A 100-year-old steam boiler in front, forced hot water in the addition, window AC units in summer, and a $4,682 Mass Save rebate. Here’s how Pespisa designed a hybrid Mitsubishi heat pump system that fit the home instead of fighting it.
A whole home heat pump was the goal for this Bedford, MA family, but the house did not offer an easy path to get there.
When the homeowners called Pespisa, they already knew what they wanted: efficient whole-home heating and cooling, plus a system that could qualify for the Mass Save rebate program. What they had was far more complicated. Their home ran on three different comfort setups: a steam boiler in the original front of the house, forced hot water baseboard in the rear addition, and window AC units during the summer.
There was no central ductwork to reuse. There was no single distribution method that would serve every room well. And in a 100-year-old home with finished plaster and original details, the wrong design could have created more disruption than comfort.
Most contractors would have pushed an all-ductless solution with wall units in every bedroom, or walked away from the job entirely. Instead, Pespisa designed a hybrid ducted-and-ductless Mitsubishi heat pump system built around the way this Bedford home is actually laid out and the way the family actually uses it.
Project Snapshot
| LOCATION | Bedford, MA |
| SYSTEM | Mitsubishi hybrid ducted and ductless heat pump |
| APPLICATION | Whole-home heating and cooling |
| TOTAL CAPACITY | Approximately 54,000 BTU / 4.5 tons across two outdoor units |
| OUTDOOR UNITS | Mitsubishi MXZ-3D24NL and Mitsubishi MXZ-4D30NL |
| INDOOR UNITS | MSZ-GX12NL x2, MSZ-GX15NL, MSZ-GX06NL, SVZ-AP12NL ducted unit |
| CONTROLS | 3 Ecobee Smart Thermostats with Mitsubishi PAC-USWHS002-WF-2 integrated controller |
| BACKUP HEAT | Existing steam boiler and forced hot water baseboard retained |
| DISTRIBUTION | Approximately 500 sq ft of new sealed and insulated ductwork |
| PERMIT | Sheet metal permit pulled with the Town of Bedford |
| WARRANTY | Standard Mitsubishi manufacturer warranty |
| MASS SAVE REBATE | $4,682 |
| FINANCING | Eligible for 0% Mass Save HEAT Loan up to $25,000 |
The Challenge: Three Climate Systems, None of Them Working Together
This Bedford home had a long history of comfort compromises.
The front of the house was heated by an old steam boiler. It still worked, but it belonged to a different era of home comfort. The rear addition was served by a forced hot water baseboard loop on a separate zone. In the summer, window AC units were the only cooling option, swapped in and out each year.
The result was uneven comfort, higher energy use, and a setup that did not match the long-term efficiency upgrades the homeowners wanted.
They had already completed a Mass Save home energy assessment and were pre-approved for the rebate program, so the system Pespisa designed needed to qualify on the first pass. This was not just a matter of installing new equipment. The design had to satisfy the home, the homeowners, and the rebate requirements.
The challenge came down to three major issues:
- A steam boiler kept the front of the house warm in winter, but did not support modern cooling.
- A forced hot water baseboard loop served the rear addition separately.
- Window AC units were the only summer cooling option, with no existing central ductwork to reuse.
The family wanted a whole home heat pump system that could bring the house together without tearing apart the original structure to make it work.
Our Solution: A Hybrid Mitsubishi Heat Pump System, Sized to the Home
Pespisa installed a two-outdoor-unit Mitsubishi heat pump system with five indoor units.
The design combined four wall-mounted ductless heads in the spaces where short installs and clean lines made sense, plus one hidden ducted indoor unit in the attic to serve the smaller front bedrooms and bathroom through brand-new sealed ductwork.
This hybrid approach allowed the home to get the benefits of both ductless and ducted distribution without forcing one method into every room.
Two outdoor heat pumps:
- Mitsubishi MXZ-3D24NL, 24,000 BTU / 2 tons
- Mitsubishi MXZ-4D30NL, 30,000 BTU / 2.5 tons
Five indoor units, matched to each space:
- MSZ-GX12NL for the master bedroom, ductless wall unit
- MSZ-GX15NL for the first-floor front room, ductless wall unit
- MSZ-GX12NL for the living room and kitchen, ductless wall unit
- MSZ-GX06NL for the fireplace room, ductless wall unit
- SVZ-AP12NL attic-mounted ducted unit serving the front bedrooms and bath
Controls:
Three Ecobee Smart Thermostats were paired with the Mitsubishi PAC-USWHS002-WF-2 integrated controller. This was a Mass Save rebate requirement and also gave the homeowners a much better day-to-day experience than a standard remote.
Backup heat:
The existing steam boiler and forced hot water systems were left in place. The heat pumps now do the daily work, while the family keeps the redundancy of two existing fuel sources for the coldest winter days.
Why This Design Was the Right Fit
A single distribution method could not have served this home well.
Putting wall heads in every bedroom would have looked cluttered and worked poorly in the smaller front rooms. Running new ducts everywhere would have been too invasive for a home with finished plaster and original details.
The hybrid approach gave the family the best of both options.
Ductless where it made sense
Open living spaces and the master bedroom were good fits for wall-mounted ductless heads. Short refrigerant line runs helped preserve finishes, and the wall units looked intentional instead of forced.
Ducted where it mattered
The smaller front bedrooms and bathroom are served quietly from one attic-mounted indoor unit through new insulated ductwork. This avoided visible wall heads in rooms where they would have felt intrusive.
Two outdoor units for better sizing
Instead of one oversized unit trying to serve the whole house, two outdoor units allowed each side of the home to receive matched capacity. This helped create a more balanced whole home heat pump design.
Full Mass Save eligibility
The system included integrated controls, qualifying equipment, and a complete whole-home design that met the rebate program’s requirements.
The Result: Whole-Home Heating and Cooling Without Losing the Home’s Character
The family now has whole-home heating and cooling from two efficient Mitsubishi heat pumps, with three-zone Ecobee control and a much quieter, cleaner setup than what they had before.
For the first time in the home’s history, the family has whole-home cooling without relying on window AC units. The visible wall heads are only placed where they make sense, while hidden ductwork serves the rooms where ductless wall units would have felt crowded or disruptive.
The original boiler systems are still in place as backup heat for the coldest days, giving the family redundancy without paying to maintain two duplicate comfort systems.
The project delivered:
- $4,682 Mass Save rebate earned on the install
- 0% Mass Save HEAT Loan financing eligibility up to $25,000
- Whole-home cooling for the first time in this home’s history
- No more window AC units
- Three-zone control with Ecobee and Mitsubishi integrated thermostats
- Cleaner aesthetics, with wall heads only where they made sense
- Hidden ductwork serving the smaller front bedrooms and bath
- Existing heat retained as backup, not ripped out
This whole home heat pump system solved the comfort problem without forcing the house into a design that did not fit.
Equipment Used for This Bedford, MA Heat Pump Installation
| System | Mitsubishi hybrid ducted + ductless heat pump |
| Total capacity | ~54,000 BTU / 4.5 tons across two outdoor units |
| Outdoor units | MXZ-3D24NL, MXZ-4D30NL |
| Indoor units | MSZ-GX12NL ×2, MSZ-GX15NL, MSZ-GX06NL, SVZ-AP12NL (ducted) |
| Controls | Ecobee Smart Thermostat ×3 + Mitsubishi PAC-USWHS002-WF-2 |
| Backup heat | Existing steam boiler and forced hot water baseboard retained |
| Distribution | ~500 sq ft of new sealed and insulated ductwork |
| Permit | Sheet metal permit pulled with Town of Bedford |
| Warranty | Standard Mitsubishi manufacturer warranty |
| Mass Save rebate | $4,682 |
| Financing | Eligible for 0% Mass Save HEAT Loan up to $25,000 |
What Bedford Homeowners Can Learn From This Project
Older homes often need more than a standard heating and cooling recommendation.
This Bedford project shows why a thoughtful design matters. A whole home heat pump upgrade can be possible even when the house has no central ductwork, multiple existing heat sources, older construction, and rooms that need different approaches.
The right answer may not be all ductless. It may not be all ducted. In this case, the best solution was a hybrid system that used each method where it made the most sense.
For homeowners with older Massachusetts homes, the lesson is simple: the system should be designed around the house, not forced onto it.
Have a Bedford Home With No Easy HVAC Answer?
If your home has steam heat, hot water baseboard, window AC units, no central ductwork, or a layout that makes every option feel complicated, Pespisa can help design a solution around the way your home actually works.
Whether your home needs ductless heads, hidden ductwork, backup heat, or a complete whole home heat pump design, Pespisa can help you understand the best path forward.