CPD articles

CPD: Rooflight installation

3 July 2017 | By Will Goodenough

Will Goodenough, key account manager with whitesales, explains the importance of correct installation and safety procedures to get the most from rooflights.

Rooflights have come a long way from crude ceiling-windows made from transparent plastic. Despite playing a major part in architecture throughout the centuries, rooflights as we now know them are a relatively new invention, and are being constantly developed to serve their purpose in more efficient and economical ways.

In an age where lightbulbs of high wattage are forbidden and budgeting carries heavier influence than ever, they offer a revolutionary and highly sophisticated way of conserving money and energy, whether in schools, offices, hospitals or homes.

So it is all the more important to demonstrate good practice when installing them, to ensure the product lives up to all its potential benefits.

Flat rooflights and installation

Rooflights are becoming more common all the time. However, instances of workers falling through improperly installed rooflights to their deaths have not been uncommon in recent years. As well as the human tragedy, this has serious consequences for employers and manufacturers, and generates a lack of confidence in the safety of the products.

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It is imperative that every rooflight is manufactured and fitted to the highest standard, and is fit for purpose. With this in mind, contractors should consider the following tips when carrying out installations or training employees:

Are my rooflights safe and secure?

Newly installed rooflights should make a room bright, comfortable and energy-efficient. However, it is important to address issues of both safety and security.

Where safety is concerned, only rooflights that have been specifically manufactured, sold and installed as “walk-on” should bear the weight of a person, with absolutely no exceptions. Falls through fragile rooflights not intended to be walked on have caused serious injuries and deaths. If you are unsure whether the rooflight is walk-on or not, check with the provider, but do not try putting any weight on it.

Whitesales’ installations include rooflights at Wadebridge School in Hampshire (above) and a sleek design at Bloor Homes’ luxury Mayfield Place homes near Windsor (below)

If rooflights are present on a roof or other surface to which access is required, there are added safety measures that can be introduced. An array of specialists design and manufacture safety features such as grates, rails and protective fences that reinforce surfaces , offer improved stability and prevent accidents.

When it comes to security, glazing materials are now far stronger than in the past, and any professionally manufactured and installed rooflight should be, by design, more than capable of remaining intact. However, the security of the rooflight will depend on the design, the purpose and the materials used.

For example, glass rooflights, particularly flat ones and those placed in-plane, are strong and durable, but their shape makes them easier targets for breaking out of their frames. Polycarbonate is flexible and strong, but prone to UV deterioration, which may make it brittle over time and easier to break. Glass-reinforced plastic (GRP) has proved to be the most flexible of materials, and forms the strongest seals.

Any rooflight can be reinforced with measures such as UV protection and locking systems. For the best performance, ensure rooflights are regularly maintained, with regular inspections by a specialist if need be.

The Importance of being ventilated

In addition to improved daylight ingress, slashed energy expenses and flexibility, rooflights offer unique potential for highly efficient ventilation. This refers both to comfort ventilation, the kind you experience opening a standard window, and smoke ventilation, which can save lives during a fire. From manual opening to rain- and smoke-sensor enabled functions, rooflights should be considered as much for innovative and efficient ventilation as for energy effic­­­iency and improved lighting.

Ventilation has been identified as a key factor in improving occupant wellbeing and performance. Studies have identified several key benefits of having a constant source of fresh air and efficient ventilation in school environments.

The Fraunhofer Institute for Building Physics in Stuttgart, Germany, found that students’ concentration improved by between 2% and 15% in well-ventilated classrooms, and even went as far as to project that a country’s conditional economic growth could be as high as 9.5% were these improved classroom conditions to be maintained and widespread.

Meanwhile, research shows that our brains use 20% of our entire oxygen intake, and that air with high concentrations of carbon dioxide inhibits good brain function, building a stronger argument for improved ventilation.

Different styles of rooflight offer a variety of ventilation functions. For maximum ventilation, smoke ventilation rooflights and specially designed vent styles offer particularly adaptable options, especially for use on flat roofs. These vary from letting a gentle breeze flow through the building to giving toxic fumes and smoke an escape route that could be potentially life-saving.

Whitesales used Em-Glaze circular low-carbon rooflights for Northbrook College in West Sussex

Rooflights may also be modified to incorporate ventilation to specification. Specialists can recommend products to meet client requirements, some of which can be modified to purpose if need be.

One example is St Lawrence Primary School in Hassocks, West Sussex, which required rooflights to improve fresh air ingress and maintain a light and airy atmosphere that could allow the expanding school to house an additional 210 students.

Reinforced and certified “walk-on” rooflights were installed on the flat roofs of the school; these could be opened and closed manually as well as automatically via rain sensor. The product maintained the smart and open style of the school, while providing improved daylight and fresh air, and installers could  adapt fixtures to the school’s specifications.

Tackling the mist

Condensation on rooflights is unsightly, and is commonly believed to be indicative of improperly installed or poor quality glazing. Although difficult to reach and rectify, most cases of misting are a purely aesthetic issue. However, noticing the placement of misting and the conditions in which it forms can help to deduce whether or not it will cause problems.

While condensation in itself is usually not cause for concern, it is worth monitoring as a means of ensuring that rooflights and windows are properly fitted and performing to their potential. Proactive checking will also help to get any potential problems diagnosed.

Misting on the internal face of glazing is usually caused by environmental factors, such as air temperature and humidity and the surface temperature of the glass, and can usually be alleviated by changing the internal conditions of the building. Maintaining an environment that is well ventilated and still comfortably heated is ideal for banishing internal misting.

Smoke ventilation at Henley Homes’ residential conversion of the Baylis School in south London

Condensation on the outer face suggests that the rooflight is doing its job perfectly. Misting is caused by a handful of environmental factors: temperature difference between the outer and inner surfaces of the glazing causing heat to be passed from the interior through the glass; heat loss by radiation, and heat exchange with the external air via convection.

These conditions cause outer faces of glazing to drop in temperature, and thus collect condensation, particularly in clear weather, which enables accelerated heat loss to the sky. The higher the U-value of the glazing, the more likely it is to experience outer condensation.

However, condensation gathering between the layers of double glazing is a sign of failure. If moisture is seeping into the inner layers, then seals have failed. This will usually be noticeable, causing sodden seals and sometimes rot. In extreme cases, the cavity between glazing can fill up with water. Under these circumstances, there is no other option but for the glazing to be removed and replaced.

However, it is not unusual for temporary misting to appear between layers of glazing under certain conditions, such as spells of particularly hot or cold weather, or in areas that experience short bursts of humidity, such as kitchens and bathrooms. Ensure problematic misting is permanent and unconditional before taking action to replace glazing.

Fragility testing and compliance

It is only in the past 25 to 30 years that rooflights have been expected to be safe, or in other words, able to support the weight of a person. Until quite recently, they were manufactured and sold on the understanding that they were fragile pieces, and not safe to be walked on. But the prevalence of rooflight-related accidents and deaths in the construction industry has been a cause for concern.

According to the HSE’s A Guide to Health and Safety in Roof Work publication (HSG33), roofers make up almost a quarter of all falling deaths in construction, and the majority are caused by falls through fragile roofing materials like asbestos and rooflights.

The Advisory Committee for Roofsafety’s partnership with the National Association of Rooflight Manufacturers has long been working towards improved safety for roofers and construction workers, and have used their experience to design testing strategies that identify a roof’s suitability for manned work.

The ACR[M]001, or Red Book, is the official testing method that roofs are subject to in order to determine their safety, and works to calculate a surface’s ability to support instantaneous loads. Roofs will be graded for non-fragility from Classes A-C, with A indicating a completely non-fragile roof.

However, due to the nature of testing and the fact that any roof environment will sustain at least some damage or wear from inspections, reputable fitters and examiners will not award a Class A rating, and even those who are awarded them do not tend to use them as a USP. This is because although testing is thorough, it does have a few weaknesses, which can cast doubt on the true condition of a roof and its suitability for human weight.

Testing is always carried out when products and roof environments are new, and do not forecast a rate at which they can be expected to deteriorate and become more fragile. For this reason, ACR[M]001 is not watertight, and is a guideline at best for proper practice. However, compliance with it is essential for all roof-based construction work, and must always be referred to before workers are admitted to a new site.

Rooflight-related accidents and deaths have made construction a fixture of health and safety regulators’ interests. It is imperative that manufacturers and installers stay up to date with the expectations of the Red Book test, and take all necessary steps to be compliant with regulations at all times.

The benefits of rooflights are many, and their few drawbacks can be easily resolved with the right knowledge. Get the most out of rooflights by knowing them well, and learning to spot any issues that might arise.

Will Goodenough is a key account manager at Whitesales and works with specifiers and contractors to provide natural daylight solutions. www.whitesales.co.uk

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A good article but no questionaire on line

Peter Lewis Bloxham, 3 December 2018

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