Most of the Indoor Air Quality (IAQ) projects focus on already existing buildings, and are already occupied. However, there is one aspect of construction that often gets overlooked in construction projects i.e. selection of construction materials. Maintaining the desired air quality start from the design stage ideally, as construction materials have considerable impact on the indoor air quality in building spaces. Considering the emergency situation like COVID-19 outbreak, American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) highly recommends more outdoor air ventilation with zero air recirculation, upgrading to high efficiency air filters with MERV 13 rating or above, and adding UV germicidal irradiation.
A simple answer to how does construction materials affect the indoor air quality is the presence of high chemical content. In construction projects, most of the materials used are new, which means they have high chemical content left from the manufacturing process. Many of these chemical contents evaporate at room temperature, and are thus called Volatile Organic Compounds (VOC). There are over thousands of such substances and many of them have negative health impact on humans. For instance, high content of formaldehyde on wood products causes respiratory irritation.
VOC Off-Gassing in New Buildings
VOC are commonly characterized by smell. In new construction buildings or spaces that undergo renovations, the indoor spaces often have this “new smell”. Most of us like the new smell, however, it’s not a good thing. The smell is caused by the presence of VOCs on the new materials. Unlike air pollutants with unpleasant smell, some VOCs have a pleasant smell, and many are odorless.
Since new materials have much higher concentration of VOCs as compared to materials that have been installed for years, new materials release VOCs at a faster rate through as process called as Off-Gassing. High concentration of VOCs can irritate the respiratory system, and can also trigger flare-ups for patients with asthma. Being exposed to VOC for long duration of time has been linked to severe conditions like organ damage and cancer.
Proper ventilation can effectively reduce VOC levels, since they diluted due to mixing of fresh outdoor air with the indoor air. When coupled with exhaust fans, the diluted level of VOC can be removed completely. Since VOC molecules are so tiny, air filters are not effective, even considering HEPA filters. UV germicidal irradiation is not effective either, since VOC are non-living substances.
LEED Requirements for Low-Emitting Materials
The LEED certification offer 1 to 3 points for low-emitting materials for reducing the negative impact of VOCs on the air quality. The US Green Building Council (USGBC) has divided materials into 7 seven categories, each with its own set of requirements:
For LEED certification purposes, the building is divided into 2 parts, interior and exterior. Building interior includes everything withing the waterproofing membrane, and building exterior is everything outside the waterproofing membrane including the membrane itself. When it comes to earning LEED credits, both, the chemical contents of the materials and an assessment of the indoor air is considered. Any tests and measurements must be conducted by a laboratory with ISO/IEC 17025 accreditation.
The following summarizes the requirements of each building, and the points earned depending upon the total number of categories (mentioned above) used:
Without Furniture: With Furniture:
3 categories used = 1 LEED point 4 categories used = 1 LEED point
5 categories used = 2 LEED points 6 categories used = 2 LEED points
6 categories used = 3 LEED points 7 categories used = 3 LEED points
Without Furniture: With Furniture:
2 categories used = 1 LEED point 3 categories used = 1 LEED point
4 categories used = 2 LEED points 5 categories used = 2 LEED points
5 categories used = 3 LEED points 6 categories used = 3 LEED points
In cases where some compliant products are not available, LEED allows the budget calculation method which considers flooring, ceilings, walls, insulation, and furniture. USGBC has provided a detailed calculation, and points earned based on total percentage of compliant materials are:
Low-emitting products make building interiors healthier, especially when combined with effective ventilation.