Structural Glazing Systems Compared: What Should Homeowners Look For?

Structural glazing can make a wall appear almost to disappear. Large panes sit together with narrow silicone joints, perimeter fixings are concealed within the surrounding construction and the view is left largely uninterrupted by framing.

That visual simplicity makes structural glazing systems rather harder to compare than conventional windows or doors. Two completed glass walls can look almost identical while the fixing concealed beneath the floor, ceiling and wall finishes is quite different.

For a homeowner planning a substantial glazed extension, frameless window or glass wall, the useful comparison therefore sits behind the finished surface. How is the glass supported? Is the perimeter fixing thermally broken? How much glass can the system accommodate? What performance has actually been tested? And, less excitingly but perhaps more importantly in 15 years' time, how would a damaged pane be replaced?

A frameless wall is very good at hiding the engineering that made it possible.

How do structural glazing systems hold the glass?

Structural glazing can be created using project-specific fixing details, often based around steel or aluminium angles. The glass is supported and packed into position, while the surrounding floor, wall and ceiling finishes conceal the structural fixing.

It is an established and highly adaptable method. The fixing can be engineered around unusual geometry, different glass compositions, building structure and the loading requirements of the individual project.

Proprietary structural glazing systems take a more standardised approach. Instead of creating the perimeter fixing primarily from separate angles and project-specific components, a purpose-designed profile performs that role.

Invisio+, developed by IQ Glass, is one example. The system uses an extruded aluminium structural glazing profile with integrated polyamide thermal breaks. The Invisio+ profile is 72 mm deep and can accommodate glass units up to 62 mm thick, allowing deeper insulating glass constructions to be incorporated within a concealed structural fixing. The Sky House Invisio+ article also describes the system as concealed within the surrounding finishes and intended for triple-glazed, large-format frameless structural glass.

Other proprietary systems are available. Fluid X Vertical, for example, is also presented by its manufacturer as a thermally broken structural glazing system and is offered with double and triple-glazed configurations.

The architectural question is therefore less about choosing between an old and a new method, and more about understanding how different systems resolve the same glass-to-building junction.

Structural glazing systems compared

The table contains an important distinction. “Thermally broken” does not describe one universally identical construction detail. Different structural glazing systems achieve thermal separation in different ways, and the performance of the finished installation still depends on the glass specification, dimensions, surrounding construction and complete perimeter junction.

What does thermally broken structural glazing actually mean?

Metal conducts heat readily. If a metal fixing creates a continuous route between the inside and outside of the building envelope, it can become a thermal bridge.

Angle-based structural glazing details can address this through insulation, packing materials and careful coordination with the surrounding building fabric. Their effectiveness therefore depends heavily on how the final project junction is designed.

A purpose-designed thermally broken profile incorporates insulating material within the fixing itself. In the Invisio system, polyamide separates sections of the aluminium profile to interrupt the conductive path through the fixing. IQ's thermal documentation identifies this break within the profile and references thermal calculations undertaken to BS EN ISO 10077-1:2017.

For a homeowner, the phrase “thermally broken structural glazing” should prompt another question: where is the thermal break in the actual construction detail?

Several products on the market use the terminology. That does not make the products equivalent. The position of the insulating material, the extent of the metal connection, the glass specification and the way the fixing meets the surrounding insulation all influence the completed junction.

A section drawing is therefore particularly useful. It allows an architect or homeowner to follow the insulation line through the floor, wall or roof and understand what happens as it reaches the structural glass.

A product name can be reassuring. A well-resolved section drawing is considerably more informative.

Can structural glazing systems use triple glazing?

Yes, although glass depth becomes an important part of the specification.

A triple-glazed structural glass unit can be considerably deeper and heavier than a typical double-glazed unit, particularly where laminated panes, solar-control coatings, acoustic interlayers or other specialist glass requirements are incorporated.

This was one of the reasons for developing Invisio+. The standard Invisio profile accommodates glass up to 41.5 mm thick, while Invisio+ increases the available depth to 62 mm.

Other proprietary structural glazing systems also accommodate triple glazing. The precise maximum glass depth varies between systems, which matters because the overall thickness of a structural glass unit is governed by considerably more than the number of cavities.

Triple glazing will not improve every project by default. Added glass means added weight, different structural requirements and a different relationship with solar gain, orientation and the wider building envelope.

For a low-energy home with extensive frameless glazing, however, a fixing system capable of accepting deeper insulating glass gives the design team more freedom to pursue demanding thermal targets without abandoning the intended architectural language.

What about large panes and mullion-free glass walls?

Structural glazing is particularly useful where glass is intended to read as a continuous architectural surface rather than a sequence of framed windows.

Adjacent structural glass units can be joined with silicone, allowing substantial elevations to be produced without conventional vertical mullions. The glass composition, wind pressure, support conditions and permitted deflection then determine the practical dimensions.

IQ's Invisio documentation uses a series of tested scenarios rather than presenting one maximum dimension as the limit of the entire system. These include four-edge supported panes, multi-pane glass walls, oriel windows, glass boxes and other support arrangements. Deflection is incorporated into the tested design criteria.

One published frameless window scenario includes tested openings up to 5 m high and 6.9 m wide at the lower reference wind pressure, with allowable dimensions reducing as wind pressure increases.

That relationship is worth understanding. A manufacturer stating that a system can produce six-metre glazing does not mean every six-metre pane is structurally appropriate on every site. A sheltered inland elevation and an exposed coastal facade impose very different demands on the glass.

Large structural glazing should therefore be assessed against the actual building, rather than treated as a catalogue size.

Tested system or project-specific engineering?

Project-specific engineering is fundamental to structural glass. Architecture has an inconvenient habit of refusing to fit neatly into product catalogues.

A bespoke angle detail can be developed specifically around the glass size, structure and loading of a particular building. This provides substantial flexibility, although the performance of that junction belongs to that individual design.

A proprietary system can begin with known profiles, established details and existing test information, then adapt those details to suit the building.

Invisio has been tested for thermal performance and structural behaviour under different wind-load conditions and support scenarios. The product information also provides recommended glass compositions for tested arrangements.

This gives the architect a technically developed starting point. Less of the perimeter fixing has to be conceived from first principles, while project-specific engineering can still address the glass size, loading and architectural conditions.

The strongest structural glazing specialists tend to operate comfortably in both territories. They use tested systems where a repeatable detail is useful, and bespoke engineering where the architecture moves beyond those conditions.

How easy is it to replace structural glass?

Replacement tends to receive rather less attention during the design of a new house. Nobody commissions a six-metre glass wall while enthusiastically imagining breaking it.

Large panes can, however, be damaged. Insulated glass units can also require replacement during the life of the building.

The way the perimeter fixing has been assembled then becomes significant. A glass unit that is deeply buried behind finishes and secured within a bespoke assembly may require sections of the surrounding construction to be opened before the pane can be removed.

The Invisio fixing was designed with a removable side section to make the installation and removal of large structural glass units more straightforward.

This has little effect on the photographs taken when the house is finished. It can matter considerably later.

Serviceability is therefore a useful comparison point between structural glazing systems, particularly on houses using unusually large or difficult-to-access glass.

Is a proprietary structural glazing system always better?

No. A well-designed bespoke fixing may be entirely appropriate for a straightforward structural glass installation, or for an unusual geometry that sits outside the useful limits of a standard profile.

Likewise, the presence of a proprietary aluminium section does not guarantee that every surrounding junction has been resolved well.

The value of an engineered system becomes clearer when several requirements have to be coordinated simultaneously: large glass, minimal visible structure, deeper insulating units, demanding thermal targets, known structural performance and future glass replacement.

There is another consideration that sits slightly beyond the product itself: what happens when the architectural detail becomes more complicated than the system?

This is where the technical capability behind the product becomes relevant.

IQ Glass has developed bespoke structural glass solutions in which the glass itself takes on roles that would conventionally require additional steel or vertical supporting elements. At one project, an unsupported laminated glass beam was designed to support a glass floor and continue above it to form the frameless balustrade. This removed the need for a separate steel beam and railing assembly.

At Model Farm, a different unsupported glass beam was used beneath a structural glass roof. The detail uses laminated glass and a precision-cut connection into the adjacent structural glass wall, allowing the beam to provide support without introducing a conventional vertical fin into the sightline. IQ states that unsupported glass beams can be manufactured up to 6,000 mm in the UK, with longer units available through international sourcing.

These are not Invisio+ features, and they should not be confused with the perimeter fixing system. They demonstrate something else that is useful when comparing structural glazing providers: the depth of glass engineering available when a project moves beyond a standard detail.

A proprietary system is most valuable when it sits within that wider capability rather than becoming the limit of it.

What should a homeowner compare before choosing structural glazing?

For a high-value residential project, ask for more than a rendered image and a headline glass specification.

Start with the glass-to-structure section proposed for the project. Establish where the perimeter fixing sits, whether it contains a thermal break and how that fixing connects with the insulation in the wall, floor or roof.

Ask what glass build-up is proposed. Double glazing and triple glazing are useful descriptions, but the actual specification may also include laminated panes, solar-control coatings, low-emissivity coatings, specialist interlayers and other elements that change the thickness and weight of the finished unit.

For large panels, ask what wind loading and deflection criteria have been used. If thermal or structural performance figures are quoted, ask what size of installation and glass specification those figures relate to.

It is also worth understanding how much of the proposed installation sits within an existing tested system and how much has been engineered specifically for the project.

Finally, ask how one pane would be removed if it needed replacing.

These questions reveal considerably more than comparing two photographs of completed frameless glass walls.

Comparing structural glazing at Sky House Design Centre

Structural glazing becomes easier to understand at full scale. A completed installation explains the architectural effect, while a section of the fixing explains how that effect has actually been achieved. Sky House already has dedicated editorial content about seeing structural glass systems at full scale in its Amersham showroom.

At Sky House Design Centre in Amersham, visitors can see products and construction details from specialist architectural and interior brands within one design destination. IQ Glass, whose showroom and technical displays are based at Sky House, developed the Invisio structural glazing range.

Seeing a thermally broken structural glazing section beside a more conventional fixing detail makes the difference considerably easier to understand than reading the phrase on a specification sheet.

For homeowners already working with an architect, a visit becomes particularly useful once glass sizes, junctions, finishes and thermal requirements need to become actual construction details. Bringing drawings allows those questions to be discussed against physical systems rather than in the abstract.

A glass sample the size of a coaster can tell you quite a lot about colour. It has rather less to say about how a six-metre glazed wall meets the floor.

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FAQs about structural glazing systems

What is the difference between structural glazing and a normal framed window?

Structural glazing conceals the principal perimeter fixings within the surrounding construction and can use silicone joints between adjacent glass units, creating a much more continuous glass surface. A conventional window generally retains a visible frame around each glazed opening.

Can structural glazing be thermally broken?

Yes. Thermally broken structural glazing systems use insulating material within or around the fixing arrangement to reduce heat transfer through the glass-to-building junction. The exact construction varies between systems, so the proposed section detail should be reviewed rather than relying solely on the words “thermally broken”.

Can you have triple-glazed structural glass?

Yes. Triple glazing requires sufficient fixing depth and appropriate structural engineering because the resulting glass units can be considerably thicker and heavier. Invisio+ accommodates glass units up to 62 mm thick.

Are frameless glass walls completely frame-free?

The finished glazing can appear frameless, but the glass still requires structural support and a secure connection to the building. In a well-resolved structural glazing detail, those fixings are concealed within the adjacent floor, ceiling and wall finishes.

Is a thermally broken system automatically better than an angle-based fixing?

No. The complete construction detail matters. A bespoke fixing can be engineered to perform very well, while a proprietary system still needs to be integrated correctly with the surrounding building envelope. A useful comparison looks at the actual thermal path, glass specification, structural performance and project detail.

What should I ask a structural glazing company before choosing a system?

Ask for the proposed section drawing, thermal information relevant to the actual configuration, maximum glass depth, structural and wind-load criteria, details of the thermal break and an explanation of how the glass could be replaced later.

Is Invisio+ the only thermally broken structural glazing system?

No. Other proprietary structural glazing systems are marketed as thermally broken. The useful comparison lies in the construction of the fixing, the available technical evidence, the glass specification it can accommodate and how the complete junction is resolved within the building envelope.

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