Windows and doors: Thermal transmittance
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The performance characteristics listed below are relevant to products covered by EN 14351-1 Windows and doors - Product standard, performance characteristics - Part 1: Windows and external pedestrian doorsets without resistance to fire and/or smoke leakage characteristics
This requirement applies to:
| Windows | Yes |
| Doors | Yes |
| Roof windows | Yes |
Doorsets and openable windows with fire resisting and/or smoke control characteristics are covered by EN 14600
Pedestrian doorsets, industrial, commercial, garage doors and windows are covered by prEN 16034 p>
Principles
The window, door or roof window shall limit energy loss by thermal transmittance.
Standards
| EN10077-1 | Thermal performance of windows, doors and shutters. Calculation of thermal transmittance. General |
| EN10077-2 | Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 2: Numerical method for frames |
| EN12567-1 | Thermal performance of windows and doors. Determination of thermal transmittance by the hot-box method. Complete windows and doors |
| EN12567-2 | Thermal performance of windows and doors. Determination of thermal transmittance by hot box method. Roof windows and other projecting windows |
Method of test or assessment
The U-value of a windor, door or roof window may be calculated according to the methods in EN 10077-1 and EN 10077-2.
The U-value of a windor, door or roof window may be measured using a hot-box as described in EN 12567-1 or EN 12567-2.
Classification
There is no classification of thermal transmittance. The Product Standard requires the U-value to be declared in units of W/m2K.
CE Marking
UK Regulations set out the worst acceptable standards for fabric properties. This value represents the area-weighted average value for all elements of that type. The allowable use of No Performance Determined (npd) is as follows:
| Location | npd allowed |
| England and Wales | No |
| Scotland | No |
| Northern Ireland | No |