The short answer
A conservatory with a polycarbonate or uncoated glass roof loses heat quickly in winter because the glazing has a poor insulation value. A modern well-specified conservatory with low-U-value glass, good wall insulation and an appropriate heating system can be comfortable in cooler months. See are conservatories too hot in summer for the opposite problem and conservatory roof options for the impact of roof choice.
Conservatories have a reputation for being cold in winter and roasting in summer, and for older structures with polycarbonate or early double-glazed glass roofs that reputation is largely deserved. However, the specification of modern conservatories — particularly the improvement in low-emissivity roof glass and insulated frames — means that a well-built conservatory can be a genuinely comfortable room in cooler months, provided the heating strategy is appropriate. The key is understanding which elements drive winter heat loss so you can specify (or upgrade) them correctly.
Winter comfort at a glance
- Main heat loss Through the roof glazing
- Best roof for winter Solid tiled or low-U-value glass
- Frame performance uPVC and aluminium thermal breaks both perform well
- Heating options Underfloor, electric panel, radiator extension
- Building regs note Permanently heated conservatory loses Part L exemption
- Quick fix Low-U-value glass or insulated roof blind
Where heat is lost in a conservatory
The roof is by far the largest source of winter heat loss in most conservatories because it accounts for a large proportion of the total surface area and is typically the least insulated element. A polycarbonate roof has a U-value of around 1.8–2.0 W/m²K — significantly worse than a modern external wall. An uncoated double-glazed glass roof is better at around 1.6 W/m²K, and a modern low-emissivity triple-glazed or advanced double-glazed roof unit can achieve 1.0 W/m²K or below. By comparison, a well-insulated solid roof section can achieve 0.18 W/m²K. The practical consequence is that heating a conservatory with a glass roof in winter is like heating a room with a large cold surface overhead that constantly draws heat away. Even a good heating system struggles to overcome a poor roof specification on very cold days.
The role of frame insulation
Modern uPVC frames incorporate multi-chambered profiles that provide reasonable thermal insulation; modern aluminium frames use thermal break technology to interrupt the conductive aluminium and prevent cold-bridging. Both perform significantly better than aluminium frames of 20 years ago, which were notorious for condensation and heat loss. If an older conservatory has aluminium frames without thermal breaks, heat loss through the frame itself is significant and replacement frames will improve comfort. The glazing units in the frame also matter: double-glazed units with argon fill and a low-emissivity coating perform substantially better than older standard double glazing.
| Roof material | Typical U-value (W/m²K) | Winter performance |
|---|---|---|
| Polycarbonate | 1.8–2.0 | Poor |
| Standard double-glazed glass | 1.4–1.6 | Below average |
| Low-E double-glazed glass | 1.0–1.2 | Moderate |
| Advanced low-E / triple | 0.7–1.0 | Good |
| Solid insulated roof | 0.15–0.20 | Excellent |
Heating options for a conservatory
The right heating system depends on the size of the conservatory, how it is used and whether it is permanently heated or used seasonally. Options include:
- Underfloor heating: the most comfortable option for a conservatory, particularly where the floor screed is at the base construction stage. Electric UFH is simpler to retrofit than wet UFH, though running costs are higher on standard electricity tariffs.
- Extension of the main central heating: adding radiators connected to the house system is a common approach. Note that a permanently heated conservatory may lose its Part L building regulations exemption — see building regulations guide.
- Electric panel heaters: low capital cost but higher running costs; adequate for occasional use or as a supplement rather than a primary heat source.
- Infrared heaters: ceiling-mounted infrared heaters warm people and surfaces rather than air, which can be more efficient in a poorly insulated space where heated air quickly escapes through the glazing.
Practical improvements for an existing cold conservatory
If you have an existing conservatory that is uncomfortably cold in winter, the most impactful improvements in order of cost-effectiveness are: first, add thermal insulated blinds to the roof (insulated honeycomb or cellular blinds trap a layer of air against the glass and meaningfully reduce overnight heat loss); second, address any draughts around frames, doors and the junction with the house wall; third, consider a roof replacement with lower-U-value glass or a solid roof. Replacing the roof is the most effective single upgrade but carries the highest upfront cost. See conservatory roof replacement cost. This page is general information; specific heating and insulation advice for your conservatory should come from a qualified installer or energy assessor.
Make your conservatory comfortable year-round
Comparing quotes from installers — for roof replacements, improved glazing or heating solutions — helps you understand what improvement is possible and what it costs.
Frequently asked questions
How can I make my conservatory warmer in winter?
The most effective improvements are: insulated roof blinds (low cost, good effect on overnight heat loss), draught proofing, and a roof replacement with low-U-value glass or a solid roof. Connecting to the main heating system helps but check building regulations implications.
What is the best way to heat a conservatory?
Underfloor heating is the most comfortable option and works particularly well if installed at the base construction stage. Extending the main central heating with a radiator is common. Infrared heaters are effective as supplements. Electric panel heaters are convenient but less efficient for regular use.
Does a solid roof make a conservatory warmer?
Yes, significantly. A solid insulated roof achieves U-values of 0.15–0.20 W/m²K compared with 1.0–2.0 for glass or polycarbonate, dramatically reducing winter heat loss. It also eliminates summer overheating and rain noise.
Can I connect my conservatory to the central heating?
Yes, but permanently heating the conservatory may remove its Part L building regulations exemption. Check with your local building control before connecting the conservatory to the main system.
Sources & further reading
- Glass & Glazing Federation — conservatory glazing U-values, thermal performance standards and heating guidance
- GOV.UK — Building Regulations Approved Document L, Part L exemption conditions and permanently heated conservatory rules
- FENSA — glazing energy ratings and low-emissivity glass performance standards
- LABC — Local Authority Building Control guidance on conservatory heating and building regulations compliance
This is general information about conservatories and orangeries in the UK, not planning, structural, legal or financial advice. Costs are typical illustrations only and are not quotes for any specific project; actual prices vary with size, site conditions and your chosen installer.