Serving the greater Houston, Texas area, including Tomball, Cypress, Waller, Magnolia, Montgomery, Conroe, The Woodlands, Willis, Kingwood, Crosby, Huntsville, Galveston, Pearland, Brazoria, Sugarland, Richmond, Katy,


FAX 281-466-2249

TACL B15309C

Spring, Texas


ZONING is the principle of adding multiple temperature zones, controlled by thermostats, on a single unit. This is done with zoning has it’s advantages and disadvantages. Whenever possible, it is always better to have an individual unit for each thermal zone, but sometimes this is not practical. For instance, two-2 ton systems costs far more to install than one 4 ton with zoning controls. Zoning is practical to help solve the following problems:


Temperature differences trying to heat/cool a two story house with one unit.

Hot or cold  areas, such as a sunroom, or media room, that change loads over the day.

Control of separate areas, like keeping your master bedroom at 72 and living room at 78 at night.

Optional control of rooms not used all the time, like  a spare bedrooms, or a hobby room.


Limitations of zoning system include:


Zone systems do not work so well with single speed systems, where compressor speed and air volume cannot be controlled. Two speed systems work better.

Multiple motorized dampers that can fail and create hard to troubleshoot issues.

May throw off air balancing depending on load.

May make heat/cool system operate out safe limits unless controls are included to limit operation.

You are generally limited to 2-3 zones maximum per unit.



An Aprilaire Zone Damper

An Aprilaire Zone Control Panel

BRAND/COST: There are as many brands of zone systems as there are AC units. They all has similar functions and abilities. The important thing is to get a qualified contractor to install it, because the installation is biggest issue in getting a good outcome. The cost to install varies with duct renovations required, and number of motor dampers that may have to be purchased, but can easily be $2000-$3000. Still much less than adding an additional system.