Do heat pumps and radiators make good partners?

The development of lower temperature heating systems, utilising renewable heating appliances such as air source heat pumps, has given rise to a number of questions. One of these is regarding where components we have come to know and love over the years fit into future heating scenarios. In the piece below we hear from Chris Harvey, head of marketing for Stelrad Radiator Group, who explains why the company feels strongly about claims that underfloor heating is the only or ‘best solution’ for heat pump installations.

More than 90% of all heating systems in the UK currently rely on radiators to share the heat around the home. Despite the arrival of underfloor heating, there is still a marked reluctance to use it upstairs in new builds and it is a complex option to fit as a retrofit solution, so radiators tend to win out most of the time. Radiators also heat up and cool down far more quickly than underfloor heating which is also a consideration when selecting the best way to share heat around the home.

It is important to remember also that radiators are poorly named. Most radiators are actually convectors – there is a small amount of radiant heat from the radiator but more than 80% of the heat is convected heat – drawn up behind the radiator where the air passes over the metal surfaces of the radiator and heats the air in the room.

New build – getting it right from the start
The key to radiators operating effectively in any situation is to size them properly at the outset, which involves accurately working out heat loss calculations to achieve the necessary number of BTUs required to provide comfort heating in each room and to select a radiator that can provide that level of heating. In new-build housing, using a heat pump-based solution is a relatively simple approach as the heating system can be designed into the home from the outset meaning that the parameters in which it will operate are known. Knowing the method of construction, the size of the rooms, the number, type and size of doors and windows allows the heat loss calculations to be done up front and radiators sized accordingly.

Radiator evolution the key to success in existing scenarios
Replacement of heating systems in older properties presents additional issues. Simply replacing a boiler with a heat pump will usually leave the existing radiators unable to provide the levels of heat needed in the home.  So, what is the cost effective and straightforward solution? Do we need to ditch radiators altogether and look for alternatives?

The simple answer is ‘no’. Radiators will work well with heat pumps, but it is necessary to increase the size of the radiators. This provides a larger metal surface area to heat the air in the room to the level required to provide comfort heating. This need not involve unsightly radiators since, even considering that modern radiators are far more aesthetically pleasing, there have been additional developments. The extra boost radiators needed can be achieved by replacing existing single or double panel radiators with the relatively new K3 radiators. These have three panels and three sets of fins to provide the additional metal surfaces needed but without increasing the radiator footprint on the wall.

Major radiator manufacturers, such as Stelrad, have anticipated the significant move towards air source heat pumps in the UK and have added new, larger size radiators to their portfolio providing that option. They have also stepped up the options on the K3 radiator designs available too.

The huge popularity of vertical radiators also offers an additional solution. Vertical radiators clearly have a smaller horizontal footprint than a traditional radiator, but can be larger by design by taking up floor-to-ceiling space. Placing two modern vertical radiators in a room may be a more practical or desirable solution than using one large standard radiator which is often placed beneath the main window.

With this increasing demand for vertical radiators, Stelrad has added a huge number of new designs and sizes giving the much wider range required for renewable heating solutions.  Vertical radiators can become part of the décor of a room, creating focal points and fitting into nooks and crannies which traditional horizontal radiators may not.

This evolution of the humble radiator ensures they remain very much ‘fit for the future’ as part of renewable heating solutions but, as always, correct sizing is essential to ensure that they keep the home warm and cosy. Can radiators work well with air source heat pumps? It’s a very definite ‘yes they can’ – and already are in a host of installations across the UK.