With questions continuing to be asked about the suitability of certain materials within the construction of tall buildings, increased requirements for fire safety mean that the correct selection and application of materials are at their most critical. In this article Adam Taylor, Business Development Manager – Building Envelope of the A. Proctor Group will seek to provide essential clarity for architects and builders on the use of membranes within external cladding.
Approved Document B: Amendment November 2018
The use of membranes within external wall construction
It is important to note that with specific reference to membranes the Regulation provides a critical exemption and further clarification is found within Regulation 7, as stated below:12.14 Particular attention is drawn to the following points.a. Membranes used as part of the external wall construction should achieve a minimum classification of European Class B-s3, d0.
Breather Membranes – vapour permeable
In selecting a membrane it is important that performance is not compromised and that compliance meets the requirements of both Approved Document B: Fire Safety and BS5250 the Code of Practice for Condensation Control.
It is crucial that specifiers understand that some European membrane products whilst quoting A2 ratings do not breathe sufficiently to comply with BS5250, meaning the use of these membranes in the UK climate could make the building unhealthy and result in a much greater risk of condensation issues and mould growth.
Vapour Permeable Membranes and fire safety
The culmination of years of research into membranes by the A. Proctor Group has led to the development of a vapour permeable membrane with a fireproof surface, which has a unique intumescent composition that actively reacts to prevent fire taking hold and that also significantly reduces the formation of droplets and smoke.
Fireshield® vapour permeable membrane is designed specifically to improve the fire protection behind cladding and has been awarded certification from both LABC and LABSS confirming that the product meets Building Regulation approval in England, Wales and Scotland.
Now Fireshield has also been awarded a British Board of Agrément Certificate. The BBA Certificate confirms that Fireshield has enhanced performance in relation to reaction to fire classification, will reduce the risk of interstitial condensation, and will have a life equal to that of the building in which it is installed. The endorsement by the UK’s leading construction certification body will provide architects, contractors and specifiers with full assurance that the product has been tested to meet the highest industry standards.
Fireshield complies with BS5250, BS4016 and NHBC requirements for vapour permeable walling underlays. It is installed and fixed to the substrate in the same manner as standard breather membranes using mechanical fixings. Applications include both commercial and residential buildings including apartments and student accommodation, as well as rainscreen cladding and applications over 18m high.
Vapour Permeable Air Tight Membranes and fire safety
There is an increasing demand to design and construct buildings which are more energy efficient, with the inevitable focus on airtightness and insulation. The need to manage the balance of Heat, Air and Moisture Movement throughout the process of the building’s life cycle will have an impact on the quality of the completed building, its performance in use, as well as the health of its occupants. However, understanding the importance of these key elements in relation to fire safety is absolutely crucial.
Many architects, developers and contractors are turning to the Wraptite® air barrier system. Wraptite offers a safer and simplified membrane system, conforms with the required Class B rating, and it provides a fully self-adhered vapour permeable air barrier certified by the BBA. It combines the important properties of vapour permeability and airtightness in one self-adhering membrane. The membrane bonds back to the substrate, ensuring a simplified design to airtightness and simple installation method.
Wraptite complies with Part B amendments for use on buildings of high rise and over 18m. Under Part B membranes need to be Class B,s3,d0 or better, whilst Wraptite is classified as Class B,s1,d0 when used over a Class A1 or A2 substrate.
For any building to have an energy efficient, healthy, moisture free building envelope there is a clear need to manage the balance of Heat, Air and Moisture movement (HAMM) throughout the building’s life cycle from design, construction, completion and use.