What Type of Glass Is Best for a Traditional Orangery?
Updated: 8 hours ago
For most traditional orangeries the best glass is low-E, argon-filled double glazing with a warm-edge spacer in the walls (around 1.1 to 1.2 W/m²K), and solar-control, self-cleaning units with a laminated inner pane in the roof lantern. Add acoustic glass near a busy road, and slim heritage double glazing on listed or conservation-area homes.
We build bespoke hardwood orangeries for heritage homes, period properties and country houses, and this is how we choose the glazing for each one.
Understanding U-values (in simple terms)
The U-value tells us how well a type of glass keeps heat in. The lower the number, the better the insulation. For example, a traditional single-glazed window might have a U-value of 5.7, while good low-E double glazing reaches 1.2 or even lower. Triple glazing or insulated roof glass can go below 1.0.
For an orangery built as an extension, Part L of the Building Regulations in England sets a limiting U-value of 1.4 W/m²K for new windows and glazed doors, so the glazing has to perform, not just look right. Better U-values also mean more comfort, lower heating bills and less condensation.
Glazing options we recommend
These are the main glass types we use, what each is for and what it adds. Most are toughened or laminated and made to size, because, as our guide to whether you can toughened glass be cut explains, a toughened pane cannot be trimmed afterwards:
Low-E double glazing (the default): two panes with a low-emissivity coating, argon gas in the cavity and a warm-edge spacer. Best for walls and doors. It gives excellent insulation, a clear appearance and better soundproofing than older units, and we set it in hardwood frames with sightlines designed to match period features. This is the baseline price.
Low-iron glass: brighter and clearer than standard float glass, without the green tint at the edges. Best in roof lanterns and large feature panes, where clarity shows. We pair it with solar-control coatings to cut glare. It costs more than standard float glass.
Solar control glass: an invisible coating that reflects excess solar heat while still letting light in. Best for south- and west-facing orangeries and for lantern glazing, so the room stays warm in winter without becoming an oven in July. A modest uplift, and usually money well spent in the roof.
Self-cleaning glass: a coating that breaks down dirt in UV light so rain washes it away. Best for roof lanterns and hard-to-reach panes. It reduces cleaning rather than removing it.
Acoustic glass: laminated with a sound-damping interlayer. Best near roads, railways or flight paths. It adds weight and cost, so we use it where noise is a real problem.
Heritage slim double glazing: thin-profile units (including slim and vacuum double glazing) with traditional-looking spacer bars and hardwood beads. Best for listed buildings and conservation areas, where conservation officers want the proportions of single glazing with modern performance. It is the most expensive of the double-glazed options.
What about triple glazing?
Triple glazing offers even lower U-values than double glazing. It’s ideal for colder regions or homes that need extra insulation. That said, it’s heavier and more expensive, and it can reduce light slightly. We only use it where the structure can support it and where the client prioritises thermal performance above all.
Appearance and proportions
In period homes we often use tall vertical panes in traditional sash-style patterns, with Georgian-style glazing bars, as on our period hardwood conservatories, where they suit the house. The aim is always to match the orangery to the rest of your home, and the glass is chosen alongside the orangery materials for the frame and base.
Roof glazing for orangeries
Most traditional orangeries include a solid flat roof with a central lantern. The glass in that lantern needs to be tough, thermally efficient and ideally self-cleaning. Because it is overhead, the inner pane should be laminated: if it breaks, the interlayer holds the pieces in place instead of letting them fall into the room. The outer pane is usually toughened, with solar control built in.
Some designs feature two lanterns or even corner sections; our guide to orangery accessories covers the options. In every case, we select the glass to reduce glare and control heat without dimming the room.
Glass costs and value
Standard low-E double glazing is the baseline. Low-iron, solar control, self-cleaning and acoustic glass each add to the glazing cost, triple glazing adds more again (plus a heavier frame), and heritage slim units cost the most. The glass is one of the things that drives the overall cost of a traditional orangery, and upgrading it in the roof is almost always worth it because that is where heat gain and loss are greatest.
Planning permission and building regulations
Glazing rarely affects planning permission for an orangery, though some conservation areas restrict reflective coatings. Building regulations matter more: glazing must meet Part L thermal targets and safety glazing rules.
Common mistakes to avoid
A common mistake is choosing cheap glazing to save money up front. Poor-quality glass leads to overheating, draughts and condensation. Another is over-glazing without proper shading or ventilation. We always factor in accessories like blinds and roof vents as part of the build.
If you would like help choosing glazing for your orangery, talk to our design team.
