Soaring energy costs have been a worry for most of us this winter. Last year Crediton u3a set up an Energy Action Group to learn how to reduce their energy use and bills without sacrificing comfort. In a series of articles, they will be sharing this knowledge and some practical tips on how to save money while keeping warm. Here local architect and energy expert Rob Rickey looks at how heat is lost from our homes, how to make our heating more efficient and to measure how much energy we are using.

A house is a complex machine for living. In order to know how to improve the comfort and economy of a home, we need to know where the energy that we pay for is going.

Did you know that about 15% of heat loss is through draughts and 25% through roofs?  In this article we will look at ways to make economical improvements that you can start today.

Heat loss from a typical house

I am a Certified Passivhaus Designer and have learned about how buildings respond to the environment. Passivhaus is a reliable low-energy standard focussing on efficiency and comfort. This chart shows how significant heat loss is in a modern house, compared to an older ‘leaky’ house and a super-efficient ‘passive’house.

You can see that even in the most energy efficient house, the main variable is the amount of heating required to provide a comfortable temperature. Solar gain (through glazing) only increases a little in a Passivhaus, but it represents almost as much (free) heating as the heating system.

Internal heat gains are those related to people using the house – cooking, bathing, appliances – which is pretty constant.

The heat losses side of the diagram shows how different building elements contribute to heat loss, walls being the largest component, mainly based on size. Note that ventilation heat loss is almost half of the heat loss through walls, and may be an area for easy wins in addressing your house.

Insulation is relatively expensive and can be disruptive; we will look at it in a later article.

How to improve your heating efficiency

There are several ways to approach improving the efficiency of heating. Reducing heat loss is obviously the most effective, but improving the efficiency of your heating system is also important.

  • If you use a boiler, make sure that it is serviced and operating properly.
  • Check that your radiators are all working correctly; start by bleeding the radiators, which will require a special key. You can find tips online about how to do this.
  • Use a timer and thermostatic radiator valves (TRV) to tailor where and when the heating is on.
  • Turn off radiators in unused rooms.

In order to assess what further actions to take, it will be useful to know how much energy you use compared to the UK average.

What is a kilowatt hour?

This is a useful unit to understand, as we will see.

A watt is a standard unit of power. You will be familiar with appliances and light bulbs rated in watts. A kilowatt is one thousand watts.

A kilowatt hour (kWh) is the quantity of energy used by a one-kilowatt electric heater running for one hour. One kWh will power a 40-watt light bulb for 25 hours. It is the unit used by utility companies to measure energy consumption; this is the number on your electricity bill.

Mains gas is measured in cubic metres on utility bills. To convert m3 of gas to kWh, multiply by 11.4. There is a more elaborate formula, but this will give a good average result. Now you can tally your annual gas and electric.

If you heat with oil, multiply the number of litres by 10.35 to get kWh. If you heat with electricity, you already have your use in kWh. Just add up the consumption on your bills to get one year’s worth.

Ofgem estimates the typical household in Britain uses 2,900 kWh of electricity and 12,000 kWh of gas in a year.

How does your home compare?

In the next article we will look at ventilation.  

If you have any queries or feedback to share please get in touch by emailing

The University of the Third Age (u3a) is a national movement of learning co-operatives for people who are retired, semi-retired or have finished raising their family.

You can find out more about the Crediton u3a group here

Mar 1, 2023

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