The open-plan living space is the defining interior of the last twenty years. Kitchen, dining room, and living room in one continuous space. No walls between them. No doors to close.
It’s also the hardest type of room to heat well — and the room where radiator selection mistakes are most expensive to fix.
Why Open-Plan Spaces Are Different
A standard room has four walls, a door, and a ceiling. The heating system heats the air in that enclosed volume, and the walls and door prevent the warm air from escaping into adjacent spaces. The BTU calculation is straightforward: room volume × insulation factor = required output.
An open-plan space doesn’t work like this. It has a larger volume — often significantly larger — and no internal walls to contain the warm air. The kitchen end of the room may be 3m from the living end, with nothing between them. The warm air from a radiator at one end of the room distributes across the entire space before it can heat the zone it was intended for.
The result, in most open-plan spaces, is a room that’s warm near the radiator and cool everywhere else — or a room that requires so much heat output to maintain a consistent temperature that the energy bills are disproportionate to the comfort achieved.
The Three Open-Plan Heating Mistakes
Mistake 1: Treating the open-plan space as a single room.
The most common mistake is calculating the BTU requirement for the entire open-plan space as if it were one room, then installing one or two large radiators to meet that requirement.
The problem is distribution. A single large radiator in a 10m × 6m open-plan space heats the air near the radiator efficiently. The air at the far end of the room — 10 metres away — receives significantly less heat. The room feels uneven: warm in one zone, cool in another.
Mistake 2: Undersizing for the volume.
Open-plan spaces have large volumes. A kitchen-dining-living space of 10m × 6m × 2.7m has 162 cubic metres of air to heat. A standard BTU calculation for this volume, with good insulation, produces a requirement of approximately 8,000–10,000 BTU. Many open-plan spaces are heated with radiators that deliver 4,000–6,000 BTU — half the required output.
The result is a room that never quite reaches the target temperature, or a boiler that runs continuously trying to compensate.
Mistake 3: Ignoring the kitchen heat contribution.
A kitchen generates significant heat from cooking. In an open-plan space, this heat contributes to the room’s temperature — but unevenly. The kitchen end of the room may be warm from cooking while the living end remains cool. A heating system designed without accounting for this contribution will overheat the kitchen end and underheat the living end.
The Right Approach: Zone Thinking
The solution to open-plan heating is to think in zones rather than rooms.
An open-plan kitchen-dining-living space has three functional zones: the kitchen, the dining area, and the living area. Each zone has different heating requirements, different occupancy patterns, and different heat sources.
The kitchen zone generates heat from cooking and typically requires less radiator output than the other zones. A single radiator of moderate output — 1,500–2,000 BTU — is usually sufficient, positioned to heat the dining area as well as the kitchen.
The dining zone is used intermittently — primarily at mealtimes — and benefits from a radiator that can heat the space quickly rather than maintaining a constant temperature. A radiator with lower thermal mass (steel rather than cast iron) heats up faster and responds more quickly to thermostat control.
The living zone is the most consistently occupied zone and benefits from a radiator that maintains a steady temperature. A larger radiator — 3,000–5,000 BTU depending on the zone’s volume — positioned on the wall opposite the main seating area distributes heat across the zone effectively.
The total output across all three zones should meet or exceed the BTU requirement for the entire space. But distributing that output across multiple radiators in different zones produces more even heating than concentrating it in one or two large units.
Radiator Placement in Open-Plan Spaces
Placement matters more in open-plan spaces than in enclosed rooms, because there are no walls to reflect and contain the heat.
Position radiators at the perimeter, not the centre. A radiator on an external wall heats the coldest part of the room — the wall that loses heat to the outside — and creates a convection current that draws warm air across the room. A radiator on an internal wall (or worse, a freestanding radiator in the middle of the space) heats the air immediately around it without creating the convection current that distributes heat across the room.
Position radiators under or near windows. Cold air falls from window surfaces and creates draughts at floor level. A radiator under or adjacent to a window counteracts this by heating the cold air as it falls. In an open-plan space with large glazed areas — bifold doors, floor-to-ceiling windows — this placement is particularly important.
Use multiple smaller radiators rather than one large one. Three radiators of 2,500 BTU each, positioned at different points around the perimeter of the space, distribute heat more evenly than one radiator of 7,500 BTU in a single location. The total output is the same, but the distribution is significantly better.
Radiator Style in Open-Plan Spaces
Open-plan spaces are visually unified — the eye travels across the entire space without interruption. This means the radiators are always visible, from multiple angles, and need to be chosen with the whole space in mind.
Vertical radiators suit open-plan spaces because they occupy wall height rather than wall width. In a space where wall sections are interrupted by doors, windows, and openings, a tall vertical radiator fits in the narrow sections that a horizontal radiator can’t use.
Flat panel radiators suit contemporary open-plan spaces — new builds, renovated spaces, industrial conversions. The flat panel profile is visually minimal and doesn’t compete with the room’s other elements. In a space with clean lines and neutral finishes, a flat panel radiator in white or anthracite reads as part of the architecture.
Oval column radiators suit open-plan spaces in period properties — Victorian or Edwardian houses where walls have been removed to create open-plan layouts. The oval column profile references the house’s original character and looks appropriate in a space with original features.
Cast iron radiators suit open-plan spaces where the radiator is meant to be a focal point — a large cast iron column radiator in a wide open-plan space has the visual weight to anchor the room and the thermal mass to maintain temperature in a large volume.
The Underfloor Heating Question
Many open-plan spaces use underfloor heating rather than radiators. Underfloor heating distributes heat evenly across the floor surface, which suits open-plan spaces well — there are no cold zones, no draughts, and no radiators to position.
The limitation is responsiveness. Underfloor heating systems — particularly wet systems embedded in screed — take hours to reach operating temperature and hours to cool down. They can’t respond quickly to changes in occupancy or temperature. In an open-plan space that’s used intermittently, this lack of responsiveness can result in a room that’s too warm when it’s occupied and slow to cool when it’s not.
Radiators respond faster. A steel radiator reaches operating temperature within 15–20 minutes of the boiler switching on. In an open-plan space that’s used at specific times — evenings and weekends, for example — radiators can be controlled more precisely than underfloor heating.
The practical solution for many open-plan spaces is a combination: underfloor heating for the kitchen and dining zones (where the floor is tiled and the heating can run continuously), and radiators for the living zone (where faster response and more precise control are more useful).
Frequently Asked Questions
How many radiators do I need for an open-plan space?
As a starting point, divide the open-plan space into functional zones and calculate the BTU requirement for each zone separately. Install at least one radiator per zone, positioned on the external wall or under the window. The total output across all radiators should meet or exceed the BTU requirement for the entire space.
Should I use thermostatic radiator valves (TRVs) in an open-plan space?
Yes, but with care. TRVs allow each radiator to be controlled independently, which is useful for managing the different heating requirements of different zones. However, in an open-plan space where the zones are not separated by walls, a TRV that closes one radiator will affect the temperature of the adjacent zone. Set TRVs to similar temperatures across the space, and use the boiler’s timer to control when the heating runs rather than relying on TRVs to manage temperature differences between zones.
Can I use a single large radiator for an open-plan space?
You can, but the result will be uneven heating. A single large radiator heats the air near it efficiently but distributes heat poorly across a large open-plan space. Multiple smaller radiators positioned at different points around the perimeter produce more even heating for the same total BTU output.
What’s the best radiator finish for an open-plan space?
Choose a finish that’s consistent with the space’s overall aesthetic and that you’re comfortable seeing from every angle. In a contemporary open-plan space, white or anthracite flat panel radiators are the most versatile choice. In a period open-plan space, oval column or cast iron radiators in white or anthracite suit the architecture better.
The Open-Plan Space Heated Well
An open-plan space that’s heated well feels consistent — warm in every zone, without cold corners or draughts. Achieving this requires more thought than heating an enclosed room: zone thinking rather than room thinking, multiple radiators rather than one large unit, and placement on external walls rather than internal ones.
The radiators in an open-plan space are always visible. Choose them for the space they’re in — not just for the BTU output they deliver.
Browse the full Modern Splash radiator range — vertical and horizontal, flat panel, oval column, and cast iron, in white, anthracite, and matt black.