When builders began to insulate houses in the 1920s and 1930s, the exterior paint began to peel. … By 1938, the problem was common enough that Architectural Record published an article titled “Preventing Condensation in Insulated Structures.” The author, an architect named Tyler Stewart Rogers, argued that insulation was not the problem; indoor humidity was. He proposed a two-part solution: vapor barriers and attic ventilation.

When it comes to insulating and air-sealing tricky spaces, spray foam is often the go-to solution. In this New England walk-out basement, Aron Jones of Big Dog Construction Inc. uses Froth-Pak™ 200 Foam System to separate the unconditioned basement from the conditioned living space above. The result is a durable and efficient layer of insulation that’s drywall-ready.

By now, almost all builders know the importance of installing a water-resistive barrier (WRB) behind siding. Most types of siding leak, so it’s a good idea (and a code requirement) to install a WRB to protect your wall sheathing from any wind-driven rain that gets past the siding.