The short answer
For a hot conservatory, roof blinds and better ventilation are the least costly first steps and often take the edge off the heat. If the room is still unusable afterwards, the cause is the clear roof itself, and only swapping it for a solid, insulated roof changes how much sun energy gets in. That replacement needs a Building Regulations application.
Why a clear roof turns the room into a greenhouse
Sunlight passes straight through glass or polycarbonate, warms the floor, the furniture and the walls, and that warmth then struggles to leave through the same roof. A conservatory is built to gather light, so it gathers heat as well. A room facing south or west, with a big roof area, catches the most.
Age makes it worse. The Eco Experts (updated 2024) put polycarbonate roofs at around 10 to 15 years, and older sheets can yellow or lose whatever solar coating they once had. If yours is nearing the end of that range, spending on blinds for a failing roof may be money in the wrong place. Our guide to insulating a conservatory roof deals with winter warmth; this page is only about summer heat.
Blinds, film and fans: the quick fixes
Roof blinds are the usual first step. They run beneath the glazing along the rafters and cut direct sun before it reaches the room. Shading fitted outside the roof stops more heat than a blind inside, because the sun is blocked before it ever passes through the roof. An inside blind still helps with glare and the sensation of sitting under a lamp.
Window film and solar-control coatings reduce what gets through, at the price of a darker or slightly mirrored look. Ceiling fans shift air but do not take heat away. None of these touches the structure, so none needs a Building Regulations application. Ask any supplier how their product fixes to your roof bars, because anything screwed through a glazing seal can start a leak of its own.
Venting the hot air at the highest point
Warm air collects under the highest part of the roof, so a way out there does more than a fan at head height. Opening roof vents, a ridge vent or a roof window near the top of the slope draw the hot air up and out, especially when a low window or door lets cooler air in below.
Cutting new openings into an existing roof is structural work, and a roof window has to meet the Part L 2021 Table 4.2 limit of 1.4, or carry a Window Energy Rating in Band B. We cover glazing in a solid roof on our page about roof windows in a solid conservatory roof. A lean-to has less height for the air to rise through, so venting matters even more there; see replacing a lean-to conservatory roof.
When swapping the roof is the better answer
If blinds and vents still leave the room too hot to sit in, a new roof removes the cause. A solid roof with insulation and a plastered or boarded ceiling does not behave like a greenhouse lid, because it is opaque and carries a layer of insulation in its build-up. Rooms with such a roof tend to feel steadier through summer and winter, though the result depends on the room's aspect, its glazed walls and how it is aired. We cannot promise a particular temperature.
Under the Building Regulations a replacement of this kind is treated as altering the structure, so building control gets an application (Homebuilding and Renovating, 2023), and the new roof must achieve a U-value of 0.15 under Part L 2021 Table 4.2. The frame is checked too, because it may be asked to carry far more than it did under polycarbonate.
What each fix costs
These are national typical figures, never Supreme prices. MyBuilder's conservatory roof replacement guide (updated 2026) gives an overall range of £2,000 to £10,000 or more, with an average of about £4,500.
| Roof option | Typical UK range |
|---|---|
| Polycarbonate | £2,000 to £5,000 |
| Glass | £3,000 to £8,000 |
| Solid | £5,000 to £10,000 |
| Structural reinforcement, if needed | £500 to £2,000 |
Blinds and film are bought separately and are not in those figures. The survey is followed by a quote that takes in the frame, the new roof and the finish. For how cover on new work operates, read what guarantee comes with a new conservatory roof. The wider service is on our conservatory roof replacement page.
Order of attempts, and mistakes that make the heat worse
Start with the cheap and reversible: shading first, then venting, then a fan. Live with the result through one hot spell before deciding anything bigger. Keep a note of the hours when the room is worst, because that tells you whether the sun comes in through the roof, through the glazed walls or through both.
If the room is still unbearable, email pictures of the roof and frame and say which way the room faces. That gives us enough to say whether a replacement is likely to help or whether better shading alone would do. A visit then looks at the roof bars, the cill and the point where the roof meets the house.
Dark blinds that sit tight under the glazing can trap heat between the blind and the roof, so leave an air gap and let it vent at the ridge. Closing every window on a hot day to keep the heat out does the opposite: the room fills with warm air and has nowhere to send it. Cheap reflective film stuck on unevenly can crack the glazing as it expands in strong sun.
Do not treat a solid roof as a cure for poor airflow either. A well-insulated room still needs a way to shed warm air on a sunny afternoon, and opening doors and high vents remain part of the answer after the work.