Opening Introduction

Air to Water Heat Pump Retrofit for an Existing UK House with Underfloor Heating and Fan Coil Cooling

Retrofitting an older house with modern heating and cooling technology presents unique challenges. This UK residential renovation demonstrates how an air to water heat pump, low-profile underfloor heating, and hydronic fan coil units were integrated into an existing property to provide year-round indoor comfort.

The system was designed to use underfloor heating for winter warmth and fan coil units for summer cooling. By combining both terminal systems with an air to water heat pump, the property was upgraded with a flexible hydronic solution suitable for residential renovation.

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Project Information

Item Details

Project Type Residential retrofit

Location United Kingdom

Building Type Existing house

System Air to water heat pump

Heating Terminal Underfloor heating

Cooling Terminal Hydronic fan coil units

Application Space heating + cooling

Control Multi-zone hydronic control

Floor System Retrofit low-profile underfloor heating

Project Background

Many existing homes were not originally designed for modern hydronic heating and cooling systems. During renovation, the available floor height, existing walls, bathrooms, corridors, and pipe routes all need to be considered carefully.

For this project, underfloor heating was selected for winter heating because it provides gentle radiant heat from the floor surface. Fan coil units were added to provide active cooling during warmer months.

The upgrade was designed around low-temperature hydronic heating, which is well matched with air to water heat pump systems. Instead of treating heating and cooling as two separate systems, this project used one integrated water-based solution for improved comfort and flexibility.

Retrofit Challenges

Unlike a new-build property, a retrofit project must adapt to the existing structure. The installation team needed to plan the pipe layout around room divisions, doorways, bathroom fixtures, and available service routes.

The project required careful attention to:

Existing floor preparation

Low-profile underfloor heating panel installation

Pipe routing through rooms and corridors

Bathroom pipe layout around fixed fixtures

Manifold connection and zone balancing

Indoor fan coil unit installation for summer cooling

Future access for maintenance and system adjustment

The upgrade was designed around energy-efficient low-temperature hydronic heating, which is well matched with air to water heat pump systems. Instead of treating heating and cooling as two separate systems, this project used one integrated water-based solution to improve indoor comfort, operational flexibility, and overall system efficiency.

Retrofit projects often involve more labour than standard heating replacement. To explain this in more detail, link here:https://www.nordthermglobal.com/blog/why-is-air-to-water-heat-pump-installation-so-expensive

System Design: Underfloor Heating + Fan Coil Cooling

The heating side of the system uses underfloor heating pipes installed across different areas of the house. Warm water from the air to water heat pump circulates through the pipework, allowing heat to rise gently from the floor surface and creating an even indoor temperature.

The cooling side uses hydronic fan coil units. While underfloor heating is ideal for comfortable winter heating, fan coil units are better suited for active cooling because they distribute cooled air throughout the room more quickly.

By combining radiant floor heating and hydronic fan coils, the system provides both thermal comfort and seasonal flexibility from a single hydronic heat source.

This combination gives the property two functions from one integrated system:

* Underfloor heating for winter comfort

* Fan coil cooling for summer temperature control

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Installation Process

1. Existing Floor Preparation

Because the property was being renovated, the existing floor areas were prepared for retrofit underfloor heating. Low-profile panels were installed to hold the heating pipes in place while helping reduce the impact on floor height.

This step is important in older homes where the system must fit within the limits of the existing structure.

2. Underfloor Heating Pipe Layout

The underfloor heating pipes were arranged across the room to provide consistent floor coverage. A clear pipe layout helps improve heat distribution and makes the system easier to connect back to the manifold.

In retrofit projects, the pipe spacing and routing need to follow both the heating demand and the physical layout of the property.

3. Corridor Pipe Routing

The hallway acted as a key connection area between different rooms. Multiple pipe circuits were routed through this space, requiring careful planning to keep the installation organized.

This type of detail is common in existing homes, where installers need to connect several zones without the open layout usually available in new-build projects.

4. Bathroom Underfloor Heating Installation

Bathrooms are often one of the most challenging areas during retrofit projects because of fixed sanitary fixtures and existing plumbing.

In this project, the pipe layout was adjusted around the bathroom fixtures to maintain useful heated floor coverage while avoiding conflicts with essential services.

5. Manifold and Multi-Zone Control

Each underfloor heating circuit was connected to a stainless-steel manifold with flow meters. The manifold allows different rooms or areas to be balanced separately according to their heating demand.

Clear zone labeling also makes future inspection, commissioning, and maintenance easier.

6. Fan Coil Unit Installation for Cooling

To add cooling capability, hydronic fan coil units were installed indoors. These units work with chilled water from the system and distribute cool air into the living space.

This completes the two-function design: underfloor heating for winter and fan coil cooling for summer.

Why Choose Underfloor Heating for Retrofit Projects?

Underfloor heating is becoming increasingly popular in renovation projects because it provides comfortable radiant heating while keeping the system hidden beneath the floor. This can be especially useful in older homes where homeowners want to modernize comfort without relying only on visible radiators.

When used with an air to water heat pump, underfloor heating can operate with lower water temperatures than many traditional radiator systems. This makes it a good match for modern low-temperature hydronic heating design.

For retrofit projects, the key is proper planning. Floor height, insulation, pipe spacing, heat demand, manifold location, and room zoning all need to be considered before installation. When designed correctly, underfloor heating can be a practical and comfortable solution for existing houses.

Key Benefits of This Retrofit Solution

This project demonstrates how an existing UK house can be upgraded with a modern hydronic heating and cooling solution while adapting to the limitations of the original building.

Key benefits include:

* Even heat distribution through radiant underfloor heating

* Active hydronic cooling during summer

* Individual room zoning through the manifold

* Better use of wall space by reducing reliance on traditional radiators

* Flexible system design for residential renovation projects

* Integrated heating and cooling from one water-based system

For more information about installation work and cost factors, read: https://www.nordthermglobal.com/blog/why-is-air-to-water-heat-pump-installation-so-expensive

Project Gallery

The following installation photos show different stages of the retrofit process, including floor preparation, underfloor heating pipe installation, corridor pipe routing, bathroom installation, manifold connection, and hydronic fan coil integration.

These images provide a practical overview of how a modern air to water heat pump heating and cooling system can be integrated into an existing residential property during renovation.

FAQ

Can underfloor heating be installed in an existing house?

Yes. Underfloor heating can be installed in existing houses, especially during renovation when floors are already being replaced or upgraded. Low-profile underfloor heating systems are often used to reduce the impact on floor height.

Can an air to water heat pump work with underfloor heating?

Yes. Air to water heat pumps are well suited to underfloor heating because both systems work efficiently with low-temperature water.

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Can the same system provide cooling?

Yes, but the cooling terminal is important. In this project, underfloor heating was used for winter heating, while hydronic fan coil units were used for active summer cooling.

Cooling performance depends on proper system design, fan coil selection, insulation level, and local climate conditions.

Why use fan coil units with underfloor heating?

Underfloor heating provides quiet and comfortable radiant heat in winter. Fan coil units add active cooling in summer, making the system more useful throughout the year.

Do retrofit underfloor heating systems increase floor height?

They can, depending on the system used. Low-profile underfloor heating panels are often selected for renovation projects because they help reduce the increase in floor height.

Is underfloor heating worth installing during a renovation?

Yes, renovation is one of the best times to install underfloor heating because the floors may already be exposed or replaced. This makes the installation more practical than adding it after the home is fully finished.

Why is retrofit underfloor heating installation more expensive?

Retrofit projects usually require more labour because installers must work around existing floors, walls, bathrooms, doorways, and pipe routes.

Read more here: https://www.nordthermglobal.com/blog/why-is-air-to-water-heat-pump-installation-so-expensive

Is this solution suitable for old houses?

Yes, it can be suitable when the system is designed properly. The key factors include floor height, insulation level, heat load, pipe routing, manifold position, and available space for indoor fan coil units.

Planning a Similar Renovation Project?

Final CTA

Whether you are renovating an existing home or designing a new hydronic heating and cooling system, choosing the right air to water heat pump and system layout is essential.

Our team can help you select a suitable solution for underfloor heating, fan coil cooling, and other residential hydronic applications.

Contact us to discuss your project requirements.