Indoor air quality tends to get less attention than other aspects of building performance, such as energy efficiency and indoor temperature. However, human health and comfort are strongly affected by substances found in the air. We spend over 90% of our time indoors according to the US EPA, and indoor air is 2 to 5 times more polluted than outdoor air on average.

To improve indoor air quality, the concentration of air pollutants must be kept under control. There are three ways to accomplish this, and the best results are obtained when they are combined:

  • Minimizing the sources of air pollution inside a building.
  • Providing a constant supply of fresh outdoor air, while removing indoor air that has accumulated pollutants.
  • Removing air pollutants directly. This can be accomplished with filters and air purifiers, among other methods.

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Which Are the Main Sources of Air Pollutants?

Tobacco smoke and car exhaust are two examples of air pollution sources that are well known by the general public. However, other pollution sources are less obvious. For example, most air fresheners and cleaning products contain harmful substances called volatile organic compounds, or VOCs. Since the scent of these products is considered pleasant, they are not normally associated with air pollution. 

Construction materials are also a source of VOCs, especially in new buildings. When the interior of a building or vehicle “smells like new”, the cause is a high concentration of VOCs in the air.

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Building certification systems like LEED and WELL give points for improving indoor air quality and for using low-VOC construction materials. LEED places a strong emphasis on energy efficiency, while WELL is mostly focused on providing healthy conditions for occupants. However, both rating systems give a high importance to air quality.

Developers can improve indoor air quality in their projects by specifying construction materials with a low VOC content. To complement this, the ventilation design can include air quality sensors. When an increased concentration of air pollutants is detected, the ventilation system increases airflow to keep them under control.

How Air Quality Is Scored in Green Building Rating Systems

The LEED certification requires a minimum air quality level, and keeping the indoor environment free of tobacco smoke. Beyond these minimum requirements, there are 8 points available for the following:

  • Enhanced indoor air quality (2)
  • Low-emitting materials (3)
  • Construction IAQ management plan (1)
  • IAQ assessment (2)

The WELL certification has the same basic requirements as LEED, plus two more: ventilation effectiveness and construction pollution management. In this case, there are up to 18 points available:

  • Enhanced air quality (4)
  • Enhanced ventilation (3)
  • Operable windows (2)
  • Air quality monitoring and awareness (2)
  • Pollution infiltration management (1)
  • Combustion minimization (1)
  • Source separation (1)
  • Air filtration (1)
  • Active VOC control (1)
  • Microbe and mold control (2)

When air pollutants are eliminated at the source, less work is required from the ventilation and air purification systems. Consider that these systems consume energy, and they have an operating cost. The most effective strategy is minimizing air pollution sources first, and then using other methods to enhance air quality. Low-emitting construction materials achieve a permanent reduction of indoor air pollution.

Indoor plants are recommended, since they absorb many harmful substances as part of their metabolism. However, flowering plants should be avoided in closed spaces, since their pollen causes irritation and allergies in sensitive individuals.

Indoor Air Quality in New Constructions

Since the materials and furniture in new buildings are of recent installation, they still have a high chemical content from the manufacturing process. As a consequence, off-gassing is higher in new buildings. Demand controlled ventilation systems are normally designed to respond to occupancy, but not directly to air pollution levels.

A ventilation system with air pollution sensors can achieve better performance than a system that only monitors occupancy. When air pollutants are measured directly, the system responds to events that don’t depend on the number of people in a building. The following are some examples:

  • New buildings need extra ventilation to remove the higher emissions from new materials and furniture.
  • Cleaning products release VOCs, and additional ventilation may be needed when they have been used recently.
  • Some activities require more ventilation than others. For example, 100 persons exercising need more ventilation than 100 persons sitting down at a conference.

Low-emitting construction materials and a smart ventilation design can achieve a permanent improvement of indoor air quality. If the developer is seeking a certification like LEED or WELL, indoor air quality can also help earn points.

 

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