Continuous exterior insulation (CEI)  is an added layer of insulation to the exterior of a wall assembly, installed to the outside of the structural sheathing and behind the cladding. The material options for CEI range from rigid foam to mineral wool to wood-fiber boards, and all have their own specific characteristics and advantages. There are also many ways to install CEI and integrate windows and doors, flashings, rainscreens, siding, and trim. There may be 10 perfectly good ways to build a wall with CEI, but the specific one that you end up choosing will depend on what your team is familiar with, what materials are available, the project budget, the project’s climate zone, and your risk tolerance.

Incorporating all the details required for continuous exterior insulation (CEI) can be a bit of a head-scratcher if you’ve never built this way before. It’s more complex than the typical 2×4 or 2×6 code-built wall that many builders are familiar with, and it can affect the placement of the four control layers. In this article I hope to clarify how to choose and install CEI based on some simple building science principles and share two examples of real-world installations with window details.

CEI adoptees

At Birdsmouth Design-Build in Portland, Ore., we believe there are five non-negotiables for any new home or remodeling project: durability, health, resiliency, comfort, and energy efficiency. We often include CEI as part of our wall assemblies because it addresses all these goals in our climate zone, Marine 4. But CEI can work in all climate zones. It is an effective strategy for builders in cold climate zones looking to improve durability, comfort, and energy efficiency, and those in hot-humid climate zones looking to manage interior moisture and create efficient and comfortable homes. In some areas, it may be the…