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Basically, the way we live and the way we build our homes has changed.

Our lives are busier than ever before. For many Kiwis winter means leaving the house for work when its still dark and returning home in the dark. We simply aren’t home enough during the day to open the windows.

For those who are home during the day, winter is just too cold to open the windows and let valuable heat out. We also produce more moisture; more frequent and longer showers, drying clothes inside - EECA estimates we release 8 litres of moisture per day into the average Kiwi home.

On top of lifestyle and climate, the way we build our homes is contributing. New homes have a much tighter building envelope. Of course this is a good thing as it keeps more heat in but it does create another problem; all moisture produced in the home will stay in the home unless it is extracted. A new home simply does not breathe on its own like a draughty old villa.


If you have a basic understanding of the differences between positive and balanced pressure,

the limitations of positive pressure and advantages of balanced are clear.

​Conventional Positive Pressure Systems
The idea is to push air into your home, slightly pressurising it and forcing damp air out through the gaps around doors and windows. It sounds simple and these are the most common systems in NZ but unfortunately there are some major downsides...

  You need to know:

  • Air from the roof space can be of questionable quality.

  • Does not meet the NZ building code NZS4303:1990 “Ventilation for acceptable indoor air quality”.

  • Heat you’ve already paid for via heat pumps, wood fire, etc is also pushed out with the damp air (can make your heat sources less efficient and more costly to run).

  • A 2011 Otago University study found claimed “free heat” available from the roof space air was grossly overstated and often non-existent when needed during winter.

Positive Pressure Ventilation

Tranzheat Does Not recommend traditional Positive Pressure Systems that draw air from the ceiling cavity/roof space as we do not believe they are an acceptable solution for a healthy home.


However, in an older (less airtight) home, a concealed dehumidifying system that introduces a small amount of fresh outside air to slightly positive pressure the home does work well.

New homes have a tighter building envelope. Of course this is a good thing as it keeps more heat in. But this is also the reason that positive pressure is not effective in a modern home. The idea of positive pressure is for air to escape through gaps, taking moisture with it... what happens when there are almost no gaps? Does the pressure drive moisture deeper into the walls and framing? And if the biggest gaps in the home are around your downlights, does the damp air you are trying to get rid of go back into the roof space, just to be pushed back down again? We’re still waiting for a study to find out for sure, but Tranzheat does not supply positive pressure systems as we do not believe they are an acceptable solution for a healthy home.

BALANCED Pressure Systems
Works by extracting air from damp areas (bathroom & kitchen), and pumping fresh outside air into all of the main living areas and bedrooms. This cycle of air through the home, results in the removal of moisture and condensation.

  You need to know:

  • Two separate air streams:
    1. Extracting moisture at sources.   2. Bringing fresh air in.

  • Incoming air is fresh from outside, not the roof space.

  • Meets the NZ building code NZS4303:1990
    “Ventilation for acceptable indoor air quality”.

  • Works well in modern homes with a tight building envelope.

  • Heat is recovered from the extracted air and transferred to the fresh incoming air (passive systems use a method different to the active one patented by Tranzheat. The type of core in the passive heat exchanger will determine how effective the heat transfer is.)

Heat Recovery, Balanced Pressure Ventilation

Tranzheat believes a Balanced Pressure System is required to properly ventilate a modern NZ home and ensure it remains healthy. This is backed up by the requirements of the NZ Building Code.



Our Passive Balanced Pressure Heat Recovery Ventilation System utilises a German made aluminium counter cross flow heat exchanger to recover up to 90% of the heat content from moist air extracted from your home.

Counter Cross Flow Heat Exchanger with Aluminium Core



Tranzheats own Patented Active Balanced Pressure Heat Recovery Ventilation System uses heat pump technology to recover the heat content from moist air extracted from your home. Tranzheat is the only system that will give you a heat gain - meaning air coming into the home is warmer than the air it replaces.




  • Positive Pressure:
    Ventilation systems that draw air from the roof space into the home and do not extract air from anywhere in the home.

  • Balanced Pressure:
    Ventilation Systems that have two separate but equal streams of air:
    1. Fresh air in
    2. Damp air out

  • Heat Recovery:
    Removing heat from outgoing air and transferring this to incoming air. Air streams do not mix.

  • Passive Heat Exchanger:
    No mechanical or electronic parts (air flow is driven by separate fans). Relies on heat from one air stream being conducted by a thin barrier and transferred to an opposing air stream.

  • Active Heat Recovery:
    A system patented by and exclusive to Tranzheat. Uses the same technology found in heat pumps to strip all usable heat from the outgoing air stream, resulting in a heat gain.

  • Heat Gain:
    When the fresh air entering the home is warmer than the air it is replacing.

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