Monopoly Roof Framing – GreenBuildingAdvisor – GWC Mag

Many new homes are designed with vaulted ceilings or low-slope roofs for aesthetic reasons. It’s challenging to build an effective vented cavity in these types of roofs, so a lot of builders turn to closed-cell spray foam thinking it’s an easy solution. While this approach can work, it’s not without risks. If the new framing lumber settles or dries and shrinks, the foam can delaminate from it, providing pathways for warm interior air to reach the cold roof sheathing and condense. Over time this has the potential to cause catastrophic roof failure. Also, roof leaks tend to be harder to detect and track down if they are retained by or work their way through a layer of bonded foam. And finally, the chemicals and blowing agents used in a lot of spray foams are toxic and have high global warming potentials, not to mention significant embodied carbon in their manufacture. For these reasons, my company, Targa Homes, in Seattle, uses the alternative method detailed here.

Order of the build

This insulated over-roof, as I call it (aka “Monopoly” framing), avoids spray foam while providing a durable and high-performance assembly. The construction sequence is as follows: