The main difference between a conservatory and an orangery lies in their structural composition: conservatories typically feature at least 75% glass roofing and 50% glass walls, while orangeries have less than 75% glazed roofing and less than 50% glass walls, incorporating more brick or stone elements for a more substantial, extension-like feel.
Glazing Ratio Requirements
Builders such as Countrywide UPVC have to follow building regulations that specify precise glazing requirements for conservatories and orangeries. For a structure to qualify as a conservatory, at least 75% of the roof area must be glazed or translucent, and at least 50% of the external wall area must be made from translucent material. These requirements ensure adequate natural light while maintaining the structure’s classification as a conservatory rather than an extension. For orangeries, the glass roof covers less than 75% of the total roof area (typically featuring a flat roof with a central glass lantern), and glass walls cover less than 50% of the wall area.
If your structure doesn’t meet these glazing ratios or if you’re removing the thermal separation between the main dwelling and the conservatory/orangery, additional building regulations apply. The “25% glazing rule” becomes relevant for extensions, requiring that the total glazed area doesn’t exceed 25% of the extension’s floor area plus the area of any existing openings. However, this limitation can sometimes be bypassed by demonstrating that the extension doesn’t increase energy loss above 25%, which typically requires improved U-values for the glazing (around 1.6 W/m²K or better) and other thermal performance enhancements.
Brick vs Glass Construction
While conservatories embrace transparency with their predominantly glass structures, orangeries strike a sophisticated balance between solid construction and natural light. This fundamental difference in building materials creates distinct experiences, aesthetics, and practical benefits for each space.
Orangeries feature substantial brick or stone elements that provide a sense of permanence and solidity. These structures typically incorporate traditional brickwork with large windows and slim hardwood frames that allow for expansive use of glass while maintaining structural integrity. The brick elements not only contribute to the orangery’s classic charm but also offer superior insulation properties. Modern orangeries often use engineered bricks and composite stone, providing homeowners with various colors and finishes while preserving the structure’s solid nature.
In contrast, conservatories are defined by their lightweight, glass-dominant construction. With at least 75% of the roof and 50% of the walls being glazed or translucent, conservatories create bright, garden-connected spaces that feel more temporary than their orangery counterparts. This extensive use of glass allows for maximum natural light but can present challenges with temperature regulation.
The construction materials significantly impact thermal performance. Brick elements in orangeries provide better insulation, making them more energy-efficient and comfortable year-round. The solid construction helps reduce temperature fluctuations, minimizing issues with condensation and dampness that can plague all-glass structures. Meanwhile, conservatories rely heavily on the quality of their glazing for thermal efficiency, with modern options featuring improved U-values (heat retention) and G-values (solar control) to enhance comfort.
Material choice also affects property value. Orangeries typically provide a higher property value increase (up to 15%) compared to conservatories (at least 5%), partly due to their superior energy efficiency and more substantial construction. The solid foundation of an orangery, laid upon concrete, ensures both structural integrity and longevity, offering homeowners a more durable home extension.
For those considering material options, modern structures offer various choices:
- uPVC frames provide affordability, low maintenance, and good energy efficiency
- Aluminum frames offer strength, durability, and sleeker profiles with larger glass areas
- Timber frames deliver a classic aesthetic but require more maintenance
The brick-to-glass ratio ultimately defines not just the classification of the structure but its character, comfort, and contribution to your home’s value.
Lantern Roof Design
Orangery lantern roofs serve as the defining architectural feature of these elegant extensions, typically consisting of a central glazed structure that sits on a flat roof perimeter. These lanterns come in various styles, from rectangular designs (the most common) to more complex domed or hexagonal configurations that require advanced engineering skills. Modern lantern designs include slim black aluminum frames for an industrial-chic aesthetic, traditional white frames for timeless elegance, bespoke color finishes to match existing decor, and minimalist frameless options for contemporary homes.
The lantern’s primary function is maximizing natural light penetration, creating bright, airy spaces while maintaining better temperature control than full-glass conservatory roofs. High-quality lanterns incorporate thermally efficient glazing options, including self-cleaning, solar control, and textured glass, with standard 28mm double glazing units being common. These energy-efficient features help regulate indoor temperatures year-round, reducing reliance on artificial lighting and heating while creating a stunning architectural focal point that enhances both the interior ambiance and exterior aesthetics of the property.
Minimum Glazing Area Standards
To qualify as a conservatory under UK building regulations, specific minimum glazing requirements must be met. The structure must have at least 75% of its roof area glazed or made from translucent material, while at least 50% of the external wall area must be similarly constructed. These standards aren’t arbitrary but serve to distinguish conservatories from traditional extensions, ensuring they maintain their light-filled, garden-connected character.
For a structure to remain exempt from most building regulations, it must meet several additional criteria beyond just the glazing ratios:
- The floor area must not exceed 30 square meters
- It must be built at ground level
- It must be thermally separated from the main dwelling (typically with exterior-quality doors)
- Any heating system must be independent of the main dwelling’s system, with separate temperature controls
- All glazing in critical locations must meet safety standards (using toughened or laminated safety glass)
If your conservatory doesn’t satisfy these conditions—particularly if you’re creating an open-plan space by removing the thermal separation—it will be treated as a standard extension and subject to full building regulations approval.
The “25% glazing rule” often causes confusion for homeowners planning extensions. This rule states that windows, doors, and rooflights in an extension should be limited to 25% of the extension’s floor area. However, this limitation doesn’t apply to structures that qualify as conservatories under the criteria above. For standard extensions exceeding this 25% threshold, you’ll need to demonstrate equivalent energy efficiency through improved U-values or other compensating measures.
For orangeries, which by definition have less glazing than conservatories (less than 75% glazed roof and less than 50% glazed walls), the same exemption criteria apply. If your orangery meets these standards, it can also benefit from the building regulations exemptions that apply to conservatories.
It’s worth noting that these minimum glazing standards may be affected by the 2022 updates to building regulations (particularly Parts F and O) aimed at reducing overheating in buildings. However, structures that qualify as conservatories under the criteria above remain exempt from these new requirements.
Thermal Performance Comparison
Orangeries and conservatories differ significantly in their thermal performance due to their structural composition, with each offering distinct advantages depending on the season and desired comfort level.
Orangeries typically provide superior thermal comfort compared to conservatories, primarily due to their reduced glazing and substantial brick elements. The solid walls and pillars in orangeries naturally retain more heat than the predominantly glass structure of conservatories. This architectural difference creates a more stable internal temperature throughout the year, with less dramatic fluctuations between seasons.
The U-value—a measurement of how well a material retains heat—plays a crucial role in thermal efficiency. The lower the U-value, the better the insulation properties. Traditional single-glazed conservatories might have U-values around 5.7 W/(m²K), while modern double-glazed options can achieve values as low as 1.2 W/(m²K). By comparison, the well-insulated walls of an orangery typically have U-values around 0.25 W/(m²K), significantly outperforming even the best glazing solutions.
For conservatories to approach the thermal efficiency of orangeries, they require specialized features:
- Solar-control glass with optimized G-values (typically 0.4 or lower) to reduce summer overheating
- Advanced double or triple glazing with U-values of 1.2 W/(m²K) or better
- Thermally efficient frames and warm edge spacer bars to prevent cold bridging
- Integrated ventilation systems such as roof vents to manage airflow
Despite these improvements, the fundamental difference remains: conservatories allow more natural light but experience greater temperature variations, while orangeries sacrifice some brightness for better temperature stability. This trade-off is particularly noticeable in extreme weather conditions.
In winter, orangeries maintain warmth more effectively due to their insulated walls and reduced heat loss through glazing. Conservatories, even with modern thermal improvements, typically require more heating to maintain comfortable temperatures. Underfloor heating has become a popular solution for both structures, providing even warmth without sacrificing wall space to radiators.
During summer months, the solid elements of orangeries help shield the interior from excessive solar gain, keeping the space cooler. Conservatories, with their extensive glazing, are more prone to overheating unless equipped with solar-control glass and adequate ventilation. For existing conservatories that struggle with temperature regulation, retrofitting a solid tiled roof has become a popular solution to improve thermal performance while maintaining the structure’s footprint.
For year-round comfort, modern orangeries combine the best of both worlds: substantial insulated elements for temperature stability with strategically placed glazing to maximize natural light. This balanced approach typically results in lower energy costs over time, potentially offsetting the higher initial investment compared to a standard conservatory.
Conclusion
Choosing between a conservatory and an orangery ultimately comes down to your priorities in design, comfort, and functionality. Conservatories offer bright, airy spaces that blur the lines between indoors and outdoors, ideal for enjoying garden views and natural light. However, their extensive glazing can present challenges in thermal performance. Orangeries, with their solid construction and refined architectural elements, provide a more permanent, energy-efficient extension that adds significant value and year-round usability to your home. Understanding the structural, regulatory, and performance differences can help you make an informed decision that best suits your lifestyle and property.