In many homes, the air conditioning is set up in such a way that it has to be overpowered to force enough cool air to the hottest room. But the rooms that were already cool to begin with get too cold, too quickly. This isn’t efficient, and it’s not necessary. That’s where zoning comes in. By dividing your house into individual zones based on where the sunlight hits, how well the room is insulated, and what the room is used for, you can achieve ultimate control over your air conditioning – maximizing comfort and savings.
The ghost cooling problem
An HVAC system cutting ghost cooling by a third sees its workload scaled back 20-30%. The savings come from lower average equipment demand throughout the day and decreased draw from ductwork or lines, as fewer areas are being conditioned at any given time.
But for all the possible efficiency gains, conventional zoned systems have limited penetration because, historically, they came with high costs, intrusive installations, reliability issues, and user-unfriendliness post-installation. Providing multiple ducts to each room involves serious construction or renovation. Existing zoning systems requiring such plumbing are in the vast minority.
Ductless HVACs are easier to retrofit into zones, given how they only require an air handler in the targeted room to pass its treated air into the space with no ductwork whatsoever. A professional split system install sydney handles the high-traffic rooms that matter most, without the cost or disruption of a full ducted retrofit. However, conventional ductless systems are not shipped with the necessary zoning hardware. The room isn’t made part of any zone, and thus can only be cooled or heated on an all-or-nothing basis.
Heat doesn’t distribute evenly, and single thermostats can’t fix that
When winter sets in, the same principles apply: Heat rises, and the upstairs will be roasting while you still need blankets to relax on the sofa. Energy bills climb because the system throws heat at an area that’s already thermally overfed. Instead of breaking a sweat in your own bed, zoning keeps the upstairs in line with the temperature you selected.
What zoning does to the compressor
There is a mechanical case for zoning that we should make more often. A typical single-thermostat system runs the compressor in binary mode: full blast, then nothing, then full blast again. This starting-and-stopping doesn’t do the unit any favors. Every start pulls a surge of electricity and stresses the motor.
Modern air conditioning systems can vary the speed of the compressor. This lets the unit make quick, small adjustments to satisfy demand instead of constantly overshooting the target. But a variable-speed compressor can’t just run at low capacity all the time – if the ducts to a part of the house are closed, the air conditioner will pick up on the low pressure and interpret it as a full load, running at full capacity and damaging the unit.
Over time, the excess wear, maintenance, and early replacement costs of a poorly zoned variable speed system will likely swamp the energy savings. So it bears repeating that variable-speed systems need variable demand profiles.
Options for homes without existing ductwork
Zoned control is essentially the practice of cooling and heating individual rooms or zones based on need. For instance, a bedroom doesn’t need to be kept as cool as the kitchen or living room. This provides more even comfort as well as lower energy bills, in part because you’re not paying to cool or heat a room you’re not using.
If you’re in the enviable position of building a new home, you may be looking around at your HVAC options. Careful, though – ducted zoning isn’t what it seems. Ducted whole-home zoning means more than just a sensor and a motorized vent in each room – it means airflow requirements. This means you need a unit powerful enough to handle the load in every zone of the house, even if you shut those zones off most of the time, and it means ducting that’s clean, straight, and well-insulated.
The thermostat war is a design failure
If one person prefers the thermostat to be set at 22 degrees while another prefers it at 25 degrees, they’re forcing the same single-point control system to work against itself. In the end, one will win, and the other will lose, and the compromise position usually requires the system to run longer than either preference actually warrants.
Zoning removes the need for compromise. If two or more people have relatively regular usage patterns in a given space, they can each have their preference set as the target. This is not an excessive demand – it’s simply recognizing the fact that one room is not another, based on who occupies it, how much external heat it gains, and what purpose it’s in use for.
A well-implemented zoning system treats the residence as what it is – a collection of several different thermal envelopes that should be managed separately, as opposed to a large box to be cooled indiscriminately by one corner of the building.
