William McDowell of Hambleside Danelaw puts the case for why GRP rooflights in metal roofing systems can help solve the many problems such as light levels that face architects when designing industrial buildings
Think rooflights and you might think of glass or even polycarbonate. But when it comes to specifying rooflights for metal roofing systems in modern industrial buildings, recent technological advances mean that GRP (Glass Reinforced Polyester) rooflights now offer the solution to many design challenges.
An increasingly tough regulatory environment and a growing focus on zero carbon means innovative products, along with clear and reliable technical information, are critical to architects. Some systems can actually enhance performance compared to other rooflight systems, while also offering a market-leading contribution to the reduction of both operational and embodied carbon.
Providing a dedicated calculator of embodied carbon, for example, can allow for any configuration of components in the rooflight, according to the requirements of the project – meaning that whatever configuration is used, the embodied carbon will always be clear and measurable. There is a dearth of embodied carbon data in the manufacturing field at present, so this is an important development.
The large new build or refurbishment warehouse projects in which GRP rooflights tend to be used usually need high levels of diffused internal lighting. Bringing free, ‘renewable’ natural light into a building during daylight hours significantly reduces the cost and environmental impact associated with artificial lighting – even when lower energy-consuming LED systems are used.
The right light level
Achieving the right level of light is critical to the working environment, health and wellbeing, productivity, safety and sustainability.
Not only is low light often a problem in industrial buildings, so is the lack of light diffusion typical with polycarbonate rooflights. This can cause significant safety issues resulting from both glare and poorly-lit areas, and it’s a problem recognised in BS5427. The standard states, “The distribution of daylight within a building should also ensure that there are no dark areas and no direct solar glare; use of diffusing rather than transparent rooflights is recommended for this reason.”
Light surveys have shown that, even in new buildings with roofs 18 metres or more above the floor, some rooflights can achieve the all-important ‘daylight factor’ of between 4 per cent and 8 per cent at floor level. This level of illumination is well above the recommendations of 2 per cent from BREEAM and the 3 per cent guideline from CIBSE guidelines.
Strength & safety
First things first: industrial rooflights should not be walked on. This is not only a safety issue, it may also damage the performance and structural integrity of the roof.
The safety performance of a rooflight must be tested as part of the whole roof assembly, including all components needed to install it and the roofing system it is installed in. Hambleside Danelaw’s high-strength Evolution GRP rooflight, through rigorous testing in accordance with Advisory Committee for Roofsafety (ACR) recommendations, is designed to deliver systems achieving Class B non-fragility for 30 years – the highest standard a rooflight installed in a metal roof system can achieve.
The service life of a rooflight is dependent on several factors, most importantly the rooflight assembly or configuration. Technological developments have led to the introduction of thinner, lighter GRP sheets which can give an expected service life of 30 years without compromising light performance, while it is generally accepted that the current market standard for service life is a minimum 25 years. Unfortunately, there are systems on the market that fall below this requirement as they either use configurations developed decades ago or materials that are not as durable as GRP.
The combination of a long service life and long period of non-fragility offers real benefits to building owners and those accessing the roof, enhancing safety and reducing lifetime costing.
In order to realise all the potential outlined above, the importance of choosing the optimum rooflight configuration for your building and your requirements cannot be overstated. It’s good practice to speak to your rooflight manufacturer for information on all the factors listed here, as well as to get a clear statement on both non-fragility classification and service life expectancy.
William McDowell is national business development manager at Hambleside Danelaw