Triple-Decker & Multifamily Insulation in Boston, MA

Triple-decker and multifamily insulation is its own kind of job. A triple-decker stacks three apartments, each on its own floor, usually with porches on the front or back and a low-slope roof on top. Air moves through the building like a chimney: cold air enters at the basement sill and the first-floor walls, rises through open framing, and escapes through the top-floor ceiling. Insulating one floor helps that unit, but the building only gets comfortable when the bottom, middle and top are handled together.

The top floor

The third-floor unit sits under the roof. Many triple-decker roofs are low-slope with a shallow cavity or no attic. In summer the unit overheats; in winter it loses heat straight up. Depending on the roof, we blow loose fill into the cavity through a small opening, spray closed-cell foam under the deck, or recommend adding insulation during the next re-roof. We look before we suggest any of them.

The walls

Most triple-deckers have empty or partly filled walls behind plaster and wood or vinyl siding. Dense-pack cellulose fills them through small holes. Balloon framing and the connections to porches need blocking so the fill stays in place and air stops moving. Porch roofs and floors that tie into the main frame are common leak points.

The basement

The first floor sits over a basement with a bare rim joist. Closed-cell foam on the rim and sill is a quick job that cuts the cold air entering the whole building. HomeGuide lists rim joist foam at $2,000 to $2,500 nationally.

Owners, tenants and Mass Save

Mass Save lists its no-cost assessments for homes with one to four units and has separate paths for landlords and renters. Boston's insulation barriers guidance describes a barrier incentive of up to $7,000 for income-verified households and a 0% HEAT Loan to fix things like knob-and-tube wiring before insulating. Somerville's Save Energy Somerville program lists $2,000 microgrants for some rental units in 2-4 unit buildings. Start with an assessment if you want those incentives. If you hire us directly, we schedule the work floor by floor and tell each unit when to expect us.