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Guideline I.3: Ventilation Design

Intent

To promote good indoor air quality by requiring a ventilation baseline based on the general procedures and information contained in the latest approved version of ASHRAE Standard 62.1. To encourage better indoor air quality by recommending that ventilation design intent be demonstrated on a regular basis to building owners and operators. To encourage best indoor air quality by further recommending adjusting ventilation requirements upward from the baseline based on setting target CO2 concentration maxima.

Required Performance Criteria

  1. Radon is best controlled using source prevention techniques rather than ventilation. For New Buildings, if construction is to occur in one of the 68 Minnesota counties considered Zone 1 by the US EPA, guidance contained in the EPA document, “Radon Prevention in the Design and Construction of Schools and Other Large Buildings,” must be followed. Major Renovations must test for the presence of radon and execute mitigation if radon concentrations are found to be at or above 4pCi/L under typical conditions.
  2. Ventilation Baseline: Meet current ASHRAE Ventilation Standard 62 for commercial and institutional buildings.

Recommended Performance Criteria

  1. Ventilation Performance Validation: In addition to required ventilation baseline criteria above, design the ventilation system so that CO2 concentrations can be monitored continuously in all continuously occupied spaces. Continuously occupied spaces are those intended for human occupancy, excluding spaces intended for other purposes such as storage rooms or equipment rooms. Compare the expected values of CO2 concentrations found in high-occupancy spaces* in the building with those expected from the building design using ASHRAE 62.1. This should be done at 3-month intervals during the initial year of occupancy and annually thereafter.
  2. Carbon Dioxide Limits on Ventilation: In addition to the required and recommended criteria described above, design the ventilation system so that the CO2 concentration in continuously occupied breathing zones (defined as the volume between 3 and 72 inches above the floor and 2 feet or greater distance from walls) cannot exceed 450 parts per million (ppm) above outdoor concentrations. Compare the expected values of CO2 concentrations found in high-occupancy spaces* in the building with those expected from the building design using ASHRAE 62.1 supplemented by the more rigorous CO2 concentration limit of this guideline (I.4D). Do this at 3-month intervals during the initial year of occupancy and annually thereafter.

*Note: For this guideline, “high-occupancy spaces” are defined as spaces in the building with normal occupancy densities higher than the average density for the entire building.

Select which guideline is relevant for the project. ASHRAE 62.2 should be used for low-rise residential buildings, ASHRAE 62.1 should be used for all others. The relevant most recent version is referred to as ASHRAE 62 below.

Implementation in the Design Process:

In Predesign and early design, determine the ASHRAE 62 requirements pertinent to the design, including applicable addenda. Work with the owner to identify high occupancy areas in the building. Determine design occupancy levels to calculate design CO2 emissions in occupied zones. Use estimated design occupancy levels or ASHRAE design occupancy levels by space type.

During Design, incorporate the requirements of ASHRAE 62 into the design process as appropriate for the phase. When the initial ventilation design is completed using ASHRAE 62, compute the expected steady-state CO2 concentrations in high occupancy areas of the building.

Determine the ventilation rate per person needed to limit CO2 concentrations to 450 parts per million (ppm) above the outdoor concentrations in all occupied zones. Use CO2 generation rates based on the activity level of occupants. See Appendix A of the ASHRAE 62 User’s Manual or other source of metabolic rates of building occupants.

Compare these ventilation rates with those calculated in ASHRAE Standard 62.1. The B3 Guideline design ventilation rate for each space is the larger of the value required from the ASHRAE Standard 62.1 or the CO2 concentration requirement above.

Coordinate with the energy analysis process, so that actual design ventilation rates are the same in both ventilation and energy design processes. The design team should consider using strategies that provide the opportunity to reduce energy use associated with ventilation. The list of recommendations includes but is not limited to:

  • CO2 or other occupancy control to reduce ventilation in the building when it is unoccupied.
  • Use of ventilation strategies that increase ventilation efficiency such as displacement ventilation.
  • Use of economizer cycles where possible.
  • Use of heat recovery strategies in the ventilation design chosen.

Through the design process ensure that the requirements of ASHRAE 62 are incorporated into the design process as appropriate for this phase. Specify appropriate instrumentation to monitor CO2 continuously in high occupancy areas of the building.

Update the design ventilation rate as any changes are made to the design occupancy levels planned for the building. Communicate these changes to the parties evaluating energy performance, so that significant changes in ventilation rate can be taken into account in energy calculations and strategies that address minimizing energy use in the building.

In the construction documents and construction administration and buyout of the project, follow a Construction IAQ Management Plan to prevent problems that will adversely affect IAQ when the building is occupied. At a minimum, utilize the requirements found in Section 7 of ASHRAE Standard 62.1 for construction and startup phases of the building. Compare the expected values of CO2 concentrations found in high-occupancy spaces in the building with those expected from the building design using ASHRAE 62. Comparisons should be conducted at 3-month intervals during the initial year of occupancy and annually thereafter.

Design:

  • I.3A: Verification that radon control prevention techniques were incorporated into early design of project.

Final Design:

  • I.3A: Verification that radon control prevention techniques were incorporated into final design of project.
  • I.3B: Verification of compliance with ASHRAE Standard 62 designed airflow rates.
  • I.3C and I.3D: List CO2 designed limits by space.

Closeout:

  • I.3A: Verification that radon control prevention techniques were incorporated into project.
  • I.3B: Verification of compliance with ASHRAE Standard 62 designed airflow rates.
  • I.3C and I.3D: List maximum CO2 commissioned limits by space.

Occupancy – Submitted annually for ten years:

  • I.3C: List maximum monitored CO2 levels by space.

EPA Radon: https://www.epa.gov/radon

EPA Radon Resistant Construction: https://www.epa.gov/radon/radon-resistant-construction-basics-and-techniques#rrct

EPA Indoor Air Quality: https://www.epa.gov/indoor-air-quality-iaq

For I4A: US EPA, Radon Zone Map: https://www.epa.gov/radon/epa-map-radon-zones

ASHRAE Standards 62.1 and 62.2: https://www.ashrae.org/resources–publications/bookstore/standards-62-1–62-2

US EPA, “Radon Prevention in the Design and Construction of Schools and Other Large Buildings,” EPA document 625-R-92-016, June 1994. http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=30004KZ6.txt

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