Synopsis: As the building industry tightens up on air-sealing and energy efficiency, builders need to be more aware of the risks associated with moisture and especially with bulk-water entry. Windows and their installation is an area ripe for major improvement for saving energy and increasing durability. The best installations keep water out, give it an escape path for when it inevitably leaks in, and block unwanted air movement. In this article, builder Brian Knight demonstrates his methods for ensuring window installations are as tight as possible.

Watch the Project House video series: Weatherproof Window Installation

As the building industry tightens up on air-sealing and improves energy efficiency, we need to be more aware of the risks associated with air and water intrusion. Materials that get wet won’t dry out as quickly or easily as they used to do in leaky, poorly insulated houses, and many of the materials being used to build houses aren’t as resistant to moisture as their predecessors. There’s no doubt that with windows accounting for such a large part of the building budget, and being one of the most direct connections to the elements, their installation deserves extra attention.

Windows are complicated, and so is their installation

Compared to solid areas of wall and roof, windows and their interface with the air barriers and water-resistive barriers (WRBs) of a house are complicated and vulnerable. Many builders and designers are confused about best practices, and inferior techniques are rampant. As windows, tapes, sealants, and WRBs evolve, so do the installation guidelines for these products. It’s not uncommon for products that are typically used together to have conflicting installation instructions. When in doubt, I follow the window manufacturer’s instructions as a bare minimum, and add improvements from there.

The best window installations include…