Are ducted heating and cooling zones worth paying for?

A ducted system without zoning conditions the whole house whenever it runs. Most households use a fraction of the house at any time, particularly overnight, so the energy going into empty rooms is the obvious waste.

What zoning gives you

• Running costs proportional to what you are actually using.
• The ability to specify a smaller, cheaper unit, since the peak load is a zone rather than the whole house.
• Better comfort, because rooms with different exposures can be balanced rather than averaged.
• Quieter operation overnight when only the sleeping zone is running.

Where zone layouts go wrong

• Too few zones, so the living areas and bedrooms end up on the same zone and the benefit largely disappears.
• Zones that ignore orientation, putting a west-facing room on the same zone as a shaded one.
• No allowance for minimum airflow, so closing most zones puts the system into a condition it cannot run in. Systems handle this with a bypass or a constant zone, and it needs designing rather than adding later.
• A single thermostat in a hallway, which measures a space nobody occupies.