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Ventilation describes the transfer of 'stale' air within the home, with fresh air outside of the house.
This process is extremely important for a number of reasons. The main reason being that it doesn't take long for pollutants to build up within the home without proper ventilation.
These pollutants can include everything from dust, cooking odours and cigarette smoke, all the way to potentially dangerous chemicals emitted from solid fuel burning processes.
Another issue affecting air quality is humidity. Many processes within the home can create a build-up of water within the air and this can lead to a host of problems, including damage, rot and mould. Fortunately, these problems can be avoided with the right ventilation system but there are many to choose from.
When we talk about 'natural ventilation', we mean that nothing has been added to the building in order to facilitate ventilation. That doesn't mean that ventilation can't happen but it isn't actively created, it relies on passive processes within the home.
These processes include the opening of windows and natural leak points within the building e.g. spaces between insulation etc.
Whilst this approach is obviously hassle-free and costs nothing, there can be one huge drawback. In order for ventilation to happen, there has to be a difference between the pressure or temperature within the house and outside the house. If it's particularly warm outside or still, then there will be no exchange of air.
Exhaust Ventilation Many homeowners will be familiar with this type of ventilation as it has become a standard feature in the majority of newly built homes.
There are two versions of exhaust ventilation, including whole-house and local. Local ventilation involves the use of small electrical fans to remove stale and humid air from specific sites within the house, the more common areas include bathrooms and kitchens. These fans are sometimes run continuously but some have the option to be turned on or off depending on preference.
The whole-house alternative includes a larger version of this system, with a variety of ducts placed within 'wet rooms' all connecting to one main device. As they remove the air from the building, a very slight negative pressure is created which causes fresh air to be pulled in from the outside. This fresh air enters the home via leak points or, in the majority of new builds, through specifically installed vents or airbricks.
This approach is fairly effective and cheap but may not be enough for homes with a lot of air pollutants or high levels of moisture.
As the name implied, supply ventilation is the opposite of exhaust ventilation, as fresh air is forced into the home via mechanical means.
This process causes a positive pressure to build and therefore the stale air within the building is forced out through leak points or vents.
Although usually installed outside of the home, supply ventilation units can also be placed within an attic space. This allows ventilation of fresh air within the house but also takes advantage of the warmer air within attic spaces, therefore preventing heat loss.
Another benefit to this approach is the air can be filtered prior to entering the house. This is particularly beneficial for individuals who suffer from pollen allergies.
One of the main problems with supply ventilation is that there is no control over the air leaving the house. This means that humidity can be pushed into wall spaces or attics, creating a breeding ground for mould and rot.
Balanced System Ventilation
This form of ventilation encompasses the best of both worlds and includes the use of both mechanical exhaust and mechanical supply systems.
This approach allows for more control over the ventilation within your home, accounting for where the air comes from, where it's going, and its quality.
Homeowners can also adapt this system in order to meet any other requirements they may have, for example, temperature control and filtration.
One of the main downsides to a system such as this is that it can be expensive to install and operate.
There may not be an overall system that is perfect for everyone but there will be one that is ideal for you.
Consider all of the options and use this information to judge which setup is the most suitable for your home and its requirements.