Continuous Insulation, Part 2 – GreenBuildingAdvisor – GWC Mag

In the first post of my three-part series on continuous insulation (CI), I covered building codes and some basic building science principles and how they relate to CI. This second part will discuss some of the difficulties builders have with getting the details right.

I remember my first time using exterior CI on a new home. I had many questions; where to put the WRB, how to attach the cladding, how to address the windows and doors, and how much insulation to use. That home is over 12 years old without any complaints from the homeowner. Would I change some of the details I implemented on that first project? Absolutely. But the design and execution seem to be performing well.

What I would do today would be based on whether I was dealing with new construction or a renovation. Other factors would be budget, the construction crews’ experience level, and how the homeowner intends to use the building. For example, maybe a family member has a health condition that requires higher than average indoor humidity, or maybe the homeowner is planning on an indoor swimming pool. I would approach those projects differently than I would building to code minimum requirements for CI outlined in Chapter 11 of the IRC.

Common materials used for continuous insulation

There are four main materials used for exterior CI, plus a new one just now coming onto the domestic market. Most installations will include some sort of rigid insulation, but fibrous insulation can be an option with certain designs and assemblies. (I won’t be covering the fibrous options in this post.) In no specific order, the most commonly spec’d materials are extruded polystyrene (XPS), expanded polystyrene (EPS), polyisocyanurate (polyiso), and rigid mineral wool (e.g. Rockwool’s ComfortBoard 80). Another product that has been around for a while in…