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.