Walls, ceilings, and indoor air quality

September 1, 2011

Photo © BigStockPhoto/Art Korad[1]
Photo © BigStockPhoto/Art Korad

By Rachel R. Belew
By its very nature, indoor air quality (IAQ) is fragile and fickle—easily disturbed by the most minute of changes to the built environment, whether during construction or occupancy. In fact, even the seemingly innocuous introduction of new products and materials, such as wall and ceiling assemblies, can damage indoor air quality and, as a result, create an unhealthy space for both contractors and occupants.

Common interior products and materials emit volatile organic compounds (VOCs), chemicals that volatize, or become airborne, at room temperature. VOCs often produce distinct odours (e.g. paint fumes), and inhalation exposure to these chemicals can trigger numerous short- and long-term health problems, including:

Understanding how the design/construction process can take this information into account is critical for ensuring optimal IAQ for projects.

Chemicals in Canada
The 1999 Canadian Environmental Protection Act (CEPA) regulates the manufacture, marketing, use, transport, and disposal of toxic chemicals, while the Pest Control Products Act (PCPA) regulates use of pesticides. The Canada Consumer Product Safety Act, which passed in 2010 as a replacement for the more lenient Hazardous Products Act, regulates toxic chemicals in consumer products. Nevertheless, according to a 2005 report by Environmental Defence, safety testing is not required for the vast majority of chemicals in commerce. (For more information, visit www.environmentaldefence.ca/reports/toxic-nation-report-pollution-canadians[2]).

When CEPA was introduced, 23,000 chemicals that had previously been on the market were granted universal approval without having undergone any safety assessments, the report notes. It was not until 2006 that those chemicals were categorized based on their toxicity—even then, only 85 were deemed “toxic,” and 67 were considered “priority substances,” meaning they must undergo further evaluation within five years. The rest of the chemicals are categorized as not needing additional safety assessments.

The Environmental Defence report also notes that while approximately 300 new chemicals are introduced into the Canadian market each year, companies are not obligated to submit their chemicals for safety testing before they enter the market. Further, companies whose chemicals are already on the market are not required to conduct retroactive safety testing. The report also states products are not required to be evaluated for safety before they are introduced to the country. Rather, post-market evaluations are conducted only after Health Canada receives complaints or concludes there is a potential risk.

Some interior spaces, like this preschool, are likely to have occupants more sensitive to the risks that are associated with indoor air contaminants. Designers should take steps to ensure a safer project. Photo © BigStockPhoto/Barbara Helgason[3]
Some interior spaces, like this preschool, are likely to have occupants more sensitive to the risks that are associated with indoor air contaminants. Designers should take steps to ensure a safer project.
Photo © BigStockPhoto/Barbara Helgason

Greater surface area, greater emission potential
A good rule of thumb for determining a product’s potential to emit chemicals is to consider its surface area. Generally, the greater a product’s exposed surface area, the more opportunity there is for chemical off-gassing. This is why the smell of a freshly painted room may seem more pungent than the smell of, say, a freshly painted barstool in the same space.

Indeed, flooring, paints, coatings, wallcoverings, furnishings, and cabinetry are the building products most commonly associated with VOC emissions—common examples include aldehydes, alcohols, and normal hydrocarbons.

Among the specific VOCs most frequently found are:

The addition of paint and other surfacing materials can significantly widen the spectrum of VOCs present in the air.

However, the list of IAQ-offenders is far more extensive than just those product types alone. It includes:

Many of these products not only have a particularly high risk of off-gassing because of their chemical composition, but they also take up a lot of surface area in a given space.

Wall and ceiling systems, therefore, can contribute greatly to indoor air pollution if specifiers, builders, and contractors fail to be diligent about using third-party-certified low-emitting products and materials.

VOC emissions versus content
Unfortunately, the marketplace is teeming with confusion over how VOCs are measured and assessed for their health impacts—particularly when it comes to interior wall and ceiling paints. Many marketers tout their products as ‘low-VOC’ or ‘no-VOC’ simply because they comply with Canadian content regulations. However, these regulations apply to exterior—not interior—paints. (Visit www.gazette.gc.ca/rp-pr/p1/2008/2008-04-26/html/reg1-eng.html[4]).

For example, Canada currently requires a VOC limit of 100 g/L in flat architectural coatings; for non-flat coatings, the limit is 150 g/L; and for high-gloss coating, the limit is 250 g/L. Such content-based regulations were developed with the intent of reducing outdoor emissions that contribute to the formation of ground-level ozone and smog. In other words, they do not address indoor emissions and human exposure. Since not all VOCs contribute to ozone and smog formation, products like ‘low-VOC’ and ‘no-VOC’ paints, adhesives, and sealants can still off-gas potentially toxic chemicals into the indoor environment.

There are also other ways that ‘low-VOC’ and ‘no-VOC’ paints can emit volatile organic compounds. First, resins, pigments, and other additives in the paint can off-gas. Second, chemical reactions between the paint and the substrate can occur during application, creating new compounds that could not have been identified during the paint’s content analysis. Third, VOCs can synergize (i.e. combine) with VOCs from other products in the space, creating new, and sometimes more potent, compounds.

Sink effects and pollution migration
Besides direct product off-gassing, one of the biggest threats to a building’s indoor air quality is what is known as the ‘sink effect.’ As chemicals from various products accumulate in the air, porous materials (e.g. carpeting, upholstered furniture, wallboard, acoustic ceiling tiles, and fabric wallcoverings) adsorb the chemical molecules, or gather them in a thin film. Over time, the materials will then re-release those chemicals into the air—sometimes as soon as within one hour. (See the December 2001 issue of Indoor Air [vol. 11, no. 4]). Given that VOCs can continuously emit from a single source for several weeks at a time, the sink effect can actually worsen IAQ by perpetuating the cycle of chemical release and re-release.

One of the ways to avoid the sink effect is through specifying third-party certified low-emitting materials, as discussed later in this article. Such products can greatly reduce chemical emissions in a built environment. Further, the fewest wet materials as possible should be used; they should also be installed after the dry materials. When this is unfeasible (as is often the case with interior paints, coatings, and sealants), one should specify only those products certified for low chemical emissions.

There are many strategies for reducing VOCs in interior spaces, ranging from careful construction site management and product installation sequencing to commissioning and building flush-out. Source control, as in selecting the safest materials or following certification programs, is also critical. Photo © Kelpfish/Dreamstime.com[5]
There are many strategies for reducing VOCs in interior spaces, ranging from careful construction site management and product installation sequencing to commissioning and building flush-out. Source control, as in selecting the safest materials or following certification programs, is also critical.
Photo © Kelpfish/Dreamstime.com

All interior finishing materials should also be installed two to four weeks before occupancy. This allows time for the building to ‘air out.’ It is important to ensure any materials containing potentially high chemical levels are installed as early as possible during construction to allow for maximum off-gassing before occupancy. Additionally, it is critical to make certain the relative humidity (RH) is below 65 per cent. Not only does high relative humidity cause moisture buildup (a precursor to mould growth), but it can also exacerbate the sink effect in certain products, such as carpeting. (See the August 2008 edition of Environmental Science and Technology [vol. 42, no. 15]).

Another issue is pollution migration. Research has shown VOCs can move from one area of a built environment to another, compromising the indoor air quality of spaces that might appear free of contaminant sources. (See the October 2010 Indoor Air (vol. 20, no. 5). Pollutant migration can occur when airborne contaminants enter and travel through air pathways. Examples of these pathways include the voids between ceiling joists and ceiling plasterboard or the cavities behind electrical outlets and ceiling light fixtures. In addition to VOCs, mould spores, insect and rodent fecal matter, and other indoor pollutants can migrate along the same routes. Contractors should take great care to seal potential air pathways to limit this phenomenon.

Ways to manage IAQ
To protect an interior space’s indoor air quality, great attention must be paid both to material selection and the overall execution of construction. The process of creating a building with good indoor air quality comprises a series of interdependent steps in which failure of one causes subsequent failure of the others. It is therefore incumbent on the project team to ensure each stage of construction is carried out with the overall goal of good IAQ.

Source control
Specifying materials bearing the “GREENGUARD Certified” mark can help ensure those building products have been tested for low chemical emissions. The GREENGUARD Environmental Institute develops third-party chemical emission standards and requires certified products to pass routine testing on an ongoing basis.

Since its inception in 2001, GREENGUARD has certified more than 12,000 products from over 370 manufacturers worldwide. A free database on its website makes it easy to find and search for these products by category, manufacturer, sustainable credit, certification, or keyword. This significantly reduces the time specifiers must spend on researching products and finding those that qualify for sustainable building points.

Construction site management
During new construction of a sensitive environment such as a school, it is critical to have an interior moisture control plan in place to prevent mould growth. If weather or plumbing leaks cause moisture or wetness in the building’s interior, additional materials should not be installed until the building is properly dried out.

All pre-installed materials should be thoroughly inspected for mould and mildew. If they are contaminated, they should be removed immediately. GREENGUARD’s American National Standards Institute (ANSI) standard—ANSI/GEI MMS 1001, Mould and Moisture Management Standard for New Construction—provides further guidance.

While ANSI/GEI MMS 1001 is applicable to commercial and multi-use construction projects in Canada, Canadian Construction Association (CCA) also provides general suggestions on mould management issues via CCA 82, Mould Guidelines for the Canadian Construction Industry. (Visit www.cca-acc.com/documents/cca82/cca82.pdf[6]).

Scheduling and product installation sequencing
Minimizing building products’ onsite storage time also minimizes their risk of exposure to moisture. Therefore, material shipment and delivery should always be based on actual construction progress. On delivery, products should be inspected not only for conforming to the final construction materials list, but also to ensure they are free from water and moisture damage.

Further, outdoor air ventilation should be supplied during the construction to help dilute contaminants and flush them out of the building. The use of temporary construction ductwork is recommended.

At left, a chair is tested in a dynamic environmental chamber. Sorbent tubes (at right) attach to the chamber, collecting VOCs for identification and measuring. Photos courtesy Air Quality Sciences[7]
At left, a chair is tested in a dynamic environmental chamber. Sorbent tubes (at right) attach to the chamber, collecting VOCs for identification and measuring.
Photos courtesy Air Quality Sciences

HVAC operations during construction in occupied buildings
If construction or remodelling must be conducted when the building is occupied or in use, the construction area must be depressurized at a rate at least 10 per cent greater than the supply. Should this be impossible, existing spaces need to be pressurized. Supplemental containment barriers need to be erected if the pressurization is inadequate for controlling construction dust and odours in occupied areas.

It is important not to place construction equipment or staging areas near air intakes for existing construction. Avoiding this helps prevent entrainment of vehicle exhaust, including carbon monoxide, particles, and VOCs. When high-emitting construction activities are performed near outdoor air intakes for existing construction, intake dampers should be temporarily sealed.

During demolition or construction in existing spaces, the HVAC system should not be operated. Further, the supply and return openings should be temporarily sealed with plastic sheeting. If the system must be operational, temporary minimum efficiency reporting value (MERV) 8 filters can be installed in return openings—they must remain clean, of course.

Building flush-out
Following completion of interior finishes and installation of new furnishings, the building should be flushed with 100 per cent clean, outdoor air for two to four weeks before occupancy. This assists in reducing VOCs and other pollution levels. Testing the air for low levels of VOCs before occupancy—with and without flushing—is also highly recommended.

IAQ testing
For new construction and major remodelling, it is important to test the building’s IAQ before occupancy. Measurements should follow protocols established by reputable standard-setting organizations or public health agencies, such as GREENGUARD and ASTM International.

Air samples should be taken either for every 280 m3 (25,000 cf) or for each contiguous floor area—whichever is greater—and be collected in the breathing zone of the air at 1.2 to 2.1 m (4 to 7 ft) above the floor. Areas with the least ventilation and greatest presumed source strength should be included. The building’s HVAC system should operate at normal daily start and stop times at minimum outside airflow for occupied mode for the duration of testing.

*Carbon dioxide monitoring is required only if the building is occupied during testing. The ventilation rate is outdoor air requirement per person. The carbon dioxide measurement is differential between indoor and outdoor conditions, based on occupancy type as defined by American National Standards Institute/American Society of Heating, Refrigerating, and Air-conditioning Engineers (ANSI/ASHRAE) 62.1, Ventilation for Acceptable Indoor Air Quality, and 62.2, Ventilation and Indoor Air Quality in Low-rise Residential Buildings.[8]
*Carbon dioxide monitoring is required only if the building is occupied during testing. The ventilation rate is outdoor air requirement per person. The carbon dioxide measurement is differential between indoor and outdoor conditions, based on occupancy type as defined by American National Standards Institute/American Society of Heating, Refrigerating, and Air-conditioning Engineers (ANSI/ASHRAE) 62.1, Ventilation for Acceptable Indoor Air Quality, and 62.2, Ventilation and Indoor Air Quality in Low-rise Residential Buildings.

Contaminant concentrations should not exceed the maximum limits in Figure 1. If this happens, additional flush-out with outside air is required, along with re-testing of the air in the same sampling locations until an acceptable level is achieved.

Moisture and mould
Perhaps counter-intuitively, cold temperatures and dry air across much of Canada can contribute to moisture development and mould growth within built environments. This is due largely to high temperature and humidity gradients: the colder and drier the air is outside, the more building occupants rely on heat and humidification inside for both comfort and safety. However, when warm, humid indoor air comes into contact with cold surfaces—such as exterior walls—condensation can form, leading to soggy sheathing and insulation and, consequently, mould growth.

To reduce risk of moisture formation caused by temperature and humidity gradients, one can install batt insulation with the facing (i.e. vapour retarder) toward the source of the warm, moist air. This means in cold climates, the vapour retarder should face the interior. By contrast, in the hot, humid climates well south of Canada, the vapour retarder should face the outside.

The maritime climate of southern British Columbia has moderate temperatures but high rainfall and humidity. Since temperature gradients between the indoors and the outdoors are not as extreme, there is less risk of condensation. However, the issue remains a concern due to the increased rainfall and persistent damp conditions. Additionally, the high rainfall levels and prolonged rainy season in the region are very unforgiving of even minor leaks in walls and roofs.

Conclusion
Not only is optimal indoor air quality critical for the health of building occupants, but it is also important in reducing the risk of legal and financial damages to designers, product manufacturers, builders, building owners, and occupants.

IAQ problems and the resulting illnesses and economic damages can also have legal and financial implications for all parties, including designers, builders, product manufacturers, building owners, employers, and occupants. According to a report by the Building Ecology Research Group, legal issues surrounding IAQ are becoming increasingly common, as are worker compensation claims. Former building occupants, employers, and owners have been known to sue designers, owners, manufacturers, and contractors for millions of dollars.

To construct a building with good IAQ, a project team must take an integrated approach to design and construction. By doing everything possible to ensure good air quality within a building, architects, builders, and facility managers can take pride in knowing they have helped created a healthier indoor environment.

Rachel R. Belew is public relations and communications manager at the GREENGUARD Environmental Institute in Atlanta, Ga. Her articles on green building and design have appeared in various interior design and architectural trade publications. Belew holds a master’s degree in journalism from Columbia University in New York City. She can be contacted via e-mail at rbelew@greenguard.org.

Endnotes:
  1. [Image]: http://www.constructioncanada.net/wp-content/uploads/2016/03/bigstock-waiting-room-interior-17450894.jpg
  2. www.environmentaldefence.ca/reports/toxic-nation-report-pollution-canadians: http://www.environmentaldefence.ca/reports/toxic-nation-report-pollution-canadians
  3. [Image]: http://www.constructioncanada.net/wp-content/uploads/2011/09/15283739.jpg
  4. www.gazette.gc.ca/rp-pr/p1/2008/2008-04-26/html/reg1-eng.html: http://www.gazette.gc.ca/rp-pr/p1/2008/2008-04-26/html/reg1-eng.html
  5. [Image]: http://www.constructioncanada.net/wp-content/uploads/2011/09/3968732.jpg
  6. www.cca-acc.com/documents/cca82/cca82.pdf: http://www.cca-acc.com/documents/cca82/cca82.pdf
  7. [Image]: http://www.constructioncanada.net/wp-content/uploads/2011/09/IAQ_12.jpg
  8. [Image]: http://www.constructioncanada.net/wp-content/uploads/2011/09/AQ_Fig1.jpg

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