Heat pumps#
Heat pumps can take heat from the ground or the air and heat your building by using the same kind of technology as refrigerators, but in reverse. Ground source heat pumps always heat water and use that to heat the building. Air source heat pumps can heat water, but they can also heat the air in the building directly. Because they produce a lower temperature than a boiler, they are usually run for long periods. That means they suit buildings in high occupancy, although long slow heating is also good for using stone as a store of heat, and, for instance, the Church of England has case studies showing a heat pump used for a church in less frequent use.
The upfront costs of installing a heat pump are relatively high but if you can raise them, the running costs make it worth it. At their best, they are 3.5 times as effficient as using electricity directly to heat the building. The UK Government aspires to help industry make heat pumps cost the same as boilers by 2030. There are generous grants available to those who want to install them now.
Unlike public perceptions, heat pumps do work even in Scotland but they have to be designed for the building and installed and configured correctly. Some of the companies offering heat pumps are poorly trained. At a minimum, you want to be dealing with people who are MCS accredited, and even better if they have some experience in your type of building with clients who can vouch for them.
How easy it is to put a heat pump in depends on the building. Ground source heat pumps are relatively expensive and require a reasonable amount of space to install - either several hundred square meters of land or the right underlying geology and access for drilling equipment that can lay pipes vertically. Air source heat pumps (ASHP) designed for commercial premises can also be very expensive. That means community buildings often need to install 2 or 3 domestic models, each about the size of a large suitcase, or to combine an ASHP with another source of heating, either temporarily or permanently. This is not practical in some buildings and can be inconvenient, although it does at least mean that if one breaks down there’s still some heat.
For pumps that heat water, if your radiators are big enough, you might be able to get away with using them, but often venues need bigger ones. Even if your radiators will work, your pipework might be too narrow to deliver the water fast enough. Changing to underfloor heating gives better results and better comfort for lower energy input, especially for lossy buildings in high use. Everyone likes warm feet!
Remember that addressing heat loss always comes first because then you can get away with a smaller heat pump, and that you can stage works, for instance, putting a small heat pump that only does part of the job until you get the heat loss sorted, putting in underfloor heat distribution and insulation when the floors need renewing anyway and the heat pump later, and so on. This kind of change takes careful planning but it’s worth it in the long run.
More information
The air to air case studies uses relatively large pumps to heat the air just enough to make people comfortable for an hour of use, contrary to our recommendation to move to radiant heating or heated seating instead, perhaps with a small heat pump on low to keep the building at a reasonable setback temperature. As a community we need a better understanding of how to model buildings to know when this is a reasonable approach to take.