Preserving Indoor Air Quality During Construction
Whether you are planning new construction or renovating an existing space, building construction is a dirty business
Whether you are planning new construction or renovating an existing space, building construction is a dirty business, and a lack of pre-planning will guarantee impacts on indoor air quality. If you develop and follow a good construction management plan, you can control the mess and greatly reduce the impact on indoor environmental quality during and after the construction process.
A good IEQ management plan will pay big dividends in terms of worker health and productivity as well as facility maintenance costs after the fact. Recent research suggests that improving indoor air quality can increase worker productivity between one and eight percent and averages about three percent. If the average cost for employee salaries in a typical Class A building is around $150 per square foot, better indoor air quality can save an employer around $4.50 per square foot just from improved worker productivity.1
A couple of excellent resources to help you prepare a construction management plan are the Environmental Protection Agency’s Indoor Air Quality Tools for Schools2 and the Sheet Metal and Air Conditioning Contractors National Association’s IAQ Guidelines for Occupied Buildings under Construction.3 These resources discuss about a half dozen controls to implement during your construction project. We have added some of our own to ensure a comprehensive construction management plan.
Prepare a construction management plan
Write a base construction management plan (CMP) and then modify as needed for specific projects before providing to contractors, building occupants, and employees. The main focus should address scheduling. This is especially important if your construction or renovation project is in close proximity to occupied adjacent buildings or workspaces. Dust, noise, and odors common to construction will impact adjacent areas and potentially affect occupants.
The CMP and good scheduling are also vital to protect building materials. Construction projects cannot avoid the weather and if ignored can seriously impact indoor air quality. Protect stored materials, especially porous material such as drywall, from moisture and microbial growth. This is much easier once the building shell is dried in. Discard any water-damaged materials to make sure they are not used in the construction.
Construction sequencing is very important in minimizing the absorption of volatile organic compounds (VOCs) by porous materials. This means completing application of wet and odorous materials such as coatings, paints, and sealants before installing absorbent “sink” materials such as carpets, ceiling tiles, and upholstered furnishings.
Related Article: Surviving a Construction or Renovation Project
Indoor air quality “time of use” problems originate from activities such as cleaning (see housekeeping below), roofing projects, or floor refinishing. Schedule these on weekends or after normal hours, when the potentially affected facilities are closed. If your project is a renovation, review the pathway interruption and source control sections to understand the importance of isolating work areas from non-work areas. Containment and isolation are especially important when renovations must be done during working hours and when business operations run 24/7.
Source control
Controlling sources means preventing or eliminating pollutants from entering the building. Do not allow vehicles, machinery, or equipment to operate or idle near entries, loading docks, or air intakes. Ensure source control is employed for all pollution-causing activities and products such as roofing tar pots, painting, concrete, block or brick cutting, etc.
Powered equipment produces exhaust fumes loaded with carbon monoxide, and the other activities give off chemical vapors or dusts that could be pulled into the building. Carbon monoxide, as most are aware, is potentially very harmful, causing asphyxiation and even death at very high concentrations, while paint and tar fumes, usually just a nuisance, can produce headaches, nausea, and dizziness if levels accumulate.
One last recommendation for source control is to locate trash containers and dumpsters away from building openings. Source control is also tied to housekeeping and worker education, as discussed below.
Pathway interruption (ventilation and exhaust)
When pollution-causing activities must occur inside the building, you need to implement steps to isolate active dirty work areas from clean or occupied spaces. Ventilation and exhaust systems are used to control and remove pollutants produced by these activities.
If the HVAC system is already installed, you can use pressure differentials to keep pollutants generated in dirty work areas from getting to clean areas. This strategy often requires building temporary barriers. We can then pump more supply air to the clean area and, if needed, increase exhaust from the dirty work area, preventing pollutants from escaping to the clean sections.
Depending on your climate and local weather, the use of 100% outside air for the HVAC system, thus diluting and exhausting contaminants, is an option, provided we protect the HVAC system (see below).
Pathway interruption can also involve using local indoor exhaust equipment. Place high-volume evacuation blowers in the dirty area and near the contaminant source activity to capture and exhaust the pollutants directly outside using appropriate lengths of flex ducts.
HVAC protection
It is imperative to protect all air handling equipment from dust, insect, moisture, and microbial contamination during construction activities. If the HVAC system is operated during construction, make sure filters are installed. Temporary filter media with a minimum efficiency reporting value (MERV) of 5 to 8 is recommended. (MERV ratings refer to how well a filter traps particles in the air; the higher the number, the better the filtering.) 4 Install new filter media when construction is completed and before occupancy.
Repair all leaks in the ducts or air handlers promptly. Clean or replace any HVAC equipment or ductwork that becomes contaminated prior to system start-up. If the HVAC system is designed with ducted return air (i.e., ductwork under negative pressure), then the return side should be damped off, sealed with plastic, or isolated during heavy construction, demolition, or pollutantgenerating activities.
Interior finishes
Emissions from adhesives, paints, floor coverings, carpets, and furnishings are unavoidable during new construction and renovation. We strongly encourage the use of low-VOC-emitting carpets, glues, paints, and other furnishings. This will reduce the number of contaminants you have to deal with as they cure and off-gas (i.e., emit vapors as they react, cure, and/or dry).
Controlling indoor pollutants from these sources is best done using the HVAC system. Ensure the interior spaces are properly cured—by ensuring that the drywall and plaster is cured and shows proper moisture content—before applying finishes. We recommend keeping the system operating 24 hours per day during the installation of all interior finishes. Another alternative is to run the system 24 hours per day for a minimum of three days at a stable temperature and a relative humidity of 60% or less.
Finally, we recommend not permitting vinyl wallpaper or other water impermeable coverings on the interior side of exterior walls. These materials tend to trap moisture and lead to mold growth and other problems.
Housekeeping
The importance of good housekeeping during construction and renovation projects cannot be overstated. Prior to installation, store building materials in a clean area protected from weather. Perform regular (at least daily) housekeeping to prevent tracking dust and debris from construction areas to clean non-work areas. Before allowing occupants to move in, perform a thorough cleaning to remove contaminants from the building.
Keep in mind that some conventional cleaners can be a contaminant source. Concentrate cleaning activities on spaces to be occupied and the HVAC system. For the HVAC, ensure all coils and fans are cleaned and filters are replaced with new ones in advance of performing the final test and balance and especially before conducting baseline air quality testing (which we also strongly recommend).
Worker education
Inform all workers about construction activities and schedules and keep occupants updated during the project. It is a good idea to train employees on how to prevent, control, and remove indoor air quality pollutants.
A good hazard communication program for all employees will train employees on reading and understanding safety data sheets (SDS), aiding them in selecting potentially less harmful products and providing guidance on proper use and waste handling. Emphasize the selection of cleaning chemicals that are low VOC emitting and make sure the SDS are reviewed and kept close at hand.
In summary
Preparing and implementing a good construction management plan preceding building projects will go a long way in protecting workers’ health and preventing poor indoor environmental quality. The absence of a construction IEQ plan will most likely affect indoor air quality negatively and may continue throughout the life of the building.
Poor scheduling or source control can lead to immediate impacts causing employee complaints and serious disruptions. Installation of moisture-damaged building materials or poor-quality paints and finishes can create difficult long-term indoor air quality issues. By employing the presented control methods, you are well along in protecting the health of construction workers during construction or renovation and of building occupants for years to come.
References
1. Experience Exchange Report, Building Owners and Managers Association International. Washington, D.C. 2018 https://www.boma.org/BOMA/Research-Resources/BOMA/Research-Resources/Home.aspx?hkey=aa84cafd-f63e-48de-8efc-43b82ffe6d41
2. Indoor Air Quality Tools for Schools, Environmental Protection Agency. Washington D.C. May, 2010. http://www.epa.gov/iaq/schools/
3. IAQ Guidelines for Occupied Buildings under Construction, Sheet Metal and Air Conditioning Contractors National Association. Chantilly, VA. 2007. https://www.smacna.org/store/product/iaq-guidelines-for-occupied-buildings-under-construction
4. Minimum Efficiency Reporting Value (MERV), Wikipedia. 2015. http://en.wikipedia.org/wiki/Minimum_efficiency_reporting_value