Although most buildings won’t have trouble meeting this prerequisite, there are some challenges that can sneak up unexpectedly if you don’t address it early. 

The most important thing to confirm is that ventilation air is provided to all occupiable spaces in the building. This may seem obvious, but the prerequisite applies to areas that are sometimes overlooked, such as circulation, back of house spaces, and active storage rooms. Check out the EQ Overview section in the LEED Reference Guide for all of the space types that must be addressed here.

The referenced standard for this prerequisite is ASHRAE 62.1-2010, which is a newer version than that referenced in LEED 2009. For mechanically ventilated buildings, this standard will be very similar for users familiar with previous versions of the 62.1 standard.

For naturally ventilated buildings, the newer standard effectively prohibits natural ventilation via operable openings as a stand-alone strategy. This is because it requires spaces to be mechanically ventilated whenever the operable windows are closed.

Fortunately for multifamily projects, USGBC released an addendum that provides alternative requirements for naturally ventilated residential units. The alternative requirements focus on providing operable windows in each residential unit, and allows teams to avoid the mechanical ventilation required by the ASHRAE standard. See the ventilation calculations exercise to learn more about the information that you’ll need to complete this prerequisite.

What’s New in LEED v4

• The prerequisites now reference ASHRAE Standard 62.1 version 2010.
• Window configuration and ceiling height are now considered in ASHRAE 62.1–2010 natural ventilation calculations.
• ASHRAE 62.1-2010 requires supplementary mechanical ventilation systems for naturally ventilated spaces in some cases.
• Teams must confirm the appropriate use of natural ventilation through the flow chart in CIBSE AM10, Figure 2.8.
• For mechanically ventilated spaces, Option 1, teams are now required compliance with the minimum requirements of ASHRAE Standard 62.1–2010, Sections 4–7; the requirements of CEN Standard EN 13779–2007, Ventilation for nonresidential buildings, Performance requirements for ventilation and room conditioning systems, excluding Sections 7.3 (Thermal environment), 7.6 (Acoustic environment), A.16, and A.17 (for mechanically ventilated spaces, Option 2); or the minimum requirements of ASHRAE Standard 62.1-2010, Section 4 (for naturally ventilated spaces).
• CEN requirements, instead of ASHRAE 62.1–2010, are now allowed for demonstrating achievement for projects outside the U.S.
• The maintenance program must comply with ASHRAE 62.1-2010, Section 8.

Readiness Review Questions

• Is the building mechanically ventilated, naturally ventilated, or mixed-mode? ASHRAE Standard 62.1-2010 addresses natural and mechanical ventilation systems using different guidelines and criteria. Mixed-mode systems must demonstrate compliance while operating in mechanical mode only.
• Do building systems supply ventilation air to all occupiable areas of the building? Occupiable areas include office spaces, corridors, active storage areas, common areas, and so on. At the beginning of the EQ section, the LEED Reference Guide offers a complete list of occupiable spaces for your building type.
• Do you have a building automation system (BAS) that measures outdoor air? If your building does not use a BAS to monitor the rate of outside airflow through the ventilation system, manual measurements of outside airflow must be taken at each air-handling unit. 

• Have the ventilation systems been tested or balanced in the last two years? If yes, do you have documentation on the measurements of outdoor airflow? Recent testing reports, which include ventilation rate procedure (VRP) calculations, may be used to compare measured outside airflow to the ASHRAE 62.1-2010 requirements. 

• Do occupants and building maintenance staff feel that the building is well-ventilated? Does the air seem fresh? Stuffy? Odorous? Occupant feedback is a valuable early-detection tool to know if your ventilation system is operating properly and complying with ASHRAE 62.1-2010 standards. 

• Do you have mechanical drawings that are helpful for managing ventilation systems and maintaining outdoor air flow calculations as required by ASHRAE? Do you have an HVAC preventive maintenance program? A set of accurate mechanical drawings will help you to determine where outside airflow measurements should be taken and provide manufacturer product information that can be useful in developing an ongoing preventive maintenance program to ensure proper system performance.
• Are your engineers trained and equipped to take outdoor airflow measurements? If not, is there an engineering firm that you can use to help complete these tests?