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Guideline I.3: Ventilation


To promote good indoor air quality by implementing appropriate outdoor air ventilation and exhaust systems and limiting the ingress of particulates and soil gases into the building.

Required Performance Criteria

Guidelines I.3A, I.3D, I.3F, and I.3G are required for New Construction projects and to Major Renovation projects that include replacement or alteration of relevant systems. Guidelines I.3B, I.3C, and I.3E are required only for New Construction projects that include 20,000 gsf or more of conditioned space, and Major Renovation projects that include 20,000 gsf or more of conditioned space and include construction, replacement, or alteration of relevant systems.

  1. Ventilation baseline: Design mechanical systems to meet the minimum outdoor air ventilation rates for all mechanically ventilated zones as specified in the current ASHRAE Ventilation Standard 62.1 (or Standard 62.2 for residential buildings).
  2. Monitor outdoor airflow rates or perform checks annually to verify ventilation rates are meeting the ASHRAE minimums in all large spaces (1,000 sq. ft. or more) which are high occupancy (25 people or more). Small ventilation systems serving a total of 5,000 sq. ft. or less are exempt from this requirement.
  3. Meet ASHRAE 62.1 Air Class (1–4) requirements for recirculation of indoor air and enclose and negatively pressurize the following spaces:
    1. Chemical storage rooms or other areas with identified risk of airborne hazard.
    2. Printer/copier rooms with high volume laser printers, copiers, and multifunctional device (MFDs), (i.e., printing equipment with dry toner). Air from these rooms should be treated as Air Class 4. Laser printers/copiers meeting Blue Angel low emission criteria RAL-UZ 171 are exempted from these requirements and are permitted to be located in an open-office space without triggering exhaust requirements.
  4. All mechanical ventilation equipment designed to deliver outdoor air must be equipped with minimum efficiency reporting value (MERV) 11 filters or better. Equipment designed to recirculate only indoor air must be equipped with MERV 8 filters or better. If the specified equipment cannot accept MERV 11 or MERV 8 respectively, specify the highest MERV-rated filter that will fit.
  5. Install permanent entryway systems such as walk-off mats or grille or grate systems at least 10 ft. long in the primary direction of travel at all regularly used entrances.
  6. Meet the Outdoor Air Intake Minimum Separation Distances as specified in ASHRAE 62.1, Section 5.5 and Chart 5.5.1.
  7. Control radon and other hazardous soil gas:
    1. For new buildings and additions, control radon and other harmful soil gas by meeting the requirements of ANSI CC-1000: Soil Gas Control Systems in New Construction of Building. This is required for all projects in Minnesota, both EPA Zone 1 and Zone 2. This includes but is not limited to:
      1. Creation of a soil gas collection plenum (this plenum is often a sub-slab gravel or crushed stone bed into which soil gas infiltrates).
      2. Creation of a continuous sealed barrier between occupied space and the soil gas collection plenum.
      3. Soil gas vent piping that has the capability to, at minimum, passively vent soil gas from the collection plenum through the roof of the building.

      Testing of radon levels after construction is required; if radon levels are found to be above 2 picocuries per liter (pCi/L) the project must install an Active Soil Depressurization System (ASD) per ANSI CC-1000.

    2. For all remodeled buildings and remodeled portions of buildings regardless of type, testing and remediation must be performed as directed in the most relevant of the following standards:
      1. For schools and large buildings: American National Standards Institute Radon Mitigation System for Schools and Large Buildings (ANSI RMS-LB).
      2. For Multifamily Buildings: American National Standards Institute Radon Mitigation System for Multifamily Buildings (ANSI RMS-MF).

Recommended Performance Criteria

  1. Implement a demand-controlled ventilation system.
  2. Develop and implement a green cleaning protocol using products that comply with EPA Safer Choice or Green Seal labels.

In almost all settings, ventilation with outdoor air is critical to ensure proper indoor air quality. Research has shown that occupant health, cognition, and productivity all benefit from the introduction of fresh air and the exhaust of polluted indoor air. Determining the proper outdoor air ventilation rate is the primary topic of ASHRAE Guideline 62. ASHRAE 62.2 should be used for residential buildings; ASHRAE 62.1 should be used for all others. Below, the most recent version is referred to simply as ASHRAE 62.

In the early design stage, work with the owner to identify the expected occupancy and activity type in all areas of the building, and use these or ASHRAE design occupancy levels to begin ventilation rate calculations. Determine the appropriate ASHRAE procedure for calculating these, either 1) the Ventilation Rate Procedure (VRP), 2) the Indoor Air Quality Procedure (IAQP), or 3) the Natural Ventilation Procedure (NVP). If using the standard VRP, it is recommended to adopt an air distribution configuration such as displacement ventilation that improves the zone air distribution effectiveness and reduces the total zone outdoor airflow. This may also result in reduced energy consumption and help meet SB 2030 energy targets.

Early in the design phase, determine a strategy for controlling emissions from printers, copiers, and MFDs. If these devices will use dry toner, emissions to the air must be contained within an enclosed room and exhausted directly to the outdoors. Alternatives to this approach include using inkjet printers rather than laser printers, or requiring laser printers to meet the emission certification of Blue Angel RAL-UZ 171. Such printers could be dispersed in an open-office setting, for example.

Throughout mechanical design, the mechanical design team should coordinate with the energy analysis team so that ventilation rates are consistent in both processes. Update the design ventilation rate as any changes are made to the occupancy levels planned for the building. Communicate these changes to the parties evaluating energy performance so that ventilation rates compliant with these guidelines can be taken into account in energy calculations. The SB 2030 program considers ventilation rates in the creation of the SB 2030 Energy Standard; ensuring that these rates are noted allows an appropriate standard to be created.

The mechanical 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:

  • Use of CO2 sensors or other types of occupancy sensors to reduce ventilation in spaces when they are 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.

For many building types, use of these strategies can significantly reduce total energy consumption and help the building achieve challenging SB 2030 energy targets.

For ventilation systems serving over 5000 sq. ft., determine how outdoor airflow will be monitored. Yearly spot checks are allowed, but if continuous monitoring is desired, ensure that air flow can be measured for all large spaces that are high occupancy and that these values are reported to the Building Automation System (BAS) or other tracking and recording device. These systems should be shown on the HVAC plans.

All new buildings, regardless of type or location, must protect against hazardous soil gases, including radon, using at least the passive measures found in the ANSI CC-1000 standard. Radon is a soil gas, and typically enters buildings through air leaks at or below grade. Therefore, passive measures such as the creation of a robust air barrier between the building’s at/below grade space and the ground is critical and effective. Further control is offered by passively venting the ground below the building’s floor slab. This is typically done with a sub-slab layer of crushed stone and perforated drain tile, which can collect soil gases migrating through the stone layer. These gases are safely routed through a vertical ventilation stack and released above the roof of the building. The ANSI CC-1000 Standards guide engineers on the design, layout, and venting requirements of the sub-slab collection plenum and vent system. Be aware that each vertical ventilation stack can vent only a limited area, and may require space for a powered fan.

Following construction, testing radon levels is also required for all buildings, regardless of type or location. Testing should be performed per CC-1000 Annex D, and be performed for radon and any other hazardous soil gas identified as a risk for the building. If radon levels are found above 2 piC/L, the passive stack ventilation system must be retrofitted with fans to provide a powered ventilation assist. These fans will require extra space for installation and access in case of replacement or maintenance. They will also require a source of electrical power since they must run continuously. Take these issues into consideration at the design stage to minimize expenses if radon testing shows fans are required.


  • 3E: Submit preliminary building plans showing the location of all primary entrances including space for permanent entryway systems.

Final Design:

  • 3A: Submit ASHRAE 62 calculations for each zone, showing the required and planned ventilation rate in each.
  • 3B: Identify the chosen method for monitoring outdoor airflow rates during operations (permanent monitoring system or annual spot checks) and, if appropriate, submit an HVAC plan identifying the monitoring equipment.
  • 3C: Submit HVAC plans identifying the ASHRAE Air Class of each ventilation zone, along with the ventilation and/or dedicated exhaust systems that will serve them.
  • 3D: Submit HVAC specifications or plans detailing the level of filtration on all mechanical ventilation equipment.
  • 3E: Submit building plans showing the location of all primary entrances and the type and placement of permanent entryway systems.
  • 3F: Submit HVAC plans showing the location of all outdoor air intakes relative to the nearest pollutant or other contaminant sources with notes indicating the distance between them.
  • 3G: Submit building plans showing all critical components of the soil gas control system, including the design and details of the sub-slab collection plenum, air barrier, and size, location, and area served by each vent stack.
  • 3H: Submit HVAC plans and specifications detailing the location and type of equipment and operating parameters of the demand-controlled ventilation system.


  • 3G: Submit results from radon tests within one year of occupancy. If radon levels are measured above 2 piC/L, submit documentation showing installation of fans and/or other components of the ASD.
  • 3A, I.3C, I.3D, and I.3H (Submitted under P.1): Ensure that the mechanical system has been commissioned and documented according to the requirements of Guideline P.1.
  • 3I: Submit a Green Cleaning Protocol that specifies the types of cleaning products and outlines the procedures that will be used to clean the premises.

Occupancy – Submitted annually for ten years:

  • 3B: Annually submit outdoor airflow rates measured for each high occupancy zone (>25 people/1000 sq. ft.) along with the associated ASHRAE 62-calculated minimum rate.