Approved Document B
TSC = The Skylight Company
Approved Document B places certain limitations on the use of rooflights, which are dependent on glazing material and site circumstances, such as building size, use of area below rooflights, rooflight size and proportion of total roof area, distance from boundary, etc. The relevant information is set out in Volume 1: Sections 3 and 10; Volume 2: Sections 6, 12 and 13 of Approved Document B, 2006 Edition.
Where applicable, the responsibility for determining that any building component complies with the relevant Regulations rests solely with the customer or specifier.
Approved Document E
This document requires that buildings are designed and constructed to provide resistance to sound and reverberation. The aim is to limit noise disturbance by including sufficient acoustic properties and insulation in areas such as internal and external walls, floors and other elements.
Rooflights should perform in accordance with these requirements and the decibel reduction value can be used in calculations for this purpose.
Further information is available in Building Bulletin 93 Acoustic Design for Schools.
Approved Document F
This document places the responsibility on the designer to comply with ventilation requirements to new and existing buildings. It states ventilation types including extract, whole building and purge and gives minimum ventilation requirements.
Rooflights are often a useful means of complying with the requirements especially where no other external aperture is available.
Further information is available in Building Bulletin 101 Ventilation of School Buildings.
Approved Document L
This Approved Document, which takes effect on 1 October 2010, deals with energy efficiency requirements in the Building Regulations (as amended) and is made up of four distinct publications which are summarised below. It should be noted that Approved Documents are guidance publications and there is some provision for trade-off with other building elements any proposal should be checked with the relevant building control body. U-Values should be calculated in accordance with BRE 2006. The document also covers areas such as Materials and Workmanship including a requirement to demonstrate appropriate use of products with CE marking, British Standards and European Technical Approvals. Whitesales continuous rooflights have undergone stringent and extensive testing and are certified to these standards.
Solar heat gain
Approved Documents L1A and L2A include requirements to limit solar gains through the summer period. The inside of the building can heat up during daylight hours due to the sun. This is termed as solar heat gain. To reduce this effect, solar control glass can be adopted to reflect heat and reduce glare from the suns rays. This lessens the burden on air-conditioning systems thus reducing CO2 emissions. In simple form, this may be body tinted glass in blue, green or bronze or more sophisticated, coated clear glass that allows maximum light transmission, but at the same time substantially reduces heat gain.
Optimum rooflight provision
A buildings design will affect the contribution rooflights can make. The optimum area of rooflights will therefore vary for each building. However, research has shown that a rooflight area of 15-20% will contribute to an overall reduction in CO2 emissions inmost buildings. Rooflights are up to three times more effective at supplying daylight than vertical windows. Where artificial lighting is controlled by daylight sensors, installing rooflights can result in a significant reduction in the energy used for lighting. Energy consumed in lighting a building is often greater than that used to heat it. In addition, the SAP and SBEM software programs take account of the contribution made by passive solar gains through rooflights. Solar gains help to offset the increased heat loss of rooflights compared to the insulated main roof.
Air permeability is the physical property used to measure airtightness of the building fabric. It is defined as air leakage rate per hour per square metre of building envelope at the test reference pressure differential across the building envelope of 50 Pascal (50N/m2). The limiting air permeability is the worst allowable air permeability. The design air permeability is the target value set at design stage, and must always be no worse than the limiting value. The assessed air permeability is the value used in establishing the BER, and is based on a specific measurement of the building concerned.
BS 6229: 1982, Code of Practice for flat roofs with continuously supported coverings, requires rooflights to incorporate upstands to raise the mat least 150mm above the uppermost roof surface to which the roof covering is bonded or dressed. The designer should ensure that the builders curb is at least 150mm high.
Various standards deal with the calculation of U-values of building elements. The conventions provide guidance on the use of the standards, indicating themethods of calculation that are appropriate for different constructional types, providing additional information about using the methods and providing data relevant to typical UK constructions. The U-value conventions were originally published by the BRE in 2002 and the 2006 edition is an update which provides additional information and reflects changes in the underlying British Standards. The U-Value calculation methods are also referred to in Approved Documents L1A, L1B, L2A and L2B.
Condensation occurs where warm moist air meets cold surfaces. As warm air rises, the risk of condensation forming at rooflight level is relatively greater than at lower level. The risk can be minimised by specifying triple skin TSC continuous rooflights and Em-Curb insulated upstands. The provision of ventilation may also assist. However, because temperature and humidity levels are clearly beyond our control, no guarantee can be given against the formation of condensation.
Condensation between the skins can also occur when the room below has high humidity levels, for example during construction fromn ew plaster or paintwork. Polycarbonate is hygroscopic and allows water molecules to filter through the water pressure forces its way through the lower skin and condenses inside the cavity. However, once the humidity level in the room is restored to normal this condensation dissipates through the breathable seals.
Health & Safety
According to the Health and Safety Executive, almost 20% of deaths in the construction industry are caused by falls from or through roofs. The majority of these falls are through fragile materials such as asbestos cement roofing or old/fragile rooflights. The Construction (Design and Management) Regulations 2007 places a duty on designers and specifiers to give proper consideration to eliminating or reducing risks at the design stage. Health and Safety Executive (HSE) Health and Safety in Roof Work draws attention to the responsibilities of those specifying rooflights.(HSE) Health and Safety in Roof Work states that where rooflights are required, designers should consider:
Specifying rooflights that are Non-Fragile.
Fitting rooflights designed to project above the plane of the roof and which cannot be walked on (these reduce the risk but they should be capable of withstanding a person falling onto them).
Protecting rooflight, e.g. bymeans of mesh or grids fitted below or above the rooflight
Specifying rooflights with a design life that matches that of the roof, taking account of the likely deterioration due to ultraviolet exposure, environmental pollution and internal and external building environment.
For specifiers the key message is to eliminate fragile materials from roof design. For contractors, provide effective fall arrest equipment or safety netting.
TSC continuous rooflights are out-of-plane rooflights, and provided they are specified with polycarbonate glazing, can be deemed to be non-fragile.
Polycarbonate continuous rooflights have been designed according to EN 1873 2005 <Actinic:Variable Name = 'E'/> to an energy of 1200J and to ACR<Actinic:Variable Name = 'M'/> 001: 2005 and can be classified as Class B Non-Fragile.
TSC offers a 10 year warranty against discolouration of polycarbonate glazing material and loss of impact strength, underwritten by the sheet material supplier.
TSC offers a post-forming warranty backed by the sheet manufacturer.
Man-safe is a termoften used within the construction industry to mean that the product can withstand foot traffic. However man-safe has no recognised definition and Non-Fragile does not qualify a product to be used as a thoroughfare.
Whilst glazing and other accessories may be designed to safely resist the impact of a human body falling against it, the wilful act of walking on any kind of roof glazing must be forbidden at all times.
The act of walking upon a glazed structure can cause microscopic damage that, in time, may have a detrimental effect upon the impact performance of the system.
Walking upon glazing may encourage a practice that could lead to general disregard for the rating of said glazing, with catastrophic consequences.
Handling and storage
While all TSC continuous rooflights and associated products are suitably packaged to avoid damage care should be exercised when handling. For moving larger items, two or more people may be needed. All products should be stored in flat dry conditions.
All TSC continuous rooflights are supplied in component form and are delivered to site in protective packaging. Full instructions and fixings are included with all products, and should be carefully studied prior to installation. We always recommend that a Whitesales approved installer is employed to carry out the works.
Fixing upstand curbs
For fixing curbs to the roof structure, drill holes in the bottom flange, 100mm from each corner and at maximum 300mm centres and screw to roof structure. The PVC-u Em-Curb is suitable for use with most flat roof systems including single ply, felt, hot-melt, asphalt, liquid and lead.
Where asphalt is specified, TSC recommend the use of PVC-u upstands with pre-fixed sheathing felt and expanded metal lathe. This must be specified if required.