Read Why Ventilation Is So Important For Indoor Air Quality - Velux

2.1 Indoor air quality

2.1.1 How to achieve good indoor air quality

As we spend 90% of our time indoors, it is crucial to understand what the quality of the indoor air we breathe is. Indoor air quality is influenced by the generation of pollutants indoors but also depends on the outdoor air around the building. Indoor air quality has a considerable impact on health and comfort. It is under pressure due to constant tightening of the building envelope, and introduction of many new materials that may emit harmful pollutants. Indoor air quality is also about human perception. Good indoor air quality may be defined as air that is free of pollutants that cause irritation, discomfort or ill health to occupants (AIVC, 1996). Generally, rooms have different needs for ventilation; bedrooms, for example, experience more intense emission of bioeffluents/CO2 than kitchens or living rooms. This could make demand controlled ventilation based on room type a good way to achieve the right indoor air quality. The quality of indoor air influences humans in several ways (Sundell, 2004a):

• Comfort: the pleasantness of the air is immediately felt when a person enters a building.
• Health: breathing poor indoor air can have negative health effects.
• Performance: high-quality indoor air can improve mental performance and general well-being.
• Other: fresh air creates a link to the outdoor environment, and fresh air through windows is a valued aspect of ventilation. An analysis by Navigant Ecofys published in The VELUX Healthy Homes Barometer 2017 (VELUX, 2017) showed that one out of six Europeans live in unhealthy buildings, i.e. buildings that are damp, overheated, have a lack of daylight or inadequate heating. The analysis also showed that 1,7 times as many Europeans report poor health when living in damp homes. Similarly, when living in a home with a lack of daylight or overheating, 1,5 times more Europeans report poor health.

Source control

Indoor air contains many different compounds, some of which have a negative impact on health or comfort (Bluyssen, 2009):

• Gases; e.g. formaldehyde, organic chemicals (VOC) and inorganic chemicals (NOX, SOX, etc.).
• Particles; e.g. house dust and combustion products.
• Radioactive gas; radon.
• Biological; e.g. mould, fungi, pollen and dust mites
• Water vapour (humidity).

Most of the pollutants come from sources indoors (Bluyssen, 2009):

• Human beings and their activities; e.g. tobacco smoke, particles from cooking, products for cleaning and personal care, consumer electronics and electrical office equipment like laser printers.
• Building materials; e.g. thermal insulation, plywood, paint, furniture and floor/wall coverings.
• Outdoor sources; e.g. pollen, traffic and industry. Radon exists naturally in the ground and enters the house through the floor construction. It is important to use the principle of source control to minimise the concentration of pollutants in the indoor air. An example of source control is to use building materials and furniture with a well-documented low emission of chemicals. Another example is to use low-emitting cleaning products, and to avoid smoking indoors. Source control can also be used as a principle to limit moisture indoors. Showering, cooking or an evening with guests raises humidity in the home, which needs to be removed by ventilation – at best at the source (e.g. a cooking hood in the kitchen or a roof window in the bathroom).