Recognizing that the ventilation rate procedure in its indoor air quality standard may be difficult to apply in existing buildings, ASHRAE says it is proposing an alternate compliance path.

Proposed addendum b is one of six addenda to ANSI/ASHRAE Standard 62.1-2013, Ventilation for Acceptable Indoor Air Quality. Public comment is open until Oct. 5, 2014. To comment or learn more, visit www.ashrae.org/publicreviews.

Responding to increasing interest in sustainability in existing buildings, Standard 62.1 is cited frequently as a criterion for evaluating ventilation systems in existing buildings. Examples include LEED-EBOM, Energy Star, and bEQ. Some building categories, such as K-12 schools and office buildings, are frequently renovated and often have multiple zone systems that provide HVAC to similar space types.

Section 6 (including the ventilation rate procedure) of the standard was developed as a design standard. As such, Section 6 and Normative Appendix A have the complexity to allow for many complex system designs and airflow pathways. The scope of the standard states in part that “the provisions of this standard are not intended to be applied retroactively when the standard is used as a mandatory regulation or code.”

“For existing buildings, it may be difficult to apply the ventilation rate procedure (VRP), particularly for buildings with multiple-zone recirculating ventilation systems,” said Roger Hedrick, chair of the Standard 62.1 committee. “This is because determination of some of the values needed to calculate ventilation rates may be difficult or impossible because required information is not available. An example is system ventilation efficiency (Ev), used in equation 6.2.5.4.”

Proposed addendum b provides an alternate path of compliance that is needed by the marketplace for those situations where information required to determine system performance is unavailable or for smaller facilities with straightforward multiple zone applications, he said.

Also open for public comment is proposed addendum c, which would revise the current definition of environmental tobacco smoke (ETS) to include emissions from electronic smoking devices and from smoking of cannabis (now allowed by some jurisdictions). The existing requirements for separation of ETS-free spaces from ETS spaces remain unchanged. The proposed addendum also would clarify that provision of acceptable indoor air quality is incompatible with the presence of ETS, including cannabis smoke and e-cigarette emissions.

Other addenda open for public comment include the following:

• d adds an exception to Section 5.8 (Particulate Matter Removal). In sensible-only cooling, the equipment’s purpose is to provide only sensible cooling. A chilled beam is an example of this type of equipment.  In this case the coil surface would never be wet and the filtration requirements intended for wetted surfaces should not apply. Latent cooling for these systems would be provided by other portions of the system, such as cooling coils in the primary air stream, which would then have independent upstream air filtration.

• e modifies Section 8, Operation and Maintenance, incorporating calibration requirements for airflow monitoring sensors and systems and harmonizes Table 8.4.1 (Minimum Maintenance Activity and Frequency) with ASHRAE/ACCA Standard 180-2012, Standard Practice for Inspection and Maintenance of Commercial-Building HVAC Systems.

• p – At present, all occupancy types are required to provide no less than the area component of the minimum ventilation rate during periods when the space is “expected to be occupied.” A previous interpretation clarified that this prohibited the use of occupancy sensors to reduce the ventilation rate to zero during these times. This proposed addendum would allow the ventilation to be reduced to zero through the use of occupancy sensors (not through contaminant or CO2 measurements) for spaces of selected occupancy types.

• q modifies Section 5.2 (Exhaust Duct Location) to clarify requirements by including air classes instead of descriptive language, and modifies the requirements by allowing positively pressurized exhaust ducts inside the space of origin.