• Refurbishment provides the opportunity to install a new or replace an existing heating system with a new more efficient type.
• There are a number of factors which need to be taken into consideration when choosing a new system:
Fuel type
In terms of CO2 emissions the best choice will be between gas (where available) and wood fuel. If choosing a wood-based system consideration should be given to availability of fuel supply.
Boiler size
The size of the boiler needs to be carefully calculated based on projected hot water and space heating demand – particularly where a building has undergone significant insulation and air-tightness improvements.
User needs
The pattern of use might determine the type of boiler selected. If, for example, a large family uses hot water at the same time, a system including hot water storage would be preferable on the other hand, a combination boiler is likely to be perfectly adequate for a small flat; Another consideration might be a boiler’s capacity to heat a space in reasonable time.
Space
The amount of available space can also determine the boiler type. Where space is at a premium, or if locating a feed tank and its associate pipework in a loft is undesirable, then a form of combination boiler is possible choice whereas if hot water storage is important for example if the system is to be integrated with solar heating or a heat pump, then a system that includes a storage system will likely be preferred.
Renewables
The inclusion of renewable sources of heating energy, particularly solar thermal, should be a consideration. The selection of a gas heating system will be determined in large part depending on whether ancillary sources of heating are to be accommodated.
NB
• The heating system examples illustrated below are for general guidance only. When specifying, confirm with the product manufacturer their installation methods and expected performance. For more detailed information, consult a heating engineer
Boiler types
• Boiler technology is in a state of technological development. This is particularly true in the case of developing systems that produce both heat and power (CHP). However, though it is important to understand the potential of these developments, the system specifier is currently much more likely to consider the selection of a more tried and tested traditional system.
• Choosing between a regular or combi/CPSU boiler depends on the heating and hot-water requirements of the household and the positions in which the boiler can be located. This must take into account requirements for flueing and ventilation. If the water pressure and pipe size are adequate, avoid using the cold loft space for water tanks and pipes, due to the risk of freezing. If this cannot be avoided, ensure that pipes are adequately insulated.
• If ‘renewable’ hot water provision (eg solar hot water or heat pump) is to be included, the choice of a normal combination boiler is precluded because the water source is from the mains. This can be overcome by the addition of a ‘thermal store’ that will provide pre-heated water to the combination boiler at mains pressure. With this combination of storage and boiler, it is essential to ensure that boiler and storage are compatible. Typically, the boiler will be of a ‘modulating’ type that is able to monitor the water temperature in the boiler and to adapt the flame with the solar water heating system demands
‘Regular’ or ‘Heat only’ boiler
• A regular boiler is one which provides space heating directly, but stores hot water in a separate storage system.
• Along with the boiler unit, it requires a feed tank, an expansion cistern, controls and a hot water cylinder.
• Regular boilers are more efficient than ‘Combi’ boilers, but require more space.
Application
• Suitable for larger homes, where there may be demands for hot water simultaneously.
• Where ample space is available for installation. (eg loft space)
