Cooling Options for Heat Pumps

With rising temperatures and increasing demand for year-round comfort, many clients are now asking about cooling options alongside heating when considering heat pumps. This guide outlines the main types of cooling, how they integrate with modern heat pump systems and what additional design considerations may apply. It's a useful reference for anyone looking to understand their options early in the design or quotation stage.

Light Cooling (non-condensing cooling)

Light cooling works by circulating cool water from a heat pump through an underfloor heating system, chilled beams or fan coil units. The compressor on the heat pump still runs but typically won’t drop below an 18°C flow temperature to prevent condensation forming. You can utilise the same pipework for heating so there is no uplift on the mechanical installation cost, however the control system will need to be capable of running the unit in reverse.

While it is a highly sustainable solution, it’s best suited to buildings with moderate cooling needs. For spaces with large glazed areas or high internal heat gains, light cooling may not be enough. It’s important that pipework and emitters are designed with condensation prevention in mind, and that the system can accommodate the lower flow temperatures used for cooling. This can be done with good heat pump controls.

Passive Cooling

Passive cooling, makes use of the natural temperature difference between the ground (or ambient air) and the internal environment of a building. It works the same as light cooling but without needing to run the heat pump compressor. This method is extremely energy-efficient and has a minimal environmental impact. Passive cooling is typically only available on ground source systems.

Comfort Cooling (condensing cooling)

Comfort cooling, involves running the heat pump in reverse to generate chilled water, as in light cooling, however the difference is that the chilled water temperature will drop below the dew point, so condensation will form. When designing and installing comfort cooling, great care should be taken to ensure pipework is properly vapour sealed and fan coil units have provision to remove condensation. This system operates in a similar way to a traditional air conditioning unit and can be delivered through fan coil units or to chilled water batteries on Air Handling Units (AHU).

Most modern heat pumps support active cooling. It offers greater control and output than passive cooling, making it suitable for more demanding applications. However, it does require careful design. Emitters need to be correctly sized for cooling loads, and condensate drainage must be managed to prevent moisture build-up. In addition, a well-integrated control system is essential to manage both heating and cooling modes efficiently.

2-Pipe and 4-Pipe Systems

Cooling and heating can be delivered through either 2-pipe or 4-pipe system configurations. A 2-pipe system uses a single set of pipes that alternate between heating and cooling, depending on the season or user input. This approach is relatively simple and cost-effective, making it suitable for buildings with consistent heating or cooling needs throughout the space. However, it does not allow simultaneous heating and cooling in different zones.

A 4-pipe system, on the other hand, provides two separate circuits — one for heating and one for cooling. This enables simultaneous operation, which is ideal for buildings with mixed-use zones or varying thermal demands, such as commercial properties or multi-residential developments. While the design and control setup is more complex, the increased flexibility and comfort levels it provides can make it a worthwhile investment.

Types of Heat Pump Cooling: Passive, Active, and Simultaneous

There are three main approaches to cooling with heat pumps. Passive cooling, as described earlier, involves using the ground loop to absorb heat passively without activating the heat pump compressor. It is extremely efficient but limited in cooling capacity, and only available with ground source systems.

Active cooling is more powerful and works by reversing the heat pump cycle to actively chill water. It’s suitable for both ground and air source systems, and while it consumes more energy than passive cooling, it delivers more control and responsiveness, especially in warmer climates or high-demand buildings.

Simultaneous heating and cooling is the most advanced form. Some heat pumps — particularly those in a 4-pipe configuration — are capable of providing heating to one area while cooling another at the same time. Kronoterm’s latest models support this functionality, which can also help improve system efficiency by redistributing energy within the building. This is especially valuable in buildings with different occupancy zones, such as offices or healthcare environments. This is the most efficient way to provide heating and cooling as the waste heat which would normally be rejected in to outside in cooling mode, is recovered into the heating or hot water production.

When Is Additional Design Work Required?

Adding cooling functionality isn’t always straightforward and may require adjustments to the system design. One of the primary concerns is condensation — cooling emitters must be designed or insulated to prevent surface moisture from forming, especially in underfloor or ceiling-mounted applications. This might involve including drainage systems or humidity sensors in the controls.

Control systems also need to be able to manage both heating and cooling efficiently. This can be as simple as seasonal switching in a 2-pipe system, or more sophisticated in a 4-pipe layout with zone-by-zone temperature management. Pipework, flow rates, and emitter sizing may also differ from those used for heating alone, and should be reviewed during the design phase.

The building fabric itself plays a significant role. Often, excessive cooling demand comes from poor solar shading or large expanses of glass. In these cases, passive design improvements (such as shading, glazing upgrades, or ventilation) may reduce the cooling requirement and result in a more cost-effective overall solution.

Why This Matters

As demand for cooling grows, especially during warmer months, it’s important that we offer clear information to clients early in the process. This helps set expectations, avoids design changes later on, and supports informed decision-making. With high-efficiency cooling options available (including passive, active, and simultaneous modes) heat pumps are a complete solution for year-round indoor comfort.