Clement Boston Heat Pumps plans most of its jobs around old houses, because that’s most of Greater Boston. Choosing a heat pump for an old house starts with the house, not the equipment: how it leaks, where air can travel between floors, and what the wiring can carry. This guide covers how those three things change a ducted install.
How old is the housing here?
Old enough that pre-war houses are the standard case. In the City of Boston, 46.7% of homes were built in 1939 or earlier, against 30.5% statewide and 11.7% nationally.
| Place | Homes built 1939 or earlier |
|---|---|
| Somerville | 59.0% |
| Belmont | 57.1% |
| Brookline | 51.7% |
| Newton | 48.8% |
| Boston | 46.7% |
| Massachusetts | 30.5% |
Those houses came with coal, then oil or gas boilers and radiators, small electrical services and little insulation. Each of those shapes the job, and none of them rules a heat pump out.
Seal the house before you size the system
An old house loses heat through air leaks more than through its walls. Sealing the worst leaks first shrinks the system you need.
Where the leaks are
- The attic floor, around chimneys, plumbing stacks and light fixtures
- The rim joist where the house sits on the foundation
- Balloon-frame bays open from basement to attic, which act like chimneys
- Old windows and doors, which matter less than most people assume
Why it changes the price
The load calculation counts air leakage. Sealing and insulating a leaky house can lower the load enough to mean a smaller outdoor unit and smaller ducts. Mass Save’s whole-home rebate also asks for proof of weatherization, so the work pays twice. The sizing guide covers how the calculation runs.
Getting ducts into a house that never had them
Ducts come from the top and the bottom: an attic air handler for the upper floor and a basement unit for the first, with closets and framing carrying runs between.
Balloon framing
Many houses built before about 1920 have balloon framing, where wall studs run from sill to roof with no break at each floor.
Those open bays can carry a line set or a small return between floors. Wherever a bay is opened, fire blocking goes back at the floor lines, because the same open bay that helps a duct also lets a fire climb.
Plaster and lath
Plaster cracks if it’s cut carelessly, and old plaster often carries lead paint. Most routes avoid finished walls by using the attic, basement and closets. Where a wall opening is needed, the estimate lists it and its repair. Small-duct and new ductwork options cover houses where full-size ducts won’t fit.
Lead-safe work
In homes built before 1978, cutting or disturbing painted surfaces falls under federal and Massachusetts lead-safe renovation rules: containment, cleanup and specific work practices. That’s part of planning any opening in old trim or plaster.
Old wiring and small electrical services
A heat pump runs on new dedicated circuits from the panel, so it never ties into old branch wiring. The service feeding the panel is the real question.
Many old houses still have 60- or 100-amp service. Some carry a heat pump fine with smaller backup heat; others need an upgrade to 200 amps. Our typical range for an electrical service upgrade is $3,000 to $6,500.
Knob and tube
Live knob and tube wiring isn’t touched by the heat pump circuits, but opening walls and ceilings can expose it, and many insurers ask about it. Where our work uncovers it, we tell you, so you can decide on replacement as its own electrical job.
Boilers, radiators and what stays
Most old houses here heat with a boiler. Converting means the heat pump takes over through new ducts, and the radiators either go or stay as backup.
Keeping the boiler as backup for the coldest nights is possible, though it changes the Mass Save rebate path and, in fossil-fuel-free towns like Cambridge and Brookline, isn’t allowed in a major renovation. Our boiler comparison and boiler and radiator conversion page cover the choice.
Comfort in an old house after the switch
A heat pump heats differently from a boiler: warm air at a lower temperature, delivered steadily, instead of hot radiators that cycle.
What changes room by room
- Rooms far from the air handler need properly sized runs and returns, or they lag behind.
- Third-floor rooms under an uninsulated roof gain heat in summer; the attic system cools them for the first time.
- Drafty rooms feel cooler with moving air; sealing their leaks matters more than raising the setpoint.
A steady setting suits the system best; our thermostat guide covers the controls.
Historic districts and the outside of the house
Interior air handlers and ducts are outside historic review. Outdoor units, line sets and roof equipment visible from the street often aren’t.
In Back Bay, Beacon Hill and the South End, district commissions limit visible equipment, and some towns have their own local districts. Rear yards and roofs usually work; the front of the house usually doesn’t. We plan placement around the review before choosing equipment; see snow stands and outdoor placement.
What the first visit covers in an old house
We measure the house room by room, look at the attic, basement and any open framing for duct routes, check the panel and service, and walk the yard for an outdoor spot.
The written estimate lists the equipment and its capacity at 5°F, every duct route and wall opening, the electrical work, permits and the rebate path. If the house has three units, our triple-decker guide covers the per-floor approach. For your own house, call us or send the form.