In building terms, ventilation simply refers to the process of changing or replacing air with external air in a given space over a period of time. It is important to ventilate homes adequately to maintain a clean and healthy living environment. A lack of proper ventilation can cause or contribute to a range of different health problems, as well as issues such as damp, which can affect the house itself.
Airflow and types of ventilation
Air constantly moves between a building and its surroundings. There are different ways of measuring airflow, including the number of complete air changes per hour and the volume changed over time, often expressed as litres per second or l/s. There are different requirements for different types of buildings but the minimum requirements might not always be adequate to fully disperse air pollutants and avoid damp and mould problems.
There are two basic kinds of ventilation. Natural, or mechanical ventilation relies on air moving through gaps, such as air bricks, trickle vents, doors, windows, and the small gaps that exist around walls, windows, and fittings.
This might be adequate for some buildings, but natural ventilation can struggle to deal with large amounts of moisture and contaminants. Vents can be forgotten about and blocked off over time, and modern homes are increasingly air-tight and energy-efficient. This is a good thing in one respect but can lead to issues with a lack of proper ventilation. In cases such as these, mechanical or controlled ventilation may be required.
Mechanical ventilation systems give the natural ventilation that is present a helping hand, to increase the air exchange in the building.
The simplest type of controlled ventilation uses extractor fans to draw moist or polluted air out of wet rooms, such as kitchens, bathrooms, or utility rooms. This is very useful but does not create a clean air flow throughout the building.
Supply ventilation brings ventilating air from outside while extract ventilation does the opposite, gently extracting out stale air and letting fresh air come in to fill the vacated space. Balanced systems are the most advanced and use a combination approach, removing stale, dirty, and polluted air while simultaneously drawing in fresh, filtered air to replace it. Some systems also pass these different air flows through a heat exchange unit, drawing out most of the heat from the outgoing air and transferring it to the incoming stream. This can help to improve your energy efficiency and lower your heating bills.
Why you should ventilate your home
As already mentioned, there are several reasons why your indoor air should be properly ventilated. Many homes suffer from damp and one of commonest causes for this is condensation. This is caused by warm, moist air hitting a colder surface, such as an exterior wall or window, which causes the water vapour it contains to condense back into water. This can give rise to black mould.
The NHS says:, “If you have damp and mould you're more likely to have respiratory problems, respiratory infections, allergies or asthma. Damp and mould can also affect the immune system.” It adds that some people, including babies, children, the elderly, and people who already have respiratory problems such as asthma, can be particularly vulnerable to damp. Damp can also damage your house and fixtures, as well as creating a generally smelly and unpleasant environment.
Good ventilation can also help to prevent the build-up or to disperse potentially harmful pollutants. These can include volatile organic compounds (VOCs), which are gases produced from a wide variety of household sources. Paints and solvents, cleaning products, wooden floor and furniture finishes, aerosols, and even new carpets can all give off VOCs.
Another little-known pollutant is radon gas. This invisible, odourless gas is given off by radioactive reactions that take place naturally in rocks and soils throughout the UK. It is normally present in such small concentrations that it is not considered harmful, but it can pool and become trapped inside buildings. Public Health England’s guide to radon says that radiation released by this gas damages our lung tissue and can cause lung cancer over a long period of exposure.
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