I.4 Ventilation Design

Intent
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. Encourage better indoor air quality by recommending that, in addition, ventilation design intent be demonstrated on a regular basis to building owners and operators. 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 Path, 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 located in these 68 counties whose exterior envelopes have more than 40% of their surface areas in contact with the ground must follow the same EPA guidance.
2. Ventilation Baseline: meet current ASHRAE ventilation standard 62.1 for commercial and institutional buildings (as of the writing of this guideline ASHRAE 62.1-2010 Updates are scheduled to be issued every three years thereafter.)

Recommended Performance Criteria

3. 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 three-month intervals during the initial year of occupancy and annually thereafter.
4. Carbon Dioxide Limits on Ventilation: in addition to required and recommended criteria within this guideline above design the ventilation system so that they 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) shall not exceed 450 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 three-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.

Compliance Tools and Resources

• For Item A: US EPA, Radon zone map: www.epa.gov/iaq/radon/zonemap.html
• For Item A: US EPA, "Radon Prevention in the Design and Construction of Schools and other Large Buildings", EPA document 625-R-92-016, June 1994. www.epa.gov/iaq/radon.pubs/index.html
• For Items B, C, D: Reference Standard: ASHRAE (2007). ANSI/ASHRAE Standard 62.1-2007: Ventilation for acceptable indoor air quality. Atlanta, GA, USA, American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc.
• For Items B, C, D: ASHRAE (2005). 62.1 User's Manual, ANSI/ASHRAE Standard 62.1-2007, Ventilation for Acceptable Indoor Air Quality. Atlanta, GA, ASHRAE.
• For Item D: B3 Guidelines Appendix I-4 Calculating CO2 Concentrations in a Zone