Mold Prevention And Control For Mechanical And HVAC Contractors

Mechanical contractors have an inherent risk of claims arising out of the heating, ventilation, and air-conditioning (HVAC) and plumbing systems installed or serviced for their customers. An effective mold prevention and control program can reduce such risks by proactively addressing moisture control and quality assurance issues during the design, construction, and commissioning phases of the project as well as investigating and correcting water intrusion and/or mold issues immediately. The following are considerations for a mechanical contractor to include in a mold prevention and control plan.

Design And Preconstruction Phase

One of the primary issues for HVAC contractors is to ensure that the HVAC system is designed properly for the building. If the HVAC system is “oversized,” the system will not run long enough to dehumidify the building. However, if the system is “undersized,” the system may run for long periods and still not be able to handle the moisture load resulting in condensation on interior surfaces. Fresh air intakes need to be carefully designed with multiple goals of diluting microbial contaminants, energy efficiency, and moisture and temperature modulation. There are several impacts on occupant comfort and health, equipment maintenance, and system economics associated with an oversized HVAC system (see Table 1). However, equipment is routinely installed with total capacities that are 50% to 200% greater than needed. According to G. Hourahan in an article entitled, “Sizing and Selecting Equipment for Proper Humidity Control,” steps for sizing equipment correctly include the following:

• Establish building design and criteria requirements (e.g., duct location and level of sealing and insulation, ventilation or filtration needs, special occupant comfort/health needs, appearance issues, building constraints, high humidity environments, etc.).
• Determine the design loads (building construction issues such as the building envelope, solar orientation, glass type and shading, insulation type/level, duct tightness/location, etc.).
• Verify system capacities (i.e., adhere to all manufacturer’s sizing, selection, and application guidelines). Do not arbitrarily increase the load (i.e., do not apply a safety factor).
• Evaluate latent requirements (i.e., consider innovative approaches to controlling moisture).

Additional design issues for mechanical contractors to consider in a mold prevention and control program include the following:

• Flashings at penetrations for piping and electrical conduits, and any other HVAC equipment.
• HVAC equipment and complete flashings.
• Insulation of chilled water pipes.
• Use of mold-resistant materials (such as fire proofing, caulks, sealants, etc.).
• Bathroom fans vented to the exterior and actuated by the bathroom light.
• Floor drain elevations.
• Use of bare, galvanized ductwork where possible and avoid interior linings such as fiberglass since such linings can serve as a habitat for mold growth.
• HVAC designed with filters that have American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Dust Spot Efficiency Rating of at least 50 percent.
• Ensure that designs are performed by qualified and experience personnel who have been trained in mold and water intrusion issues.
• Consider incorporating an automated building monitoring system (to measure relative humidity, temperature, and carbon dioxide) into the design to proactively monitor the performance of the building’s ventilation system.
• Peer review of mechanical system designs (including shop drawings and detail drawings). Consider the use of a third-party design review.
• Document any recommended changes given to the Architect/Engineer of Record. Obtain approval from the architect/engineer prior to proceeding. If the recommendation is rejected, restate the recommendation in writing with a copy to the owner, general contractor, and project file.
• Pre-qualify potential subcontractors and evaluate their experience and technical qualifications.
• Inform general contractor/construction manager and subcontractors of mold prevention and control program.

Early start-up of mechanical systems: Procedures and policies for the early start-up of mechanical systems should be established. Depending on the geographical location of the project and the type of project, an early startup of the mechanical system may be done to provide heating or cooling and/or drying out the building of excess humidity. However, if the system is to be turned on while there is still construction dust being created, precautions should be taken so the interior ductwork does not become coated with construction dust, which is especially problematic if the ductwork is lined with fiberglass. The construction dust provides a food source for potential mold growth.

Construction Phase

During the construction phase, an inspection procedure should be instituted and documented throughout construction of the project with a plan to identify mold and potential water intrusion. Photos of all key installations should be taken. Independent inspections of major phases of the construction work should be considered as such third-party inspectors may become pre-deposed experts for the defense of a mold or water intrusion claim. The inspection procedure should include the following:

• Inspect materials to be used and delivered to the site. Confirm that they are free of mold and water damage.
• Confirm that all plumbing, electrical, and duct penetrations are properly sealed to ensure water cannot enter the structure.
• Assure materials are properly stored and protected from moisture.
• Seal door and window openings, pipe chases, elevator shafts, roof openings and penetrations from weather.
• Insulate all chilled water pipes.
• Remove standing water from the building(s).
• Protect ongoing and completed flashings, waterproofing, roofing and vapor barriers during construction.
• Repair damaged materials promptly.
• Keep drains open and unobstructed.
• Repair plumbing leaks immediately.
• Remove trash and debris from the building on a regular basis.
• Remove wet and/or moldy materials from the site immediately.
• Install sump pumps and place them in operation as early as possible to prevent flooding. Consider battery-operated sump pumps.
• Place equipment that requires water (such as tile saws, mixers, etc.) in tubs during indoor operation to control the spread and seepage of water.
• Test plumbing and HVAC systems in accordance with local and national codes to ensure there are no leaks and keep signed test records with project documentation.
• Use various methods of testing of piping (such as air tests) prior to water tests.
• Charge domestic water lines to the building structure for as long as possible prior to the installation of drywall to help identify potential hidden leaks.
• Confirm proper backfilling of trenches within the buildings to prevent water from entering.
• Inspect shower receptor installations for proper sealant.
• Check bathtubs for leaks with special attention to overflows.
• Confirm proper installation of protection plates on framing members per code to protect plumbing lines.
• Seal ductwork at separations if demolishing existing systems and remove from building.
• Confirm that procedures are followed to ensure that construction dust being created does not cause the interior ductwork to be coated with dust in the event of early start-up of HVAC systems.
• Confirm the receipt and execution of all change orders and schedule changes are documented and maintained in the project files.

Prior to turning over mechanical systems to the client, the following are prudent steps to consider:

• Conduct a documented walkthrough inspection with the general contractor or owner (as appropriate) to identify and correct nonconformances. The walkthrough inspection should cover all critical areas.
• Measure the humidity levels of the building.
• Check condensate pans to ensure they are clean. The condensate drain should be checked to ensure it is working properly.
• Maintain the documentation of the walkthrough inspection in the project files.

Upon final acceptance of the mechanical systems, an operations and maintenance manual should be provided to the client that includes both general and equipment-specific manufacturers’ operations and maintenance procedures and mold prevention tips for owners (such as responding to water intrusions immediately, fixing water or sewer leaks immediately, using air-conditioning in hot/humid weather, keeping HVAC system drip pans clean and unobstructed, maintaining humidity levels between 30% and 50%, communicating mold prevention tips to building occupants, etc.). The owner should be informed that extended shutdowns of the HVAC unit such as during nights and weekends or other periods where the building is unoccupied may appear to be cost-effective but in reality may create fluctuations in the moisture content throughout the building and create an environment conducive to mold growth.

Education And Training

Education and training are important elements in a contractor’s mold control and response program. Essentially, personnel should be trained in accordance with the contractor’s specific procedures for controlling mold and water intrusion issues and how to respond to such issues. Additionally, personnel should receive mold awareness training that includes the causes of indoor mold growth, toxicological impact on human health (real or perceived), and risks associated with mold growth to third parties. Customers should also be provided with information and guidance on maintenance procedures and mold prevention tips as previously discussed.

Response Procedures

Upon notification of water intrusion and/or mold growth, the site should be inspected immediately since mold may grow on water damaged materials within 24 – 48 hours. Notification should subsequently be provided to the insurance carrier and other parties affected by the water intrusion. The following basic parameters should be determined during the preliminary investigation:

• How long has the water intrusion occurred?
• What is the source of the water/moisture intrusion? Is the source from sewage?
• Has visible mold growth occurred?
• What is the size of the water damage or mold growth?
• How can the source of water intrusion be corrected?

A qualified professional, experienced in indoor air quality and mold assessments, should be consulted if necessary. The following is a checklist for investigating and evaluating moisture and mold problems:

• Assess the size of the water damage or mold area (in square feet).
• onsider the possibility of hidden mold.
• Clean up small mold problems and fix the source of moisture before they become large problems.
• Select a remediation manager for medium or large mold remediation projects.
• Investigate areas associated with occupant complaints.
• Identify and correct the source(s) of water/moisture intrusion.
• Note the type of water-damaged materials.
• Check inside the air ducts and air-handling unit.

The source of water/moisture intrusion and damaged porous materials should be removed and replaced as soon as possible to minimize the extent of the damage. The New York City Department of Health (NYCDH) and the United States Environmental Protection Agency (USEPA) have established remediation guidelines for performing mold remediation in schools and commercial buildings. Remediation should be performed by qualified and trained personnel.

Table 1 – HVAC Oversizing Impacts

Comfort

• Large temperature differences between rooms
• Degraded humidity control
• Drafts and noise
• Occupant discomfort/dissatisfaction Equipment
• Larger ducts installed
• Increased electrical circuit sizing
• Excessive part-load operation (i.e., frequent cycling, shorter equipment life)
• Nuisance service calls

Economic

• Higher installed costs
• Increased operating expense
• Increased installed load on the public utility system

Health

• Potential to contribute to mold growth
• Potential to contribute to asthma and other respiratory conditions

(Reference: Hourahan, G. “Sizing & Selecting Equipment for Proper Humidity Control.” ARI Magazine. Spring 2003: 24-34)

REFERENCES

• Arthur J. Gallagher Construction Services. “Mold Action Plan: A Map to Avoiding Mold Litigation.”
• Hourahan, G. “Sizing & Selecting Equipment for Proper Humidity Control.” ARI Magazine. Spring 2003: 24-34.
• Mahoney, D. and Spear, J. “Mold Risk Assessment & Remediation.” Professional Safety. Aug. 2003: 20-31.
• Sheet Metal and Air Conditioning Contractors’ National Association, Inc. Duct Cleanliness for New Construction Guidelines. Virginia: SMACNA, 2000.

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