We designed an exterior envelope renovation for large sections of MDI High School, part of AOS 91 on Mount Desert Island. Sealander Architects and contractor E L Shea completed the project in the summer of 2017

Exterior envelope renovation

The original portion of MDI High School dates back several decades, and is one of the many Alonzo Harriman-designed school buildings in Maine. The school underwent major renovations and additions in 2001. Portions of the renovated exterior walls have suffered from water intrusion since that time. While we could identify the cause of the water intrusion, Sealander Architects and the school took an opportunity to fix the envelope deficiencies by not only making the building more weathertight, but also more energy-efficient and with better interior lighting levels.

Solution

The exterior envelope renovation reclads the building with single-skin metal panels over spray foam insulation. The panels are kynar-coated aluminum. The spray foam is a water-based 2.0 pound per cubic foot (PCF) product. High-performance glazing on this project is low-e double glazed fiberglass fixed units and awnings. We tuned the low-e material to respond to solar gain on each elevation. We effectively tripled the overall u-value of the exterior envelope.

Thermal System

The existing opaque walls were an assembly of wood clapboards, building paper, gypsum sheathing, metal studs with batt insulation, and gypsum board on the interior. Energy modeling of this assembly confirmed that the overall R-value was less than R-13. We added four inches of spray foam and a single skin metal panel sheathing fastened to metal framing girts. A stand-off gap between the new girts and existing gypsum sheathing provides a thermal break.

This solution might be categorized as mid-range in expense, although it will provide decades of life to the school. See our project at the Brooklin School for an example of a less expensive alternative.