Energy Efficient Doors and Windows: Design and Build

Windows and doors are an indispensable element to building a house. They provide ventilation, light, heat from sunlight, and a means to enter and exit a space. They also function to protect the interior space from the outside elements. In order for doors and windows to be energy-efficient, they must create a tight seal at their edges and insulate from the cold, as well as functioning (opening and closing) to provide ventilation.

Designing windows and doors and building them from scratch was the most challenging aspect of this project. Not only did I have to design a window design which seals out the elements and provides optimum insulation and sunlight, but I also needed to acquire materials and design a shop process for milling the windows to precise tolerances needed to assure proper operation of the window unit.

Designing a full set of custom windows was too much of a task. If I did this project again, I would acquire salvaged windows, and then design my house around them!

The joinery for the window was was fun to design:

The window joinery took three tries to get right. Mock-ups of the joinery were important for me, in order to understand how the rails and stiles fit together. The window joint is a double-lap joint.

The joinery is pegged (square pegs in round holes) in order to make it stronger and more stable. The peg holes are offset in order to draw the joints tighter, so that clamps are not required for the assembly (I don't own enough clamps to clamp all of these windows!)

Here are the finished windows units, ready to be installed. The glass units are 3/4" double pane insulated glass, with low-emissivity coating.

The doors have a square mortise and tenon. The tenons are cut on a table saw and the mortises cut with a square-mortise machine (a drill press with a square bit). Precise milling of the wood is critical to ensure a consistent and tight fit for the joints.