Air conditioning the entire house will result in a high cost air conditioner with high operating costs. Energy Air introduces zoning so that only the areas currently being occupied are air conditioned at any one time, resulting in a smaller more efficient air conditioner.

Most people only air condition the main rooms, such as the bedrooms, family room, lounge room, dining room, kitchen and study. The laundry, bathroom, ensuites etc are left unconditioned either because they are not occupied sufficiently as is the case with the laundry or because the air motion will cause them to be excessively cold as is the case with the bathroom. The temperature in these rooms is generally found to be more satisfactory than if the house was not air conditioned at all.

The philosophy behind zoning is that people rarely use the entire house at the same time. The bedrooms are usually used only at night and the family room, lounge room, kitchen etc in the mornings or evening. When the rooms are not being used they are simply switched off.

To work out the heat load, the air conditioner needs to cool the largest zone. Usually this is the open plan area that includes the kitchen, lounge room, dining room, family room etc and this is considered a single zone. These rooms normally do not have doors. If there are any other rooms that could be on at the same time such as study/home office or baby room then the heat load from this should be added to the heat load for the unit.

It should be kept in mind that the heat load for the air conditioner is calculated on a design day of 32C dry bulb temperature and 25C wet bulb temperature. If you don’t mind the temperature increasing slightly on a design day then the additional load of the study/home office and baby room can probably be ignored.

Supply air grilles are placed in all rooms to be air conditioned and a filtered return air grille placed in a central location such as the hallway. It is essential that the air from each room is able to get to the return air grille so the doors will either need to be undercut, have grilles  installed in them or be partially left open to ensure this happens. Whistling of air or lack of air flow is the result if this is not done satisfactorily.