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RCI April 2017

ROOFLIGHTS & ROOF VENTS Letting in the light By Kirsty Crossley, specification manager fabrications, safety and lighting at Kingspan Insulated Panels Have you noticed how much better everybody seems to feel when the clocks have sprung forward again and the days start to get longer? It is not just the prospect of warmer weather that lifts the spirits, but a whole host of other benefits that come from the simple act of being exposed to more daylight. This makes it all the more surprising that there is currently no requirement in our Building Regulations for minimum levels of daylight to be provided. The topic of healthy buildings is often under debate in our industry at the moment. Issues such as indoor air quality, fire safety and thermal performance are quite rightly canvassed as being essential considerations. The simple requirement for daylight in promoting health and wellbeing is not always recognised, yet it is thought that as many as 1 in 3 people in the UK are affected by Seasonal Affective Disorder (SAD) to some degree. As well as our state of mind, there has been extensive research around the positive impacts of daylight on our cognitive ability, our eyesight, our sleep patterns, how quickly we recover from illness or incapacitation, even how much pain relief hospitals may need to administer. The amount of daylight in schools and colleges affects how well young people study. From a commercial 078 APRIL 2017 RCIMAG.COM perspective, it impacts on how productive employees are and how many days they take off sick. Basically, human beings were never designed to spend what is estimated to be as much as 90% of our time indoors, disconnected from the natural world and the flow of seasons that affects our circadian rhythm – the normal cycle of sleep and alertness. When this cycle is disrupted we become vulnerable to inadequate levels of sleep, poor concentration, illness and depression. Reducing artificial lighting The other compelling reason to include good levels of daylighting in our buildings is that it can help to save energy by reducing the amount of artificial lighting and therefore electricity, that is needed. This, in turn, keeps energy bills down and reduces carbon emissions, making clients even happier and helping to tackle climate change. However, it is also important to remember that there is a fine line to tread. Over exposure to sunlight carries its own health risks, whilst excessive solar gain can lead to buildings overheating and becoming reliant on energy hungry cooling systems to keep occupants comfortable. Finding the optimum level of daylight to reap all of the benefits and none of the costs can be a challenge. Much depends on the type of building, occupancy and use, as well as considerations such as orientation. After that the choice of product is crucial to meet the required target emission rates (TER) as set out in Part L2A, whilst maintaining ambient indoor environmental quality. The material limiting U-value for windows and rooflights in non-domestic buildings is 2.20 W/m².K. However, when calculating overall TERs for new builds, account is given to Uvalues, psi values and other mitigating thermal envelope performance factors. So, a material limiting design, for example, may be compliant but may also add cost to space heating. To meet the specification set out in the Notional Building, which offers a basic route to compliance, a Uvalue of 1.8 W/m².K is required for rooflights in a top-lit building with a 15% framing factor, and 1.6 W/m².K for windows in a side lit building with a 10% framing factor. It should be remembered that vertical windows will generally only allow daylight to travel as far as 6m inside, so for large buildings such as distribution warehouses, rooflights are the only practical way to introduce natural light into the building. Using modern materials, such as polycarbonate, also ensures that the quality of the light that is transmitted remains consistent and in accordance with stated G-Values throughout the building lifecycle, with minimal deterioration over time. Thermal performance has also improved over the years, with some polycarbonate rooflight products now capable of achieving U-values as low as 0.8 W/m².K, and 1.3 W/m².K as commonplace – well within the regulatory requirement. The material helps to limit solar gain, making it possible to maximise the benefits of natural light without affecting the overall energy efficiency of the building. Selecting a rooflight that is part of a fully integrated roofing system will allow the very best performance to be achieved with the greatest ease from the point of view of the roofing contractor, as the different components are designed to work together without specialist glazing experience being required. Providing better levels of daylight in our buildings is a simple and effective way of improving quality of life and of getting the best out of those who live and work there. Whether installed as part of a roof refurbishment, or as part of a new building design, introducing rooflights is a measure that could pay for itself many times over in terms of energy savings and productivity. Let in the light, and see what a difference it can make. www.kingspanpanels.co.uk Kingspan Day-Lite Trapezoidal, KS1000 DLTR, polycarbonate rooflights are designed to be an integral part of the Trapezoidal Roof panel system Including good levels of daylighting in our buildings can help to save energy by reducing the amount of artificial lighting that is needed Providing better levels of daylight in our buildings is a simple and effective way of improving quality of life and of getting the best out of those who live and work there


RCI April 2017
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