Heating InstallationLexington, MAResidential

Multi-Zone Heating System

Project Overview

Uneven heating is one of the most frustrating problems for homeowners in large, multi-level homes. The root cause is almost always a single-zone system trying to maintain one temperature across spaces with very different heating loads. Hot air rises, so upper floors receive heat from below while the first floor — where the thermostat usually sits — reaches setpoint first and shuts the system down, leaving upstairs cold.

Zoning solves this by treating each area of the home as an independent heating zone with its own thermostat. The motorized dampers direct heated air only to zones that are calling for it, which not only improves comfort but also reduces energy consumption because the system is not heating spaces that have already reached temperature.

For this Lexington colonial, the three-zone configuration transformed daily life. The homeowner no longer adjusts the thermostat throughout the day — each zone maintains its own setpoint automatically. Bedrooms are set to 68°F for sleeping comfort, the first floor to 71°F for daily living, and the basement to 65°F. The result is better comfort with less energy consumption.

The Challenge

This 4,500 square foot Lexington colonial had a single thermostat controlling the entire home's heating — a common configuration from when the house was built in 1985. The first floor consistently overheated to 76°F while the second-floor bedrooms struggled to reach 67°F. The finished basement was either too warm or too cold depending on the time of day. The homeowner was adjusting the thermostat 5–6 times daily trying to find a compromise that didn't exist. Meanwhile, heating costs were excessive because the system ran at full capacity trying to satisfy the thermostat located on the warm first floor, while the upper floors never received adequate heat.

Our Solution

We retrofitted the existing single-zone system into a three-zone configuration using motorized bypass dampers installed at key trunk line junctions. Zone 1 controls the first floor, Zone 2 covers the second floor, and Zone 3 manages the finished basement. Each zone received its own Honeywell T6 Pro programmable thermostat. We installed a zone control panel in the mechanical room that coordinates the dampers, thermostats, and furnace blower to deliver heat only where and when it is needed. The system includes a bypass damper that opens when only one zone is calling for heat, preventing excess static pressure in the ductwork. We also balanced all supply registers using a digital anemometer to ensure even airflow distribution within each zone.