Keeping a Conservatory Cool in Summer

A conservatory gets too hot because the sun comes in through the roof and the walls faster than a closed room can lose the heat. Every fix below does one of three things: stops the sun before it reaches the glass, cuts what the glass lets through, or takes the heat out once it is inside. If the roof words are new, start with what conservatory roofs are made of.

All figures installed and including VAT, except row 4, which is the price of the unit. Rows 3 to 6 and 8 checked 14 September 2026, rows 7, 9 and 10 checked 20 August 2026. Row 8 includes the £400 to £700 of electrical work its publisher says has to be added. No publisher prices the tinted or solar control option on rows 7 and 9 separately. Row 2 is an absence, not a small number. We have found no independent measurement of how much cooler any of these makes a UK conservatory, so we say where each fix works rather than quote a percentage.

Read the two tables separately. Direct transmission counts only the sunlight that passes straight through, not the heat the sheet absorbs and passes on, so an 8 per cent sheet cannot be set against a 22 per cent glass.

What the first table shows is that glass against plastic is the wrong question. A clear polycarbonate roof lets through a similar share of the sun's energy to standard low-E glass. The tint or the coating is what moves the number: solar control glass lets through 17 to 42 per cent, against 53 to 70.5 per cent for standard low-E. The cost is light. Across the Pilkington Suncool range, light transmission falls from 70 per cent to 28 per cent as the g-value falls from 0.42 to 0.17.

Manufacturer technical data, checked 20 August and 14 September 2026. The polycarbonate solar factors come from a data sheet dated 2015, the most recent we have found that publishes them. All figures are for the glazing, not the frame: the government defines g-values as centre pane values that “should not include the effect of frames”.

Outside the glass: awnings and shade sails

UKHSA's checklist says “external shutters, roller blinds or awnings are also very effective.” Shade outside the roof stops the sun before it reaches the glass. We have found no published price for an awning or a shade sail on a conservatory, so this rung has no figure. What would give it one: two installer quotes for the same roof.

On the glass: solar control film, £700 to £1,840

Fitted film for a typical conservatory is £700 to £1,840. Reasonably evidenced, three publishers, 2025 to 2026, checked 14 September 2026. The scopes differ: one publisher prices the whole conservatory and gives a lower floor of £500 elsewhere on the same page, and the other two price the roof only. Film is also sold by the square metre, but publishers measure that against different areas, floor or glass, so a price per square metre is only comparable within one quote.

Check the glass before film goes on. Film puts glass under thermal stress, and ordinary annealed glass tolerates far less of it than toughened: one film installer puts the limit at roughly a 35 to 58°C difference across an annealed pane, against up to about 250°C for toughened glass. Low-E coated sealed units need a compatibility check first. Thin evidence, one publisher, undated, checked 14 September 2026. Ask the installer to confirm in writing which glass you have.

Just inside the glass: roof blinds, from £1,200

Manual roof blinds fitted at 3m × 3m are £1,200 to £2,500. Reasonably evidenced, two publishers, 19 June 2026, checked 14 September 2026. A blind under the roof stops direct sun reaching you and cuts the glare, but it sits inside the glass, so the heat has already come through by the time it meets the blind.

If the roof is due for replacement anyway, the spec is where summer heat gets decided. A new glass roof at 3m × 3m is £2,000 to £7,000, typically £4,000. Reasonably evidenced, four publishers, checked 20 August 2026. Choosing solar control glass takes the sun's energy let through down to 17 to 42 per cent, at the cost of some daylight. Sizes, coatings and prices are on glass conservatory roof cost.

A like-for-like polycarbonate roof at 3m × 3m is £1,900 to £3,500. Reasonably evidenced, two publishers, April 2024 and July 2026, checked 20 August 2026. Glass on the same roof costs £500 to £1,000 more, Thin evidence, one publisher, 15 August 2024. On a sheet roof the tint decides the heat: at 25mm, direct sun through the sheet runs from 63 per cent for clear down to 8 per cent for a heat-reflective grade, on Ultraframe's figures. The sheet options are compared on what replacing a polycarbonate roof costs.

Neither upgrade has a published price of its own. No publisher we have found prices solar control glass separately from standard low-E, or a tinted sheet separately from clear, so ask for both on the same quote.

A tiled or solid roof at 3m × 3m is £6,000 to £11,000 installed including VAT, typically £8,075. Well evidenced, four publishers agreeing within 1.05x on the floor. Checked 20 August 2026. It is the dearest fix here and the only one that takes the glazing out of the roof, so the sun no longer comes in through the top of the room.

It is not the whole answer. The walls are still glazed, the room loses the daylight the roof let in, and the conservatory stops being exempt: the work goes to building control and the roof has to meet 0.15 W/m²K under Approved Document L Table 4.2.

That makes the choice simpler than a list of ten suggests. If the room is only hard to use in a hot spell, film, blinds or a fan cost a fraction of this. If it is too hot to use on most sunny days and the roof is near the end of its life anyway, start with what a new conservatory roof costs, then get conservatory roof quotes for yours.

Every figure here was last checked on 20 August or 14 September 2026, with its evidence grade beside it. To price the roof itself, use our conservatory cost calculator.