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Window Requirements Of The Building Regulations

 

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Introduction

A number of Building Regulations pertain to windows, specifically Part N of the Building Regs, which mainly relates to their safety and energy efficiency. As a result, most windows are now supplied as double-glazed units, with a draught-excluding strip attached and ventilating ‘trickle vents’ included.

Energy Efficiency

  • By law, if any complete window (including the frame) is replaced or added to a building, the new window should include argon-filled double glazing, and allow suitable ventilation - usually via tickle vents set into the head of the frame.

This rule does not apply to replacement glazing (where the window frame remains in place), to listed buildings or to buildings in conservation areas.

No component of a house affects overall energy consumption as much as windows. Per square metre, windows lose more heat in the winter and gain more heat in the summer than the walls or the roof. This is because glass is a poor insulator and represents little barrier to radiant heat, so single glazed windows (that our homes were fitted with as standard up to the 1990s) allow a considerable amount of energy to be wasted as heat persistently ‘leaks’ away.

This heat loss is significantly reduced in double glazing as the air gap between the two panes of glass is an effective insulator to both heat and to a lesser extent, sound.

The energy efficiency of glazing is measured by its thermal conductivity, or ‘U-value’ in BTU/hr/m3/oC, where the lower the number, the better the insulation. Conventional single glazing has a U-value of around 5.0, whereas current building regs require double glazing with a U-value no greater than 2.0 to be fitted.

Safety Glass

Safety glazing, meeting British Standard 6206: 1982, must be fitted to;

  • Any window pane less than 800mm (31½in) above floor level
  • Any window pane less than 300mm (12in) from a door
  • Any window pane in or surrounding a door whose width or height is greater than 250mm (10in)
  • All Fire Egress windows

There are two kinds of safety glass;

  • Toughened or tempered glass has been heat treated so that instead of breaking into potentially lethal shards, it cracks into lots of small, blunt lumps.
  • Laminated glass is constructed from two layers of glass that sandwich a layer of clear plastic. If impacted, this glass won’t break into pieces, but instead retains its shape.

Fire Exit

  • In the absence of an external door or second flight of stairs, all rooms in a basement or greater than 4.5m above ground level, except kitchens, must have a window through which someone can escape a fire.

This window must be at least 450mm (17¾in) high and 450mm (17¾in) wide, with an unobstructed openable area of at least 0.33m² (3½ sqft). The bottom of the window must be sited no more than 1100mm (43¼in) above floor level (or 600mm (24in) in a loft room). This window must be fitted with safety glass.

Safe access to window controls

Controls to open windows must be within safe reach, with no obstruction to lean over;

  • A window control must be no higher than 1.9m (6ft 3in) above floor height.

To lean over an obstruction that is 600mm (24in) deep and 900mm (35½in) high (such as kitchen base units), the window control must be no higher than 1.7m (5ft 7in) above floor level.

If the control cannot be put within these limits, a remote manual or electric system must be installed.

Safe access to clean windows

Windows must be accessed safely for cleaning purposes.

  • Where a window cannot be reached by a secured platform or 9m long ladder, it must be possible to clean the exterior of the window from the inside the building.

These reversing windows should have a mechanism that holds the window still whilst it is reversed for cleaning.

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