This blog is part of a series about high-performance window installs. Check out Part 1: How to Prep the Rough Opening, and Part 2: Positioning the Window in the Rough Opening
Exterior Sill Taping
Once the unit is set into the rough opening the unit is ready for exterior window tape. The exterior window taping acts as the primary waterproofing connection to the WRB. When taping to the exterior side of the window frame it’s best to start with the sill first so each tape joint can be ship lapped from the sill to the jambs and then header of the window. For the window tape connection from the WRB to the window frame’s sill it’s best to use TESCON PROFIL or CONTEGA SOLIDO IQ. These tapes are vapour permeable if there’s condensation between the window frame and the EXTOSEAL ENCORS tape the water can dry through diffusion (see How to Prep Rough Openings blog post for overview of the sill tape install). Many high-performance window frame sills include weep holes, so the tape needs to be adhered below these holes and not clog any drainage from the weep holes.
There’s typically a metal sill pan attached to the exterior side of the window frame’s sill that’ll conceal the tape connection behind. It’s best practice to install a strip of TESCON NAIDECK or fasten through some adhesive that’ll water seal the mechanical fasteners from the metal pan to the window frame. The metal pan should slope to the exterior and shed the water to the exterior side of the finish siding. The window tape connections to the frame should be taped to the WRB.
Some builders will be reluctant to tape the window’s exterior sill frame because they want to allow drainage between the EXTOSEAL ENCORS and the window frame – this is commonly a concern with flanged (nailing fin) units.
475 is comfortable recommending taping the exterior sill with TESCON VANA, TESCON PROFIL, or CONTEGA SOLIDO IQ because all of these tapes are vapour permeable. Any moisture behind the tape can dry outwards through diffusion. And the watertight seal from the exterior will prevent most of the moisture from occurring to begin with. (Check out this blog for more info).
Exterior Header/Jamb Taping
The WRB at the header of the units can overlap the frame and be taped to the frame using the double sided CONTEGA SOLIDO IQ-D tape. This tape is double-sided so the top side adhesive strip is adhered to the backside of the membrane and then the main adhesive backing is adhered to the window frame. This allows each waterproofing layer to be ship-lapped to promote drainage.
If using the ADHERO membrane then the adhesive from the ADHERO can be applied directly to the window’s header. If the unit install wasn’t sequenced to allow the membrane shiplap at the header then a wide tape can be used to water seal the joint. The tape should adhere at least 1” up the WRB. The Pro Clima tapes use a pressure activated adhesive to bond to the substrate and is a watertight connection. The Pro Clima tapes have been simulated age tested to ensure that the adhesion lasts at least a 100 years. The tape needs to adhere to the window frame at least a ½” to ensure best adhesion.
The corners are the common leak areas. If the unit is in line with the WRB then a simple overlap of the tape at the corners is easiest.
If the units are located interior of the sheathing / within the window buck then it’s best practice to place a daub of CONTEGA HF of VISCONN in the corner and then tape over it with a window tape corner detail. See this video for pre-making the window corner tape using a small cut and fold in the tape. It’s best to use TESCON PROFIL, or CONTEGA SOLIDO IQ for these corner tapes since there’s a split in the release strip backing to create an easy install.
