Written by Jon Davies
Technical Sales Support and Education Manager, Pro Clima New Zealand

We from pro clima have been working with Sika, Tremco and Bostik on this matter and have conducted several tests. While dealing with all three companies it became apparent that there is a wider issue in the industry that no one had addressed until now. Seemingly there have been significant issues in regards to the plasticiser migration with bitumen based tapes (compatibility issue), and sealants not bonding to substrates (adhesion issue).

While there is no compatibility issue with pro clima's sill tape as it is free of bitumen, there is an adhesion issue with the very top layer — a thin polyethylene foil that acts like a bond breaker, and therefore there was no sign off from any sealant supplier in the New Zealand market. To overcome this issue we engaged with current suppliers of foil backed tape, but they will not guarantee the adhesion of their foil tape to any substrates. As a result there was no system in the New Zealand market providing any guarantees.

International best practice is not to use wet sealants but to tape the window / door frames to the openings. Our pro clima CONTEGA IQ is one option. With this option you would normally not need any sill tape, however this will not comply with the current requirements of the New Zealand Building Code. You might have seen the new Smartfit Window system from FWDS. This concept is one step towards the elimination of sill tapes.

Coming back to the current issue, we have also been told by the sealant suppliers that they have issues with bonding to standard wall underlays due to the water repellant coatings. As an intermediate solution (before we see the industry changing to taping the windows and door into the openings), we will offer a pro clima foil tape — available within the next few weeks.

We from pro clima will be able to sign off on the adhesion of the new pro clima foil tape to any substrate within the window and door opening. The sealant providers will then sign off on the adhesion of their wet sealants to the surface of our foil tape. This will provide a system with guarantees for the window and door installers.

From our end, we will try to reduce the costs of the tape as much as possible into the market to ensure this does not add significant expense.

The main advantage of this new pro clima foil tape will be that it can be applied around the entire window and door opening on any substrate and provide a surface for adequate adhesion of wet sealants.