Cold conservatory in winter: heat it, or insulate first?
A conservatory loses its heat through its glazed surfaces, which make up most of its envelope. Heating before treating those surfaces amounts to heating the outdoors: the first useful step is not fitting a radiator, it is reducing the exchange between the room and the glass.
A dense curtain acts on both causes of discomfort: it limits the loss at night and it removes the cold-surface sensation when you sit beside it. A 620 gsm fabric in three layers gives up to 7 °C difference at the glass.
Why a conservatory cools faster than a room
Two reasons, and they compound. The first is the proportion of glazing: where an ordinary room has one window across four walls, a conservatory is almost entirely glazed. The second is thermal mass, the ability of materials to store heat. A conservatory has very little: it warms quickly in the sun and empties just as quickly once the sun goes.
According to ADEME, windows account for 10 to 15% of the heat loss of an ordinary home. In a conservatory that proportion is no longer comparable, since the window is the wall.
The order of works, from free to costly
It is the only useful ranking: each step makes the next less necessary.
| Step | What it addresses | Cost |
|---|---|---|
| 1. Close before dusk | The solar heat gathered during the afternoon stays in the room instead of leaving through the glass. | None |
| 2. Cover the large glazed surfaces | Night-time loss and the cold-surface sensation. This is the step that changes felt comfort the most. | Moderate |
| 3. Treat the junctions and the floor | Draughts through thresholds and joints, which the curtain does not cover. | Variable |
| 4. Heat | The complement, once heat no longer escapes so fast. | The highest, in fitting and in use |
What a curtain can and cannot do here
It can reduce the radiant exchange between your body and a large cold surface, which is the primary cause of discomfort in a conservatory. It can also hold the evening's warmth. It cannot seal a badly made junction nor make up for a complete absence of heating in deep cold.
The Union des Fabricants de Menuiseries makes a useful point: the ADEME estimate does not count air leakage around joinery already installed. In a conservatory, where junctions are numerous, that share is far from negligible, and this is where the curtain and the draught-proofing complement each other rather than replace each other.
The constraints specific to a conservatory
They explain why a standard curtain rarely fits.
| Constraint | Consequence for the choice |
|---|---|
| Wide spans, often in one piece | A made-to-measure panel avoids the gaps between widths, where air passes. |
| Unusual height | The curtain must reach the floor to close the air gap, not stop at the sill. |
| Strong sunlight during the day | The same panel serves winter against cold and summer against overheating, provided it is opened by day in the cold season. |
| Load-bearing structure, not always a wall | The fitting is planned before ordering: ceiling, structure or track, rarely a classic wall rod. |
The summer question is covered separately in conservatory curtain against sun and heat, and the reasoning by fabric weight in which weight to choose.
Frequently asked questions
Should a conservatory be heated all day in winter?
Rarely. Most conservatories are not occupied continuously, and their low thermal mass means they warm up quickly. Heating on demand, having first reduced the losses, costs far less than keeping it constantly warm.
Is a curtain enough to make a conservatory usable in winter?
It changes the felt comfort, especially near the glazing, and it reduces night-time loss. On an uninsulated conservatory in deep cold, it does not replace heating, it reduces the need for it.
Should conservatory curtains be closed during the day?
Not in clear weather: solar gain is the best thing a conservatory has, and it is free. Open wide while the sun is on it, close before it goes. In overcast, cold weather, keeping it closed is defensible.
Which material for a conservatory?
A dense fabric, three layers, 620 gsm. Below 300 gsm the thermal effect stays marginal and the panel dresses without insulating. Colour has no bearing on performance.
The whole season is gathered on our winter curtains page, and our made-to-measure thermal curtains are built to the dimensions of your glazing, including wide spans.
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