Why Is My Conservatory Too Hot in Summer & Too Cold in Winter? (Fixed)

If your conservatory is unbearable in July and Arctic in January, you're not alone — it's the single most common complaint we hear in Plymouth, Plympton and across the South West. The good news: there's a clear cause, and a clear fix. We've covered the two halves of the problem in detail on our too hot in summer and too cold in winter pages — this guide ties them together with the science.

The science: why glass & polycarbonate roofs fail you

In summer

Glass and polycarbonate let solar energy in very efficiently. Once it hits your floor and furniture, it converts to long-wave heat — which the same roof traps inside. It's exactly how a greenhouse works. Cracking a door open barely touches it because the heat source (the roof above your head) is unchanged. By 2pm on a sunny July day, internal temperatures of 35–40°C are completely normal.

In winter

The same roof has terrible insulation values (U-values of 2.0+ vs. ~0.15 for a warm roof). Heat from your radiators escapes straight up. Hours of heating, gone in minutes. In a typical Plymouth winter, a glass conservatory bleeds enough heat to drag down the whole heating system — your boiler runs longer to compensate, and your bills reflect it.

Year round

Massive temperature swings cause condensation, mould around the frames, and that familiar musty smell. Rain on polycarbonate is loud enough to drown out a TV. Many homeowners just stop going in there — which is a shame given a typical conservatory is 12–18m² of potential extra living space.

Why tinted film, blinds and AC are sticking-plasters

• Roof blinds: still let heat through, get dusty, expensive (£800–£2,000), look dated
• Solar film: reduces light too, peels eventually, doesn't help in winter at all
• Portable AC: fights the roof — never wins. Expensive to run, noisy, ugly
• Extra heater: heats the outside more than you. Adds £20–£40/month to your winter bills
• Underfloor heating: works, but only for the cold problem, not the heat. £3,000–£6,000 fitted

Adding up the cost of two or three of these "fixes" gets you most of the way to a proper warm roof — without actually solving the underlying problem.

The real fix: an insulated warm roof

A SupaLite warm roof brings your conservatory's roof U-value down to around 0.15 W/m²K — better than most house extensions built in the 1990s, and 13× more thermally efficient than a glass roof. The result:

• Comfortable temperatures all year — typically within 2°C of the rest of the house
• Heating bills drop noticeably (most customers report 10–25% savings)
• Rain noise eliminated
• Condensation gone
• The room becomes part of your house, not a seasonal annexe
• House value rises — buyers see usable square footage

Real customer results

We've fitted hundreds of warm roofs across Plymouth, Plympton, Plymstock and the wider South West. The pattern is consistent: the room that was unbearable in July becomes "the nicest room in the house" by August. Customers who used the conservatory two months a year now use it daily.

Common mistakes to avoid

• Throwing money at symptoms. Blinds, AC, heaters, fans — they all fight the roof. The roof is the problem; replace it once, properly.
• Waiting for a heatwave to act. Lead times stretch out in summer. Book the survey in winter or spring and you'll have the roof on before the next hot spell.
• Assuming a darker tinted glass will fix it. It cuts a bit of light and a bit of heat, but the U-value is still poor — winter doesn't get any better.

It's the single biggest comfort upgrade most homeowners can make to a conservatory — and unlike new flooring or furniture, it pays you back in energy bills. See typical warm roof costs or book a free survey.