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Home Ventilation System

WarmNdry can be supplied in kit form or fully designed and installed.

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Operating Principles

The purpose of the WarmNdry is to ventilate your home with introduced air which is fresher and drier than the air inside your home in a controlled manner.  Air from the roof space replaces stale humid air which causes condensation, which can lead to mould and damp problems, or at least to reduce them to an acceptable level.

The diagram shows how the system works. Air is transferred from the roof space because it is always warmer than the outside air.  During the colder nights, the roof space cools down (but usually not as cold as outside) and air flow into the home is reduced, but NOT stopped completely, to control condensation by providing adequate ventilation.

A small continuous supply of fresh air into the home is required to banish condensation during winter.  The ventilation air supply positively pressurises the home causing stale air to be gently forced out through cracks under doors, floor boards etc.  This method of positive pressure ventilation (PPV) is the most cost effective way to reduce moisture built up in the home.


Outside doors and windows could be left open, which will allow in the necessary fresh air, however there are a number of draw backs with this approach such as security, inability to control the flow rate (too much or not enough) and the increased heating cost that would be required to overcome these cold draughts in winter.


Heat Pumps (reverse cycle air-conditioners) do not de-humidify in heating mode and are only effective in summer cooling mode.  Room de-humidifier units are very expensive to run and like moisture crystals have little effect on moisture. None of them provide the necessary fresh air ventilation that your home requires.


Multifunction Smart Home Ventilation Controller

The WarmNdry Touch controller is a programable smart controller that manages filtered fresh air ventilation, solar heat recovery and around home air distribution automatically.  

The amount of ventilation and air transfer is determined by the temperatures measured in the roof space and the living room.  

The owner can define set points that the controller will use to calculate air flow algorithms and automatically control the amount of air movement required to maintain air quality and comfort level.

Fresh Air Ventilation

All houses need a small amount of air introduced from outside to keep us humans healthy.  Houses that have good draft proofing and new homes are too airtight and suffer from insufficient fresh air ventilation.  Indications of poor air quality and insufficient ventilation are:

  • Condensation on windows
  • Musty smells
  • Damp and mildew
  • Water stains on ceilings and walls
  • Rotting timber work
  • Cold in winter and hot in summer
  • High energy bills
  • Health issues especially asthma

The WarmNdry system is a mechanical ventilation system using a special EC fan which is economical and quiet with full speed control from 0 to 100%.  Opening a window allows fresh air in however it is not controllable or secure.  WarmNdry works 24/7 all year and is basically set and forget.

Condensation Control

Before WarmNdry

HVS Window Before

After WarmNdry

HVS Window After

Condensation can be eliminated with a small amount of fresh filtered air ventilation into the home.  Air needs to be introduced even when the outside temperature is low.  The amount of fresh air is determined by the size of the home, number of occupants and how bad the problem is.  Too little fresh air and the problem does not get managed and too much will make the home unnecessarily cold during winter or too hot in summer.

The WarmNdry smart controller is designed specifically to manage the problem when the outside temperature is cold by reducing air flow to an absolute minimum and then automatically increasing fresh air as the temperature increases.

What Is Condensation ?

Condensation inside the home is a result of too much moisture in the air.    Inside air is made up of outside air plus whatever we add to it.  The occupants of an average home will add up to 15 litres of water to the air per day from breathing, showering, cooking, drying clothes etc. 

When moist air cools down below its  ‘dew point’,  such as when it contacts a cold surface, the moisture falls out of suspension.  Water pools on surfaces and runs down walls etc.  Glass windows are usually the first places to show evidence of condensation because they are the coldest surfaces.  Condensation is a symptom, poor air quality is the cause.

What Problems Can Condensation Cause ?

Condensation left untreated can promote mould, mildew growth and damage wood work, furnishings and clothing.   Mould spores are known asthma and allergy triggers.  Unpleasant odours are caused by damp conditions.  Damp houses take more energy to heat, feel unhealthy and are unpleasant to live in. Dust mites thrive in moist conditions.

Heat Recovery


Heat Recovery via the roof space is a cost-effective way to provide FREE heat in autumn, spring and winter during the day.  Sun on the roof warms the roof space much more than the outside air, the WarmNdry takes advantage of this and increases air flow which over ventilates the home thereby benefiting from the free heat and lots of fresh warm air.


The graph shows temperature changes in the roof space during a typical day.  The sample was for the 10/5/08 and shows a minimum temp of 12 and a maximum of 28 degrees.  The actual outside minimum was just 10.8 and a maximum of just 17 on that day.  The difference between the roof and outside temperature is considerable and available as free heat by automatically transferring warmer roof air into the house as required.  During summer the heating facility is turned off when the roof is too hot.


The period above the red line is the Heat Recovery period and totalled 8 hours on this particular day. That is 8 hours with the fan operating at maximum capacity.  During this period, warm air (19 to 28 degrees) is transferred into the home reducing the need for other more expensive heating while flooding the house with fresh air as well.

Summer Cooling

During summer the system can increase ventilation when the roof is cooler than the house helping to reduce inside summer temperatures.  Most of the benefit will be later on in the night as the outside and roof cool faster than inside the home making it more comfortable for sleeping.

Air Transfer

Warm or cool air generated in the living room can be distributed around the home, typically to the bedrooms.  The WarmNdry controller can manage a separate air transfer fan to automatically operate at pre-set temperatures.  Air transfer is completely independent to the fresh air ventilation fan and can therefore be operated independently or in combination depending on the air ducting design and the mode set on the Touch Controller.


Flexible ducting installed in the roof space is used to distribute air around the home.  The duct design is determined by the location of inlets and outlets and what aspects of the control system is being used.  If air transfer is required in addition to fresh air ventilation, a second fan with its own ducting is used.  Customer service can assist with the duct design to meet individual requirements.


The number of ceiling outlets required will depend on house size, layout and barriers to air flow throughout the home.  Normally two to four outlets is sufficient however if internal doors get closed, extra outlets may be required.

Ducting design and layout

150mm (6 inch) flexible ducting is typically used to direct the fan output to required locations throughout the home.  Usually the ducting is located in the roof space which provides easy access to all of the rooms on that level.

Ceiling Outlets

The two main types of ceiling outlets are:

  • Cone – used to direct air across the top of the ceiling suitable for all ventilation conditions. Also used as the inlet vent for heat transfer.
  • Down Jet – used to direct air flow from the ceiling outlet to the floor suitable for heat or warm air transfer.


Flexible Ducting

The two types of ducting are :

  • Nude ducting is used for ventilation designs, the air from the roof space is being distributed to rooms via ceiling outlets so there is no need for the more expensive insulated type.
  • Insulated ducting is required for air transfer where warm or cool air is extracted from one room (main lounge where a heater or cooler is located) to other room via the roof space.


Duct splitters and branches

The two types of duct splitters that can be used to split the ducting into two or more ducts which allows branching to multiple outlets are :

  • Y splitters which have a single inlet and two outlets which divide the air 50:50.
  • Branch Take Off’s (BTO) which have a single inlet and one 45 degree outlet and a straight through outlet which are more suited to a drop off branch from a main trunk.


G4 Air Filter

Fresh air ventilation which is taking air from the roof space needs to be filtered to stop any disturbed dust in the roof from entering the system.  The filter supplied for WarmNdry is a 10 micron or G4 rated filter which stops pollen and dust particles >10um. The filter will not stop smoke and is not designed to. Heat Transfer does not require any filter as it is simply moving house air from room to room.

EC Electric Fans

EC fans connect to the Smart Controller to vary speed and air flow. EC (Electronically Commutate) fans are brushless, permanent magnet DC motors with onboard electronics available for controlling a fan rotor. EC fans achieve high efficiency levels reducing energy and heat loss providing longer service life. EC fans speeds are controllable between 0 and 100% without the humming noise associated to older AC fan types.

WarmNdry can be supplied in kit form or fully designed and installed


Setup Screen 3

The  type of system to be installed is set in Setup Screen 3.  The ducting is designed to facilitate the type and is dependent on home design.


Uses a single fan for fresh air ventilation only but no air transfer. Split 50% of the air flow to the main living room where the controller is located and the other 50% split between bedrooms. Nude ducting is suitable as are cone vents in the ceiling.

Standard layout


Uses two fans for fresh air ventilation only and no air transfer. Split 50% of the air flow to the main living space and the rest to other rooms. Nude ducting is suitable as are cone vents in the ceiling.

Dual layout


Uses two fans, one for fresh air ventilation and one for air transfer. Split fresh air from the roof space to the main living room where the controller is located and the other 50% to the passage.


The second fan extracts air from the main living room where the heater and or cooler is located and sends it to the bedrooms.  The fresh air from the ventilation fan is dispersed by the second heat transfer fan.  Nude ducting is suitable as are cone vents in the ceiling for the first fresh air part however insulated ducting and down jets are required for the second Heat Transfer part. Use a cone for the inlet.

Combo layout

Heat Transfer

Uses one or two fans for Heat Transfer but no fresh air ventilation. Warm or cool air is extracted from the main living room and is sent to the bedrooms. Insulated ducting and down jets are required for Heat Transfer. Use a cone for the inlet.

Heat Transfer Layout