Thermal Transmittance
Thermal Transmittance, the measure of how much heat will pass
through one square metre of a structure when air temperatures on
either side differ by one degree, is generally applied to doorsets.
U-values are expressed in units of Watts per square meter per
degree of temperature difference (W/m2K).
The thermal transmittance performance of a doorset will vary
according to the particular doorset design therefore the following
details need to be considered:
Doorset size and configuration
Frame component materials and dimensions
Operating gap dimensions
Type, size and position of seals
Door face material
Glass type and glazed area
BS EN 10077-2-2003 calculations have been determined for Forza 44mm
and 54mm flush leaf based doorsets using the following
criteria:
Door leaf dimension: 2040 x 926mm incorporating Forza standard
hardwood lippings
Facing material: 0.5 veneer
Door frame: Forza type DFT104 2P
Door frame operating gaps: head/jamb & threshold 3mm
Acoustic and fire seals: product specific
BS EN 10077-2-2003 Calculated U-value
Forza 44mm leaf: configuration type SGS32AS 2.1W/m2K
Forza 54mm leaf: configuration type SGS34A60S 1.8W/m2K
The performance of glass within doorset vision panels and glazed
screens will vary depending on the type and thickness of glass
used. For guidance, typical (U-Value) performance for glazed
elements are as follows:
Single Pane: 5.4W/m2K
Double Glazed: 2.6W/m2K