What types of gas and oil boilers are available, and what should you consider when buying a boiler?

For 23 million homes across the country, a boiler remains the most popular way of achieving a heating and hot water system. Whether gas, oil or LPG, there is plenty that can be done to make your renovation or build as energy efficient as possible.

Certainly the savings from installing the latest boiler technology soon add up, particularly if your project features an existing model that has seen better days. There is also the bonus of being able to add solar thermal panels to take advantage of even greater benefits.

For those working on an older property, having a new high-efficiency boiler installed is also one of the quickest ways to improve the energy rating of your home — fitting a condensing boiler could see your home jump one clear band on your EPC (energy performance certificate). The only other single measure that achieves this jump is installing cavity wall insulation.

One point worth remembering is that you do not have to replace like-for-like. Replacing a dated model is an ideal opportunity to get the boiler off the floor to free up some space for more cupboards or worktops.

The size of your property and your household’s requirements for heating and hot water will determine which boiler is best for your home and lifestyle. In line with Building Regulations, all boilers have to be condensing and there are three main types – ‘combi’, system and regular – which are each suitable for different types of homes:

  • Combination or ‘combi’ boilers do not store water, they heat it straight from the mains on demand. This means you don’t need a hot water cylinder or a cold water tank in the loft. Another benefit is that they provide instant hot water. Combi boilers (dependent on the model) are ideal if you have up to two bathrooms and if you have limited space within your property. Three in four boilers installed today are combi boilers, and if your home has one to two bathrooms and you have a good water mains pressure, I would recommend a combi boiler.
  • Unlike combi boilers, regular boilers (also known as heat-only boilers) work on the principle of stored water and require a separate hot water cylinder, which in turn determines how many bathrooms can be supplied. Regular boiler systems require more space than either a combi or system boiler as they often need an expansion tank in the loft. This type of boiler is suitable for homes with more than two bathrooms and where hot water usage is high but where water pressure is low.
  • In a similar way to regular boilers, system boilers also use stored water, which allows several hot water taps to be fed at the same time, making them ideal for larger homes. In contrast to regular boilers, however, system boilers have some of the major components of the heating and hot water system built in, making them more efficient, and less space-consuming as there’s no need for a feed or expansion vessel in the loft. They are connected to either a mains pressure hot water storage cylinder or a more traditional low-pressure, tank-fed cylinder.

What about external oil boilers? What is their benefit?

The major benefit is the space-saving aspect. They were originally designed for properties that were previously heated by a coal-fired central heating system, with the coal fire and back boiler sited in the fireplace within the living room.

Houses with this type of heating system tend not to be large, so to replace this very manual heating system with an automatic one wasn’t always possible as there was nowhere in the house to site a freestanding boiler. Nowadays, they prove equally ideal where you want to free up space — in the kitchen, for instance.

I’m building a new home and considering renewables, although, due to cost, I may instead look to adding them in the future. As such, what do I need to consider when choosing a boiler now?

You certainly don’t need to do this all at once, but there are points to consider as early as possible. For instance, if you are thinking of installing solar thermal panels at a later date then it is worth opting for a twin-coil hot water cylinder that will be compatible with the panels further down the line.

Similarly, a boiler provides a high-temperature energy source, but an air-source heat pump runs with a much lower temperature level, so your radiators will need to be sized to be able to cope with the change in the levels should you decide to opt for this in the future.

Air-to-air-source heat pumps should not be forgotten here. They run independently so are ideal should you decide to extend or convert a loft or garage at a later date without wanting to disturb your existing boiler system. The right level of insulation is also key to making all of this technology work at its best.

However, if you are building a new home and budget allows, it makes sense to dismiss boilers altogether and install a renewable heating source such as a ground- or air-source heat pump instead.

It is also worth considering installing low-temperature heat emitters while you are still at a planning stage to increase efficiency further. I would strongly recommend underfloor heating is used wherever possible, as this will be compatible with either a renewable energy source or, if you choose to go down the boiler route, a gas or oil-fired condensing boiler. It is also important that your chosen boiler will be able to accept preheated water.

Does the efficiency of a boiler degrade over time?

If it does, it is very minor, and regular servicing will help keep the boiler operating efficiency at its optimum. What generally happens with boilers is that they tend to last so long – typically 12 to 15 years – that by the time they need replacing, technology has moved on and become much more efficient.

It’s worth noting that when it comes to getting the best efficiency, latest technology, research, development and, importantly, reliability, paying more for your boiler upfront can often pay dividends long-term.

Does the humble boiler have a future in the British home?

I think the future for boilers is rather like car technology; they will get more efficient and greener in emissions. We will see the introduction of new technologies such as gas-absorption heat pumps that can generate heat at efficiencies of around 150 per cent.

Presently this technology is too physically big for wholesale adoption in UK homes, however it will reduce in size as new components and applications are developed. We will also see a wider take up of fuel-cell technology, again physically too big at the moment, but very exciting as it is a boiler that generates electricity as it operates.

Essentially I think the future for boilers is still to be connected to mains gas, but they’ll be working in partnership with a heat pump or solar, or both. Already growing in popularity are Worcester Bosch Group’s new Split and Hybrid air-source heat pumps, which combine a boiler with a heat pump.

With the Split system there are two options: the Hydrolight or Hydrocomfort.

The Hydrolight connects the externally sited heat pump to an oil or gas-fired boiler, therefore providing heat pump-generated heating and hot water in the spring and autumn, and boiler-generated heating and hot water in the colder winter months. This ensures that the heat pump operation only takes place when the air temperature is not exceptionally cold and the heat pump’s COP (coefficient of performance) is kept high.

The Hydrocomfort, on the other hand, connects the externally sited heat pump to the heating and hot water system and houses a 9kW immersion heater as a back-up during sub-zero temperatures.

The Greenstar Plus Hybrid system combines the advantages of an external heat pump and indoor intelligent Hybrid manager that works alongside selected Greenstar boilers, to provide a smart system for homeowners keen to cut heating costs and CO? emissions. You simply have to input current fuel tariffs into the control unit and the system calculates the optimum fuel efficiency and then automatically selects the most effective energy source depending on the outside temperature and the current tariffs. So the boiler will not fire up if the control system decides it is more energy and CO? efficient to operate the heat pump instead.

Heating controls is another area which is going from strength to strength.

About the Expert:

Martyn Bridges is director of technical support at Worcester Bosch Group.

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