Checklist

Window and door technology is starting to grow up. There is, however, a clear challenge for this industry. The market requires more thermally efficient products that have guaranteed fire performance, high security and comply with the sustainability and recycling agendas. The question of thermal performance has become more urgent because of the revision to Part L of the Building Regulations, which is due to come into force early next year. Additionally, the Disability Discrimination Act and the Accessible Environments Standard mean careful consideration must be given to how the doors will function in use.

1 Windows

Energy rating, thermal performance and types of materials have to be considered when specifying windows.

Window energy rating

Thermal performance is becoming easier to specify, using the British Fenestration Rating Council scheme. This classifies windows in a similar way to white goods, with an A to G rating. This covers the unit’s general performance relating to energy flow and use over a year. An A-grade window will have a zero energy flux. The energy rating takes on board the impact of new technologies. These include more and better coatings, triple glazing, variable transmission coatings and evacuated cavities. Specifiers will need to use these technologies to decrease carbon emission levels to an acceptable level.

Thermal performance

To get good thermal performance, double-glazed units should be specified with air gaps of 16 mm. Any smaller and there is too much heat conduction, and any bigger and there is too much convection. Metal frames are now available with thermal breaks to reduce heat loss and the risk of condensation. The use of warm edge-spacers or at least stainless steel spacers are also important factors in improving performance in all double-glazed units.

Aluminium

Aluminium provides clean visual lines and is highly durable. It is usually made from recycled metal, which reduces the amount of embedded energy needed to produce the product, although it is a high-energy material when originally smelted. It needs a good quality thermal break, which should be specified from the outset. Ensure you specify by performance or named supplier, including the exposure, durability and quality of finish required. It can be finished by anodising or with a polyester powder coating. Bright colours and high gloss finishes are the most difficult in terms of quality and the least durable.

PVCu

PVCu has poor environmental credentials, as it requires a lot of energy to produce and is difficult to recycle. Because of this the Glass and Glazing Federation has introduced a recycling scheme for PVCu waste.

Timber

Timber has good environmental and recycling credentials. Schemes such as the Forestry Stewardship Scheme and the Scandinavian Timber Initiative mean specifiers can be confident the timber has been sourced sustainably.

High-performance doors and windows can be specified with confidence.

2 Doors

Doors have to be specified with an eye to their thermal performance, fire performance and access characteristics.

Thermal performance

It is now possible to specify doors with adequate thermal performance, as good quality thermal breaks are becoming less rare and air infiltration levels have improved to match those of windows. Be wary of sourcing products outside the UK. Although there are many high-quality products out there, it is a complex business to check what standards they meet.

Fire

Doors need to perform well in a fire and yet be easily operable by people with disabilities. Fire performance must be either to BS 476 or to the harmonised standard BS EN 1634 and BS EN13501. The European standards are tougher and may be preferable as the specifier can be sure that an A-class product is non-combustible. The door and frame should be specified as one unit and fire and cold smoke sealing should be checked to ensure the correct standard is being specified. Doors should carry an identification label on the top or hinge side.

Ironmongery

Specify multipoint locking as a starting point. The relevant security standards for doors are the PAS 23 and PAS 24, and for windows BS 7950. Additionally, the draft standards prEN 1627,1628,1629, and 1630 can be used to specify increased levels of security if required.

This has also given makers the opportunity to allow casements to open more than 90° or for the hinge point to move, allowing easy cleaning from the inside.

Design for the disabled also needs to be considered. Smoother locking mechanisms and door handles requiring less pressure to operate are appearing. Powered doors using sensors and remote controls are available for homes. New guidance has just been published that tackles the conflict between Part M of the Building Regulations, which deals with disabled access and Part B, which deals with fire. See www.gai.org.uk for details.

Installation

Installation is becoming easier because of devices that enable doors and windows to be positioned without contravening the manual handling regulations. Locating the window or door prior to fixing can result in more accurate final positioning, and also ensures specifiers’ CDM responsibilities are addressed.