Supplying Timber Issue 9 0 - Autumn 2025 - Flipbook - Page 70
———— TIMBER KNOWLEDGE SHEET ————
TIMBER KNOWLEDGE
exceptionally energy e昀케cient.
Nonetheless, a key factor is
the type of glass used. Whether
it is double, triple or quadrupleglazed, an insulating glass unit
(IGU) is an important part of
how timber windows conserve
energy.
The glass can be produced to
optimise or control solar gain,
reduce noise transmission, selfclean and give extra security.
The choice of glass, the spacing
between the panes, and the
gas used in the unit all a昀昀ect
the energy values and window
energy ratings.
There are two ways to measure
energy e昀케ciency: U-values and
the Window Energy Ratings
(WERs). WERs are produced
by the British Fenestration
Ratings Council (BFRC), the
body responsible for the most
↑
Image: Common
types of timber
windows.
commonly used energy rating
system in windows and doors.
• For newbuilds, the average
U-value of all windows must
be 2.2 or under. WER ratings
range from A (best) to G with
higher ratings increasingly
common.
• Requirements vary by
building type, so be sure
to check the relevant
building regulations (Part L
Conservation of Fuel & Power,
or equivalent in Scotland or
Ireland).
Window Types
Side hung casement
This is the most common
type of window, which opens
outwards and has a 100%
openable area. It usually has
a maximum width of 600mm
and height of 1,500mm. Hinges
Timber window security checklist
Most insurance companies require locks to be 昀椀tted to ground 昀氀oor windows.
Windows manufactured by the Wood Window Alliance are 昀椀tted with security
ironmongery and comply with enhanced security regulations BS 7950: 1997
Speci昀椀cation for enhanced security performance of windows for domestic
applications.
‘Secured by Design’ (SBD) windows comply with BS 644:2009 Timber
windows. Fully 昀椀nished factory-assembled windows of various types.
Speci昀椀cation, the BM TRADA Q Mark scheme and the British Woodworking
Federation Timber Window Accreditation Scheme (with third-party enhanced
security compliance).
Laminated glass can also improve the security of windows.
SUPPLYING TIMBER
70
AUTUMN 2025
attach the sash directly to the
frame, and it can use di昀昀erent
hinge mechanisms, allowing
the window to be cleaned
from inside. Modern timber
昀氀ush casement windows can
provide the same draught- and
weather-proo昀椀ng as a lipped or
“stormproof” casement.
Projecting top hung casement
Popular windows in 昀氀ats and
medium-to-high-rise buildings
with a 100% openable area. A
“topswing” or “H-type” hinge
mechanism allows the sash to
rotate on the outside of the
frame, for easy cleaning and
painting. The mechanism often
incorporates an “espagnolette”
locking system and child safety
locks which restrict opening
to 100mm, but which can be
overridden.
Tilt and turn
Popular in Europe and
increasingly in the UK with
a 100% openable area. As it
tilts from the bottom it allows
secure ventilation, while turning
the handle in the opposite
direction opens the window as a
casement inside the room.
Vertical sliding sash
A traditional window type,
synonymous with the Georgian
and Edwardian eras, with a
