top of page
  • Mihai

Exploring House Retrofit Heating Systems: A Closer Look at Heat Pumps

As we navigate towards more sustainable living, retrofitting our homes with efficient heating systems is a topic gaining traction. In this post, we're delving into the nuances of various heating systems, particularly focusing on heat pumps and their feasibility in retrofit scenarios.

Ground Source Heat Pumps in House Retrofitting

Ground source heat pumps, while efficient, come with a hefty installation tag. They require a considerable space, often needing a soundproofed area for installation.

When planning to install a ground source heat pump, it's important to carefully consider the location and type of loop system. The most economical option usually involves a ground loop, which requires digging shallow trenches and installing either straight or 'slinky' pipes at a depth of 1.5 to 2 meters. This method needs space around the building for the loop. If space is limited, an alternative is to drill boreholes, which go down to about 150 meters, with the loop inserted into these holes. Although installing boreholes is more costly, they offer a more consistent temperature due to their greater depth compared to the ground loop approach.

These heat pumps are most efficient when paired with an underfloor heating system. However, retrofitting underfloor heating can be a complex and costly process. This is particularly challenging in homes with suspended floors, where converting to a solid floor is necessary. For more insights on suspended timber floor insulation, check out our detailed post here.

Biomass Boiler: The Burden of Logistics

While biomass boilers present an alternative, they are often dismissed due to the logistical challenges they pose. The need for constant sourcing and storage of wood pellets, along with additional space requirements, makes them less desirable for many homeowners.

Air Source Heat Pumps (ASHP)

Compared to ground-source heat pumps, air-source heat pumps are more commonly used. While they function similarly, they extract heat from the outside air instead of the ground and are generally more affordable.

There are two main types of air-source heat pumps. Air-to-air systems generate warm air to heat a building, while air-to-water systems heat water for use in space heating and domestic hot water systems.

Although they operate on a similar principle, an ASHP typically has a lower Coefficient of Performance (COP) than a ground source heat pump, especially during winter when heating demand is highest. This is because winter air temperatures are much lower than ground temperatures, which remain relatively stable throughout the year (usually between 8 – 12°C). The significant difference between the source (air) temperature and the desired output temperature during winter means the pump's efficiency is greatly reduced.

Retrofitting Heat Pumps: A Viable Option?

Heat pumps have been a part of the home heating landscape for many years, with the inception of the first ground source heat pump dating back to the late 1940s. Despite their historical presence, the market for home heating has been largely dominated by gas boilers.

Nevertheless, installing heat pumps is a viable option for almost any home, provided certain key conditions are met. Among the most critical is the home's insulation quality (with an HLI of less than 2), as effective insulation is essential for the efficient functioning of heat pumps. On the other hand, poorly insulated homes might necessitate larger pumps, which can lead to higher installation and operational costs. In such scenarios, opting for a heat pump may not be the most advantageous choice.

Underfloor Heating and Radiators

Choosing between radiators and underfloor heating in a refurbished, well-insulated house depends on several factors. Radiators, being simpler and more cost-effective, suit houses with intermittent occupancy due to their quick response. However, they operate at higher temperatures, limiting integration with low-temperature heating sources. Underfloor heating, though more expensive and complex to install, offers better quality heating and compatibility with low-temperature heat sources like solar thermal systems. It's ideal for continuously occupied spaces but less responsive. Combining both systems can be effective, in accommodating different heating needs in living and sleeping areas. A common solution in heating system design is to use a hybrid approach, installing radiators in the upper levels of a house and underfloor heating on the ground floor. This strategy effectively balances the different heating needs and characteristics of living and sleeping spaces. Selection criteria include cost, speed of implementation, heating patterns, and comfort levels.

Can You Pair a Heat Pump with Your Existing Boiler?

Yes, you can. This combination can be especially useful in extreme cold, where a heat pump might not suffice alone.

Heat Pump Sizing Matters

Proper sizing of your heat pump is crucial. Factors like your local area's lowest winter temperature play a role in determining the right size. A professional heating engineer can provide valuable insights tailored to your home and requirements.

Important Considerations

- Adaptability: Retrofitting a heat pump in an existing system can be a smart move. However, it's important to note that radiators might need to be larger due to the lower temperature output of heat pumps compared to traditional heating systems.

- Hot Water Integration: Heat pumps can also heat your water, allowing continued use of your existing hot water tank, albeit with some potential adjustments for compatibility.

Retrofitting Challenges

- Type Selection: The choice between ground and air source heat pumps can significantly affect the installation process. Ground source pumps are more challenging to install, requiring extensive space for horizontal pipes or deep vertical holes for small gardens.

- Location Constraints: For air source heat pumps, selecting an accessible outdoor location is crucial for maintenance and efficiency.


Heat pumps offer a sustainable and efficient heating solution, but they require careful consideration of your home's specific needs and conditions. If you're contemplating a heat pump retrofit and need professional advice, consulting with a qualified heating engineer is essential. They can guide you through the necessary home upgrades, such as improving insulation or adjusting your existing heating system, to ensure your home is ready for a heat pump.

For expert advice on retrofitting heating systems and more tailored guidance, contact MTS DNC ENERGY CONSULTANTS LIMITED.

Disclaimer: The information provided here about heat pump design is for general informational purposes only. It is not intended as a comprehensive installation guide or design specification. Each home is unique, and insulation requirements can vary greatly depending on specific conditions and local building codes.

For accurate and detailed guidance tailored to your specific situation, it is essential to consult with a qualified professional. They can provide a thorough assessment and ensure that any insulation work is carried out safely, effectively, and in compliance with all relevant regulations and standards. Additionally, always adhere to local building codes and regulations, and consider the environmental impact and long-term sustainability of the materials and methods chosen for insulation.

7 views0 comments


Post: Blog2 Post
bottom of page