Where the warmth goes
Heat moves from warm to cold, and it moves fastest through thin, single-layer surfaces. A conservatory is made of exactly that: a lot of glass or polycarbonate on the walls and a thin sheet roof. In winter the room is separated from the cold outside by far less material than the house next to it.
The roof is a big route for that heat. Warm air rises, so heat gathers under the roof and passes through it, while the glazing on the sides adds to the loss. Gaps make it worse: perished seals around the glazing bars, ill-fitting doors and vents left open let cold air in as fast as the heat escapes.
Do not expect a single cure. Cold in a conservatory is usually the sum of a thin roof, tired seals and no heat source, and the work is to find which of those you can change at what cost. On a bright winter day the room can feel quite pleasant, then lose its warmth soon after sunset, which points at the roof and glazing rather than a draught. Notice when the room turns cold, because the timing tells you which fault to chase first.
The roof options, from light to heavy
Because the roof does so much of the damage, it is the first place to look. The choices differ in how far they change the room.
| Route | What changes |
|---|---|
| Reseal and repair | Stops draughts at the seals and bars |
| Insulation panels | Fitted into the existing frame |
| New glazed roof | Better glazing units on the frame |
| Solid tiled roof | Replaces glazing with a built-up roof |
A solid roof is heavier, so the walls and frame are checked, and it needs Building Regulations approval. For scale, MyJobQuote (20/10/26) gives a typical UK range of £3,200 to £6,000 for a conservatory roof, and the Eco Experts (29 April 2024) give £2,300 to £6,000. Frame condition and size move the price, and so does whether the walls need strengthening for a heavier covering.
Our guide to solid, glass or polycarbonate roofs compares them in more detail, and insulation panels are the lighter route that keeps the existing frame. Cost is not the only measure: the room also has to stay light enough to enjoy.
Heating the room, and the exemption
The obvious answer to a cold conservatory is to heat it, and here the Building Regulations come into it. A conservatory can be exempt, and one of the conditions in Approved Document L, paragraph 0.14, is that the house heating system is not carried into the room. Radiators plumbed from the house boiler, or underfloor pipework connected to it, do exactly that.
An independent heater does not extend the house system, which is the point the condition turns on. If you are considering anything fixed, such as an electric underfloor mat or a wall heater, ask building control before it is fitted. Dover District Council reads its conservatory exemption more tightly still, and treats exempt conservatories as unheated.
If you want the room to be a heated part of the house, the better route is to plan it as an extension from the start, with a roof built to the energy standards that apply. That is covered in turning a conservatory into an extension and in the page on heating a conservatory, where the rule is set out in full.
Lower-cost steps before a new roof
Not every cold conservatory needs a new roof, and a repair makes more sense when the frame and glazing are sound. Some steps cost little and are worth taking first.
- Replace worn rubber seals and door brushes so the frame stops leaking air.
- Fit a door between the house and the conservatory and keep it shut at night.
- Check the roof vents close fully; a vent that sits slightly open is a permanent draught.
- Use thick curtains or blinds on the glazed sides, and a thermal blind where the roof allows.
These steps will not turn a thin roof into an insulated one, but they take the edge off a draughty room and show whether the roof really is the problem. If the room is still cold after the seals are sorted, the roof is the next question.
Our conservatory roofs team can look at the frame, the glazing and the junction with the house in a single visit, so the figure you receive in writing comes from the roof itself and not a guess from a distance.
