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Zenith Ventilation



After more than a decade spent dedicated to the prevention of mould, condensation, musty smells, and poor indoor air quality, I would like to share with you three of the most common causes,
and solutions!


Do you have Mould problems now? But you don’t remember having them 30 or so years ago? Human beings have long relied upon the open fire as a source of heat and historically the family home was reliant upon a fireplace to heat the home. Because the major fuel force for fire is oxygen, a fire place would also provide a great ventilation system by pulling fresh air into the building. In most cases, we have replaced the fireplaces with either unflued gas heaters which actually add moisture to the air or we are not heating at all.  Skyrocketing electricity prices have resulted in changed consumer behaviours. I have found that people are not heating their houses in winter, rather just individual rooms with gas or electric devices and they rely on the blankets in the bedrooms. Whilst this is good for reducing electricity consumption, it is detrimental to the indoor air quality of the home. As air temperature decreases, relative humidity increases, this inverse relationship generates damp air. This is due to the fact that cold air cannot hold as much moisture as warm air.
This may explain why in your home there is condensation on the windows in the morning in winter and it is not there at night. The warm air from the heater is able to hold the moisture that is in the air. When you got to bed, the heater gets turned off. overnight the temperature drops, and the cold air cannot hold onto the moisture so it condenses on the cold surfaces such as windows, window frames and cold ceilings that dont have insulation.

Picture of CDF10 with a push/pull ERV

Key Learning

 Keeping the house warm in winter is imperative for humidity control.
 Increase air temperature by using heaters or conditioning, preferably dry heat sources or
flued gas heaters
 Keep windows closed when it is cold and wet outside
 Ventilate using heat recovery ventilation
 Insulate your home
 Use dehumidifiers to reduce the humidity such as the Dantherm CDF10


Relative Humidity

Do you always have the windows open, but cant seem to stop mould growth within the house. Do floors and some surfaces feel damp? A natural and instinctive response to the discovery of mould in your home to prevent dampness and mould is “open your windows” Now, this is not always correct. Mould which is a form of fungi occurs naturally both inside and outside the home. There is fungus/moss/mould/mildew on concrete driveways, brick retaining walls, eaves, rock surfaces, footpaths, tree trunks, the list goes on. If it wasn’t for mould our gardens would be knee-deep with
leaves, our tips would be overflowing. Mould is an important part of the ecosystem, however we don’t want it in our homes, therefore we need to create different conditions inside to outside.

Given mould is everywhere outside. If natural ventilation was the answer to preventing mould, there wouldn’t be any mould outside would there? Don’t get this wrong, we need fresh air. If you want to
ventilate naturally you can open your windows, but only open windows when the prevailing conditions outside are suitable. This is when it is dry outside, under 55% Relative Humidity (RH) is a guideline as to when to ventilate naturally. In all other times, it’s best to have windows closed and use climate control devices such as heaters, air conditioning, air purifiers, and dehumidifiers. Heat or Energy Recovery Ventilation (ERV) is also a great way of introducing fresh air without introducing the outdoor conditions, this is a way of ventilating without having to open your windows
and it is very efficient as ERV’s have up to 95% temperature efficiency which will help to reduce electricity costs.

In January this year, I inspected clients home on the northern beaches of Sydney who were experiencing these exact problems. The timber floor felt damp, metal handrails felt damp and there
was fungal growth on leather and cotton items such as leather lounges and shoes. Windows and doors were wide open in an attempt to alleviate the problem. The root cause was the combination of the outside temperature which was 27.5 degrees Celsius coupled with 65.9% RH. This equates to a dew point of approximately 20.5 degrees. In layman’s terms this means that any surface below 20.5 degrees will have condensation (dew) at that point in time. So this is why the floors and steel handrails felt damp, they were damp with condensation!

Mould growth will occur if RH% is above 60, which explains the mould growth on some items within the home of this client and many others like it. Understandably, this client thought they had a problem with their house, there wasn’t a problem with the house at all. The problem was allowing the outside conditions to permeate the home without the appropriate treatment. The solution which I recommend and the client implemented was to keep the windows closed whilst the air is humid and to use climate control to manage the ambient temperature within the home. The house never had air conditioning installed, so I suggested some fixed dehumidifiers (to remove the humidity) and some decentralised energy recovery ventilators (to supply some fresh air without all of the humidity)


CDF 40

Key Learning

 Relative humidity in conjunction with air temperature is the cause of mould formation.


 Installation of Dantherm CDF 40 wall mount fixed dehumidifier
Installation of a heat recovery ventilator, It could be a decentralized or Centralized (ducted) system, depending on budget and also access.


Musty Smells

Do you ventilate your house but cannot get rid of musty smells? Something that is commonly overlooked is the sub-floor of a building. I have spent the past 25 years crawling beneath houses as an Electrician and Mould Remediation Expert. It would come as no surprise to you that often the subfloor is a dark, damp area with minimal to no airflow. Even if your subfloor is bone dry, it still needs to be ventilated. Unventilated cavities begin to breed mould and bacteria unless there is air changes within the cavity, musty smells will begin to form and the only treatment to permanently eradicate the smell is courtesy of the installation of a Zenith Ventilation subfloor system.

Subfloor Ventilation

Key Learning

Key learning:
 Subfloors are out of sight, and more often than not out of mind until they begin to smell

Subfloor Ventilation Installation


Written by Marcus Pine, August 2020