External Doorset Characteristics

When you receive a specification for an external doorset it is likely to contain many performance requirements, but it might not be clear what these are and how they can be evaluated.  In this blog BWF Technical Director, Kevin Underwood selects a few of the many possible performance characteristics for an external doorset and gives a brief insight into how they are assessed, measured and calculated.

Emergency Exit

If the doorset is on an escape route then it might be fitted with either a push pad or lever handle to allow a safe and effective escape through a door with one single operation, or to cater for more urgent situations, where possibly more than one person might be trying to open an exit door then a panic exit device operated by a horizontal bar could be fitted. These emergency exit and panic devices and the hinges on which the door leaf is hung must be conformity marked (CE or UKCA) appropriately.

Sound Reduction

If a level of sound reduction is called for, this can be determined through an acoustic test which measures the sound blocked by the doorset at different frequencies which can be reported as a single figure for ease and adapted to suit specific noise profiles such as for road traffic.

Thermal Energy

The amount of thermal energy that is lost through the door can be calculated or measured in a test and this is reported as its U-value.  The U-value, or thermal transmittance, indicates the energy that would pass through each square metre of the door’s surface area every second and for every degree in temperature difference there is from inside to outside. A lower U-value indicates that less energy is lost showing that the doorset is well insulated.

Sometimes specifiers will ask for the solar transmittance value, or g-value, for the glass or for a glazed doorset as a whole. This is a measure of the energy from the sun that can pass through the doorset effectively acting as a heat gain rather than a heat loss. The g-value can be obtained from the glass unit manufacturer or from one of the online configurators available from the leading glass manufacturers. It is also possible to obtain a figure for g doorset which is the value shown in Energy Ratings. This value is 0.9 x g-value x proportion of the doorset that is glazed.

Draughts and Watertightness

To show how well a doorset will let in draughts, or withstand wind driven rain without leaking, or whether it will be damaged by a high wind it can be tested for air permeability, watertightness and resistance to wind load. In these tests the doorset is first subjected to air at low pressure alone to see what volume of air leaks past the weather seals. A water jet is then introduced to see at what air pressure the doorset starts to let in water. Finally the air pressure is increased to a level replicating a high wind to see how much the doorset distorts and flexes or whether parts are dislodged or damaged. The air pressures used in the test can be matched to the weather conditions expected at a particular location and can take into consideration highly exposed sites at altitude or near the coast.

General Mechanical Strength of Doorset

To assess the general mechanical strength of a doorset it can be tested for vertical load, static torsion, soft and heavy body impact and hard body impact and the results of these tests can be matched to the expected use of the doorset whether this is light duty as would be the case for a private home or severe duty as could be the case for a doorset in a hospital for example. Another measure linked to the use of the doorset is its ability to withstand repeated opening and closing. Under test, a doorset can be cycled up to 1,000,000 times depending on its anticipated duty class.

Security

For new build dwellings in England and Wales and for all doorsets in Scotland there is a recommendation for doorsets to meet a level of enhanced security. One way to show this is by testing the doorset to an enhanced security standard such as PAS 24. In PAS 24 the doorset is first checked to see whether there are any simple ways of manipulating the locks or fittings to gain entry.  This includes a check on the lock cylinders and letterplates. Each locking point is then subjected to a bi-directional mechanical load to see whether they are strong enough to resist a forced entry with an additional mechanical load applied to any potential weakness identified during a physical check of the doorsets strength. There is an attempt to remove any glazing or to cut through any area of the doorset and finally there is a series of impact tests using both soft and hard impactors to replicate a shoulder barge or hitting with a hammer.  If it is not possible to create a hole big enough to allow any locks to be accessed on the inside then the doorset is considered to have passed.

It should be noted that U-values, g-values, acoustic attenuation and the doorset’s ability to open if it is used on an escape route are essential characteristics for external doorsets as stated in Annex ZA of the designated standard BS EN 14351-1:2006+A2:2016 and therefore must appear on the declaration of performance under conformity marking rules.