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Heating and central heating

How to Heat an Extension or Conservatory

New rooms with lots of glass can be the hardest to keep warm. Planning the heating early makes all the difference.

3 min read · Updated October 2026

Glazed conservatory with a radiator, plants and a wooden chair

Extending your central heating

Most extensions are heated by adding radiators or underfloor heating to the existing system. An engineer will check that the boiler has enough spare output and that pipework can reach the new space without starving other rooms.

Glazed rooms need more heat

Bifold doors, roof lanterns and conservatory glass lose heat faster than walls. The radiator needed for a glazed extension is usually much larger than for a similar-sized room with solid walls. Underfloor heating is popular here because it doesn't take up wall space.

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Separate control

Consider separate control for the new space:

  • A separate heating zone with its own thermostat
  • Smart radiator valves for a single radiator
  • Electric heating for occasional-use rooms or conservatories separated by external doors

Common questions

Can my boiler heat an extension?

Often, if it has spare capacity. An engineer can calculate the extra heat needed.

Is underfloor heating good in an extension?

It's very popular, especially with tiled floors and lots of glazing.

Why is my conservatory so cold in winter?

Glass loses heat quickly. Better glazing, blinds and enough heat output all help.

Keep reading

Underfloor heating pipes laid in loops across a floor next to a manifold and a wall radiator

Underfloor heating vs radiators

Underfloor heating gives gentle, even warmth without radiators on the walls. Radiators are cheaper to fit and quicker to respond. Here's how they compare.

Cut-away house with upstairs and downstairs heating zones, each with its own thermostat

Heating zones explained

Zoning splits a home's heating into areas with their own controls, so you can heat upstairs and downstairs – or an extension – at different times and temperatures.

Tape measure along the top of a radiator with a label showing an output of 1,500 watts

Radiator output: BTU and watts

Every radiator has a heat output figure. Understanding it helps you choose one that will actually heat the room.

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