Mechanical ventilation systems

Mechanical ventilation systems force fresh outdoor air into your interior and take the stale air outside. This helps control the quality of the air within your home. The availability of artificial ventilation, safety concerns and the need for privacy means that we all are becoming used to leaving the windows closed. This increases the demand for mechanical ventilation, which is not an effective use of energy as opening a window is a simple method, doesn’t use electricity and doesn’t cost anything.

If you live in an airtight home, it will probably have one of the many mechanical ventilation systems on the market. These systems supply filtered outdoor air into your home and extract stale air outside. More advanced systems will also supply air to the location you want and at the time you want. Any ventilation system which is not regularly maintained may not be working efficiently – not an ideal way to use precious electricity.

Spot ventilation
This term means using extractor fans in a specific area such as in your kitchen, WC or bathroom. They instantly and quickly improve air quality by removing air pollutants and moisture from the source. These self contained systems of ventilation are ideal for the cooler and warmer months when windows are not opened. One tip is to check the location of your extractor fans and position them as close to the source as possible for maximum efficiency and effectiveness. In your kitchen check the extractor fan above your hob – does it remove the exhaust fumes to the outside of your property? The majority re-circulate the air back into your home which does not help with moisture or odour control.

Whole home ventilation
This term means using a system of extractor fans and ductwork which provide fresh air and remove any stale air from the whole house. These are used when natural ventilation and spot ventilation are not considered sufficient. This system control and regulate ventilation throughout your home. There are three types available; systems which only supply air, systems which only remove old/stale air and balanced systems which do both. Exhaust, supply and balanced ventilation systems are not as energy efficient or cost effective as energy recovery systems as they do not regulate moisture levels of air being supplied into your home.

Spot & whole house ventilation tips
* Avoid placing extractors near to fresh air supply vents, windows and doors to save fresh air being extracted without having time to circulate.
* Avoid placing extractors near to fuel heaters and fireplaces as the fuel gases released may be drawn back into the interior by the extractor, causing hazard to human health.
* Car emissions from your garage, radon and dust can be drawn into your home by extractors/exhausts.
* Always opt for a manual control of the ventilation device (even if you have an automatic system) so you can control the amount of use.

Heat recovery ventilator (HRV) & energy recovery ventilator (ERV)
A HRV system is way of maintaining heat levels with your room and minimising energy loss whilst providing fresh ventilation from outside. This reduces your utility bills by reusing warm air in the winter and reusing cool air in the summer. If you live in a climate that has extremes of temperature over the seasons, it can be highly cost effective. Climates that maintain steady temperatures throughout the year may not benefit with this system as the energy used for the fans can outweigh energy savings.

HRVs work by heat exchangers which transfer heat from exhaust air and use it to heat the air that is drawn in from the outside. An ERV system operates exactly as a HRV system however it also draws moisture out of your interior. The moisture is drawn out of the warm air coming into your home and is then transferred into the exhaust air, allowing it to escape outside. Up to 80% of energy can be recovered using one of these mechanical ventilation systems.

Heating, ventilation and air-conditioning systems (HVAC)
This all-in-one system has multiple functions. It is important to check that the air-conditioning element does not just recirculate the air as this does not provide any ventilation. It merely recirculates your indoor air, which when thinking about indoor air pollutants, VOCs, odours and stale air, means that the quality of air will not improve. If you have air conditioning throughout your home, any airborne contaminants will be circulated into every room – giving rise to health problems. Some systems also control humidity levels, which increase the amount of energy needed for operation. HVAC systems typically use a lot of electrical energy depending on the energy efficiency rating, the condition and the frequency of use.

Passive stack ventilation
These are found in concealed kitchens and bathrooms without any access to natural outdoor air. Typically theses rooms face problems with moisture and condensation from the amount of heat and water in use. This ventilation method makes use of the stack effect, and uses vents and vertical ductwork to the roof to draw cool fresh air into these rooms in a cycle that also draws out the warm stale air.

Other ventilation methods
A combination of artificial and natural ventilation is a good balance. This means that any areas that are around the outside of the building will make the most of natural ventilation methods such as doors, window and wall vents. Whereas areas that are in the middle and without any access to natural ventilation will be controlled by mechanical ventilation systems. This helps to make the house as efficient as possible in energy use. Although the ideal would be to naturally ventilate the whole house without using electricity, the majority of built homes will need mechanical assistance in some areas.

Building Regulations
As a last note, your local building regulations & building codes will determine the standards necessary regarding natural and mechanical ventilation systems in residential houses. Check with your local council for details.

If you have enjoyed reading about mechanical ventilation systems, you may find the natural ventilation article of interest. Natural ventilation is a much healthier and environmentally friendly method of improving the air quality in your home.

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