Natural light is an essential element in modern building design, with rooflights playing a crucial role in bringing daylight into commercial and public spaces. However, when specifying rooflights for any new-build or refurbishment project, safety must always be the primary consideration. When it’s coming to rooflight specification one thing should never be compromised: the use of laminated glass for the inner pane of all glazed rooflight units.
Understanding laminated glass
Laminated glass consists of two or more panes of glass bonded together under high temperature with an interlayer – typically polyvinyl butyral (PVB) or, for higher strength applications, ionoplast material. This construction creates a safety feature that is vital for overhead glazing: if breakage occurs, the glass remains bonded to the interlayer, preventing it from falling from the unit.
When properly specified with the correct thickness of materials, a laminated inner pane can also hold unexpected loads that might land on the rooflight, such as a maintenance worker or dropped tools, significantly reducing the risk of serious accidents.
Why insist on laminated inner panes?
Protection for building users
The primary concern with any overhead glazing is the safety of people beneath it. If a rooflight's inner pane breaks, a laminated construction ensures that glass fragments remain adhered to the interlayer rather than falling and potentially causing injury to building occupants below. In contrast, toughened glass, while stronger than standard glass, shatters into small pieces upon breakage, which can still fall and pose a risk to people underneath.
While British Standards allow for the use of toughened glass in certain circumstances where rooflights are less than 5 metres above floor level (subject to risk assessment), aligning with the Rooflight Association's recommendation that inner panes should always be laminated, regardless of height or location.
Non-fragility performance
Beyond protecting those beneath the rooflight, proper specification must also consider maintenance staff and others who may access the roof. A rooflight with appropriate laminated glass can achieve non-fragility classification, meaning it can prevent someone accidentally walking or falling onto it from falling through, even if the glass is already broken or damaged.
It's important to note that non-fragility is measured on the entire roof assembly – the glass specification, the framing system, and how the glass is secured all play vital roles. Not all laminated glass will automatically achieve a non-fragile classification; an enhanced specification may be necessary.
Testing and classification
Industry standards define a clear fragility test sequence that provides a standardized approach to testing glazed roofs, resulting in classifications that help specifiers select the right solution for each application:
Class 0: Walk-on rooflights with unrestricted access
Class 1: Can resist substantial impact without fracturing and remains retained by the supporting framework. Once/if fractured, it can resist a static load.
Class 2: Similar to Class 1 but permitted to break under impact. Still required to withstand a static load after fracture.
Class 3: No direct standing on glass. Requirement for falling equipment to not penetrate the glass.
The testing takes into consideration both the threat of people falling onto the rooflight (soft body impact test) and tools or equipment falling onto it (hard body impact test), as well as the residual strength of the glazing if the glass breaks (static load test).
Beyond Safety: Additional Benefits of Laminated Glass
While safety is the paramount concern, laminated inner panes also offer additional performance benefits:
Thermal efficiency
When specified within a properly designed insulated glass unit (IGU), laminated glass contributes to reduced heat loss. Importantly, it can be incorporated into both double and triple glazed units. This versatility allows for optimal thermal performance alongside the essential protective qualities. Low-E coatings can be applied to reflect heat back into the building, while the cavity between panes can be filled with argon gas to further enhance thermal performance.
Solar control
Excessive solar gain can make internal spaces uncomfortable without air conditioning or ventilation. The specification of the outer pane can include solar control properties to limit heat transfer from the sun while still maintaining good light transmission levels.
Innovative rooflight solutions for your buildings
COXDOME’s portfolio of glazed rooflight solutions is designed with safety as the top priority. Lumiglaze is featuring a laminated inner pane and achieving Class B non-fragile to ACR(M)001 The rooflight is adhere to rigorous safety standards, including reaction to fire testing (EN 13501-1) and external fire performance (EN 13501-5).
Ensuring long-term safety and thermal performance
The specification of rooflights should never compromise on safety. Regardless of the height or location of a rooflight, an inner toughened pane for overhead glazing should not be deemed acceptable. By insisting on laminated inner panes in all glazed rooflight applications, building owners and specifiers can ensure the safety of both building occupants and maintenance personnel while also benefiting from optimal thermal performance.
When specifying your next commercial rooflight project, remember that safety and performance go hand in hand and a laminated inner pane is non-negotiable for both.