Nobody replaces a roof because a room is cold without first asking what is making it cold. The roof is the obvious suspect, because it is the biggest surface you can see, and it is the most expensive part to change. It is also only one of several places where a conservatory gives up its warmth.
This page is a diagnosis. It looks at how a glazed room behaves in winter, how to tell a draught from a cold surface, which fixes cost little, and when the roof genuinely is the cause. It does not compare insulation products; for that, see our guide to insulating a conservatory roof. The wider service is on our conservatory roof replacement page.
Everything here is general advice about how conservatories behave. No local weather figures appear here, because the page sticks to what can be sourced. A survey of your own conservatory is what turns the general picture into a plan.
Why a glazed room feels the cold more than the house does
The house around it has walls, a cavity or insulation, and a roof space above. A conservatory has frames, panes or sheets, and a thin roof, with very little between the room and the outside air. Warmth leaves it in two ways. Air that has been heated leaks out through gaps, and it is replaced by cold air coming in. Heat also passes straight through the glazing and the roof material, which is why the surfaces feel cold to the touch even when no draught is blowing.
Cold surfaces change how the room feels
Sitting beside a cold pane, or under a cold roof, you lose warmth to it directly. A thermometer may say the air is a reasonable temperature while you are still uncomfortable. That is one reason why turning the heating up often fails: the surfaces stay cold, and the extra heat disappears faster.
Why it is worse than the summer picture suggests
Conservatories are bright and warm for part of the year, so owners expect them to behave like any other room. In winter the same glass that gave the sun's warmth in September has little sun to give, and the structure that kept the cold out at least a little never had much insulation to begin with. The result is a room that swings between extremes and feels worse than a room with solid walls.
None of this is a fault in your conservatory. It is how a lightly built, glazed room works. The useful question is which of the causes below you can change at a sensible cost.
Telling a draught from a cold surface
A draught and a cold surface need different fixes, so it is worth separating them. The simplest check costs nothing. On a still, cold day, close the doors and windows and walk the room slowly, holding the back of your hand near each joint in the frame. Moving air is easy to feel at the corners, around the door, at the base of the frame and where the roof butts the house.
Signs of draughts
Look for worn rubber seals on the opening windows and doors, gaps where the frame meets the dwarf wall, and cracked or shrunken sealant around the panes. Gutters that are loose or hanging away from the frame can let air in at the eaves. A ridge cap that has lifted at one end is a gap you can sometimes see from the garden.
Signs of cold surfaces
If the room is cold but still, the problem is probably the glazing and the roof. Streaming condensation on the inside of the roof panels on cold mornings points to a cold surface meeting warm, moist room air. Inside multiwall polycarbonate, grey or green staining between the walls of the sheet means the end seals have failed and water is entering. That is a defect, and it is a reason to read our guide on whether to repair or replace a conservatory roof.
Often the answer is both, and that is a good reason to deal with the cheap things first.
The inexpensive fixes that come before any roof work
Several changes cost little and should be done whatever you later decide about the roof. They also show you how much of the problem is the roof, because once the draughts are gone, what remains is the cold from the surfaces.
Seals, sealant and gaps
Replacing worn rubber gaskets on windows and doors, resealing around the panes and packing gaps at the base of the frame is mostly a matter of a few hours and some materials. These jobs should be done on a dry day before the weather turns.
A door between house and conservatory
Closing the door between the two spaces is one of the most effective steps you can take, because it keeps the warm house air from being drawn out into a cold room. If the doors are leaky, fit draught excluders. Where the doors have been removed, putting them back is cheaper than any roof.
Floors, blinds and curtains
A bare tiled floor is cold underfoot and radiates cold upward. A thick rug helps the feel of the room, and thermal blinds on the glazed walls cut some heat loss at night. None of these changes the roof, and none promises a particular saving, but together they can make a cold room tolerable for far less than a new roof costs.
Heating the right amount
A single small heater in an uninsulated glazed room can chase its own tail. If you plan to heat the room regularly, the sensible time to do it is after the surfaces have been improved, not before.
Where the roof fits among the causes
The roof is the largest single surface in most conservatories, and the one with the least insulation. Whatever material it is made of, a conservatory roof is thin. A polycarbonate sheet, a double-glazed unit and a tiled solid roof sit at very different points on the scale of warmth, and that is a major reason why owners turn to the roof last but often benefit from it most.
Age and condition matter
The Eco Experts give about 10 to 15 years for a polycarbonate or glass roof, and HomeBuilding quotes around 10 years for polycarbonate. A roof past that age often has crazed or yellowed sheets, failed end seals or tired glazing bars. A roof in that state loses more warmth than it did when it was new. If yours is at or beyond that age, the cold may be the roof ageing rather than the roof design.
Three ways to change the roof
The first is to leave the roof and add insulation inside, for example as panels fixed beneath the glazing bars. The second is to replace like for like, with a better-specified glazing unit. The third is to move to a solid roof. MyBuilder puts solid roofs at £5,000 to £10,000, glass at £3,000 to £8,000 and polycarbonate at £2,000 to £5,000, and our guide to conservatory roof replacement costs goes through what moves those figures.
Only a solid roof gives the room something built like a house roof, with insulation, a ceiling and a covering on top. It brings a Building Regulations application with it, and your frame must be fit to bear the load.
What a new roof will not cure
A new roof leaves every other cause in place. If the cold comes up from the floor, in through the walls or past the door, a better roof will help only a little. We say this before the quote is written, because it is a common source of disappointment after a replacement.
Glazed walls and frames
The glazed walls often have a greater area than the roof, and old frames lose warmth through their metal or timber as well as through the panes. A solid roof does nothing for them. Secondary glazing or replacement panes are a separate job with a separate cost.
Light is part of the trade
Going solid reduces daylight. For many rooms that is a fair price for a warm, usable space; for a room used as a plant room or a bright breakfast area it is not. Some owners keep a glazed lantern or roof windows in a solid roof to hold on to some of the light, though each opening gives back some of the warmth you gained.
Condensation and mould
A cold room with people and plants in it produces moisture, and cold surfaces are where that moisture lands. A better-insulated roof warms the inside face and cuts condensation there, but the room still needs somewhere for damp air to go. Opening vents on dry days, running a dehumidifier in winter and wiping the glass where it streams are all unglamorous parts of a warmer room.
A sensible order for a cold Stroud conservatory
Put the causes in order of cost and effect, and the sequence is usually clear.
- Seal the draughts: gaskets, sealant, frame base and the door between house and room.
- Cover the cold surfaces you can: blinds, rugs and curtains.
- Check the roof's age and condition. A roof with failed seals or crazed sheets is worth repairing or replacing, whatever the cold.
- Decide how you want to use the room. A winter living space points towards a solid roof; a summer-weekend room does not need one.
- Get the frame looked at before committing to a heavier roof.
Paperwork and VAT
A solid roof replacement is covered by the Building Regulations, as Homebuilding and Renovating explains, and we handle the notification. Most roofing work attracts standard-rate VAT, which your quote will show. Roof insulation installed in a house carries zero-rate VAT until 31 March 2027, and the quote will show if that applies to you.
What we do when you ask
We survey the room, look at the frame, roof and abutment, and take photographs of your roof. The written quote then gives one price for the work, so you can decide whether it is the right place to spend. If a few inexpensive fixes would do more good than a new roof, we tell you so. When the roof is the right answer, we clear up and take the waste, and the work comes with a 10-year workmanship guarantee in writing.