Orangery vs Conservatory Glazing: A UK Homeowner's Guide

Expanding your home with a new glazed extension can dramatically enhance living space, natural light, and property value. For many UK homeowners, the choice often comes down to an orangery or a conservatory. While both offer beautiful, light-filled additions, their fundamental differences lie in their construction, particularly their glazing and roof structures. Understanding these distinctions, alongside relevant UK Building Regulations, is crucial for making the right decision for your home and lifestyle.

This guide will delve into the technical aspects of orangery and conservatory glazing, exploring their unique characteristics, performance considerations, and how they interact with UK Building Regulations. Our aim is to provide you with the expert knowledge needed to navigate this important home improvement decision.

Understanding the Basics: Orangery vs. Conservatory

Before diving into the specifics of glazing, it's essential to grasp the core structural differences between these two popular extensions.

Conservatories: Predominantly Glazed

Traditionally, a conservatory is characterised by its high proportion of glazing. This includes the walls and often a fully glazed or polycarbonate roof. The aim is to maximise natural light and create a space that feels very much connected to the garden. Modern conservatories have evolved significantly from their early Victorian counterparts, now offering much better thermal performance, but the emphasis on glazing remains.

Orangeries: A Blend of Solid Structure and Glazing

Orangeries, originating from the 17th century, offer a more substantial, 'room-like' extension. They feature more solid wall construction, often with brick or stone pillars, and a distinctive flat roof perimeter with a central glazed lantern or rooflight. This blend provides a greater sense of permanence and insulation compared to a traditional conservatory, while still allowing ample natural light to flood the space.

Glazing Performance and U-Values: The Thermal Heart of Your Extension

The thermal performance of your extension's glazing is paramount, impacting energy efficiency, comfort, and compliance with UK Building Regulations. This is primarily measured by the U-value, which indicates how effectively a material insulates. A lower U-value signifies better insulation and reduced heat loss.

Understanding U-Values for Glazing

• Glass Panes: Standard double glazing typically has a U-value around 2.8 W/m²K. However, modern high-performance double glazing, often featuring low-emissivity (low-e) coatings and argon gas infill, can achieve U-values as low as 1.2 W/m²K.
• Triple Glazing: For superior thermal performance, triple glazing offers U-values as low as 0.8 W/m²K, providing excellent insulation and sound reduction.
• Frame Material: The U-value of the entire window or door unit (known as the 'overall U-value' or 'U_w') is also influenced by the frame material. Timber, uPVC, aluminium, and composite frames all have different thermal properties.

UK Building Regulations Part L (2022 England) for Extensions

For new extensions, including orangeries and conservatories that are not 'exempt' (more on this below), the glazing must meet specific thermal performance standards. The current requirements (Part L 2022 England) are stringent:

• Windows and Doors (New Build): Maximum U-value of 1.2 W/m²K
• Windows and Doors (Replacement): Maximum U-value of 1.4 W/m²K
• Walls: Maximum U-value of 0.18 W/m²K
• Floors: Maximum U-value of 0.18 W/m²K
• Roofs: Maximum U-value of 0.15 W/m²K

These values ensure that new extensions contribute positively to the overall energy efficiency of the dwelling. Achieving these U-values often necessitates high-performance double or triple glazing, thermally broken frames, and well-insulated solid sections.

Orangery Glazing Considerations

Orangeries, with their more substantial structure, offer greater flexibility in glazing design and performance.

Roof Glazing: The Lantern

The defining feature of an orangery is often its roof lantern or series of rooflights. These can be specified with highly efficient glazing:

• Self-Cleaning Glass: Treated with a special coating that reacts with UV light to break down organic dirt, which is then washed away by rain.
• Solar Control Glass: Designed to reflect a significant proportion of the sun's heat, preventing overheating in summer while still allowing light in. This is crucial for comfort.
• Low-E Glass: Reduces heat loss through the roof in winter.
• Tinted or Opaque Options: For specific aesthetic or privacy requirements.

The U-value of the roof lantern glazing will also contribute to the overall roof U-value calculation, which must meet the 0.15 W/m²K requirement for the entire roof structure if the orangery is not exempt.

Vertical Glazing: Windows and Doors

Orangeries typically feature large windows and bi-fold or sliding doors. These must meet the 1.2 W/m²K U-value for new build extensions. Frame materials like thermally broken aluminium, high-performance uPVC, or engineered timber are common choices, offering durability, security, and excellent thermal performance.

Conservatory Glazing Considerations

For conservatories, the sheer volume of glazing means that careful selection is even more critical for year-round comfort and energy efficiency.

Roof Glazing: The Largest Surface Area

Conservatory roofs are predominantly glazed or use polycarbonate. While polycarbonate is a more budget-friendly option, its thermal and acoustic performance is significantly lower than modern glass. For glass roofs:

• High-Performance Double Glazing: Essential for thermal regulation. Look for units with low-e coatings, argon gas infill, and a U-value of 1.0 W/m²K or lower if possible.
• Solar Control Glass: Absolutely vital for conservatories to prevent them from becoming unbearably hot in summer. This glass can reject up to 80% of the sun's heat.
• Self-Cleaning Glass: Highly recommended due to the difficulty of cleaning large glazed roof areas.
• Tinted Options: Can help reduce glare and provide a cooler aesthetic.

Vertical Glazing: Walls of Light

As with orangeries, the vertical glazing (windows and doors) must meet the required U-value of 1.2 W/m²K. The choice of frame material and glazing specification will directly impact the overall thermal performance and structural integrity of the conservatory.

Building Regulations and Exemptions: A Critical Distinction

This is where the 'orangery vs. conservatory' debate often becomes most complex for homeowners. Not all glazed extensions automatically require full Building Regulations approval for thermal performance.

Exempt Conservatories

A conservatory is typically exempt from the full thermal performance requirements of Part L if it meets all of the following criteria:

• It is at ground level.
• It has a floor area of 30m² or less.
• It is substantially glazed (at least 50% of the wall area and 75% of the roof area must be translucent material).
• It is separated from the main dwelling by a door and/or window that meets Building Regulations standards (e.g., a thermally efficient external door).
• It has an independent heating system or no heating at all.

If your conservatory meets these criteria, you may not need to demonstrate compliance with the stringent U-values for walls, floors, and roofs. However, the glazing itself (windows and doors) within the conservatory should still meet the replacement window U-value of 1.4 W/m²K.

Orangeries and Non-Exempt Conservatories

Most orangeries, due to their solid roof construction and higher proportion of solid walls, will not meet the 'substantially glazed' criterion for exemption. Therefore, an orangery will almost always require full Building Regulations approval, meaning:

• The entire structure (walls, floor, roof, and glazing) must meet the U-value requirements specified in Part L (e.g., 0.18 W/m²K for walls, 0.15 W/m²K for roofs, 1.2 W/m²K for windows/doors).
• You will need to submit plans and calculations to your local Building Control body.

Similarly, a conservatory that exceeds 30m², is not separated from the main house, or has integrated heating will also fall under full Building Regulations and must comply with all Part L requirements.

Legal Note: While we avoid strong legal terms, it's important to understand that proceeding with an extension that does not comply with Building Regulations, where required, could lead to issues with local authorities, potential difficulties when selling your property, and in some cases, the requirement to alter or even remove the structure. It is always advisable to consult with your local Building Control body or a qualified professional early in your planning process.

Comparison Table: Orangery vs. Conservatory Glazing & Structure

Feature	Conservatory	Orangery
Roof Structure	Predominantly glazed or polycarbonate	Flat roof with central glazed lantern/rooflights
Wall Structure	Predominantly glazed (over 50%)	More solid walls, brick/stone pillars, less than 50% glazed
Thermal Performance (General)	Historically lower, but modern glazing significantly improves this. Prone to overheating/cooling if not specified correctly.	Generally better due to solid roof and walls, easier to integrate with main house heating.
Building Regulations (Exemption)	Often exempt if specific criteria met (e.g., <30m², separated, substantially glazed).	Rarely exempt; typically requires full Building Regulations approval for thermal performance.
Vertical Glazing U-value (Part L 2022)	1.2 W/m²K (new build), 1.4 W/m²K (replacement/exempt)	1.2 W/m²K (new build)
Roof U-value (Part L 2022)	N/A if exempt; if not exempt, 0.15 W/m²K for the entire roof.	0.15 W/m²K for the entire roof (including lantern).
Feel/Aesthetic	Light, airy, 'outdoor' feel, strong connection to garden.	More 'room-like', substantial, integrated feel, architectural statement.
Cost Implications	Generally lower initial cost, but can be higher if high-spec glazing is used to meet non-exempt regulations.	Generally higher initial cost due to more complex construction and materials.

Benefits of High-Performance Glazing

Investing in superior glazing, regardless of whether you choose an orangery or a conservatory, offers numerous advantages:

Making the Right Choice for Your Home

The decision between an orangery and a conservatory, and the glazing specifications within them, should be based on several factors:

• Desired Aesthetic: Do you prefer a light, garden-integrated space or a more substantial, architectural extension?
• Intended Use: Will it be a dining room, living room, office, or simply a seasonal sunroom? This will influence thermal requirements.
• Budget: Orangeries typically have a higher upfront cost due to their complex construction.
• Planning Permissions & Building Regulations: Always check with your local authority. While many conservatories fall under permitted development, larger or more integrated extensions (like most orangeries) will require full planning permission and Building Regulations approval.
• Thermal Performance & Energy Efficiency: Consider how important year-round comfort and low energy bills are to you.

Ultimately, both orangeries and conservatories can be stunning additions to a UK home. The key is to understand the implications of their differing structures and glazing requirements, particularly concerning UK Building Regulations. By prioritising high-performance glazing and working with experienced professionals, you can ensure your chosen extension is a beautiful, comfortable, and energy-efficient space for years to come.

For expert advice on glazing options, U-values, and compliance with UK Building Regulations for your orangery or conservatory project, consider consulting with specialists like Shard AG. Our team can guide you through the technical specifications and help you select the ideal glazing solutions for your unique requirements.