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The heatwaves are hitting, summer is well and truly here, and many people are starting to swelter in their homes. For those who already have an air-to-water heat pump, a natural question tends to crop up: "It’s basically an air conditioner running in reverse, so can I use it to cool my house?"
The short answer is: mechanically yes, but practically, it’s complicated…
Mechanically speaking, your heat pump is 100% capable of reversing its cycle. Instead of pulling heat from the air to warm your water, it can pull heat from the water and reject it to the outside. But as our Head of Business Development, Jez Climas, points out, the hardware isn't the issue:
"The bottleneck here isn’t the appliance itself—it’s your heating distribution system."
Here at City Plumbing, we want to help you understand exactly why that bottleneck happens and the best ways to overcome it to achieve true year-round comfort.
Why Standard Radiators Can't Provide Effective Heat Pump Cooling
When your heat pump is heating in the dead of winter, it’s designed to operate at peak flow temperatures of around 45°C to 50°C. Because the water entering your radiators is 20 to 30 degrees warmer than the room, you have a massive temperature difference driving that heat into space. It also helps that radiators are at the bottom of the room; as they warm the air, it naturally rises, creating a nice convection current.
All of that falls down when you try to put cold water through those exact same radiators for two main reasons:
The Condensation and Dew Point Risk:
Your peak cooling load in the summer is often quite similar to your peak heating load in the winter. Between the ambient outside temperature and the sun beaming through the windows, you're still looking to move several kilowatts of heat out of the house. But you can't just make your radiators 20 or 30 degrees cooler than the room because they would literally freeze. Realistically, you are limited by the dew point.
According to technical insights from the CIBSE Journal, proper insulation is critical because uninsulated pipework carrying chilled water will sweat heavily in domestic spaces. If you drop the water temperature much below 15°C, you’ll start to see condensation form on the outside of the metal, which will drip straight onto your carpets.
Poor Cold-Air Distribution:
Radiators sit at the bottom of the room, but the cold air sinks. If you do manage to get some cooling from a standard radiator, it just creates a small pool of cold air right at the floor, leaving a massive well of hot air trapped above it.
With normal radiators, the practical answer is no. You could run a flow temperature of 15°C for a tiny bit of relief, but it’s rarely worth the hassle.
The Air Conditioning Design Advantage: Forced Convection
This is exactly why air conditioning indoor units look the way they do. They are mounted high up on the wall so the convection current actually cools the whole room. They use fans for forced convection to pull serious cooling out of a smaller temperature difference, and they have built-in condensate drains to safely carry away water when the heat exchanger gets cold.
Can we achieve something similar with a water-based system? Of course. Large office buildings run on chilled water systems all the time, often running flow temperatures as low as 6°C.
The issue in a domestic setting is the sheer level of workmanship required. Every single millimetre of that pipework has to be perfectly vapour-sealed. Pipe clamps can’t touch the bare pipe; they have to clamp onto the outside of the insulation to prevent cold bridges. If you miss a spot, the pipe sweats, and you get major condensation issues.
Domestic Alternatives: Fan Convectors and Underfloor Cooling
If you want water-based cooling at home, you need to change your emitters.
1. Fan Convectors
You can swap standard radiators for fan convectors—brands like Jaga, Mitsubishi, Daikin, and Panasonic all make them. They look similar to a radiator but contain a high-surface-area heat exchanger and a built-in fan, allowing them to safely drop a few hundred watts or a kilowatt of cooling into a room.
2. Underfloor Heating Adaptation
Underfloor heating is another option. Because it covers a massive surface area and has excellent radiant contact with the room, cooling the floor can make a space noticeably more comfortable.
However, you still have to be incredibly cautious with your flow temperatures. Condensation under a carpet is a mould disaster, and condensation on tiles turns your floor into a skating rink. To do this right, you need specialised thermostats and very precise weather-compensation controls to make sure you never cross the dew point. As our Head of Business Development, Jez Climas, has previously explained in Installer Online, running a heat pump efficiently requires matching your system's flow temperatures seamlessly to external weather shifts.
Hybrids vs Separate Systems: Finding the Practical Alternative
In the past, when clients asked our design team for a combined heating and cooling system using just a standard heat pump, we’d look at the numbers. More often than not, we found it was simply cheaper and more effective to keep the systems separate.
Under current permitted development rights, if you have a detached home, you generally don’t need planning permission for a second outdoor unit, provided it meets strict size and boundary distance criteria.Because standard air conditioning split systems are manufactured in eye-watering quantities globally, the economies of scale mean the equipment is remarkably cheap.
Installing a dedicated heat pump for your heating and a completely separate split A/C system for summer cooling usually costs less and ensures both systems are perfectly optimised for what they do best.
The Ultimate Hybrid Solution: The Samsung Quint System
However, there is a really exciting new option on the market right now that our team is incredibly proud to supply: the Samsung Quint system.
It uses a single outdoor unit (available in 12kW and 16kW outputs) that features standard hydraulic connections for your wet heating system, along with dedicated refrigerant connections for multi-split or mini VRF cooling.
Even better, it features built-in heat recovery: if the system is running in cooling mode during a hot summer day, the first thing it does is dump that rejected heat straight into your domestic hot water cylinder. Only when your hot water tank is fully heated will it start venting that waste heat into the atmosphere.
From an installation and project management standpoint, it's brilliant because it keeps the trades separated. Your heating engineer handles the wet heating install, and an F-Gas engineer handles the refrigerant pipework. It delivers premium, high-wall cooling and efficient wet heating from a single outdoor unit, without having to shoehorn complex ductwork or high-risk chilled-water pipe insulation into a domestic home.
Optimise Your Home's Climate with City Plumbing
Whether you are looking to upgrade your current radiator setup to support a heat pump, explore separate air conditioning split systems, or invest in the game-changing Samsung Quint system, City Plumbing has the stock, expertise, and design support to help you get it right—and to help you create a home that stays comfortable all year round.
Contact your local City Plumbing branch or visit our website today to explore our full range of low-carbon heating and cooling technologies.
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