Project Overview
Ductwork is the circulatory system of a forced-air HVAC system, and when it fails, no amount of furnace or AC upgrades can compensate. This Framingham home had a textbook case of ductwork that had simply reached the end of its service life. Forty years of thermal expansion and contraction, moisture exposure, and accumulated damage had left the system operating at a fraction of its intended capacity.
Our approach to ductwork replacement starts with engineering. Manual D calculations determine the correct duct sizes for each room based on its heating and cooling load, the distance from the furnace, and the number of bends in the run. This ensures that every room receives its designed airflow — not just the rooms closest to the furnace.
The difference was immediately apparent. Rooms that had been chronically underheated and undercooled were now reaching temperature within minutes of the system cycling on. The furnace and AC system both ran shorter cycles because conditioned air was actually reaching the rooms instead of leaking into the basement. The homeowner described it as getting a new HVAC system without actually replacing the equipment.
The Challenge
The 40-year-old ductwork in this Framingham home was in severe disrepair. A blower door test combined with duct leakage testing revealed that over 30% of conditioned air was being lost before reaching the intended rooms. Multiple sections of flex duct in the basement had collapsed or separated from their connections. Rigid metal trunk lines had rusted through at several joints. The return air plenum had a large, unintentional gap that was pulling in unfiltered, unconditioned basement air. The homeowner had noticed that rooms farthest from the furnace barely received any airflow, and the system ran continuously without ever reaching the thermostat's setpoint during extreme weather.
Our Solution
We performed a complete ductwork replacement — removing all existing supply and return runs and designing a new duct system based on Manual D calculations for proper sizing and airflow distribution. The new trunk lines are fabricated from 26-gauge galvanized sheet metal with Pittsburgh seams for durability. Branch runs use insulated R-8 flex duct with secure mechanical connections at every junction. Every joint was sealed with fiber-reinforced mastic (not tape, which degrades over time) and visually inspected before insulation was applied. We installed a new return air plenum with a properly sealed filter cabinet, and added a second return air register in the upstairs hallway to improve air circulation on the second floor. Post-installation duct leakage testing confirmed less than 4% total leakage — well within Energy Star specifications.
Results & Outcomes
- Duct leakage reduced from 30%+ to under 4%
- All rooms now reach thermostat setpoint within normal cycle times
- System runtime reduced by approximately 25% — less wear and lower energy costs
- Second-floor rooms now receive proper airflow for first time
Project Details
Service
Heating & Cooling
Location
Framingham, MA
Duration
3 Days
Equipment
Custom Fabricated
Scope
Residential
Result
Completed Successfully
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