A general consensus within the scientific community is that the rate of new oil and gas reserve discoveries has significantly fallen in recent years. Furthermore, these discoveries are becoming more and more risky and costly to access! For example, in April 2010, deep-sea oil drilling cost BP more than 2 billion pounds for damages and clean-up costs due to a catastrophic oil leak at the Deepwater Horizon rig, in the Gulf of Mexico [1]. So in future years, it may get harder and more expensive for energy companies to produce and supply fuel to the public. In the UK, most properties and businesses are still heavily reliant on fossil fuels for heating, so an expected rise in fuel prices will become increasingly relevant to people and households.

On average, householders tend to use 85% of the energy available to them for central heating and hot water heating [2]. In comparison, electrical use for washing machines, dishwashers and other appliances makes up a much smaller contribution to our overall energy use (15 %) [2]. Hence, there is more potential to make bigger energy savings if we focus our efforts on reducing heat waste. Plus, by achieving this goal we can also save money on our fuel bills!

Using your heating controls more efficiently is the easiest way to make fuel and money savings, whilst increasing the comfort of the home. Below are a few tips for heating devices that are commonly found within the home. With the exception of the time switch or programmer, most of the devices shown below, are only relevant to households with wet central-heating systems (i.e. boiler and radiators). The table below shows the cost and CO₂ savings that can be achieved by fitting or optimising heating controls.

Table 1: Cost and Carbon/CO₂ Savings for domestic heating control measures, in a typical 3 bed room semi-detached property [3].

1) Time switch/ Programmer: This device allows you to set the time for when heating/hot water comes on or off. It is better to have a set programme that follows your daily routine, so that the heating is off when the property is unoccupied [3]. However, it is advisable that during extensive periods of absence in severely cold weather, the heating is switched on/off every day, using a programmer, to reduce the risk of frozen or cracked water pipes.

• Hot Water Heating: During the summer, when you are less likely to have the central heating on, setting a shorter program for hot water heating can lead to significant energy and fuel savings. Heating water twice a day (e.g. morning and evening) for a few hours should ensure there is enough hot water to last a full day [3]. Alternatively, planning ahead and switching it on manually, when hot water is required could help save more fuel. If you have a low hot water demand and the hot water cylinder is well insulated (e.g. solid foam, hot water jacket), it may allow you to just heat the water during the morning. Extra insulation helps the water to remain hot throughout the day [4].
• Warm-up Time and Cool-down Time: Depending on the property’s structure, and the weather outside, the warm-up time and cool-down time can vary significantly. The warm up time is time the property takes to warm to a comfortable room temperature (18-22^oC)) [3]. The cool-down time is the time taken for the house to cool down to a temperature that does not feel comfortable. It is usually quite quick for most modern homes but longer for older properties with solid walls [3]. Generally, it is good practice to incorporate an extra 30 minutes to 1 hour within the heating programme to ensure the house is comfortable before waking up or arriving home. Plus, to match the cool-down time, switching the boiler off 30mins – 1hr before going to bed will save extra fuel.

There is a common belief that during shorter periods of absence (e.g. 30 mins-2 hrs), more energy can be saved during the warm-up stage by keeping the unoccupied property at a warmish background temperature (i.e. more energy is saved by shortening the property’s warm-up time). However, this approach is unlikely to save enough money to make it worthwhile [3] Looking at similar scenarios that involve warm-up and cool-down periods, for example oven cooking, it is not common practice to save fuel by leaving an oven at low heat, for hours between use. So why should our approach be any different on a larger scale – in this case, our home? By following this approach and keeping heating off when the property is unoccupied for short time periods, we can save more money and fuel.

• Improving Warm-up Time: A more efficient way of shortening a property’s warm-up time is to ensure that draughts are minimised and walls, windows and loft space are properly insulated [4]. Insulated homes take less time to warm to a comfortable room temperature (18-22^oC) as they ‘trap’ heat more efficiently. For more information on home insulation, have a look at http://www.energysavingtrust.org.uk/Home-improvements-and-products/Home-insulation-glazing

2) Room Thermostat: This device constantly measures the air temperature of a room and automatically switches the boiler on and off, within a heating programme, to keep the house at a desired temperature [3]. If you have a room thermostat that is over 12 years old, it may worthwhile investing in a new one, as modern ones tend to measure air temperature more accurately [3].

• Set Temperature: Usually a room thermostat should be set between 19 and 20^oC, however this should be raised to 21-22^oC for homes with very young, elderly or vulnerable residents. Lowering the thermostat by just 1 ^oC can save around £50 per year [3].
• Operation: A thermostat helps to save on fuel consumption whilst the house heats up, because it makes the boiler cut-off before the property gets too warm [3]. As the room warms beyond the set temperature, the thermostat makes the boiler switch off. As a result, when the room starts to cool below the set temperature, the thermostat will automatically switch the boiler on again, to warm the property back up. This process continues for as long as the boiler is programmed to heat the radiators. This essentially means that even if the house is too cold, a thermostat will not operate and switch the boiler on at that time, if the boiler has not been already programmed to do so (see time switch/programmer section). Also, turning the thermostat to a higher temperature will not make the room heat up any faster [3]. This will depend on the room size, radiator size, thermostatic radiator valve (TRV) settings and the weather outside [3].
• Situation within Property: A thermostat has to be situated in a room that is representative of the whole property [3]. In most cases, this tends to be the hallway. So putting it in a cellar, sun-room or kitchen is a bad idea, as these rooms are typically colder or warmer than the rest of the house. The thermostat would measure the air temperature of these rooms and automatically assume that the rest of the property was at the same temperature too. Thus, it would regulate the boiler output according to an air temperature that is mis-epresentative of the whole property’s temperature. For example, if the thermostat is put in the kitchen or the hottest room, the boiler is likely to cut-off before the other rooms reach a comfortable temperature. In the similar way, if it is situated in the cellar or coldest room, it is likely to cut-off well after the other rooms exceed the desired comfortable temperature. So in this case, fuel savings can be achieved by identifying a more suitable room for the thermostat.
• Positioning Within a Room: Because a thermostat has to measure an accurate air temperature it has to be free from obstructions such as curtains or furniture [3]. It is better to not have a room thermostat positioned too close to existing heat sources (e.g. radiators, ovens, fires or heaters) [3]. For similar reasons as discussed above, the intense warmth from the heat source, would lead to air temperature measurements that are misrepresentative of the room and property temperature. As a result, the boiler is likely to cut-off before the other rooms reach a comfortable temperature.

3) Thermostatic Radiator Valves (TRVs): These devices are fitted to control the flow of hot water into individual radiators. They do this by sensing the surrounding air temperature and adjusting the temperature of radiator accordingly [3]. Lower settings (e.g. 1-3) help the radiator maintain a cooler temperature. Higher settings (e.g. 4 – 5) help to maintain make a warmer temperature.

• Saving Energy: Fuel can be saved if TRVs are turned to lower settings in rooms that are not used often or rooms that have other heat sources (e.g. oven, fire, sun) [3]. A system with a room thermostat but no TRVs, would rely too much on the property’s room thermostat (see section 2) to maintain the temperature of individual rooms. Some rooms need less heat than others so this may lead to energy and fuel wastage as the boiler overheats these rooms, in response to the room thermostat, usually situated elsewhere in the property. So TRVs save boiler fuel by reducing temperature in rooms that are overheated and redistributed to other rooms that need it the most [3].
• Effects on Room Thermostats: Usually a room with a room thermostat will not have a radiator fitted with a TRV [3]. However, if a TRV has been fitted to the existing radiator, it should be turned to the highest setting [3]. In a way, the thermostat and boiler uses the heat from this radiator, and its resulting room temperature, as a baseline for all whole property. Radiators in other rooms with different TRV settings produce heat relative to this ‘baseline radiator’. If this radiator is left at a lower setting, the boiler will take more time and more fuel to reach the room thermostat ‘set’ or ‘boiler cut-off’ temperature (e.g. 19-20^oC). Meanwhile, other rooms with radiators that have higher TRV settings, will warm faster than the ‘baseline room’. By the time the boiler does ‘cut-off’, these rooms may feel too warm or overheated. Therefore, energy and fuel can be saved by ensuring that the ‘baseline radiator’, with the room thermostat nearby, is turned to highest TRV setting.

4) Cylinder Thermostat: This device keeps a constant check on the temperature of water stored in your hot water tank [3]. In a similar way to a room thermostat, it switches the boiler on and off to keep the water a set temperature. It should be set to 60 ^oC [3]. This is considered to be an optimum temperature as it is both low enough to minimise energy waste but high enough to reduce significantly the risk of Legionella bacteria growth [3].

• Legionella Bacteria: Legionnaires’ disease is a relatively rare type of pneumonia [5]. The germ that causes Legionnaires’ disease is called Legionella pneumophila which can be present in natural water or manmade water supplies that rely on recirculation water systems. People catch Legionnaires’ disease by inhaling small droplets of water suspended in the air which contain Legionella bacteria [5]. To reduce the risk of an outbreak or rapid growth of this bacterium, water supplies must be kept warmer than 55 ^oC [5].

[1] http://www.bbc.co.uk/news/world-us-canada-10656239

[2] http://www.energysavingtrust.org.uk/Easy-ways-to-stop-wasting-energy/Stop-wasting-energy-and-cut-your-bills/Tips-to-help-you-stop-wasting-energy

[3]http://www.energysavingtrust.org.uk/Home-improvements-and-products/Heating-and-hot-water/Thermostats-and-heating-controls

[4]http://www.energysavingtrust.org.uk/Home-improvements-and-products/Home-insulation-glazing

[5] http://www.patient.co.uk/doctor/Legionella-and-Legionnaires’-Disease.htm