Heat pumps are becoming more mainstream in the design and construction of new homes in the UK, and more builders are including them in the specification discussions. Homeowners, however, have practical questions about comfort and the space requirements of heat pumps and how they will impact the way their home functions. This article provides a simple explanation of heat pumps.
How Heat Pumps Work
Unlike conventional heating systems, heat pumps do not burn fuel to produce heat. Instead, they move heat from one place to another and work in a similar way to a refrigerator but in reverse. An air source heat pump draws heat from the outside air and a ground source heat pump collects heat from the ground. Once the heat is collected it is then concentrated and fed into the home’s heating and hot water systems.
Because heat pumps use electricity to move heat, they can produce more heat than the energy consumed. They are one of the key innovations in the construction of lower carbon homes in the UK.
Air and Ground Source Systems
Air source heat pumps are the more common systems in the UK. The ground works for an air source heat pump are minimal, and the units are relatively small, resulting in a quicker and less invasive installation. Ground source systems require large areas of land with suitable ground conditions, which is why they are commonly seen on larger sites and new home developments.
Heating pumps
Heat pumps can provide efficient low temperature heat for well designed and built homes. They do, however, still require suitable quality of building fabric as the best insulation and airtightness of a building greatly helps heat pumps perform to their optimal ability. For these reasons, builders predominantly look first to the building fabric (walls, roof and floors) when considering heat pump installation. It’s important to include good quality windows and to detail building junctions in a way that minimises thermal bridging.
With regards to older properties, improvements to draughts, loft and window insulation can also be done along side the installation of a heat pump. A heat loss calculation can be done to accurately determine heat pump system size and not rely on guesswork.
Emitters and distribution
Heat pump systems can be run at lower flow temperatures than traditional systems. For this reason, standard radiators may be replaced or upgraded to accommodate the lower temperature flow. Under floor heating systems are a good distribution system for new and refurbished buildings to help evenly heat large surface areas.
Pipework should be assessed to see if it is of an adequate size. If it is too small, the flow will be restricted and the system performance negatively impacted. The entire system should be assessed for improvements not just the heat pump unit itself.
Storage and hot water
The majority of heat pump systems include hot water cylinders. Space for the cylinder needs to be incorporated early on, particularly in smaller homes as airing cupboards are often full. Also, heat pump cylinders are often larger than the compact tanks that have been used in some homes previously. The heat pump also heats water to a controlled temperature, and it undergoes higher temperature cycles for hygiene.
Siting and noise
Outdoor units require unrestricted airflow and need to be sensitively positioned. Builders also need to consider the route of the refrigerant or water pipe-work and how the unit will appear from the street. Modern heat pumps are fairly quiet, but if a unit is placed against a wall in a narrow passage, the sound will be amplified. Thoughtful siting is necessary.
There are differences in planning rules throughout the UK, as well as in Conservation Areas and with listed buildings. It is a good idea to check with the local authority what the rules are, before any work is begun.
Controls and living with the system
Weather compensation helps the system stay efficient and is particularly useful if the system is being run during changing outdoor temperatures. The system should also be run at lower temperatures continuously. Homes with heat pumps may require a shift in behaviour to help the system function at peak efficiency.
A clear handover by the contractors is essential. Users should understand how to operate the system, what the normal operating sounds are, and the general feel of the radiators. Many concerns with heat pump systems are due to misunderstandings that could be prevented with a clear handover.
CONSIDERATIONS FOR ELECTRICAL AND INSTALLATION
The route of the electrical cables and consumer unit position also need consideration. The electrical supply may need upgrading to meet the additional load and additional work may need to be undertaken to the electrical installations to facilitate the controls. Installers need to be properly trained and the commissioning need to include balancing and flushing the heating circuit to verify flow rates.
WORKING TOGETHER
The best outcomes happen when builders, designers, and installers work together early on. Decisions made at various stages of the project relating to the position of the cylinder and heat emitters impact other decisions. For example, if the position of the heat emitters is changed this may impact the decision of where the heat cylinder should be placed. Making each decision separately often results in rework and frustration.
PLANNING FOR THE FUTURE
As building regulations and standards evolve and more homes transition from fossil fuel boilers, working knowledge and understanding of heat pumps will increase. Treating heat pumps like a boiler swap is not the answer. This will help deliver homes that meet occupants’ needs for comfort and efficiency and are easy to use.
