An analysis of your heating bill, preferably over the past year, is the first step.

Energy used for heating is also measured in kilowatt hours (kWh). If fuel other than electricity is used such as gas or coal then your supplier should convert the quantity supplied into units of kWh. Otherwise use the typical conversion factors below:

Oil	7 kWh/m3
Bottled gas	9 kWh/m3
Brown Coal	4 kWh/kg
Black coal	7 kWh/kg
Wood	3 kWh/kg

Space heating demand

If you use gas or oil to produce hot water as well as space heating, subtract 3,000 kWh/year for a typical four person family. If you use gas for cooking as well as for space heating, subtract a further 600 kWh/year. The balance will be your heating demand.

For example

	kWh
annual gas bill	21,600
hot water	- 3,000
cooking	- 600
annual heating demand	18,000

To convert this to the heat loss multiply by 0.9 (conversion efficiency for a gas boiler in good working order)

i.e. heat loss = 18,000 x 0.9 = 16,200 kWh

Dividing by the floor area of your home (say 90 m²) gives a heat loss per unit area

= 16,200/0.9 = 180 kWh/ m²

Comparison with average family homes

You can now compare your heat loss per square metre with typical values for various levels of insulation and building construction.

insulation standard	heat loss kWh/ m2	typical age
poor	250	pre 1945
partly	200	1965 – 1976
well	150	2000 –
super	100	sustainable building code level 4

If your heat loss is lower than these normative values, then your house has a high standard of construction, additional insulation has been added and your boiler is in good condition.

If your heat loss is higher, then it may be due to one of the following causes -

• insufficient insulation
• the fabric of the building is in a poor condition
• temperature setting of your room thermostat is too high

Oil boilers

Oil boilers tend to have a lower efficiency than gas boilers so the heating bill will be higher for the same heat loss.

Heat pumps

Heat pumps are a renewable heating source with a very high efficiency as these devices only concentrate the heat, not produce it. Typical efficiencies are 350-400% (heat out/energy in) and so the heat demand will be very much reduced with a consequent reduction in the heating bill.

Reducing heat loss

The heat loss of a home depends upon a number of factors including -

• type of dwelling such as detached, semi-detached or attached or whether it is an apartment
• number of stories
• condition of the fabric such as doors and windows
• level of insulation

Heat can be lost in many different ways from the home and the sketch shows the relative heat losses from the major building elements for a typical home. These losses could well be different for each home depending upon the type of dwelling and its age.

The average life time of a dwelling in the EU is now more than 100 years. Over the years the building standards have increased in all Member States consequently the older the dwelling, the poorer the insulation standard.

Thermal insulation

The level of thermal insulation in a home is more difficult to determine as in the UK prior to 1965, there was no requirement to have any thermal insulation fitted to houses. Subsequent revisions of the building regulations required ever increasing amounts of insulation particularly the revisions in 1976 and in 1995.

Increasing the level of insulation to that closer to today's standards will improve the fabric of the dwelling, extend its life and reduce any condensation that might be present. In this way, savings can be made in terms of energy, money and the environment.

Boiler age and efficiency

If it is more than two years since your heating system was checked, it is worth arranging a service visit. Servicing your system will also allow the service engineer to undertake a 'health' check to ensure your system is operating safely and at optimum efficiency. This will minimise your heating bill and save the environment.

If your system is more than 15 years old, it is worth asking the service engineer about the condition of the system, the availability of spare parts and the cost of replacing the existing system with a newer and more efficient heating system. As many home owners have added additional insulation in order to reduce their heating bills, it is desirable that the engineer recalculate the heat loss and size the boiler for the reduced heat loss so the boiler will operate less of its time at part load and lower efficiency.

Renewable heating sources

When it becomes necessary to rep lace your existing boiler you should consider whether a renewable heating source like a heat pump or biomass boiler would not be more cost effective. A survey form is attached which can be used to identify which renewable source might be more suitable.

Grants

Grants may be available to add additional insulation to your home or to replace your boiler with a higher efficiency boiler or to replace your boiler with a renewable heating source. It is worth checking with your local energy advice centre and utility company.

Potential for using renewable energy sources