What Are Zone Control Systems?

A zone control system divides your home into separate areas, each with its own thermostat, and uses motorized dampers in the ductwork to send heating or cooling only where it is asked for. One furnace and one air conditioner serve the whole house, but the upstairs and downstairs, or the bedrooms and the living area, can each hold their own temperature.

It is a fix for one of the most common complaints in any house: one floor is too hot while another is too cold.

How zoning works

Each zone has a thermostat. When one of them calls for heat or cool air, a central control panel opens the damper for that zone and keeps the others closed or partly open. The furnace or air conditioner then starts and delivers air just to the zones that asked for it.

The system also has to protect the equipment. A good design includes a way to relieve extra air pressure when only a small zone is open, whether by sizing the zones carefully, using a variable-speed blower, or adding a bypass. Otherwise the equipment can run too hard or freeze up.

Ways to zone a house

Common layouts include a separate zone for each floor, a zone for the sleeping area, one for a bonus room over the garage, or one for a finished basement. Larger homes may have three or four zones.

Another route is to use ductless mini split units, such as the Mitsubishi Electric systems Air-Tech installs, to serve a room or addition on its own. These provide independent control without adding to the existing duct system, and they work well when a room never matches the rest of the house.

How to tell whether you need zoning

Zoning is worth considering if you notice a pattern like these:

• A two-story home where the upstairs runs much hotter in summer and the downstairs is chilly.
• Rooms with large west-facing windows that bake in the late afternoon sun.
• A room over the garage or an addition that never feels right.
• Areas that are rarely used and do not need to be conditioned all day.
• Family members who disagree about the temperature.

Before adding zones, though, have a technician rule out simpler causes such as dirty filters, leaky or crushed ducts, a poorly sized system or weak insulation. Zoning cannot compensate for a system that cannot deliver enough air in the first place.

Why closing vents is not a substitute

It seems logical to close the registers in rooms you do not use. In most homes it backfires. Your blower is designed to move a certain amount of air, and shutting off outlets raises the pressure inside the ductwork. That can increase leaks, make the blower work harder, reduce airflow across the coil and in summer even lead to a frozen evaporator coil.

A zone system manages this pressure on purpose, with dampers and controls designed for the job. Closing registers by hand does the opposite, with nothing to protect the equipment.

Zoning can also help in the shoulder seasons. On a spring afternoon the upstairs may want cooling while the downstairs still wants a little heat, and separate thermostats let each area get what it needs without one part of the house paying for the other.

Planning a zoned system

Good zoning starts with a review of the whole house: duct layout, equipment capacity, where the temperature problems really are and how the family uses each space. It is much easier to design zoning into a new installation than to fit it around old equipment, though retrofits are common.

If uneven comfort has been wearing on you, Air-Tech can look at your Pasco, Kennewick or Richland home and tell you whether zoning is the right answer. Call (509) 392-2021 to arrange a visit.