Changing the position where a window sits in a rough opening can improve overall performance and durability. Most of us in residential construction are used to installing outie windows — a nail-fin or flanged unit set flush with the siding or cladding. It’s simple, fast, and we are familiar with the details of connecting the water and air control layers to the window. It’s an assembly we’ve been working with for years. But as more clients start asking for high-performance builds, or if you’re working on deep energy retrofits, you’re probably going to start running into a change in window installations.
Innie and middie windows are growing in popularity. These styles of installation are common in commercial work, but they’re still new for many residential contractors. Getting them wrong can mean water problems, poor air-sealing, comfort issues, and callbacks. Done right, though, they can improve energy performance and durability. Here’s what you need to know.
Outies are what most of us are used to seeing in the field. The window sits flush with the exterior cladding and is usually installed using a nailing fin.
An innie pushes the window to the far inside edge of the rough opening. The window head is fully protected by the building’s framing.
The middie places the window in the middle of the wall assembly — roughly one-third to two-thirds of the way into the opening.
Here’s the quick way to think about it:
Takeaway: Know your client’s goals and your crew’s skill level (additional training may be a necessity). The detailing gets more complicated as you move from outie to middie or innie. That being said, the benefits in performance and durability often outweigh the cost.
Randy Williams started his construction career in the mid-1990s installing electrical, plumbing, and HVAC systems with his brother. In the early 2000s, his family branched into building and renovating homes. By 2005, Randy was working full time as a general contractor. He furthered his education in 2009 becoming an energy auditor. Today, Randy works with other contractors, homeowners, and utilities performing energy audits, building diagnostics, energy design, and code compliant testing, and assisting in the design of energy-efficient homes. He is also a contributing author to several trade publications and occasionally teaches home diagnostics testing and building science topics at different trade shows and training events.
