Sorting Out Your Cold (or Boiling) Conservatory
The original idea behind conservatories was to create a bright, light-filled space that brings the outside in. Which sounds lovely in a brochure. But in practice, what you get is a room with a massive expanse of glass or polycarbonate overhead that does basically nothing to stop heat escaping in winter or block solar heat in summer.
Polycarbonate roofs are particularly bad. They’re cheap, light, and let loads of light through. But they have virtually no insulation value. Your heating just goes straight through them. And in summer, they let all the sun’s heat in while trapping it inside. It’s like parking a car in the sun with the windows closed – you know how that goes.
Glass is slightly better but not much. Even modern double-glazed units in a conservatory roof aren’t great at insulation compared to a solid wall or proper roof. The angle doesn’t help either – a roof takes the full force of the sun, unlike vertical windows which only catch direct sun for part of the day.
What Are Your Options?
So you’ve got options, and they’re all a bit different in terms of cost and how much they help.
You can add conservatory roof insulation to your existing roof. This works better with polycarbonate than glass. Companies make foil-backed insulation panels that fit into the gaps between the roof bars. They’re usually made of something like Kingspan or Celotex and have a layer of reflective foil on one or both sides. This helps quite a bit with heat retention and cuts down the glare from the sun.
The downside is you lose some light and it still doesn’t get you anywhere near the insulation value of a proper roof. But it’s cheaper than replacing the whole thing. A fair bit cheaper actually.
Another option is fitting an insulated ceiling under your existing roof. The roof stays as it is, but you build a new insulated ceiling underneath at the height where your roof meets the walls. This creates an insulated space below and leaves a void above where air circulates. You end up with a room that’s much more comfortable, though you lose the ceiling height and obviously all the view of the roof structure and sky. Some people don’t mind this, others hate losing that sense of space.
Or you replace the whole roof with a solid insulated one. This is the most effective option but also the most expensive and involved. You’re essentially taking off the glass or polycarbonate and building a new insulated roof structure with proper tiles or slate on top. The U-value drops from around 2.6 down to 0.15 or better, which makes a massive difference to how the room feels.
What Actually Happens When You Insulate
The main thing is temperature stability. An insulated conservatory stays closer to the temperature of the rest of your house. It doesn’t heat up rapidly in the morning sun or lose all its heat the minute the sun goes down. That’s the key difference really.
In practical terms, this means you can use the space through winter and summer. You’re not avoiding it all summer because it’s unbearable, or giving up on it through winter because it’s too cold even with the heating on full. It becomes somewhere you can actually sit without constantly adjusting the thermostat or opening windows or whatever.
There’s also the noise factor, which people forget about until you mention it. If you’ve got a polycarbonate roof, the sound of rain is incredibly loud. Any kind of insulation – whether it’s panels between the bars or a full replacement roof – cuts that down dramatically. Some people like hearing the rain, but when you can’t hear the TV or have a conversation when it’s chucking it down, it gets old pretty fast.
The Technical Bits
U-values measure how well something insulates. Lower numbers are better – it means less heat escapes through the material. A typical polycarbonate conservatory roof has a U-value around 2.6 to 3.0. That’s terrible. Outside walls in modern houses have to be 0.3 or lower, and roofs around 0.15.
When you add insulation panels between the roof bars, you might get that down to around 1.5 to 2.0. Still not brilliant but noticeably better. You’ll feel the difference but it’s not going to solve the problem completely.
An insulated ceiling under the existing roof can get down to around 0.5 to 0.8 depending on how much insulation you pack in. That’s getting into reasonable territory.
A full replacement solid roof gets you to 0.15 or better, which meets current building regulations for roofs. This is proper insulation, the same standard as building a new extension.
The better the U-value, the less heat escapes through the roof. That means lower heating bills and a more comfortable space. It’s not just about winter though – good insulation works both ways. It keeps heat out in summer as well as keeping it in during winter. That’s what people don’t always realise.
Cost and Time
Adding insulation panels to an existing polycarbonate roof is the cheapest option. You might pay a couple of thousand pounds depending on size. It can sometimes be done in a day or two, which is handy if you need to keep disruption down.
Fitting an insulated ceiling is mid-range price-wise. Probably three to five thousand for an average-sized conservatory. Takes maybe two to three days to install, possibly a bit longer if there’s electrical work involved like adding downlights.
Full roof replacement with a solid tiled roof is the expensive option. You’re looking at upwards of five thousand and into double figures for larger conservatories. The work takes around four to seven days typically, sometimes longer if the weather’s bad or there’s complications with the existing structure.
Obviously these are rough figures. Actual costs depend on your specific conservatory, where you live, and who you use. But as a general rule, you get what you pay for. The cheapest option gives you some improvement, the middle option gives you quite a bit more, and the full replacement solves the problem properly. It’s worth getting a few quotes to see what the actual numbers look like for your situation.
Does It Actually Make a Difference?
Yes. The difference between an uninsulated and properly insulated conservatory is night and day. Instead of a room you avoid for large chunks of the year, you’ve got space you can actually use. Properly use, not just duck in and out of.
People who’ve had it done usually say they wish they’d done it sooner. That’s the most common thing you hear – “why didn’t we do this years ago?” The conservatory goes from being a problem – too hot, too cold, too noisy – to being just another room. You can put normal furniture in there without it fading in the sun, you can work in there, kids can use it as a play space, whatever you need really.
Some people give up on their conservatory entirely and just shut it off. Stick a radiator in there on frost protection and forget about it. But you’ve got this space that cost money to build, it’s taking up room in your garden, and you’re not using it. That seems daft when spending a few thousand pounds would turn it into somewhere usable.
The other issue with leaving a conservatory unused is maintenance still needs doing. They still need looking after – seals perish, gutters block, the structure deteriorates whether you’re using it or not. At least if you’re using the space you notice when things need attention and get them sorted before they become expensive problems.
Insulating the roof properly means you actually get value from the investment someone made – whether that was you or a previous owner. Instead of an expensive garden ornament that’s too hot or cold most of the time, you’ve got an actual room.