The Clement W20 Steel Window Technical Specification
A traditional, tried and tested robust window, designed in the 1950s, but still in demand today. W20 may be used in all types of building where strong, durable frames, efficient opening casements and hard wearing fittings are required.
Part L Regulations
Compliant to Part L, using the centre pane glass U value method.
Made to suit your individual requirements W20 windows are generally manufactured in accordance with BS 6510:2010 specifications for hot rolled steel windows. The mild steel sections used for Clement window and door frames are precision rolled in Switzerland using only recycled steel to suit Clement’s unique profiles and tolerances. All frames and ancillary profiles are hot dip galvanised to BS EN ISO 1461 and available with a factory applied polyester powder coating to BS EN ISO 13438 from the RAL colour range, exceeding the minimum paint thickness over the zinc of 60 microns.
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 T glazing bars whose ends are tenon riveted and/or welded to the frame and 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 are available as tubes or as box mullions which can be either hot rolled or manufactured from sheet steel. Pressed metal cills are available in a choice of profiles. Trickle vents can be fitted in accordance with Part F of the Building Regulations.
The W20 range of windows is available with multi point locking to BS 7950 or traditional single point locking and other security devices if required.
W20 windows can be fitted into timber subframes, or direct to brickwork, concrete or stone. Windows are installed using fixing lugs or direct using stainless steel screws.
W20 can be supplied with various glazing options, from both inside or outside including:
- Clear glazing
- Genuine T bars
- Leaded lights, using real lead that is soldered by hand in a diamond or rectangular pattern in variable widths of lead
- G+, no grille in cavity
Combinations of fixed lights, top hung, side hung, bottom hung, horizontal and vertical pivot windows are available as well as single and double doors in both ‘open in’ and ‘open out’ configurations.
W20 windows are available as single or double glazed with double glazed units up to 16 mm. When working on highly sensitive, Listed Buildings there is an option for outside single glazing with either putty or silicone fronting. All opening vents are weather-sealed using EDPM.
In accordance with Glass & Glazing Federation best practice, Clement steel windows are factory glazed, however, our concealed fixings mean that fixed light windows need to be glazed on site after the frames have been installed. Glazing beads are made of aluminium.
W20 windows can be supplied shaped, with shaped heads, and ‘curved on plan’.
Dimensions (Provided for guidance purposes only)
Nominal profile width: 32mm
Typical sight lines: fixed lights perimeter: < 40mm
Hinged 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 discussed with one of our sales consultants.
|WINDOWS||Min (mm)||Max (mm)||Min (mm)||Max (mm)||Max (mm)|
Source: Steel Window Association
W20 windows meet the weather-tightness (air infiltration, water penetration and wind loading) performance criteria within BS 6375-1:2009 appropriate to the specified design wind pressure.
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. Water tightness 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 tests at pressures ranging from 1200Pa to 2400Pa.
Test Pressure Class BS 6375-1 1989 Edition
|Window Type||Air||Water||Wind||BS 6375-1 Exposure Category|
|Side hung (open out)||300||200||2000||2000|
|Side hung (open in)||200||100||1600||1200|
Source: Steel Window Association
W20 windows when double glazed with argon filled low-E warm edge insulating glass units, will have a typical “U” value of 2.9.
The average sound reduction index (SRI) of a single glazed unit is approximately 30 dB, but this varies with window type and size and glass thickness.