7.3 Windows & Doors

Windows and Doors: Where Openings Meet the Water-Resistive Barrier

Why This Matters for the Exam

Window and door openings are, in practical terms, one of the most common real-world sources of building envelope leaks — and this exam tests that reality directly. Every window or door opening is a deliberate interruption of the wall's water-resistive barrier (WRB) described in Section 7.2. If that interruption isn't flashed and integrated back into the WRB correctly, water finds the gap. Expect this domain to blend with the Moisture Intrusion/Protection domain (Section 7.4) — the exam does not treat windows/doors and moisture protection as fully separate topics, because in real construction they aren't.

Flashing Integration at Window and Door Openings

Every window and door rough opening cuts a hole through the wall sheathing and the WRB behind the cladding. That hole has to be resealed back into a continuous water-managing system, or the opening itself becomes the wall's weakest point. The general sequence a supervisor needs to understand:

1. The rough opening is prepared and, in most assemblies, a sill pan or sill flashing is installed at the bottom of the opening first — this is the critical detail, because the sill is where any water that does get in will collect, and it needs a path back out, not a path into the wall cavity.
2. The window or door unit is set into the opening.
3. Flashing is installed at the jambs (sides) and head (top) of the unit, integrated with the WRB already on the wall so that each layer overlaps the one below it and sheds water outward and downward — the same shingle-style, bottom-up logic covered in full in Section 7.4.
4. The WRB is lapped back over the flashing at the top of the opening, completing a continuous water-shedding path from above the window, down and around the opening, and back out onto the wall's drainage plane.

The critical exam concept is sequence and lapping: work bottom to top, and each piece must overlap the piece below it so water is always directed outward and down, never trapped behind or channeled into the wall. A window installed with flashing in the wrong order — for example, WRB lapped under the head flashing instead of over it — creates a hidden path for water directly into the wall cavity, even though the finished wall looks correct from the outside.

Energy Performance: Understanding U-Factor

Windows and doors are also tested from an energy-performance angle, which connects directly to Chapter 9's energy-code content. The key metric to know is U-factor: a measure of the rate of heat transfer through a window or door assembly. The lower the U-factor, the better the assembly performs as an insulator — meaning it loses less heat in winter and gains less heat in summer.

This is the inverse relationship of R-value (used for insulation elsewhere in the code), which you may see contrasted in exam questions:

A question that asks which of two windows has better energy performance based on their U-factors is testing whether you remember that a lower U-factor is better — the opposite direction from R-value questions elsewhere in the energy-code material.

Egress Windows: The General Principle

Bedrooms (and certain other habitable spaces) are required to have at least one window that functions as an emergency escape and rescue opening — commonly called an egress window. The underlying principle, which the exam tests as a concept rather than a fact to memorize in isolation, is life safety in two directions: the opening has to be large enough and low enough on the wall that an occupant can climb out unassisted in an emergency, and it has to be accessible enough that a firefighter in full gear can climb in to perform a rescue.

That means an egress window is evaluated against several dimensions at once — minimum opening area, minimum width and height, and a maximum height of the sill above the finished floor — not just "any window will do." When you encounter an egress-window question on the exam, your open-book job is to locate the correct code table for emergency escape and rescue openings and confirm the specific figures against the scenario described; your conceptual job, which this guide is teaching you now, is to already understand why those figures exist and what they're protecting against, so you recognize the right code section the moment you see a bedroom-window question.

Common Exam Traps

On the Exam

Expect this section to test sequence (the order flashing and WRB integration happens at an opening), the U-factor/R-value direction distinction, and recognition of when an egress-window question is being asked so you go to the right code table. As with the rest of this chapter, the exam is checking whether you understand why the code requires what it requires — that understanding is what lets you navigate the book quickly under time pressure.