W20 Technical Specifications

A traditional, tried and tested heavy duty framing system, designed in the 1950's. W20 windows may be used in all types of building where strong, durable frames, efficient opening casements and hard wearing fittings are required. Projects may be new build or refurbishment where the original fenestration is to be maintained, windows are manufactured to fit existing apertures. Steel windows may be installed using lugs/screws direct to brickwork, concrete, stone or screwed into subframes.

The W20 range consists of:
Fixed light, top hung, bottom hung, side hung, horizontal and vertical pivots, single and double doors.

Features include:
Available double single or double glazed with up to a 16 mm double glazed unit.

Specification
The windows are manufactured generally in compliance with BS 6510.  All frames and ancillary profiles arehot dip galvanized to EN ISO BS:1461 and available with afactory applied polyester colour coating to EN ISO 13458 BS:6497.

Description
Frames are manufactured from hot rolled mild steel profiles with corner joints mitred, welded and dressed square and flat. Small panes can be formed with tee glazing bars whose ends are tenon-riveted and/or welded to the frame and whose cross joints are interlocked and welded with rigid joints.

Composite windows can be assembled by connecting windows horizontally and/or vertically with mullions and/or transoms of hot rolled slim steel profiles, box sections, tubes or box mullions manufactured from sheet steel. Pressed metal cills are available in a choice of profile. All frames and ancillary profiles are hot dip galvanized to BS EN 1461   They can be further finished with a factory applied polyester colour coating to EN ISO 13458 BS:6497.

Glazing

Glazing is typically completed on site, from inside or outside, with single glass or insulating glass units up to 16mm, using factory finished beads, bedding and capping sealants in accordance with BS 8000-7.  Option for single glazing: glazing from outside with spring clips (supplied by the glazier) and metal casement putty fronting.

Weatherseals

Ventilators shall be weather sealed with polymer rubber gaskets retained in a groove within the profile and secured by suitable adhesives.

Dimensions (mm)
Nominal profile width - 32mm
Typical sight lines: fixed lights perimeter < 40mm
Hinged or pivoted casements < 70mm

Windows and doors for composite panels are purpose made, generally within the limits shown in the table below; sizes outside these limits may be considered with consultation.

Appearance

W20 windows provide the traditional qualities of slender sight lines of framing and glazing beads, which maximizes solar gain thereby saving energy through reduced use of artificial lighting. Polyester powder coating is available in a range of standard RAL colours.

Performance
Wind resistance, watertightness, air permeability
All W20 windows meet the weathertightness - air infiltration, water penetration and wind loading – performance criteria generally as in BS 6375: 1 appropriate to the specified design wind pressure.

BS 6375-1:1989
Air permeability was measured in terms of opening joint length (m³/h/m) against progressively increasing test pressures through 200Pa (class A), 300Pa (class B) up to 600Pa (class C). Class B, or a maximum value at 300Pa of about 16 m³/h/m, was the UK standard requirement. Watertightness was measured in resistance to leakage at progressively increasing test pressures, 300Pa being considered the most severe UK requirement. Wind load resistance entailed deflection and gusting

Heat

W20 when double glazed with Argon filled low-E warm edge insulating glass units will have a typical U ‘Value’ of 2.9.

Sound
Average sound reduction index (SRI) of a single glazed unit is approximately 30 dB, but varies with window type and size.