Difflex Thermo ND and Linopore UV+
Hartmut Layer’s eyes light up when he talks about the production of Difflex Thermo ND –highly breathable sarking membranes for steep roofs based on polyester fleece. They are inserted between the roof tiles and the sheathing of steep roofs. And they make sure house owners can live without roof damages for at least twenty years – dangers such as mold, dirt, or insects become history. Last year, these foils accounted for 65 percent of the BWK group’s turnover.
Due to their outstanding tear resistance, sealing performance, and anti-slip coating, the sarking membrane layers have convinced BWK’s customers – retailers and craftspeople alike. The German manufacturer gets these results by using high-quality polyester nonwoven fleece combined with a special multi-layer coating.
The Difflex Thermo ND and ND Plus layers act like a breathable jacket for buildings. And the durable housewrap is especially tear proof, UV-stable, impervious, but still highly breathable. Although these foils cost twenty percent more than other underlays on a polypropylene basis, the investment pays off, as the foils can be laid more rapidly, which is then cheaper.
The best of all: when the quality of cheaper foils degrades after a few years, letting rainwater penetrate, or warm air leak, the BWK foil still protects and saves money for many years to come. Not to mention the cost of premature dismantling and renovation. After all, Layer offers a 20-year warranty on his premium product – much more than the average six years offered by most companies from the business. The BWK group sells its foils in 40 countries and via 1,500 wholesalers. With its high-quality polyester foils, the family-owned company notches up a market share of 25 percent.
Linopore UV+: the patented UV protection against aging
The sun’s ultraviolet rays, with wavelengths of between 10 and 80 nanometers, attack the bonds of the polymer chains. That is the reason why roofs suffer early when inferior sarking membranes are used. BWK and its subsidiary LHB GmbH & Co. Beschichtungs-KG, with production sites in Saxony and Saxony-Anhalt, produce a patented, microporous membrane named Linopre UV+. So-called HALS (hindered amine light stabilizers) protect these layers against aging, independent of their thickness and color.
Thus, even after an aging test at 100 °C, it retains 80 percent of its tear resistance and tensibility. Just compare that to the EN 13859 norm, which detects the durability after UV exposure and heat aging at only 70 °C. And the German Roofing Contractors Association (ZDVH) demands testing at only 80 °C.
LHB inline produces the polypropylene fleece with widths of up to 5.60 meters, coating it with a polypropylene film. This patented functional layer, with its sd value of 0.02 meters, makes it highly water vapor permeable as well as resistant to water penetration. Moreover, the sarking membrane’s coating ensures increased UV stability and heat resistance, making it ideal for dark roofs and as a makeshift roofing.