The standard range of casement windows used in the UK was derived
from the English Joinery Manufacturer's Association (EJMA) designs
of some 50 years ago. These became adopted in BS 644: Timber
windows. Fully finished factory assembled windows of various types.
Specification. A modified type is shown on the preceding page.
Contemporary building standards require higher levels of performance
in terms of thermal and sound insulation (Bldg. Regs. Pt. L and E),
air permeability, water tightness and wind resistance (BS ENs 1026,
1027 and 12211, respectively). This has been achieved by adapting
Scandinavian designs with double and triple glazing to attain U
values as low as 1„2 W/m^2 K and a sound reduction of 50 dB.
Further refs:
BS 6375 series: Performance of windows and doors.
BS 6375-1: Classification for weather tightness.
BS 6375-2: Classification for operation and strength characteristics.
BS 7950: Specification for enhanced security performance.
High Performance Timber Casement Windows