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Chapter 4

Heating and Cooling

Introduction

Space conditioning is the chief contributor to electrical energy use in most homes. Making your home better at retaining coolness (‘coolth’) and warmth will help to make your home both more comfortable and affordable to live in.

If you live in a cold climate, you’ll probably spend more energy on heating, while those in warmer climates will spend more on cooling. In Australia, heating contributes on average more to total energy consumption in a year than cooling. This is partly because a large proportion of Australia’s population living in colder areas like Victoria, compared to warmer ones like the Northern Territory. On top of this, heating appliances are generally much less energy efficient than cooling appliances.

Steps to improve your space conditioning
Step 1: Check your equipment

For most households, spending money to replace operational but inefficient equipment is not a top priority. With this in mind, it makes sense to take a look at what’s already present in your home to confirm that everything is working properly. Check for signs of corrosion, remove any buildup of debris on or around the equipment, and make sure that all filters are clean.

Consider replacing your equipment if it is more than 10 - 15 years old or if it needs frequent repairs, as there’s a good chance that it may not be running as efficiently as it did when first purchased. Additionally, improvements in efficiency standards mean that newer units generally do their jobs better than older ones. Not only can replacement save you on repair costs down the line - it can also help you to save a significant amount on your total energy consumption and bill.

Step 2: Check your home for drafts & insulation

Air leaks:

Drafts cause your home to lose up to 25% of its heat 1. Sealing drafts around the home could see you saving up to a fifth of your total energy consumption.

Try to pick a windy day and shut all the windows and doors around the house. Take a walk around the home and try to notice any seeping light, drafts or gaps. You can also hold incense or a candle to see the movement of smoke or wet your arm to feel for air leaks.

A diagram of a home with a small gap at its base letting out little squiggly lines of air. The text reads drafts cause your home to lose 25% of its heat.

In particular, pay close attention around the following:

  • Junctions between the building material (outside)
  • Windows and doors
  • Electrical outlets
  • Flooring and baseboard
  • Any other openings around the home

Depending on the area of the leak, gaps can be sealed with weather-proofing strips, caulking or fillers.

Insulation:

The presence of insulation in your walls and roof cavity can have a big impact on your home’s need for heating and cooling. Insulation slows the movement of heat in and out of the building envelope of your home - greatly reducing the need to heat or cool in the first place.

Depending on the age of your home, it might not have the recommended minimum amount of insulation on the attic floor. Consider getting an assessment if you are unsure.

Also consider installing insulation for walls, floor and pipes to minimise heat transfer in and out of your house.

A darkly lit room with a window shutter opening inwards.

Professional home energy audit:

Australian Building Sustainability Association (ABSA) website contains a list of accredited Home Energy Rating Scheme assessors who can provide deeper insight into the state of your home’s energy efficiency. If you’d like to leave the job to a professional, or if your home is too large to perform an audit yourself, you can search their database at www.absa.net.au/find-an-assessor.


Step 3: Check your heating & cooling habits

Once you’ve made sure that your heating/cooling system is working efficiency and that your home isn’t bleeding heat through gaps and uninsulated spaces, it’s time to look at the second component in efficiency: how you use the devices themselves.

In addition to dressing right for the circumstances (rugging up in the cold and vice versa for the heat), below are some tips for minimising heating & cooling loads in the home.

Summer/hot climate

  • Set the temperature sensibly: Don’t ‘over cool’ your home by setting the AC on full blast - every degree of heating required results in increasingly large amounts of energy.
  • Cool only the rooms you need: Minimise the total area that requires heating by closing doors.
  • Use shade to cool the home: For example, by drawing window blinds when the sun is shining down.
  • Use fans to help cooling: Fans require much less in the way of energy consumption compared to AC units, but can often have a significant impact on comfort levels.

Winter/cool climate

  • Set the temperature sensibly: As with cooling a hot house, every additional degree of heating requires more energy and will rack up your costs further.
  • Heat only the rooms you need: As with cooling, try to avoid heating unoccupied spaces.
  • Use the sun to heat the home: Let the sun in through your windows as much as possible throughout the day by opening blinds on those that receive direct light.
A rich orange sunset engulfs the silhouette of a surfer about to walk back in the surf. A young woman, wearing a beanie, gloves and a winter jacket is wondering past an iced over lake.

Companion fans:

In addition to being an effective, low-cost option for beating the heat on a moderately hot day, fans also augment the operation of other heating & cooling devices - saving you a few dollars in the process.

Cooling:

Running a ceiling or pedestal fan while the AC is on helps to move cool air around the space. This should allow you to keep the AC’s thermostat down by a couple of degrees, allowing the system to run at an overall lower cost

Heating:

Ceiling fans can help to keep a room feeling warm if they are switched into ‘winter’/reverse mode - where blades rotate in the opposite direction, sucking air up instead of pushing it down. In doing so, the cool air on floor level is mixed with the warmer air that ordinarily sits at ceiling level. In doing so, the ceiling fan ‘evens out’ the overall feeling of warmth in the room.

An old rustic brown apartment building with identical balconies lie contrast to a white air conditioner system hanging off the outside of the apartment.

Air conditioners vs heat pumps:

The main difference between a standard air conditioners and a heat pump (also known as a ‘reverse cycle air conditioner’ when used for space heating/cooling) is that a standard AC unit can only move heat in one direction - from inside the house to outside - while the direction a heat pump is reversible.

This means that you can use a heat pump for heating and cooling, while an AC unit can only be used for cooling. Because of their greater versatility, heat pumps tend to be more expensive than air conditioners.

The heating effectiveness of a heat pump is limited by climate - in colder regions many units will not function when the temperature drops to about 5°C. This means that they are not appropriate for places with longer, colder winters where temperatures regularly get so low. Check the specifications of individual units to determine which ones - if any - could work in your region.

Cooling: If you do live in a region where a heat pump is a viable option, it may make sense to choose one if you haven’t already got another major heating appliance (such as a wood or gas furnace) in place, provided it fits in your budget.

Choosing the right equipment

Whether you’re just moving into a new home and starting from scratch, or have been in the same place for over a decade, you’re bound to purchase some new heating & cooling equipment sometime. When that time comes, it’s important to know the pros & cons of each option: fans, evaporative coolers, heaters and air conditioners.

Step 4.1: Air conditioners and heat pumps

Air conditioners and reverse-cycle air conditioners (aka heat pumps) are popular options for keeping a home feeling cozy. While air conditioners are good for cooling during the summer months, heat pumps will both heat and cool a space - as long as it isn’t too cold outside.

Split systems

When choosing an air-conditioner, make sure it is the right size for your household. Split systems are more suitable if you want to cool just one or two rooms within the home, while ducted systems (discussed below) are the choice for an entire home. Both systems pump clean air in, meaning you don’t have to keep windows or doors open for circulation.

A diagram of a home, with a condenser outputting hot air outside of the home and connected to the outlet releasing cool air into the home.

Split system air conditioners come in two ‘components’:

  • The condenser (or compressor), which moves warm air in or out of the home. This component sits outside the home.
  • The outlet, which is the point where the air in the home is exchanged with the condenser. There are generally one or two outlets in the home.

Standard vs Inverter split systems

Inverter split systems work more efficiently than standard systems. Standard systems operate at only one intensity until the space reaches a set temperature, at which point it switches off. This on/off/on cycle repeats over and over again during operation as the temperature fluctuates above and below the target temperature.

Inverter systems, on the other hand, can operate at a variable speeds, running at a high capacity until the set temperature is reached, then switching to a lower capacity to maintain this temperature. This means less energy fluctuation and greater energy efficiency.

Make sure you look at the star rating system, and kWh consumption to compare energy efficiency between models.


Window & portable air conditioners

Window-mounted and portable air conditioners do the same job as a split system, but with both condenser and outlet located inside the unit. They are usually cheaper to purchase and install than split system ACs, but are also less efficient for similar-sized units.

There’s also the obvious advantage that they can be moved from room to room as needed.

Ducted systems

Ducted systems consist of one central heating/cooling unit and a series of ducts leading air into every room. These systems require professional installation and are not generally selected unless being installed for a new home.

Ducted systems are more appropriate for large households, but may not be the best choice if you think you’ll only need to heat or cool one or two rooms, as they can be very energy demanding and thus costly to run. When buying a new ducted system, compare the energy efficiency by asking for the average kWh required to run the unit in a year. Look for systems with similar functions and capabilities, but less kWh consumption.

Ducted air-conditioning systems are able to consistently maintain the temperature of the entire home, but many units also have ‘zoning’ capabilities, allowing the user to modify the temperature for specific rooms/zones. It is important to ‘zone’ the temperature if the rooms are unoccupied to avoid unnecessary electricity use - and cost.

A diagram of a two story home, with a central unit in the attic letting out hot air, and tubing connecting the central unit to an outlet in the top story and an outlet in the bottom story.

  A mapped outline of Australia is depicted with heat mapping showing that the top of Australia is too humid for evaporative cooling, while the north east coast of Australia is also less suitable. The rest of Australia is green and suitable for evaporative air conditioning.
Step 4.2: For cooling

Fans

Fans are a popular way to stay cool in hot weather, but they do not actually reduce the temperature of the air in a space. Instead, they increase your thermal comfort by helping perspiration evaporate more quickly off your body - which makes you feel cooler. This means that fans are most effective when directed towards you - as opposed to aimlessly swishing air around a room. It also means that there’s no benefit in leaving a fan on when you’re out and about.

The two most common types of fans found in households are pedestal fans and ceiling fans. Both are cost-effective to run and provide good relief in moderately hot weather conditions. Because of their size, ceiling fans help to make larger spaces more comfortable, while pedestal fans are better for ‘point and shoot’ applications. Both are inexpensive to run, but only ceiling fans have a ‘winter’ setting (see ‘Companion fans’ explanation above).

Evaporative coolers

An evaporative cooler is essentially a fan that blows over or across water, turning hot dry air into cooler, moist air. In the process of evaporation, water absorbs heat, making the room feel cooler. Because they are effectively humidifying the air, evaporative coolers work best in hotter, drier climates - and are not generally recommended for humid climates.

See the image of Australia for the areas where evaporative cooling will work best.


Step 4.3: For heating

Oil heaters - for room heating

Possibly the most popular type of electric heating device in Australia, oil heaters turn electricity into heat by slowly warming up a chamber full of oil. The heated up unit heats surrounding air through convective heat transfer - where heated air rises so that more cool air can be ‘drawn up’ and heated, creating a self-driven, circulating current of warm air.

Oil heaters are great for heating closed, well-sealed spaces, provided that they are the appropriate size for the room in question. They take time to warm up, but once they do they are good at keeping the entire space feeling comfortable.

Some oil heaters come equipped with timers, but many simply have a range of arbitrary and nondescript heat settings such as ‘high’ and ‘low’ or numbers 1 through 10. Getting to know which setting is right for your space can be a process of trial and error - keeping a thermometer in the room is a good idea to keep track of the temperature, and you can monitor the electricity consumption of your heater with a smart plug (like carbonTRACK's).

Radiant or bar heaters - for personal heating (and bathrooms)

Unlike oil heaters, radiant heaters do not directly heat up the air in a room; instead, they instantly warm whatever objects (or bodies) they are facing. They are therefore great for helping you to keep warm - but only if you’re sitting directly in front of one. This makes them a good option for bathrooms, which don’t need to be kept warm for extended periods.

Fan heaters - for personal heating (or small spaces)

Like radiant heaters, have an element that generates radiative heat for instant relief from cold, but they also incorporate a fan, which brings in a convective heating component as well. This makes them a bit better than radiant heaters at warming up a modestly-sized space - but not so good for heating a larger space.

Underfloor heating - for room or whole house heating

Another option for households is underfloor heating, where a network of either pipes or wires is installed underneath a concrete floor. The system takes advantage of the thermal retention properties of concrete and the natural tendency for warm air to rise. Underfloor systems are usually switched on overnight (on cheaper, off-peak rates) as they can consume large amounts of electricity. Additionally, because they are so energy-hungry it’s especially important to ensure that your home is very well-insulated and as draft-free as possible.

Underfloor systems require significant construction in their installation, so if one is not already present in your house it’s unlikely that you will choose to have one installed.

Non-electrical heating:

This book focuses on electricity-driven means of air conditioning, but many homes rely on non-electrical means such as gas heating and wood furnaces instead. If you have either of these, make sure it is in good working order and that you’ve taken the other steps described here for keeping your home comfortable - such as an equipment and draft checks.

1Energy use in the Australian residential sector 1986–2020

In the next chapter, we’re looking how you can improve your energy consumption from water heating.

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