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HVAC and Ventilation

HVAC And Better Ventilation and Air

Ever wondered what HVAC stands for? It stands for Heating, Ventilation Air Conditioning

In Melbourne we all have heating and cooling and many homes also have air conditioning but do we ever pay attention to the ventilation that is needed to keep a home and it’s occupants healthy with the air that they breathe?
Healthy and fresh indoor air is the key to a good quality of life. 
It is much more pleasant to work when the air quality is good, without having to open the windows all the time and to come home to fresh air. 

Without a ventilation system to provide fresh air, moisture, odours and other pollutants can build up in the home. A ventilation system helps to circulate fresh air using ducts and fans, rather than relying on airflow through open windows or air vents.

Ventilation is one of the ways to supply fresh air to a home or office space through passive forces, usually wind speed or pressure differences between outside and inside.  

Good ventilation is very important for an energy efficient home. 

As homes are now becoming more airtight with better window sealing and gaps in floors and walls being eliminated, less fresh air enters or leaves a home.
Better air tightness means that indoor air pollution from things like your gas stove top, cleaning products, gas heating and mould spores remain within a home. This is why good ventilation is required and even more so in colder weather.
Ventilation also helps control moisture, leading to mould growth and structural damage. 

Ventilation Standards in Australia

Some building code requirements dictate how ventilation must work. The Building Code of Australia (BCA) suggests that at least 10% of the floor area should have windows and other ventilation openings. In addition, in a room with no ceiling fan, the BCA requires that effective cross-ventilation should be provided.

Ventilation can be natural or mechanical. 

So let’s first explain what ventilation is and what types of ventilation strategies there are. Why do we need it? And why is it needed in our homes or buildings?

Ventilation

Ventilation is the process of bringing outside air into a building or room and distributing the air throughout the building or room. The primary purpose of ventilation in homes is to produce a healthy atmosphere for people to breathe in. 
Why is adequate ventilation in homes and buildings so important?

Adequate ventilation in a building provides good air quality by removing pollutants and CO2 and helps control humidity, lowering the risk of condensation. It is also possible to improve energy efficiency and thermal comfort.  
Air quality can be affected by a range of contaminants, from low-level irritants (dust, pollen) to radon and volatile organic compounds. 

In damp or colder areas, and especially in uninsulated buildings, there is also significant potential for condensation if the humidity is too high, leading to mould growth and various health problems. 

For example, asthma rates in Australia are high by global standards, and inadequately ventilated homes have significantly affected the respiratory system.
In addition, many people who have come to Australia from cold climates report that their homes in Australia are colder and more difficult to heat than in cointries who do deal with flucuationg temteratures 

Ventilation strategies

There are three methods for ventilating a building: natural, mechanical, and hybrid (mixed) ventilation.

Natural ventilation

Natural ventilation, which most Australian homes rely on, is a combination of open windows and structural defects (gaps and holes around windows and doors). 
This type of ventilation is largely imperfect; good natural ventilation relies on natural pressure and temperature variations. The best designs use the principles of crossflow and chimney to create airflow into and through a building.

Although opening windows and doors allows for natural ventilation, many people keep their homes closed all year because they rely on ducted heating and cooling.

Why can’t we just rely on natural ventilation for fresh air? 

Natural ventilation is unpredictable and uncontrollable – it cannot be relied upon to ventilate a house uniformly. 
Natural ventilation depends on the airtightness of the house, outside temperatures, wind, and other factors. Today, modern homes are so airtight that virtually no energy is lost. In mild weather, the natural ventilation of some homes may not be sufficient to remove pollutants. 

Also, in windy or extreme weather, a home that has not been properly sealed becomes drafty, uncomfortable and expensive to heat and cool.
Therefore, a mechanical ventilation system is essential.

Moreover, ventilation is still a problem in Melbourne in older homes. Thermal insulation measures implemented back then often causes not enough outside air to get through the cracks of windows and doors. This generates a potential conflict of interest between practical thermal insulation and the fresh air need, which mechanical ventilation systems can resolve.

Mechanical ventilation

Mechanical ventilation is something most Australian homes are unfamiliar with, but many have experience with it in other buildings like offices and hospitals. 
Mechanical ventilation with heat recovery (MVHR).
These are used to deliver reliable ventilation to maintain excellent indoor air quality in occupied buildings. It supplies fresh filtered air into the building and removes damp and stale air. 

Mechanical ventilation provides continuous fresh air in a controlled manner.

Mechanical systems are often considered unnecessary for homes, but varying Australian climatic conditions encourage us to have better-sealed homes. As a result, bretter ventialtion and air quality has become more important. 

Mechanical ventilation offers a way to solve this problem by using fans to move air into and/or around a building. Mechanical fans control mechanical ventilation. Fans can be installed either directly in windows or walls or in air ducts to move air into or out of space. This system removes indoor pollutants, including CO2 and volatile organic compounds (VOCs). 
A balanced mechanical ventilation system is one in which the air supply and exhaust have been tested and matched to the design specifications.

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The Benefits Of A Ventilation System

  • Better indoor air quality. Indoor air can be more polluted than outdoor air, and the average Australian spends 90 percent of the day indoors. 
  • Ventilation systems can significantly improve a home’s air quality by removing allergens, pollutants and moisture that can cause mould problems.
  • More control. When homes rely on airflow through walls, roofs and windows for ventilation, you have no control over the source or amount of air that enters the house.
  • The right ventilation system will source the outside air from where the quality is best. You do not want air from a damp crawl space or your garage and have cars with their motors running putting that air into your home.
  • Appropriate locations for ventilation and exhaust such as smaller rooms that can have issues with condensation and mould and small bedrooms and bathrooms.
  • Improved comfort. Mechanical ventilation systems provide a constant flow of outdoor air into the home and provide filtration, dehumidification, and treatment of the incoming outside air.

If you choose a mechanical ventilation system, you must ensure that the unit and its installation comply with Australian Standard (AS) 3666.1 “Air handling and water systems of a building – Microbial control”. 

This will determine the required flow rate and noise level. In addition, the unit must comply with AS 1668.2 “Mechanical ventilation for acceptable indoor air quality”.

Mixed or hybrid ventilation

Hybrid ventilation uses natural driving forces to create the desired volume flow. It uses mechanical ventilation when natural ventilation flow is too low.

When natural ventilation alone is insufficient, exhaust fans (with proper set-up and planning) can be installed to increase ventilation rates in rooms containing patients with airborne infections. However, this simple type of hybrid ventilation must be used with caution. 

Fans should be installed where room air can be exhausted directly to the outdoors through either a wall or the roof. 

The size and number of exhaust fans will depend on the desired ventilation rate and must be measured and tested before use. 

Heating And Cooling And Ventilation

There are more options for better ventilation with your ducted heating and cooling system.We can advise you on what brands do have stand alone ventilation products. Daikin is one such brand that does have MVHR options.
See our article about HVAC Tips

Air Purification and Air conditioners

Top of the range air conditioners can offer Ionisation filters. These can cope with day to day amounts of pollutants. All air conditioners come with dust filters but for smaller particles like smoke or CO2 you need more that a dust filter.

Ionisation Filters

Ions (charged particles) are generated inside the air conditioner’s indoor unit, and are used to trap or break down pollutant particles such as dust, pollen or bacteria. The ions attach to the unwanted particles to break them down by:

  • Oxidisation 
  • Changing the electrical charge of the particle which means it will be attracted to a surface where it is trapped.

HEPA filters are still the better purifiers

The best way to filter out very fine particles such as smoke, mould spores, pollen and viruses is with a HEPA filter (high-efficiency particulate air)
You often see these advertised on vacuum cleaners to stop the spread of fine dust and particles. 

HEPA filters are a dense filter and do not cope with large air flows through the filters. They are not suitable for air conditioners that have to disperse high volumes of air.
If you are looking for an air purifier, you may be best to get a smaller stand alone system.

Want professional help for your home or building ventilation’s system?

Then why wait? Contact us now! Beyond Heating and Cooling experts are highly knowledgeable and and get your HVAC concerns sorted out.

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