Positive pressure or roof cavity ventilation systems are the most common type available in New Zealand. They bring filtered air from the roof space or outside into the living spaces through a single, or multiple ceiling vents. This forces the stale air to leak out through gaps, windows and doors.

Some ventilation systems have an optional electrical heating unit to provide some pre-heating of air coming from the roof cavity when it is cold. 

These are known as electric in-line duct heaters. These are electric resistance heaters, and a lot of the heat can be lost between the heater and the outlet. Therefore, they are not very efficient or economical to run.

Most electric in-line duct heaters don’t have sufficient capacity to meet a home’s heating needs and they are a relatively expensive and inefficient way to heat a home. You will get more effective heating from other heaters, for example, heat pumps.