Heating a home in a more sustainable way

Posted by Howard Elston on Sun 20 May 2018

The colder weather has arrived (at last)! For anyone trying to live a more sustainable lifestyle, it’s likely using gas or electricity for heating causes a guilty pang. Is turning on the heater somehow letting the team down?

Reluctance to switch on the heating

Now is a good time to think about heating. Why might heating be needed in our homes? What are the ways to minimise the contribution to climate change?

Are you living in a 10 Star NatHERS rated home?

In theory, any home less than a 10 Star NatHERS rating requires some energy input to keep the occupants comfortable in winter and summer. A 10 Star rating means the house relies on passive heating and cooling methods such as north facing windows, thermal mass and excellent insulation.

These 10 Star houses do exist, but chances are you aren’t living in one. Here's an example of a 10 Star home designed by The Sociable Weaver. It's a display home at The Cape sustainable home development in Cape Paterson.

10 Star home designed by Sociable Weaver

Most suburban houses are rated at 6 Stars (or much less) so active heating and cooling is needed to keep the occupants comfortable throughout the year. Gas heaters, bar heaters, hydronic heaters, wood fires and reverse cycle air conditioners are common ways of heating Melbourne homes.

So, some type of heating is probably necessary for your home.

Does that let everyone off the hook just because most houses need heating? No. We need to be clever about how to meet the need.

Let’s consider a few ideas for making home heating more sustainable this winter.

Minimise the amount of heating required.

Become more sustainable by investigating what can be done to reduce the amount of heating needed to keep your home comfortable in winter.

Start with small improvements. A previous article listed 3 no (or low) cost ways to reduce the amount of energy used to heat a house. 1. Turn down the thermostat 2. Close doors between rooms 3. Stop drafts

Well insulated house reduces heating losses Next consider if your home has sufficient insulation to keep the heat indoors. Insulation helps to make good use of energy coming from the heater. Installing or improving the insulation in the walls and ceiling does cost money. However, Energy Freedom points out the savings can be as high as 50% of the normal heating bill.

Think about the method used to heat your home.

If your home has a relatively new heating system, use it wisely and you’ll be doing the best you can.

However, there is the possibility of making a significant improvement. This applies to anyone with a reverse cycle air conditioner or anyone whose home has an inefficient heating system that is due for replacement.

Why those two situations? A reverse cycle air conditioner is an efficient heating device so it should be the first heating choice if already in the home. The high efficiency also means anyone considering replacing a heating system should seriously consider adding a reverse cycle system to their shopping list.

Reverse cycle air conditioner (aka heat pump).

Reverse cycle, split system, heat pump, air conditioner, … What are we talking about? Looking at retailer advertisements it seems that even the people selling these devices can be a bit confused with the terms..

Fortunately, Tim Forcey (Energy Adviser and ATA guru) put together a layman’s guide to understanding the technology. Let’s start with heat pump.

As Tim points out, a heat pump does exactly what the name says. It pumps heat from a cold place to a hot place. A good example is the humble refrigerator. It pumps heat out of the cold box and into the warmer air in the kitchen.

Heat pump schematic

A reverse cycle air conditioner is a heat pump that can move heat in two directions, either into a room or out of a room. Older style air conditioners only pumped in one direction, taking heat out of a room. Also, some older air conditioners had a low efficiency which explains the reluctance to use the modern equivalent.

In winter, the heat pump moves energy from the cold air outside to warm the air inside a room. Yes, strange as that may seem, there is heat in the air on a cold winter’s day. The term “split system” refers to the heat pump using two separate fan units. One fan unit is located inside the house and one outside. A refrigerant fluid circulates between the two units and moves heat around. Energy is extracted from the air outside the house and pumped to the fan unit inside. There the refrigerant fluid warms the air in the room before coming back to the outside fan unit for reheating.

In summer, the reverse happens. The heat pump pumps heat from the room you want to keep cool and sends that energy outside where it’s warmer.

Why bother with a heat pump?

Panasonic reverse cycle air conditioner

A reverse cycle air conditioner is very, very good at its job. Every one energy unit of electricity consumed by a heat pump produces up to six energy units of heating. How good is that? Looked at another way, Tim says the pump produces up to five units of renewable energy. Why renewable? The energy is coming from the atmosphere, not from burning fossil fuels.

Wait a minute, I hear you say. The reverse cycle air conditioner does use electricity. Most electricity comes from coal fired power stations. How can this help with sustainability?

Renewable energy alternatives to fossil fuel based electricity are readily available these days. It’s easy to select a Greenpower alternative and run the heat pump on solar, wind or hydro power.

The bottom line is that using a heat pump to meet heating and cooling requirements is a sustainable option. And remember, with efficiency levels of 400+%, a split system air conditioner is more economical to operate than many other heating and cooling systems. Having one device to do both jobs helps with the economics as well. Remember the old days of using an air conditioner for hot days and a completely separate gas-fired ducted heating system for cold days?

Another step towards a sustainable community

We can reduce the amount of heating needed in a home through good operating habits and installing insulation. Once the heating load is reduced, consider using a reverse cycle air conditioner for heating (and cooling in summer). It’s one of the most efficient ways to keep a home comfortable.