Envelope Retrofit Costs

Howland Exterior InsulationWe are completing two projects that involve re-cladding existing building envelopes. These are buildings whose exterior walls had little to no insulation. Part of our task was to provide increased energy efficiency to these buildings. Cladding costs on both projects, interestingly, ran around $18 per square foot, even though the projects were a bit different. I should note these are commercial projects, competitively bid.
Howland Hall is a wood- and masonry-framed college building in Calais, one story in height. We provided continuous exterior insulation, some new windows, and either vinyl clapboard or metal siding. Windows went into new openings, which meant each window included reframing or masonry work to create the opening. Windows and siding together cost about $17.75 per square foot.
Longfellow Hall is a wood-framed K-12 school building on Great Cranberry Island, two stories in height. Lead-containing clapboards and shingles were removed. The existing windows were less than five years old. They were removed and then reinstalled. We added three inches of continuous insulation to the wall assembly. Cladding was glass fiber reinforced cement clapboards. Siding costs were $18 per square foot.

Self-perform contractors are generally more competitive, and window costs can run $25-50 per square foot.

Howland Hall was built by a northern Maine general contractor that self-performs virtually all their work. If this project was built by a general contractor with higher overhead and subcontractors, we would not be surprised to see prices in the $24 per square foot range.
Longfellow Hall is on an island, which makes everything expensive. This project was also built by a general contractor that self-performs quite a bit of the work. We could see prices 30 percent higher depending on the bidding environment.
Is the $18-24 per square foot range indicative of current siding replacement and envelope retrofit projects? It’s probably not a bad place to start. Add to this the cost of fenestration, which could run $25-50 per square foot, and then the cost of repair work to the inside of the envelope, perhaps another $10 per square foot. Add all those together and an envelope retrofit starts looking like a $40 per square foot project.

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Principal at Sealander Architects, Ellsworth Maine. Revit guru. Married with 3 children. Avid gardener. Lived in San Francisco for nine years. Master in Architecture from Columbia University Bachelor of arts in religious studies, Wesleyan University. Graduated Staples High School, Westport CT. Hope to spend some time in Hokkaido before all is said and done.