A membrane may be used for sealing the perimeter of windows or protecting the backing-wall on a façade. The membrane may need to be vapour-permeable (eg breather membrane) or vapour tight (eg vapour control layer) and can have a fixed or variable level of vapour permeability, the latter being referred to as an ‘Intelligent’ membrane. A membrane can be both airtight and vapour tight, and can even also be vapour permeable (see ‘Intelligent’ Membrane below).
This means Ethylene Propylene Diene Monomer, and is a rubber based material which is very flexible and excellent at maintaining weather and air tightness but does not facilitate vapour permeability and if used incorrectly can promote interstitial condensation.
Absolutely not! This is a very common misconception in that the EPDM reference is often used for applications which clearly don’t require the properties of this type of membrane or where it may be inappropriate for use, and even where a non-EPDM membrane is actually being used. The term ‘EPDM’ should not be used generically to cover all façade applications as problems can and will arise due to the potentially misleading terminology. The only time a membrane should be called ‘EPDM’ is if it actually is!
These membranes are so-called due to their ability to promote the drying out of a building by having a variable ‘sd’ (equivalent air layer thickness) value whereby as localised humidity increases, the sd value decreases (the membrane becomes more vapour-open) and the sd increases (becomes more vapour-tight) in less humid conditions.
An EPDM membrane can be exposed to both weather and UV indefinitely. A typical breather membrane (NOT an EPDM material) is normally covered within a few weeks or months of application so doesn’t need to be permanently durable without protection. Some membranes need to be covered within six to twelve months due to potential UV degradation but would resist weather ingress in the meantime. Although most breather membranes will resist typically 600 Pa driving rain resistance, they are normally effectively secondary seals due to being protected by rainscreen or similar cladding which acts as the primary seal.
Breather membranes need to be capable of withstanding driving rain (usually to a minimum of 600 Pa) and by definition need to be vapour permeable and the measurement of this is by reference to the membrane’s vapour resistance (measured in MNs/g – Mega Newton seconds per gram). Another widely used measure is the ‘sd value ’ – this is the equivalent air layer thickness in metres (m). In the case of both measurements, these can only be stated based on the specific thickness of the material. For optimum vapour permeability, the vapour resistance of a membrane should be < 0.6MNs/g.
In this case, the sd value should be as high as possible (eg illbruck ME003 has an sd value of 107m) and a minimum vapour resistance of 200 MNs/g.
Whilst all materials fixed to the external wall have to be non-combustible (Class A1) or of limited combustibility (A2-s1, d0) to EN13501-1, there are certain exemptions including for membranes, which are required to be minimum Class B-s3, d0. illbruck ME010 Façade UV & Fire Membrane achieves Class B-s1, d0 when tested with SP025 Adhesive. Most membranes, including illbruck ME220 (EPDM) and ME501/ME508 (Intelligent) are Class E as are most sealants. More information can be found in our Approved Document B 2019 Fire Safety.
There are various options of self-adhesive strips or full face self-adhesive, enhanced acrylic self-adhesive, gaskets and proprietary site applied adhesives.
All illbruck membranes are compatible with each other and although not all adhesives are appropriate with all membranes, it is possible to bond different types of membrane to each other by selecting the correct adhesive. In terms of vapour control, it is recommended to always use a more vapour open membrane to the exterior to facilitate escape of moisture and avoid damage within the wall construction.
Apart from 3rd party testing for properties such as air and weather tightness and reaction to fire, most illbruck membranes have BBA accreditation, thus satisfying the requirements of various specifiers, clients and building warranty providers.
CPD seminars and webinars are available which include information on the relevant building physics and regulations relating to membranes. The ‘illbruck assured’ training programme delivers both theoretical and practical training and can be tailored to suit individual clients’ needs. Site delivered ‘tool-box talks’ are also regularly provided on request.