Patent Glazing

Patent Glazing is a non-load bearing framing system mainly used in overhead glazing.

It can also be used in vertical situations.

Its slim profiles allow the full use of natural light in the building. Patent Glazing is a drained and ventilated system of dry glazing comprising a series of longitudinal support members, known as ‘Patent Glazing Bars’, fixed to the building structure, and glass infills, either single- or double-glazed.
Developed as a two edged supported system, Patent Glazing is an economic alternative to four edge support curtain walling.

 

 

Essential features

Key to the Patent Glazing system is the design of the aluminium section that provides continuous support to the long edge of the glass or composite infill panel. In addition to supporting the infill it is designed to incorporate:

seatings to provide continuous support to the sides of the glass pane cap or wings, to retain the glass pane and impede direct water penetration without restricting thermal channels or grooves under the seating, to collect and drain away any water that may penetrate beyond the wings and cap fittings, for attaching the load bearing element to the structure.

The glazing bars project either internally or externally to the glass on a roof application and are traditionally T-shape in cross section, although hollow box sections are also used.

GLASSOLUTIONS CONTRACTING offers Patent Glazing that can be either:

Supported:

The Patent Glazing bars support the self-weight of the system, stress caused by wind and snow loads.

These loads are transmitted to a secondary structure and through to the structural frame. Such systems are used for canopies, northlights and large multi-pitched roofs such as atria.

 

Self supported:

The system can bridge a 6m gap, extend to any length, and support the self-weight of the system and stress caused by wind and snow loads.

These loads are transmitted directly to the structural frame without the need for additional steel or timber supports.

Such systems are used for hipped lantern and sky lights, rectangular, pyramid, octagonal or multi-faceted features.

Design criteria

The design of a Patent Glazing system must be in accordance with BS 5516 Design and installation of sloping and vertical patent glazing.

Patent Glazing is a non-load bearing system, not designed to take any structural loads of the building.

However, it must be structurally strong enough to support wind loads, snow loads and the self-weight of the installation. Allowance must also be made for building movement, maintenance loads and safe access for internal and external cleaning.

The infill glass panels must withstand the stress and deflection caused by wind and snow loads. The correct choice depends on pane size, dimensions, support and loadings.

GLASSOLUTIONS strongly recommends the use of laminated glass in single-glazing or as the inner pane of a sealed unit where it is necessary to minimise the risk of glass falling down after breakage.

Given the loadings, the bar span between structural supports, bar centres and degree of slope, GLASSOLUTIONS CONTRACTING will calculate:

  • the glass thickness or double-glazing unit configuration
  • the correct size of glazing bar Most Patent Glazing systems were designed and tested on the basis that the glazing bars are set at 600mm centres. This can

be increased, but needs to be correctly designed by GLASSOLUTIONS CONTRACTING. Where the bar span exceeds the available

glass size, or to meet safe handling requirements, joins can be made in the length of glazing in the form of a silicone joint, or a non-structural transom or ‘H’ frame per-pendicular to the glazing bars.

Weather-resistance

There are no standard tests for the weather-resistant properties of Patent Glazing. If the design recommendations of BS 5516 are followed, good weather-resistance is achieved.

The minimum recommended pitch for Patent Glazing is 15°. Where the slope is less than 15° care must be taken to ensure the integrity of weather-resistant properties and to avoid the build-up of dirt in the drainage channels.

Openings

Opening lights provide natural ventilation in Patent Glazing and, where necessary, smoke ventilation compliant with BS 7346 : Part 1.

These lights can be mechanically or remotely operated. If necessary they can also be linked to the building management system.

Building tolerances and movement

In order to ensure the accuracy required to achieve the best appearance of the completed installation, it is necessary to establish specific limits for dimensional and positional tolerances of the supporting structure at an early stage.

Guidance on structural tolerances can be found in BS 5516. Allowing for building tolerances means that the structural opening and fixing areas in a building, will not always be plumb, square and true dimensionally. Also, during a building’s lifespan, the fixing points and openings may be subject to movement. Thus, when designing a Patent Glazing application, consideration must be given to such tolerances.

 

Glazing

The glass infill panel is a key contributor to the building’s internal environment. Patent Glazing systems can incorporate most of the glass types and configurations in laminated form from the SAINT-GOBAIN GLASS range:

  • SGG CLIMAPLUS sealed units to reduce heat loss
  • SGG SOLAR CONTROL to decrease dependence on air-conditioning
  • SGG STADIP SILENCE to reduce noise, especially impact noise from rain.

The glass predominantly determines thermal performance of an installation, however the frame may conduct heat and bridge this insulation.

Unless the frame is thermally improved, condensation may occur as well as heat loss.

Double-glazed units used in sloped applications should be stepped at the bottom edge to allow drainage. The upper glass pane of the unit extends beyond the lower glass pane.

Fabrication

Patent Glazing bars are cut from sections of extruded aluminium alloy 6063-T6 to BS 1474. Normal finishes are polyester powder coated or anodised. Fasteners are either stainless steel to BS 304515 Grade A2 or mild steel bright zinc plated.

Gaskets are extruded thermo plastic rubber quality 98625 BS 4255 : Part 1:1986 Grade C.

Key criteria when considering Patent Glazing:

  • Overall size and dimensions
  • Wind speed and loading
  • Roof pitch
  • Dual or mono pitch
  • Length of bar
  • Width of panels
  • Flashing details
  • Glass specification
  • Surface finish
  • Opening vents
  • Fixing substrate
  • Purlin supports
  • Height from ground
  • Hips / gable end