The terms orangery and conservatory are used interchangeably in sales brochures, which creates more confusion than it needs to. There are real differences between the two, and those differences affect the planning position, the building regulations requirements, the thermal performance, and the cost. Understanding which is which helps you specify what you actually want.
What Each One Actually Is
A conservatory is a glass-roofed extension where more than 75% of the roof area is translucent (glass or polycarbonate), and more than 50% of the wall area is glass. This specific definition matters because conservatories meeting this description were historically exempt from building regulations under Part L (energy efficiency). That exemption changed with the 2010 revision to Part L: conservatories are now only exempt from the energy efficiency requirements if they are separated from the main house by an external-quality door and have their own heating system (or no heating at all).
An orangery has a solid, insulated roof with lantern lights (glass sections in the ceiling, not covering the whole roof), solid masonry or brick piers, and typically much lower glass-to-solid wall ratios. It functions thermally more like a conventional room extension. For planning and building regulations purposes, it's treated as an extension rather than a conservatory.
In practice, many modern structures marketed as orangeries are something in between: part glass roof, part solid lantern, brick piers, good glazing. The planning and building regulations position depends on the specific proportions, not the marketing name.
Planning Permission
Both conservatories and orangeries fall within the same permitted development rules as extensions. For single storey structures at the rear of a house, the same size limits apply: 4 metres depth for a detached house, 3 metres for semi-detached and terraced, both extendable under the Neighbour Consultation Scheme.
The exemption from building regulations that applied to conservatories did not extend to planning: a conservatory still counts against your permitted development allowance. It still needs to comply with planning conditions. The exemption was only ever from Part L energy efficiency requirements.
If your property is in a Conservation Area, the usual restrictions on rear extensions visible from the road apply. A glazed structure is not treated differently from a masonry one for planning purposes in Conservation Areas.
Building Regulations Position
This is where the conservatory/orangery distinction matters most in practice.
A traditional conservatory (all-glass or polycarbonate roof, more than 50% glazed walls, separated from the house by an external door) can still be exempt from building regulations in total, provided it doesn't exceed 30m2 in floor area. This means no building control application, no completion certificate, and no energy performance requirements for the structure itself.
However, "no building regulations" doesn't mean "anything goes." You still need to ensure the foundations are adequate, that the connection to the house doesn't breach existing fire safety, and that drainage is properly managed. The fact that building control won't inspect doesn't mean these things don't matter: they do, particularly for foundations.
An orangery-style structure with a solid insulated roof does not qualify for the conservatory exemption. It requires building regulations approval and must meet Part L energy performance requirements: insulated roof, glazing to current U-value standards, and the thermal envelope treated as part of the house. This adds cost but produces a much more usable space throughout the year.
If you want to use the space year-round, build to building regulations standard. A polycarbonate-roofed conservatory exempt from energy requirements will be very cold in winter and very hot in summer unless it has independent climate control. An orangery or fully compliant extension is more expensive upfront but dramatically more liveable.
Materials and Specification
The choice of frame material is one of the most important decisions for both cost and long-term performance.
uPVC: The most common and lowest-cost option. Modern uPVC profiles perform well thermally and require minimal maintenance. Not appropriate for all house types aesthetically; uPVC frames on a Victorian brick house can look incongruous.
Aluminium: Slimmer profiles than uPVC, more contemporary look. Thermally broken aluminium performs well. More expensive than uPVC but significantly better aesthetically on many modern and period properties.
Timber: The traditional choice for period properties. Requires more maintenance than uPVC or aluminium (periodic painting or staining). Thermally good if specified correctly. More expensive than either of the above.
Hardwood vs softwood timber: Hardwood (iroko, oak) is more durable and dimensionally stable but costs significantly more. Softwood (typically engineered for glazing applications) requires more regular maintenance.
For glazing, specified to building regulations standard means a minimum centre-of-glass U-value of around 1.0-1.2 W/m2K for double glazing, with a total frame/glass assembly (Uw) of 1.6 W/m2K or better. Roof glazing should be solar control glass to reduce summer overheating.
Costs
| Structure type | Approximate cost (2025) |
|---|---|
| Basic uPVC conservatory, 15-20m2 | £15,000 - £25,000 |
| Mid-range uPVC or aluminium conservatory, 20-25m2 | £25,000 - £45,000 |
| Orangery, aluminium or hardwood, 20-25m2 | £45,000 - £80,000 |
| Bespoke hardwood orangery with lantern, 25-35m2 | £70,000 - £120,000+ |
These figures are for supply and installation of the glazed structure and include foundations, basic electrical connection, and plastered walls. They exclude: flooring (underfloor heating is a popular addition, adding £2,000-£5,000), bi-fold or sliding doors if separate from the main glazed walls, and VAT.
Bespoke work from specialist manufacturers carries a premium over volume-produced systems. The difference in quality and longevity usually justifies the additional cost for a structure that will be in place for decades, but it's worth comparing like for like in any quote evaluation.
Realistic Use and Limitations
Before committing to a conservatory or orangery, be realistic about what it will be used for in the British climate. Orientation matters enormously. A south-facing glass extension gets intense sun and heat in summer and good passive solar gains in winter. A north-facing glass extension gets no direct sun and can be cold year-round even with good glazing performance.
The very best conservatories and orangeries are used year-round as main living spaces. The least successful ones become storage rooms because they're too hot in summer and too cold in winter to use comfortably. The difference comes down to: good glazing specification, solar control glass, underfloor heating or radiators, ceiling fans or opening roof lights for summer ventilation, and appropriate use of external shading if south-facing.