Adding value to fenestration design

Ian Osborne of Kestrel Aluminium Systems explains how the aluminium industry has evolved to reduce waste and optimise production, enabling the material to compete with PVCu in a range of sectors

The increasing preference for aluminium in window and doorframe construction owes much to its versatility and design life value. Widespread specification is resulting in increasingly diverse projects across the client spectrum, from prominent commercial clients in the public and private sectors to ‘high end’ self-builds.

Despite the competitive nature of the sector, a few manufacturers are achieving clear differentiation through their technical and service capabilities. This has been prompted by increasing demand for a high level of flexibility in product performance and assistance required by specifiers throughout the design process.

Tight building schedules have also put added pressure on lead times, making the ‘just in time’ approach to manufacturing impractical. Maintaining stock of the extensive range of standard profiles used in window and door fabrication has, therefore, become essential. Typically, this requires ongoing availability of profile lengths from 1.1 to 6.1 metres. It enables fabricators to keep wastage levels to a minimum and provides lasting assurance that costs can be kept at a consistently competitive level. The knock-on effect has been a clear trend in the proportion of commercial and residential work accounted for by aluminium rather than PVCu.

For orders in which bespoke features such as RAL colours are involved, production methods and equipment need to guarantee a quick turnaround. Where once the norm for site delivery was several weeks, the demand now is for just a few days. This requires use of the very latest fully automated production techniques and the necessary confidence to invest in them. The need for sustainable manufacturing in addition has led to the highest levels of powder recovery ever achieved.

In terms of aesthetics, window and door design has not only kept pace with requirements of contemporary architecture, but is positively influencing it. Use of sleek profiles which maximise the glazing area while remaining secure, strong and energy-efficient has become commonplace. However, there is cause for concern that some manufacturers are compromising the required aluminium thickness. For effective long-term performance, a specifier should make clear the minimum requirement in accordance with standards such as BS 6375 Part Two – Specification for operation and strength and BS 4873 – Specification for aluminium alloy windows and door sets.

To put the value of technical input from a manufacturer into perspective, fenestration accounts for up to 40 credits of the 119 available in a BREEAM assessment. Consequent demand for lower U-values and collaboration with specifiers therefore prompted Kestrel Aluminium Systems to develop a 70 mm casement window. Scheduled to be available early in 2020, it will provide the highest standard of acoustic performance and weather tightness – a clear illustration of innovation driven by design needs.

Projects that have benefitted from such collaboration include the newly refurbished and renamed ‘Ellen Terry Building’, part of Coventry University. The Grade two listed, art deco, former Gaumont Palace Theatre’s design required an elegant run of modern, thermally broken commercial doors that matched the original facade. In addition to the minimum requirement of PAS 24 the specification included incorporation of card scanners and perfect replication of the original doors’ slim sight lines. This has been achieved through use of ‘lay bars,’ leading the University FM team to comment: “These new doors have recaptured the original design purpose while the increase in natural light has resulted in consistently positive feedback.”

A limited refurbishment schedule also placed pressure on HTL Windows and Doors to undertake a frontage upgrade on the entrance to ZSL Whipsnade, the UK’s largest zoo. A five-week period prior to Easter gave little time for manufacturing, fabrication and installation of automated doors, which considerably exceed Building Regulation requirements, a 60 mm window system and 125 mm curtain walling. Consequent enhancement of natural light allows visitors immediate views into the main zoo areas but just as importantly for the client the end result makes a clear statement about ZSL’s standards for Whipsnade’s facilities management in the 21st century.

Ian Osborne is technical manager at Kestrel Aluminium Systems