Synopsis: Natural builder Ben Graham and custom woodworker Mike Lamp demonstrate how they recently designed and built a 3-1/2-in.-thick R-10 wood door using salvaged cherry lumber. The door’s construction details, product selections, and design choices are explained thoroughly. The second half of the article shows how Graham and Lamp installed the 140-lb. door and integrated it into the home’s building envelope. Exploded drawings show how the door and its two-piece jamb assembly are constructed.

We recently completed a deep-energy retrofit to an 80-year-old Vermont farmhouse. The many improvements we made included new windows, new mechanical systems, and the addition of 4 in. of exterior mineral-wool insulation. Not surprisingly, the project also called for new energy-efficient exterior doors to complement the home’s high-performance building envelope.

For an ultra-efficient house like this one, entry doors are often sourced from Europe, where high-performance doors are more mainstream than in the United States. Unfortunately, most European offerings have a sleek, modern appearance, and our clients wanted something that would fit the style of their farmhouse. With limited options, we set out to build a pair of attractive entry doors that would rival the efficiency of the best-performing units on the market. In addition, we wanted to do so by using common building materials that are readily available.

The 31⁄2-in.-thick R-10 doors that we built are made from site-harvested cherry. They are filled with 2-in. rigid-mineral-wool insulation and include triple-pane low-e glass. We installed the doors in custom-built jambs with a crucial double-weatherstripping detail to help make the entry airtight. Finally, we outfitted each door with the best-built hardware we could find.

Aesthetics and performance drive design

One of the first decisions we had to make was whether to build inset or overlay doors. In the United States, virtually all…