• Cooking

• Appliances

In his book The Big Switch Saul Griffith estimates what proportion of household emissions each of these areas contributes.

• Heating – 36.4%

• Water Heating – 24.6%

• Cooking – 5.7%

• Lighting – 4.9%

• Cooling – 3.4%

• Appliances – 25% (fridges = 8%)

​These numbers shouldn't necessarily be taken as gospel - they will vary widely depending on where you live, the design of the home and the household's lifestyle and preferences.  I live in Queensland and you rarely need to heat your home here, but you might spend more than his estimate on summer cooling.  

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Heating and Cooling

Depending on where in Australia they live, people need to either heat their home in winter, cool it in summer, or both.  How much this costs depends on a number of factors.

• The type of heating and cooling used – ‘state of the art’ reverse-cycle airconditioning can reduce costs, but often social housing has no built in system and tenants make up for it by buying their own (often cheap) portable systems which may cost more to run.

• Orientation – homes that are oriented to benefit from winter sun and summer shade cost less to heat and cool than those that are poorly oriented.

• Ventilation – homes that are designed to allow through breezes in summer have less need for artificial cooling.

• Insulation and air-tightness – homes that are both insulated and air-tight cost less to heat and cool than those which are uninsulated and/or leak lots of air.  ‘State of the art’ would see ceiling, walls and floor all well insulated, and in cold climates, double-glazed windows also help.

 

Hot Water

A number of factors influence the energy costs associated with hot water.

• The type of system.  Older style electric storage systems consume more power than more up-to-date heat pump systems, continuous/instantaneous heaters or solar heaters, with the best option depending on the type of housing and household.

• The temperature setting.  The ideal setting for a hot water system is about 60 degrees Celsius – above this the system chews more electricity to warm the water only for it to be too hot to use and need to be diluted at the tap.

• Water-tight taps and fittings.  A leaky hot water tap or pipe will lead to heated water being slowly siphoned from the system, increasing the amount of water heated.  Low flow shower heads can also greatly decrease water use including hot water.

 

Lighting

Light fittings use more or less light depending on the type, and switching mechanisms can also save power.

• LED lights use less power than flouros, whether tubes or compact.

• Outside security lights can be fitted with motion sensors which will mean they don’t need to be left on all the time.

 

Cooking

Cooking appliances are another major source of energy use.  Unlike other appliances, there are no formal energy rating systems for ovens, cooktops and microwave ovens so understanding how to get the best energy efficiency on these items can be a little murky.  Here are some things to think about.

• Gas stoves lock the household into using fossil fuels indefinitely, as well as having health impacts on household members.  As we decarbonize our energy system, an electric stove powered by renewable energy clearly produces less emissions than even the most efficient gas cooktop or oven. Electricity also has the edge in safety as gas carries the risk of both fires and leaks.

• The most energy efficient form of electric stove is an induction cooktop, which cooks by magnetic induction rather than direct heating.  However, for a rental situation the drawback is that these stoves only work with certain types of saucepans so your tenants may move in only to find they have to buy a whole new set of saucepans before they can cook anything!

• Fan-forced ovens overall are more energy-efficient than older style convection ovens.

• Maintenance and regular replacement of elements and oven seals also improves energy efficiency as these items deteriorate over time.

 

Appliances

Appliances are the main area of home operation that are primarily in the control of the tenant, since they supply their own appliances and set them up.  The main energy-using appliances include fridges, washing machines, dishwashers TVs, computers and other media devices.  Tenants also supply their own light bulbs in most tenancies.  Low income tenants often find themselves paying more for the energy used on these appliances because their low incomes mean they can only afford to buy cheap or second-hand appliances which may have lower energy ratings. 

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The Commonwealth Government has an energy rating system for appliances which gives a handy independent guide.  They rate appliances (their list includes fridges, washing machines, TVs, dryers, dishwashers and air conditioners) by providing both a rating on a five-star scale, and an estimate of annual energy consumed.  The important caveat for this is that the rating only applies to new appliances – as appliances age they can consume more power for a range of reasons.  Choice also has a handy guide to energy use in appliances. Unfortunately you need to be a subscriber to see the details.

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I've explored some of these issues in more depth in the Climate/Housing Blog and there's more to come - subscribe for updates.