Building Regulations - Windows
Replacing windows and doors now needs to meet certain standards
in the Building Regulations to reduce energy loss. This means that
you need to comply with the Building Regulations when installing
replacement windows, doors, or rooflights in both domestic and
non-domestic buildings.
What regulations do the windows have to comply with ?
Thermal insulation.
The replacement windows will need to meet the new thermal
insulation requirements. If the replacement windows have wooden or
plastic frames, then the glazing needs to achieve a maximum U-value
of 2.0 W/m² K, while for metal frames a slightly higher U-value of
2.2 W/m² K is allowable. Please note that these values are very
difficult to achieve and many double glazing units currently on
sale will not meet these new standards.
Means of escape.
All first floor windows in dwelling should
ideally have opening lights large enough to allow you to escape
through them if you were trapped in the room by a fire. This also
applies to rooms in bungalows, which open into a hall (unless the
hall itself has an external door through which you could escape).
To meet this requirement, all such windows should have an
unobstructed openable area of at least 0.33 m² and be at least 450
mm x 750 mm in either direction. The bottom of the openable area
should not be more than 1100mm above the floor.
Safety glazing.
Low level glazing i.e., glazed areas within
800mm of floor level and glazing in doors within 1500 mm of floor
level should generally be of the type so that if broken, it will
break safely. In practice this means such glazing should be
laminated or toughened glass. Ordinary glazing can still be used in
small pane sizes, however, provided the glass is sufficiently
strong to resist breakage. The Approved Document to Part N of the
Building Regulations gives maximum sizes according to the thickness
of glass, e.g., in a single pane less than 1.1 m² - 8 mm glass
would be satisfactory.
Structural safety.
If the replacement windows are wider than
those they replace, or involve the replacement of bay windows, then
the Building Control Officer will need to be satisfied that proper
structural support is provided above the window. In older
buildings, the timber frame of the window was often sufficiently
strong to carry the load of a wall or roof above it without a
lintel. Obviously in these cases , a lintel needs to be installed
when the window is replaced, or the new frame carefully reinforced
to carry the load.
Ventilation.
The Building Regulations require that adequate
ventilation is provided for the occupants in the building and this
should be considered when deciding on the size of the opening
lights in the replacement windows. For most rooms, one or more
opening windows equalling 5% of the floor area, with background
‘trickle’ vents of 8000 mm² will be adequate. For kitchen, utility
rooms and bathrooms an extractor fan is also normally required.
Further Information is available in the Advice Note on
Replacement
Windows
Contact
Tel: (01446) 704689
Email: buildingcontrol@valeofglamorgan.gov.uk