The Internal vapour control diffusible membranes by SIGA are called Majrex & Majpell. Majrex is the next platform in intelligent vapour diffusible membranes and the world's first with Hygrobrid technology. Detailed care is required when attaching membranes to the structure. Externally, it is acceptable to use mechanical fixings (MF) provided care is exercised to ensure flush embedding. For Internal fastening, SIGA has developed a specialised double sided tape called Twinet that negates the need for MF. Twinet allows the membrane to adjust to structural movements. Such movements and imperfect embedding (generally the result with a stapler) could potentially cause MF original membrane penetrations to widen compromising airtightness. Your choice of fastening depends on the level of airtightness and its intergity that you are wanting to achieve. Ultimate integrity can be achieved using Twinet on the inside for a small incremental cost. As always with this type of build, it is the detail that is important. (MF cannot be used for metal structures).
In an airtightly constructed home like a High Performance Build or Passive House construction, air infiltration is greatly reduced. Therefore the effects of any VOC off-gassing are more pronounced. Some people are more sensitive to these elevated levels than others. So it is vital that products used in such builds are 'genuinely' VOC free and not off-gassing after installation, which can last for years. SIGA products are specifically designed to ensure that there is no off-gassing of VOCs because the products are free of solvents, high boilers, plasticisers, chlorine, formeldehyde, caoutcho, typically found in the production of tapes. SIGA manufactures its products in-house and so is able to control the quality fastidiously. No off-gassing also means that the products do not deterioriate in performance because the binding elements do not off-gas . Ask your passive house designer/building designer to ensure that products being specified reflect this standard, because low VOC is not good enough when there is an alternative available.
That's a very pertinent question! The quality tapes are tested independently on a variety of different areas. Essentially, specialist laboratories have test facilities where product is artificially aged in hot/cold 'cabinets' and the so called 'stickability and durability is tested... how does it stand up to temperature variations, ageing resistance, brittling, effective Sd (diffusion layer thickness), tensile strength and so on. In our own in-house benchmarking tests some competitor tape give up the fight after 30 days! Independent testing by TU Berlin award a 50+ Year durability rating for Siga product. It would be too easy to ask them to test our tapes to a 75 or 100 or 200 year rating, but the point is how practical is that and will the consumer believe these stretched ratings? The lifespan of the average building is required to last 50 years; the reality is that it will most likely be refurbished well before that. Siga tapes installed over 25 years ago in building structures being refurbished are still sound and performing their air barrier continuity. So we also have the practical confirmations of our Durability awards. We do not believe it serves any purpose to extend laboratory testing claims to beyond 50 Years and then use that to claim that those tapes last longer than others especially to 100 years, when one will not be around to verify that! In fact some would say it is downright misleading. Siga rests comfortable in the knowledge that it is the only airtightness industry manufacturer to R&D and manufacture it products to the highest standards. Other brand products are sub-contracted out.
