The last few years has seen increased demand for heat pump installations in both new build developments and retrofit projects. However, while the end goal is the same, the approach to installation varies significantly, explains Gary Muir, Regional Specification Manager at Grant UK.
While heat pumps offer a highly efficient and sustainable way to heat homes, their successful integration requires a different approach to heating system design and installation compared to traditional fossil fuel systems. Understanding the differences between new build and retrofit heat pump installations is key to ensuring that properties are future-proofed for both performance and homeowner satisfaction.
New builds
One of the greatest advantages of installing heat pumps in new build developments is the ability to plan and design the entire heating system from the outset. Heat loss calculations can be accurately performed at the design stage, allowing developers to specify the correct heat pump output, heating distribution system and heat emitters, such as underfloor heating or radiators. With this level of planning, new build developments can ensure that heating systems are perfectly matched to the property’s requirements, avoiding common pitfalls such as oversizing or undersizing the heat pump.
Building regulations already require new homes to meet stringent insulation and airtightness standards, making them well-suited to heat pump technology. However, careful system design is still essential. Even in a highly insulated property, a heat pump that is oversized will short-cycle, reducing efficiency and increasing wear. Conversely, an undersized unit may struggle to meet heating and hot water demand during colder months. In large-scale developments, ensuring each plot or house style is assessed individually for heat loss and system specification rather than adopting a one-size-fits-all approach, can help prevent these issues.
Heat pumps operate differently from traditional boilers, particularly when it comes to domestic hot water production. Unlike a gas combi boiler, which provides high-temperature water almost instantly, a heat pump system requires a separate, appropriately sized hot water cylinder which must be accommodated within the property, such as inside an airing cupboard. It is also important to understand that heat pumps cannot fulfil space heating and hot water demand at the same time. Instead, when a demand for hot water is called for, the heat pump will divert its operation (from space heating) to meet the hot water demand and then revert back to space heating once the hot water demand is fulfilled. The controls that are fitted with a heat pump, therefore become crucial when it comes to the correct operation of the system, with developers and their installers using appropriate setback control settings to help the heat pump achieve the space heating and hot water requirements effectively and efficiently.
For housebuilders, there is also the question of timing. In many developments, heating systems are installed months before the homeowners move in, meaning that an important final step, homeowner education, can sometimes be overlooked. Heat pumps require different operational habits than traditional gas boilers and educating buyers on how to use their system effectively is crucial for efficiency and satisfaction.
A customer handover is crucial when homeowners first move in and this can be achieved by providing clear documentation, offering demonstration sessions and ensuring that customer service teams are equipped to answer questions that will help to bridge this knowledge gap. Developers should also work with their installers to ensure that heat pumps are fully commissioned and set up before handover, avoiding issues when homeowners first move in.
Retrofitting
While heat pumps are becoming an essential part of the new build sector, they are also seeing increasing uptake in retrofit projects. Retrofitting a heat pump into an older home presents a different set of challenges compared to a new build. Existing homes may have been designed around high-temperature heating systems, with smaller radiators and pipework that may not be optimised for heat pump operation. In many cases, modifications are needed to ensure that a heat pump can work efficiently and these can range from relatively simple upgrades such as swapping out radiators for larger, low-temperature models, to more extensive work, such as improving insulation and airtightness.
Before specifying a heat pump in a retrofit scenario, an in-depth assessment of the property is essential. Older buildings may have higher levels of heat loss due to poor insulation, single glazing and less efficient building materials. Without sufficient insulation, a heat pump system may struggle to maintain comfortable temperatures without running at higher costs. For homes with high heat losses, where possible, energy efficiency improvements such as cavity wall insulation, loft insulation and window upgrades should be carried out either before or alongside the heat pump installation.
Unlike a gas boiler, which can be installed in almost any location inside a property, an air source heat pump requires sufficient flow of outdoor air to operate. Retrofitting in a built-up area or a home with limited outdoor space can present challenges in terms of placement but there are solutions from specifying small, compact sized heat pumps through to wall-mounted installation options. Either way, it is imperative that the unit has adequate airflow while remaining compliant with planning and noise regulations. Developers or housing associations working on retrofit projects must consider therefore available external space, proximity to windows and neighbouring properties, and any planning restrictions that may affect installation.
Another key consideration is the heating distribution system within the home. Standard radiators in older properties may not provide sufficient heat output at lower temperatures, meaning they need to be replaced with larger radiators, fan-assisted units or underfloor heating to ensure effective space heating. Upgrading pipework and ensuring that the system has been correctly balanced is also crucial for long-term efficiency and performance.
For those working on large-scale retrofit projects, ensuring that installers are fully trained in heat pump system design and installation is critical to project success. Many gas engineers are now transitioning to heat pump installation but there is a steep learning curve. Heat pump systems require knowledge of the refrigeration cycle, system controls and hydronic design. Choosing experienced and certified installers, working with manufacturers for technical support and investing in training for in-house teams can help ensure that installations are carried out correctly and efficiently.
Whether in a new build development or a retrofit project, there are common mistakes that developers should be aware of. Skipping a room by room heat loss calculation can result in an incorrectly sized system leading to inefficiencies and higher running costs. Failing to check insulation levels in retrofit properties can leave homeowners with higher bills and lower comfort levels. In both cases, incorrect system commissioning, including failure to ensure the correct flow rates, refrigerant pressures and control settings, can compromise performance. Addressing these potential issues during the planning stage will help to avoid costly remedial work and dissatisfied homeowners.
The UK government has committed to expanding heat pump adoption, with growing incentives and regulations set to increase demand in both the new build and retrofit sectors. For housebuilders and developers, the shift away from gas boilers represents both a challenge and an opportunity. Those who embrace heat pump technology and invest in well-designed, properly installed systems will not only future-proof their developments but also deliver homes that meet the expectations of a more energy-conscious market. As the housing industry moves towards a low-carbon future, understanding the key differences between new build and retrofit heat pump installations will be crucial to delivering high-quality, sustainable homes.
For more details about how Grant UK can help support heat pump installations visit www.grantuk.com