Pro Installer June 2015 - Issue 27 | Page 39

39 PRO INSTALLER JUNE 2015 PRO NEWS @proinstaller1 Intelligent membranes Interfaces where windows require sealing to the building structure demand innovative, clever solutions in order to comply with more onerous Building Regulations. The need to eliminate thermal bridging and significantly reduce uncontrolled air leakage requires robust sealing solutions to meet legislation and ensure long-lasting performance. The provision of weather and airtight perimeter window seals is more often than not achieved with the inclusion of membranes as secondary seals behind rainscreens or insulation to built-up walls. Whilst the traditional membrane material of choice is EPDM, this is being superceded by ‘intelligent’ membranes incorporating variable moisture vapour permeability. These can be used to provide either airtightness or weather tightness. In the latter case, they act as a breather membrane, preventing ingress of precipitation whilst allowing any dampness behind to escape as moisture vapour. illbruck’s ME501 The choice of material is important in terms of vapour control and when an inner and outer layer is involved, it is essential to consider the relative vapour permeabilities to allow moisture to travel from inside to out. The internal membrane should therefore be more vapour tight than the external. This allows the building to dry out and prevents condensation and mould growth. If EPDM is used both internally and externally, interstitial condensation and mould growth can result as moisture is unable to escape. An intelligent membrane can be used internally and externally to manage the vapour control factors to avoid these problems. Alternatively, EPDM can be used as an internal airtight seal with an intelligent membrane on the outside; which still maintains the ‘inside tighter than outside’ principle. Is your supplier letting you down? k ee e* w m 2lead ti N ow ly From on £p36a5 er le f SITE DELIVERY AVAILABLE The membranes used to seal the windows to the structure can be connected to the air barrier membrane or an external breather membrane to maintain continuity of the building envelope. Fixing to the window frame can be by integral self-adhesive strips, site-applied proprietary adhesive, or gasket. The latter provides a mechanical fix which is not affected by low application temperatures or damp substrates. The proprietary solvent-free hybrid adhesive also offers an advantage compared with typical ͽ