The idea behind this credit is to ensure good indoor air quality (IAQ) for a project for occupancy. IEQc3.2 can be seen as a belt-and-suspenders credit: even if the IEQc4: Low-Emitting Materials credits are pursued, along with IEQc3.1: Construction IAQ Management—During Construction, IEQc3.2 ensures that the building ends up with the intended result. (Although it’s typical to do so, you don’t have to pursue any of those credits to go after this credit.)

The goal is to minimize IAQ issues that result from construction or renovation activities in order to improve the comfort and health of the occupants.

The credit has a direct impact on occupant health and comfort, and it is often very important to the owner and occupants, that their new, LEED-certified building should smell “green” when they move in.

Flush out or testing?

The flush-out of indoor air required under Option 1 is frequently pursued by projects seeking a certain and predictable path.

Performing testing under Option 2 leaves open the possibility that despite all other efforts, the building could fail the tests, putting the credit in jeopardy.

You might wonder why, if a building earns the IEQc4 credits and IEQc3.1, there would be any chance of failing IAQ testing. For whatever reason, it happens. This might be due to VOC emissions from materials not covered by IEQc4, or from the undetected use of materials not meeting the spec.

Another reason for pursuing Option 1 is that the costs of IAQ testing are commonly greater than those of a building flush-out. Testing costs vary depending on the size of the building, the number of samples tested, and the travel and field work the testing agency needs to perform. Large buildings, or buildings with multiple independent HVAC systems, require more testing samples. One test is required for each separate ventilation system within the building, with not less than one sample per 25,000 ft² of contiguous floor area.

On the other hand, the energy expenditure for flush-out under Option 1 can be large, and there may not been enough time after installation of finishes but prior to occupancy to conduct the flush-out. The tenant may also prefer the solid results of a test. All of these factors can push a project toward Option 2.

Two flush-out options

Under Option 1, you have two paths for performing the flush-out. Path 1 is performed prior to occupancy: provide 14,000 cubic feet of outdoor air per square foot of building space. Relative humidity must be maintained at 60% or below and temperature must be maintained at 60 degrees or above.

If there isn’t enough time prior to occupancy to follow Path 1, Path 2 allows you to reach the 14,000-cubic-foot threshold in phases. Path 2 requires an initial flush-out of 3,500 cubic feet per square foot, and then a daily flush-out that begins three hours before occupancy and continues until the end of occupancy for the day. During this period, a ventilation rate of 0.3 cfm per square foot must be maintained. This may be higher than the designed ventilation rate, so plan ahead for this. 

Common pitfalls to avoid

This credit is typically easy to achieve if you plan ahead and avoid these common pitfalls:

• Early in the design of the mechanical systems, take into account the requirements for flush-out to ensure that the HVAC system is able to supply the required ventilation rate which is often higher than normal design conditions.  Once the mechanical design is confirmed, the mechanical engineer should provide the contractor with the flush-out duration so that it can be worked into the construction schedule as soon as possible. 
• If a flush-out is performed during very cold or very humid weather, maintaining minimum temperature and humidity levels may be impossible or require a lot of energy loss. Consider the testing path if these conditions are likely for your project.
• All permanent finishes have to be installed prior to flush-out. Also, all construction must be completed including punch-lists. Make sure that subcontractors are informed of the credit requirements and that all work is appropriately scheduled so as to not introduce contaminants after the flush-out.
• If you go for testing (Option 2) and fail, you can opt to do a flush-out and retest prior to occupancy, but your schedule needs to allow for it. Build in some schedule and budget contingency in case retesting is required. 

Timeframe for credit implementation

The schedule for the implementation of either options must be managed carefully and depends on when the construction is complete. The credit needs to be implemented after construction and before occupancy. For the purpose of this credit, construction completion is defined as:

• All interior finishes are installed, including millwork, paints and carpet
• All HVAC systems are functional
• All punch-list items are complete
• Furniture should be in place but is not required

It is vital that communication be established early on among the team in order to meet the requirements of the credit and minimize risk of failure.

Alternative approaches

In naturally ventilated buildings or other situations where using the HVAC is not possible or desired, alternatives such as temporary supply and exhaust fans placed in the windows are also possible. (Simply opening the windows is not enough, however.) Like natural ventilation in general, this approach works best for relatively dry, moderate climates where the temperature and humidity conditions required by the credit are easy to maintain.

If using fans, ensure correct placement of fans to provide an even flow of fresher outdoor air across each space, preventing short-circuiting. Check the EPA IAQ Design Tools for Schools Controlling Pollutants and Sources information on exhaust or spot ventilation practices during construction activity (although written for schools, it is applicable to any type of project). (See Section 5: Ventilation Techniques). 

Consider these questions when approaching this credit

• Ask your mechanical engineerto run these preliminary calculations:
  • Is the HVAC system capable of performing the ventilation rates required for flush-out?
  • Can indoor temperature and humidity levels be maintained during the flush-out considering the scheduled season of the flush-out?
  • What is the estimated duration of the flush-out under Path 1 and Path 2 and how will this affect the construction schedule?
• Important conversationsthat need to occur between the general contractor, building owner and occupants:
  • When do occupants need to move in? Is the date flexible? 
  • Can the schedule allow time for a flush-out after construction completion and prior to occupancy? How much time is available?
  • Will the project pursue a full flush-out (Option 1 – Path 1), or will occupancy occur during the flush-out (Option 1 – Path 2)?
  • How will the basic requirements for having all finishes installed and construction complete be communicated to subcontractors?
• Things to considerwhen implementing IAQ testing:
  • Does your building have multiple, separate ventilation systems?
  • How many samples are required? 
  • Is your construction team confident that it can ensure contamination levels below credit limitations at the end of construction?
  • Is there time at the end of the construction schedule to allow for flush-out and retesting if initial test results are above allowable levels for contaminants?