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 | | NEW MULTI-FOIL BBA CERTIFICATE FOR RAFTERS | | | Web Dynamics | | 08/11/2007 | | | Multi-foil insulation has created considerable controversy since its introduction in the UK, primarily due to the high performance claims made by some manufacturers, compared to traditional thermal insulation products. It represents an alternative approach to insulation and its ease of use has attracted great interest in the construction industry. With the introduction of a new Part L for England and Wales in 2006, the need for better thermal insulation and increased air tightness was emphasized so any product that helps achieve this is at an advantage in the market place.
Multi-foils consist of multiple layers of reflective aluminised foils interspersed by materials such as wadding or foam and can be up to 50 mm thick. The outer layers are highly reflective, helping to increase the resistance of any adjacent air spaces, which are required in this type of insulation. The inner core helps trap the air and reflect it inside the product, thus minimizing any heat loss from conduction.
Web Dynamics holds a BBA Certificate for a multi-foil insulation with its product Thinsulex. Thinsulex can be installed in pitched roofs below and/or above the rafters and, combining it with additional insulation, can help a roof structure reach required U-values. Since this Certificate was issued, there has been a great interest in BBA approval in the market sector and other multi-foil products are currently being assessed by the BBA, the latest being Web Dynamics’ Rafterfit which has just been awarded BBA Certification.
The make up of Rafterfit is very similar to Thinsulex, i.e. layers of wadding in between reflective aluminised foils. The outer layer emissivity (a measure of the energy emitted by the foil) being lower, means that more heat can be reflected from the outer surface than in Thinsulex. Rafterfit is installed only between rafters, allowing for additional insulation to be installed under them. This solution is primarily designed for use in the refurbishment market where the home owner wants to carry out a loft conversion without having to make changes in the roof structure or remove the existing roof tile underlay.
Just as its sister product Thinsulex, Rafterfit also has a high water vapour resistance so when installed in conjunction with a non permeable roof tile underlay, the air layer above the product must be ventilated. If the additional insulation used under rafters is not foil faced, a vapour control layer should be used to make sure that there is no risk of condensation. Rafterfit will also promote air tightness in a roof and could help decrease the amount of air going through the additional insulation, thus minimizing the amount of heat loss due to conduction. The air gaps on either side of Rafterfit must be maintained, while a second layer of insulation under the rafters is needed to achieve the required U-values for a roof structure.
The rigorous BBA assessment covers factory production control, aspects of durability, installation, compliance with all UK Building Regulations and determines the product as being fit for purpose. The BBA certificate for Rafterfit will provide clarity and guidance to consumers, designers and building control, a desirable feature in this controversial area.
The BBA has also awarded a Certificate for another multi-foil system, Kontrol, offered by John Cotton Limited. | |
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