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 door sets. 

U-values are expressed in units of Watts per square meter per degree of temperature difference (W/m2K).

The thermal transmittance performance of a door set will vary according to the door set design therefore the following details need to be considered:

• Door set size and configuration

• Frame component materials and dimensions

• Operating gap dimensions

• Type, size and position of seals

• Door face material

• Glass

• Glass type and glazed area

• BS EN 10077-2-2003 calculations have been determined for Forza 44mm and 54mm flush leaf-based door sets 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 SG44.32A30S 2.1W/m2K

• Forza 54mm leaf: configuration type SG54.35A60S 1.8W/m2K

The performance of glass within door set 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