In general, the boiler efficiency is determined by measuring how well an appliance turns fuel into useful heat. Boilers are rated on the SEDBUK 2005 or the updated, SEBBUK 2009 rating systems (Table 1) [2]. If your boiler is more than 15 years old, it is likely to be SEDBUK G-rated [1]. By replacing an old G-rated boiler with new condensing one that is A-rated, you can save potentially 25-30 % on your fuel bills and up to 1,2000 kg of CO₂ emissions [1].

Table 1. SEDBUK 2005 and SEDBUK 2009 rating systems [2]. Under the newer 2009 system a SEDBUK 2005 90% efficient A-rated boiler is regarded as 88% efficient. The 2% difference between SEDBUK 2005 and 2009 is mainly down to differences in efficiencies between using a boiler for space heating in the winter months and only using it for water heating in the summer months.

1. What kind of boiler do you have?

The main difference between a non-condensing boiler and a condensing one is the type of flue [1]. A flue is a pipe that sticks outside the external wall adjacent to the boiler. It allows boiler exhaust gases like carbon dioxide and water vapour to escape from the property.

If your boiler has a plastic flue pipe, which emits visible steam (i.e. water vapour) then it is a condensing boiler. Alternatively, an older non-condensing boiler will have a metal flue instead of a plastic one because the exhaust gases are hotter– hot enough to melt plastic [1].

“Back” boilers situated behind main fireplaces are usually old enough (+20 years) to be non-condensing and inefficient. These types of boilers are usually decommissioned or bypassed if a new condensing boiler is installed [3]. So in this case, another suitable space (e.g. ventilated cupboard) would be identified for the system, before installation.

If you are interested to know your boiler’s efficiency and SEDBUK rating have a look at the national boiler efficiency database at www.sedbuk.com. Use Table 2 to see how much you could potentially save off your fuel bills!

Table 2. Approximate fuel cost savings for replacing current boiler with SEDBUK (2005) A-rated boiler (88 % heating efficiency with regards to the updated SEDBUK 2009 rating system). Calculated by subtracting boiler efficiency for each SEDBUK rating (B-G) from SEDBUK A-rated boiler efficiency (88%) [2].

2. Why change to a condensing boiler?

Condensing boilers are more efficient than non-condensing boilers because they have a ‘condensing’ mode that kicks in at regular intervals during their operation [1]. During this operation mode, they extract heat from the exhaust gases (i.e. products of combustion including water vapour), which turns steam back into liquid water. This is achieved through an additional ‘heat exchanger’ (i.e. a good heat conductor with a large surface area) which works by transferring heat from one substance to another without them making contact. As water vapour cools and condenses to form water droplets, the boiler will utilise this extra ‘latent’ heat to warm pipes and radiators [1]. As a result the ‘condensing’ mode increases boiler efficiency by up to 12 %, compared to a non-condensing boiler.

3. Types of Condensing Boiler and Suitability

If you decide to replace your boiler, the type of condensing boiler you choose to have installed will depend on its suitability for the property and your lifestyle or needs. A qualified installer should be able to provide advice on the cheapest, most efficient option however a few guidelines are outlined below.

There are two types of condensing boiler:

• ‘System’ or ‘Open Vent’ [1]: This is a more common/standard heating system that is programmed to heat and store hot water within a separate hot water tank, for later use. Therefore, a large amount of hot water can be made available to multiple taps at any one time. However, not all properties are compatible with this type of system as they may lack space for a hot water cylinder (e.g. ground floor flats). Also, to avoid wasting energy and money, it requires more consideration for your lifestyle and habits, as water has to be heated in advance, using a time programmer.
• Combination or ‘Combi’ [1]’: This type of system provides instant hot water without the need for a hot water cylinder, or hot water programme timer. When a tap is turned on, the boiler ignites and allows mains water to be heated as it flows through a tray situated above a heat exchanger. As a result, they may be a slight delay before hot water flows through the tap because it is being heated on demand within the boiler. To allow more efficient operation, the pressure gauge displayed on the ‘combi’ boiler should read between 0 and 1 Bar [3].

The main benefits of using a ‘combi’ are that it increases hot water efficiency and saves space within the home. By heating water on demand, it reduces the amount of fuel needed for hot water heating and reduces the space needed for the system. So it is ideal if you don’t need a lot of hot water each day (e.g. occasional washing up and showering as it takes longer to run a bath) or you want to save money and space. However, potential problems could arise if more than one tap in the house is being used at the same time, as the water pressure will drop significantly. Therefore, combi boilers are not recommended if the property has a low mains pressure or multiple baths or showers (that are not electric).

4. Biomass Boilers

A stove burning logs or pellets can heat a single room or it can be fitted with a back boiler to provide space heating to radiators or just hot water heating. A more expensive, larger scale alternative is a Biomass boiler central heating system that burns pellets, logs or chips. Most pellet and chip biomass boilers have automatic fuel feeders which refill them at regular intervals from fuel storage units called hoppers [4]. Log burning boilers and stoves are fed by hand [4].

Factors to consider before deciding to switch to biomass fuel [4] are:

• Space: These boilers need a large, dry area close to the boiler site for wood storage. Wood pellets have to be stored in purpose built silos.
• Flue: Biomass boilers and stoves need a vent which is specifically designed for proper operation. Most existing chimneys can be fitted with a lined flue, which is relatively inexpensive.
• Smokeless Zones: You will need to check if your property is within a smokeless zone (See http://www.uksmokecontrolareas.co.uk/locations.php). Wood can only be burned within exempted appliances.
• Planning Permission: You need to talk to your local authority if your flue will extend 1m or more above the height of your roof. If the property is in a Conservation Area or World Heritage Site, you need to speak to the local authority if you plan to install a flue on the principal elevation visible from a road.

5. Types of Boiler Fuel and Suitability

Selecting the fuel best suited for heating your property depends on many factors which include:

• Fuel cost and availability
• Efficiency of system used to convert that fuel to heat
• Environmental impacts associated with the heating fuel

In general, natural gas is the cheapest and ‘cleanest’ of the common fossil fuels, including oil and LPG (Table 3). However, all fossil fuels have a greater impact on the environment than wood logs or pellets, which are considered to be carbon ‘neutral’. This means that the higher CO₂ emissions (Table 3) emitted from wood fuel boilers are ‘balanced’ or ‘zeroed’ out by tree/plant intake of CO₂ from air during photosynthesis [4]. However, the emissions associated with wood fuel transport to the property have to be negligible for this to be true (i.e. fuel has to be sourced locally). Wood fuel is generally more expensive than natural gas due to economic ‘supply and demand’ factors, however, if bought in bulk loads (e.g. per tonne) it can significantly reduce your potential costs [4].

Heating system efficiency varies depending on fuel type. Typically natural gas and oil condensing boilers are very efficient, reaching efficiencies over 90 %. However, wood pellet systems can also reach similar fuel efficiencies (85-90 %) and have the added advantage of being carbon neutral [5].

Table 3: Cost and CO₂ emissions per unit energy (kWh) for each fuel type [5,6, 7]

Sources:

[1] http://www.energysavingtrust.org.uk/Home-improvements-and-products/Heating-and-hot-water#Whatsortofboilerdoyouhave?

[2] http://www.sedbuk.com

[3] Energy in the Home, J Green and W Innes, NEA, 7^th edition, 2008

[4] http://www.energysavingtrust.org.uk/Generate-your-own-energy/Wood-fuelled-heating

[5] http://www.waterprofessionals.com/pdfs/fuel_energy.pdf

[6] http://www.engineeringtoolbox.com/co2-emission-fuels-d_1085.html

[7] http://www.forestfuels.co.uk/about-us.php

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

Carbon Trust Reduction Label is a public display of the carbon footprint (or embodied carbon) of a product or service from source to store and product disposal. The product also asserts a commitment on the part of the producer to a ‘reduce or lose’ policy whereby if they fail to reduce the carbon footprint of the product over a two year period they will have the label withdrawn by the Carbon Trust (carbon-label.com). The scheme is not limited only to on-pack labelling; it could be on websites, catalogues, mail packs, product manuals etc. This gives the retailer or manufacturer the flexibility in their method of communication.

The strategy was launched and is verified by the Carbon Trust. Unlike the voluntary offset market there is a standard certification process. For a product to be certified the first step is to develop a carbon footprint of the entire production process. Following this the Carbon Label Company (CLC) or a consultant can then certify the product for compliance according to set standards.

How Labelling works

So how will a sticker on the pack of a product help reduce carbon emissions in the atmosphere? The flow chart below shows how carbon labelling is expected to lead to carbon reduction.

As can be seen from the flow chart there are two forces at work, the policy commitment and the change of consumer behaviour. Through labelling, these two elements will come into play and force down emissions.

Two forces at work

The ‘reduce or lose’ policy will be effective in cutting down emissions. When a retailer commits to the policy, he is saying that in the next two years the amount of carbon emitted throughout the life-cycle of the product will decrease. Before a particular product is certified the carbon emissions at every step of the supply chain is measured. This information is a valuable tool that can then be used to know areas of highest reduction. Moreover, since carbon reduction is strongly linked to energy savings which is inextricably linked to cost savings, organisations will have an added incentive to reduce. Therefore this aspect of carbon reduction labelling leads to reductions directly.

However the second force at work, market behaviour, does not reduce CO2 directly. In fact it is a long winded way to arrive at a relatively simple destination. The CLC believes that carbon labelling empowers the consumer to choose those products that have smaller carbon footprints and therefore contribute less to climate change.

Potential limitations

Although the process is rigorous and more reliable than carbon offsetting (where no verification process or body exists) it is not without its limitations.

First, there is yet no universally acceptable way of calculating life-cycle carbon. Although Carbon Trust published a methodology for assessing a product’s carbon footprint, it did not give any guidelines officially on how to measure a company’s entire supply-chain carbon impacts. Businesses use different methodologies therefore it undermines the credibility of the concept. For example HSBC, the self-acclaimed world’s first carbon neutral bank, excludes impacts from its supply chain and project financing. Conversely Vodafone has extended its analysis to consider emissions from customers as well as supply chain [1]. Due to the differing methods there is no way firms can benchmark their carbon impact e.g. whether the carbon emitted during the use of the product count. This is equivocal on the Carbon Label Company’s website [2].

Secondly, customers do not understand the scheme. One of the most important phrases, ‘embodied carbon’ is still a mystery to consumers. Also when a product is labelled, say ‘CO2-100g’, it does not help the buyer know whether it’s good or bad. Labelling is supposed to be a public declaration, but it will not be effective if the public does not understand the declaration no matter how much work has been done behind the scenes to come up with the figure. The lack of clarity with regards to the meaning of the figures works against the purpose of the scheme itself. For example about 90% of the emission associated with potatoes occurs during cooking. The label does not explain that therefore consumers will continue to use the same inefficient cooking methods and nothing is achieved.

The success of labelling depends largely on change of market behaviour. Much money is required to raise customer awareness over a period of time (say 3-5 years). Perhaps choice editing may be a more effective approach. If a customer who was concerned about the environment went to buy a certain product and was told by the staff that they no longer sold that product because its carbon footprint was too high, I doubt that the customer will be enraged. B&Q’s decision to stop selling patio heaters [3] in 2008 is a good example of a company taking decisive action against climate change. I don’t know of any environment supporter who was angered by their decision.

[1] http://www.endsreport.com/index.cfm?action=report.article&articleID=17155

[2] Some parts of the Carbon Label website include the carbon emitted during use of the product e.g. http://www.carbon-label.com/business/faqs.htm#answer (retrieved 23rd May) while according to this definition emission use is not included.

[3] http://www.guardian.co.uk/environment/2008/jan/22/carbonemissions.climatechange (retrieved 26May)