The Abbey Hill Academy in Stockton-on-Tees is an educational establishment for students aged 11-16 with learning difficulties and disabilities.

The learning environment is never more critical for such students and since the Horizons Specialist Academy Trust became custodians of the school in 2013 refurbishments have been taking place to restore the 1970’s building.

In addition, to heating and hot water upgrades and a new roof, the striking walkway that had a rooflight canopy was replaced and upgraded to enhance the exterior aesthetics of the building. The unusual shape of the building meant that the upgraded rooflights allowed a greater degree of light into the body of the school enhancing both the practical elements and also pupil and staff wellbeing due to the increased availability of natural light.

“The rooflight canopy had definitely seen better days and was no longer fit for purpose having been exposed to the elements for so many years,” said Jim Lowther Sales Director Xtralite. “We were able to specify the latest rooflight technologies to replace the existing ones to ensure a quality restoration was undertaken.”

Four 20m x 2.2m, one 9 x 2.2m and other elements were all fitted from the X-Span range of products, a thermally enhanced self-supporting rooflight. All were double glazed with a toughened outer and laminated internal glass.

“Glass is a good choice for atria, canopies and walkways and in this situation allowed the almost exact replacement of product albeit by those that are far superior,” said Jim. “Furthermore X-Span complies with BS6399 system Part 1 (Code of Practice for dead and imposed loads), Part 2 (Code of Practice for wind loads) and Part 3 (Code of Practice for imposed/snow loads) delivering a premium solution of aesthetics and practicality.”

Further information can be found by visiting or by calling 01670 354 157.

Around 8 million people a year are expected to be sheltering under Kalwall at the beautifully-designed new bus station at West Croydon. Designed by Transport for London Architects, this is an unusual example of how translucent Kalwall can offer many different advantages above its normal use for translucent traditional building cladding and rooflighting.

The brief for this project was to create a user-friendly waiting and assembly shelter to service the thousands of passengers using this important and busy transport hub linking the 150 buses an hour with the adjacent tram stop and West Croydon railway station providing routes to Canada Water and east London, and via the tram network to Beckenham and Wimbledon.

The normal choice of construction for a translucent and weatherproof canopy would be to glaze the roof with glass, However in-house architect Martin Eriksson and the project team at TfL realised that Kalwall offered a better solution in this location which would not only solve the brief and contribute to a better design but would offer many other benefits over traditional glazing.

For example, since Kalwall is much lighter than glass it meant that the supporting structure needed to be less strong and far less chunky. In additional, not only would the shelter be less high but the vertical supports would be less obstructive and open up a better view of the environment including the very attractive church nearby which had previously been blocked from the view of waiting passengers.

Unlike conventional glazing, highly insulating Kalwall is far more attractive than glass while eliminating shadows and glare and the stark contrasts of light and shade; improving the experience for passengers below.

Also, due to the way it diffuses natural daylight downwards and at night reduces vertical illumination and reflection upwards, it controls light pollution on the surrounding high rise buildings. Soil and detritus are less obvious on Kalwall than on glass and maintenance and cleaning is much simpler because access scaffolding is not required and maintenance staff can safely walk across its surface.

One of the main attractions of specifying high performance Kalwall for conventional buildings is its unique effect on both the interior and exterior. Internally, rooms are flooded with diffused natural daylight which creates a stimulating and very attractive environment. Although translucent, it also offers the big advantage of privacy while the elevations appear crisp, simple and inviting. When illuminated at night they emit a very attractive ethereal glow.

Apart from being specified for all types of new build, Kalwall is increasingly used for the refurbishment of cladding or rooflights on aged buildings. Case studies and technical information are available from Structura UK Ltd, Tel: 01233 501 504 or visit
Structura UK is the exclusive distributor of the Kalwall translucent daylight building system for England, Wales and Northern Ireland and a leading supplier, fabricator and installer of glass curtain walling, rainscreens, glass atria, windows and other architectural glass building products.

Will you see the light?

Since the late 1950’s GRP has been a feature of many commercial, industrial and agricultural buildings across the UK, bringing the free resource of natural daylight into the workplace.
GRP is a strong thermoset material with good impact resistance and consists of, among other components, polyester resin which is reinforced by a glass strand mat.

The success of Filon rooflights resulted in several UK based manufacturers continuously producing GRP. Eventually, this involved the use of alternative plastic materials such as PVC. As a brittle material, this was at times subject to damage due to storms, foot traffic on the roof and UV degradation.

This didn’t stop the efforts of thermoplastic manufacturers to try to compete with ‘Filons’ and other GRP rooflights though and polycarbonate in-plane rooflights were born and have since steadily encroached on the GRP rooflight market. There are many positive attributes to polycarbonate such as it providing high levels of light transmission, being very strong and having a good fire rating. There are however, many aspects that should be considered in rooflight material choice for profiled roof applications and we shall discuss them now.

Thermal movement

A thermoplastic material such as polycarbonate has much greater thermal movement than GRP and over 5 times more than the surrounding steel sheets.

If no allowance has been made for this movement such as oversized fixing holes, it could create some problems particularly around the fasteners such as the sheet cracking and at the end laps with seals potentially failing. It is also possible for rooflights with an insulating box detail, such as those used in composite panel roofs, for the rooflight to expand but find resistance. The material will have no room to move as it will be constrained by the surrounding metal roof panels and so could belly out – bulge out of shape between the purlins.

Light Distribution

Another significant consideration is the type of illumination required in the building. GRP has high levels of light transmission and is also a naturally diffusing product. It will provide an even distribution of natural daylight across the area to create a balanced illumination reducing bright spots, shadows and hot spots.

Thermoplastics like polycarbonate, when used as in-plane rooflights however, tend to be clear or colour tinted. They are much less diffusing and allow more light to pass directly through the rooflight. This can create localised bright spots with solar glare and also hotspots due to the nature of direct sunlight.

The first images show two very similarly constructed equestrian centres but one is fitted with polycarbonate rooflights and the other with Filon GRP rooflights. The images clearly show a very different lighting pattern: the polycarbonate rooflights allow light to pass directly through so that their position is clearly replicated on the floor – even the purlins are casting shadows on the ground; the GRP rooflights in comparison provide a very even light distribution, so much so that there are not even any shadows visible around the horse and rider – the perfect conditions for easily spooked horses.

The second pair of photographs show a supermarket distribution centre, firstly with polycarbonate rooflights and secondly after the rooflights have been replaced with Filon GRP. Again, in the first picture, the position of the rooflights is clearly visible by the bright spots on the floor. The picture with new GRP rooflights has eliminated all of the bright spots and reduced localised internal temperatures without compromising lux levels – much more suitable conditions for storing some supermarket goods and foodstuffs.

The example projects highlight the importance of selecting the appropriate rooflight material. For your next industrial, commercial or agricultural building, please give careful consideration about the type of light distribution required. If an even spread of diffused light, without shafts of light, hotspots or dark corners is preferred, then GRP is likely to be the most appropriate choice.

Written by Mark Wilcox, Sales Director, Filon Products Ltd