Zoning for the Live Oak house where the back bedroom reads 80 while the thermostat says 74

Two thermometers, six degrees apart

The call came from a two-story in River Woods. The hall thermostat downstairs read 74 and was satisfied. The thermometer on the nightstand in the back upstairs bedroom read 80 at four in the afternoon, every afternoon from May to September, with the west sun on the windows. The family had tried closing downstairs registers by hand, which made the air handler whistle and did not move the bedroom more than a degree.

That pattern, one thermostat in the right place for half the house and wrong for the other half, is what zoning exists to solve. But not every uneven house is a zoning house, and the first job is sorting them.

Which Suwannee County houses zoning helps, and which just need duct repair

Zoning helps:

• Two-story homes in River Woods and the newer subdivisions, where heat rises and the west rooms bake.
• Long ranches in Sherwood Forest with the master bedroom at the far end of the trunk.
• Acreage homes at Eagle’s Pointe and Savannah Plantation with a guest wing or bonus suite used part of the time.
• Houses with a home office or a nursery that need a different temperature from the rest.

Duct repair helps instead when the hot room is hot because the duct feeding it is crushed, disconnected or undersized, which is common in ranches with original attic flex and in any house with an addition that was tied in by a handyman. In a manufactured home with a belly duct, a sagging or torn belly produces the same symptom. We test the airflow at the register before recommending dampers; putting zoning on a broken duct system is an expensive way to keep a room hot.

Dampers, a panel and a thermostat per zone

A zoning system puts a motorized damper in each trunk or branch serving a zone, a thermostat in each zone, and a control panel in the attic that tells the air handler and the dampers what to do. When the upstairs calls for cooling and the downstairs does not, the downstairs damper closes partway and the equipment runs at a reduced capacity to the upstairs only. A bypass or, better, a variable-speed blower manages the pressure so nothing whistles.

The Lennox zoning equipment we install is built for its communicating systems, so the thermostat, the panel and the variable-capacity heat pump all talk. On a cheaper single-stage system, zoning can still be done, but the equipment has to be chosen carefully or it will cycle itself to death serving a small zone.

Ask about zoning your house

Sizing zones so the system is not choked

The rule we follow: no zone so small that the system cannot run to it without overpressuring the ducts. For most Live Oak two-stories that means two zones, up and down. For a long ranch, two or three: living areas, bedrooms, and perhaps an addition. The equipment is sized to the whole-house load, and the variable-capacity range is checked to be sure it can run low enough to serve the smallest zone alone on a mild day. Ducts are measured and, where necessary, enlarged so the smallest zone still receives enough air.

Does zoning save money, and is there a rebate for it?

It usually trims the bill because unoccupied zones are not conditioned to the same setpoint, and because the hot room no longer forces the whole house to be overcooled. The exact amount depends on how the house is used; we will not invent a number. The FPL and SVEC programs are aimed at high-efficiency heat pumps and smart thermostats rather than zoning panels, so count any rebate as belonging to the equipment the zoning is attached to, and ask where Cook’s stands on contractor enrollment. Lennox’s own seasonal promotions sometimes include controls, so ask what is running. [[CONFIRM WITH JERRY: enrollment and current Lennox promotions]]