Radiators suit a heating climate
Britain and Ireland spend far more of the year needing heat than needing cooling. A wet heating system with radiators and a room thermostat (and TRVs) is the normal way to do that. It changes the room more slowly than a blast of conditioned air, which many people prefer: less draught, less fan noise, and heat that sits in the building fabric rather than only in the air.
That slowness is also the limitation. A radiator circuit will not pull a hot room down. If the problem is overheating, you need shade, ventilation, or actual cooling. A bigger radiator does not fix a heatwave.
Claims that do not stand up
- “Ireland only gets a few days above 20°C.” That is not true. Summer days around and above 20°C are a normal part of an Irish and British summer. Days above 25°C are less common, and they are no longer rare in the south of England. The heating season is still much longer than the cooling season. That is the claim worth keeping.
- “Radiators just win against forced hot air.” Forced warm air (ducted furnaces, common in North America) heats the air quickly and can feel draughty, noisy, and dry. Wet radiators are usually the better heating emitter for a UK house. They are not a better answer if the house also needs cooling, filtration, or fresh air from the same system.
- “A new forced-air system costs about the same as radiators.” Not in the UK. Wet radiators are the standard install and are usually the cheaper heating system. Ducted air needs routes for ducts that most existing houses do not have.
- “Drop the thermostat 5°F with underfloor heating.” Five degrees Fahrenheit is about 3°C. A warm floor can feel comfortable at a slightly lower air temperature because your feet are warm, but that is not a design allowance. Size the system to the heat loss. Do not knock 3°C off the room temperature and assume the house is still heated. See underfloor heating vs radiators for when a floor is actually the better emitter.
Radiators
Use them when
- The job is heating, which is most of a UK or Irish year
- The house already has a boiler or an air-to-water heat pump
- You want room-by-room control with TRVs
- You heat in bursts: bedrooms and evenings warm up faster than a screed floor
They will not
- Cool a room
- Give catalogue output at heat-pump temperatures unless they are large enough — use the radiator new output check
- Replace ventilation or take moisture out of the air
Air conditioning
In UK houses “air conditioning” usually means a split or an air-to-air heat pump: refrigerant between an outdoor unit and one or more indoor fans. It cools well. Many of the same units heat well too, because they are heat pumps. They do not heat a hot-water cylinder. A ducted whole-house system, the American HVAC layout, is uncommon here because the ducts are hard to fit and the heating season does not justify ripping out a working radiator circuit.
Cooling is worth adding where the house actually overheats: top-floor flats, large south- and west-facing glass, and new airtight homes. Approved Document O exists because overheating is now a design problem in England, not because every house needs air conditioning. A fan, external shading, and night ventilation still come first when they are enough.
An air-to-water heat pump on radiators or underfloor heating is a different machine. Some can cool through fan coils, or gently through a floor, but floor cooling is limited by condensation. It is not a substitute for a split in a humid British summer.
Which to fit
- Most existing UK and Irish houses: keep the wet radiator system for heat. Add a split only in the rooms that overheat.
- Well-insulated house, heat pump planned: enlarge the radiators or use underfloor heating so the flow temperature can stay low. Cooling is a separate decision.
- Small flat with no wet system: an air-to-air heat pump can be the heating and the cooling. You still need a plan for hot water.
- New build that needs both, and has a proper route for ducts: one air system can be simpler than two. That is a minority of British houses, not the default.
Related
Guidance only. Cooling plant and gas work belong with people qualified for that work. Check heat loss before changing emitters, and treat an existing wet system to BS 7593.