Another material that deserves a mention when it comes to advanced building materials, is the semi-permeable membrane, ”Housewrap” from Tyvek. Manufactured by the Du Pont stable, Tyvek Housewrap is an intelligent product that has been designed with performance in mind. It is a unique nonwoven web structure with microscopic pores, small enough to resist bulk water and air molecules, but large enough to let smaller moisture vapor molecules pass through – quite clever!
Where is Housewrap most commonly used?
It has become synonomous with framework structures (light steel and timber frame). Applied as it’s name would suggest, the product is wrapped around the external framework structure and allowances made for the product to be wrapped into all openings. Not all breathable membranes perform air, water and moisture protection functions equally. The difference is in the manufacturing process of perforated versus non-perforated membranes. Non-perforated DuPont™ Tyvek® is continuous spunbonded, non-woven sheeting with a fibrous structure that naturally allows moisture vapour transmission but, the micropores are small enough to resist liquid or bulk water and air infiltration. Simply put, external moisture is prevented from entering whilst at the same time, internal condensation build-up is allowed to escape.
In South Africa, framework structures are on the increase due to their energy efficiency and performance charactoristics. A semi-permeable membrane would form a critical material in a typical wall section of a framework structure. It is important to note the difference between a product like Tyvek Housewrap and undertile membranes often used in roofing applications. The latter, although designed to prevent water penetration, is unable to allow condensation to escape. The result, is that in a walling scenario, any internal condensation that may build up as would be the case in a bathroom or kitchen environment, will be unable to escape. Unfortunatley I have experienced such membranes on framework sites with the common reason being that the undertile membrane is cheaper in cost. Now whether you are an architect, builder or the client, one should be wary of distinguishing this difference as it will effect the overall thermal comfort of the structure.
There is a range of Tyvek materials suitable for many different applications, commonly, the Housewrap lends itself well to framework structures, whether timber or light steel frame. Applied in a wrapping application the membrane is taped together where it has been suitably overlapped with Tyvek Tape which helps to create a seamless, protective sealed envelope. The tape is constructed of an oriented polypropylene film coated with a specially formulated permanent acrylic adhesive and as a result, compliments the properties of the Housewrap.
So in future, consider the materials on your project, a little investigation into their properties and charactoristics may astound you and add value to the end-product. By wary of imitations and check technical data before making your decision. For more information on Tyvek and where it can be found in South Africa, leave your contact details here.