The terms ‘glass garden room’, ‘winter garden’, ‘conservatory’, ‘sun room’, and ‘orangery’ are used almost interchangeably by homeowners and sometimes even by suppliers. This creates genuine confusion when you’re trying to specify a project — because these structures differ significantly in thermal performance, planning status, cost, and year-round functionality. This guide cuts through the terminology and gives you a clear picture of what each type of structure actually is, and which one makes sense for your project.
Clearing Up the Terminology
Traditional Conservatory
A traditional conservatory is a glazed extension with a glass or polycarbonate roof, typically attached to the rear of a house. Victorian and Edwardian styles with uPVC or timber frames are the classic version. The defining characteristic — and the major limitation — is poor thermal performance. Single or basic double-glazed polycarbonate roofs conduct heat very readily, making traditional conservatories uncomfortably hot in summer and cold in winter. Modern building regulations (in force since 2022 in England) have effectively ended the traditional polycarbonate conservatory as a viable new build option. Any new glazed extension now requires performance standards that bring it much closer to the ‘garden room’ or ‘winter garden’ specification.
Glass Garden Room
A glass garden room is a contemporary glazed structure — typically with slim aluminium frames, double or triple-glazed glass, and thermally broken profiles — designed to function as a genuine additional room rather than a seasonal space. Unlike a traditional conservatory, it is designed to be usable year-round with normal domestic heating. In planning terms, a single-storey glass garden room attached to the house is typically treated as an extension, subject to the same Permitted Development rules as any other rear extension (maximum 3m single-storey depth for semi-detached/terraced, 4m for detached, under current PD rights in England).
Winter Garden
A winter garden — in the premium architectural sense — is a high-performance glazed room designed specifically for year-round comfort, with advanced insulation, climate control, and often automated ventilation, shading, and heating. The key differentiator from a glass garden room is the specification level: a winter garden typically uses triple-glazed units, thermally broken aluminium profiles with superior insulation values (typically Uf ≤ 1.6 W/m²K for the frame), integrated ventilation systems, and often combined heating solutions including underfloor heating and infrared ceiling panels. A winter garden is the product you specify when comfort, aesthetics, and year-round functionality are all non-negotiable.
Glass Room or Veranda with Pergola
This is the category where Wintalya’s products sit — outdoor structures that use a pergola or aluminium frame as the primary structure, combined with glass roof panels and optional glass side enclosures. This type of structure is typically positioned in the garden or on a terrace, rather than as a direct extension of the house, though lean-to configurations are also common. The advantage over a traditional extension is that it can often be installed without planning permission (as an outbuilding or canopy), and it delivers a deliberately indoor-outdoor character rather than fully interior feel.
Thermal Performance: The Critical Distinction
The most important technical specification in any glazed structure is the overall heat loss coefficient — how quickly the structure loses heat to the outside in cold conditions. This is what determines whether you need constant heating to maintain comfort in winter, or whether the structure’s own insulation retains warmth effectively.
Key specifications to understand:
- U-value of glazing — measures heat transfer through glass in W/m²K. Double glazing with low-E coating achieves approximately 1.1–1.4 W/m²K. Triple glazing achieves 0.5–0.8 W/m²K. The lower the number, the better the insulation. For a year-round winter garden in the UK, triple glazing is strongly recommended for the roof and at least low-E double glazing for the walls.
- Thermal bridge — the point where inner and outer aluminium faces of a frame profile connect. Thermally broken profiles insert an insulating polyamide bar between the faces, preventing cold bridge conduction. Non-broken profiles transfer cold directly from outside to inside, creating condensation and discomfort.
- g-value (solar factor) — measures how much solar energy passes through the glass. High g-value lets in more heat from the sun (useful in winter) but also more in summer (a problem in south-facing structures). For UK conditions, a balanced g-value of 0.3–0.5 with selective low-E coating is generally optimal.
- Air infiltration — at joints, seals, and opening vents. A well-engineered winter garden should achieve ≤1.5 m³/h per metre of seal length at 50Pa test pressure. Poor sealing is the most common source of cold draughts in glazed rooms.
Planning Permission: What the Rules Actually Say
Planning rules for glazed extensions in England under Permitted Development Rights (Class A, Class E) are as follows for a typical detached house:
- Single-storey rear extension permitted up to 4m depth (detached houses) or 3m (semi/terraced), maximum 4m height
- Side extensions are more restricted — maximum 4m high and no wider than half the width of the original house
- Outbuildings (including glass rooms in the garden) permitted up to 50% of the total garden area, maximum 2.5m height within 2m of a boundary, 4m height otherwise
- These rights are removed entirely in Conservation Areas, AONBs, National Parks, and for listed buildings — formal planning permission required
- The ‘neighbour consultation scheme’ allows extensions of 4–8m (detached) or 3–6m (semi/terraced) via a prior approval process, not full planning permission
In practice, most glass garden rooms and winter gardens in typical residential settings can be built under Permitted Development, but always confirm with your local planning authority before committing to a design.
Cost Guide: What Each Type Costs in the UK
- Traditional conservatory (uPVC, polycarbonate roof, basic): £15,000–£25,000 — largely obsolete under 2022 building regulations for habitable rooms
- Glass garden room (aluminium, double-glazed, lean-to): £25,000–£55,000 depending on size and specification
- Premium winter garden (triple-glazed, thermally broken, full climate control): £50,000–£120,000+
- Wintalya glass room/pergola hybrid (aluminium pergola frame, glass roof, optional glass sides): competitive with glass garden rooms; contact for project-specific pricing
These are supply and installation figures for completed projects in the UK market. The wide ranges reflect significant variation in size, specification, glazing type, heating systems, electrical work, and groundworks. Always obtain a fixed-price contract that includes all elements — ‘supply only’ prices can be misleading when professional installation costs are added separately.
Which One Should You Choose?
Choose a glass garden room or winter garden if: you want a genuinely indoor space that functions like a room extension; year-round fully heated comfort is non-negotiable; you want to add demonstrable value to your property via a permanent structure. Choose a Wintalya glass pergola system if: you want an indoor-outdoor experience rather than a fully interior room; you value the ability to open the roof and sides in good weather; you want a premium architectural garden feature rather than a house extension; or planning constraints make a full extension difficult.
✔ Interested in a bespoke winter garden or glass room system for your property? Wintalya designs and installs premium glass structures across Europe. Contact us to discuss your project.
