IN Brief:
- Crittall Windows is offering AGC Glass Europe Fineo vacuum insulating glazing across its steel window and door range.
- Fineo 8 is 7.7mm thick, with a declared centre-pane Ug value of 0.7 W/m²K and a laboratory Rw rating of 35dB.
- Whole-window thermal, acoustic and safety performance must be verified for each frame and installation rather than assumed from the glass specification.
Crittall Windows is making Fineo vacuum insulating glass available across its steel window and door systems, extending the glazing options for new construction and refurbishment projects where relatively slender frames are part of the specification. The glass is manufactured by AGC Glass Europe and provides thermal insulation in a unit much thinner than many conventional sealed double- and triple-glazed alternatives.
The standard Fineo 8 glass unit measures 7.7mm in total thickness. Its declared centre-pane thermal transmittance, Ug, is 0.7 W/m²K under the specified test method, while the reported weighted sound reduction index is Rw 35dB. These figures refer to the glazing configuration rather than to every steel window, glazed door or installed facade assembled around it.
Vacuum insulating glazing uses two glass sheets separated by a very small evacuated cavity. Tiny internal support pillars keep the sheets apart against atmospheric pressure, while a hermetic seal closes the perimeter. One of the glass surfaces has a low-emissivity coating that reduces radiative heat transfer, and removing most gas from the cavity limits the conduction and convection that would otherwise occur through an air-filled gap.
Fineo 8 contains two glass sheets of approximately 3.8mm each and a vacuum gap of about 0.1mm. The support pillars hold the panes apart against external air pressure, while the edge seal maintains the evacuated space. The insulating mechanism depends on limiting gaseous conduction and convection through the gap and reducing thermal radiation through a low-emissivity coating; the pillars and perimeter remain distinct heat-flow paths.
The 0.7 W/m²K figure is identified as Ug, the thermal transmittance through the glazing itself. A complete window has a separate Uw value that takes account of its frame, glazing area, edge losses, spacers or sealing configuration and the dimensions of the assembly. A steel frame can create a different heat flow path from the insulated pane, making project-specific testing or calculation essential where the designer is demonstrating compliance with building performance requirements.
The same distinction applies to the published acoustic measurement. An Rw rating describes the weighted sound insulation measured for a specified sample under controlled conditions, rather than an assured reduction at the facade of a particular building. Opening joints, vents, glass size, installation workmanship and the surrounding wall construction can affect the sound transmitted through a complete window assembly.
Crittall’s product range includes traditionally proportioned steel profiles and newer systems aimed at contemporary performance requirements. A thin insulating pane can preserve more of the slender glazing geometry associated with steel windows, particularly where refurbishment limits the depth of the rebate or the visual proportions must be retained. It does not by itself establish that an existing frame can take a replacement unit without checking glazing supports, seals, bead clearances and the condition of the opening sections.
An existing steel window may have worn seals, distorted profiles or glazing rebates that were not designed for this unit. Surveying must establish the actual rebate depth, supporting blocks, bead clearances, drainage and condition of the frame before replacement glass is specified. A factory-glazed new Crittall system and a retrofit into an old frame are different assemblies and cannot be assumed to share the same documented performance.
Where an older building has protected architectural features, changing the glazing can also require planning or listed-building consideration. A thinner unit may help preserve established sightlines, but neither Crittall’s wider availability claim nor the glass specification establishes consent for a particular property. Frame proportions, reflections and the treatment of existing glazing bars remain project-specific matters.
Light transmission presents another element of the technical balance. Published Fineo 8 data place visible light transmission at approximately 79% for the standard configuration, although coatings and alternative specifications can change the figure. Thermal insulation, solar gain, glare, safety and acoustic requirements need to be considered together, especially where overheating assessment or daylight performance is part of the design brief.
Offering the glass within Crittall’s range makes it possible to specify the window system and its insulating pane together, with the manufacturer assessing compatibility across its profiles. The claim is an expansion of available glazing options; it is not evidence that every configuration has already been tested to one identical thermal, acoustic or safety rating. The applicable whole-window figures will depend on each documented assembly.
The product announcement does not identify a named construction project, an additional manufacturing line or a new contract value. Project specifications should therefore be based on the technical schedule for the chosen assembly, including glazing thickness, declared Ug, calculated or tested whole-window Uw, safety requirements, and compatible frame and hardware details. Site installation and surrounding wall junctions must also be considered when assessing envelope performance.
Fineo 8’s 0.7 W/m²K centre-pane value and 35dB laboratory acoustic rating offer defined material properties for comparison. The separate values for the complete Crittall window or door will determine what can be declared for a particular building, especially where energy compliance, weather resistance and conservation constraints apply.
