CO2 Monitoring for LEED Credit

CO2 monitoring for LEED credit is part of an overall indoor environmental quality (IEQ) strategy designed to balance the need for clean, comfortable air for building occupants with minimal energy usage. Proper CO2 monitoring can gain the LEED project points towards the goal of LEED certification.

Although LEED v4 is now available, teams may still register projects under LEED v3/2009 until June 1, 2015.

What is the same between LEED v3 and v4?

Before the CO2 monitoring point can be awarded, there are 2 prerequisites: Minimum Indoor Air Quality Performance, and Environmental Tobacco Smoke (ETS) Control. The intent of the Minimum Indoor Air Quality Performance Prerequisite is to establish minimum indoor air quality (IAQ) in buildings, thus contributing to the comfort and well-being of the occupants. The intent the Environmental Tobacco Smoke Control prerequisite is to prevent or minimize exposure of building occupants, indoor surfaces and ventilation air distribution systems to environmental tobacco smoke.

Once the prerequisites are met, both LEED versions allow for CO2 monitors placed in densely occupied spaces to be used to monitor IAQ, and to give a warning if the CO2 levels rise above pre-determined limits.

In both LEED versions, using CO2 monitors as part of an overall IAQ strategy is worth at most 1 credit.

In addition, both LEED versions require CO2 sensors to be re-calibrated every 5 years, and for the sensors to be accurate to within 75ppm or 5% of the actual CO2 level, whichever is greater.

What is different between LEED v3 and v4?

Before gaining IEQ points in LEED v4, a new “green cleaning” prerequisite has been added for commercial buildings. This includes green cleaning procedures, materials, and services that are within the building and site management’s control, and include the organization responsible for cleaning the building and building site.

LEED v4 classifies building projects into one of four standards: Building Design & Construction (BD+C), Interior Design & Construction (ID+C), Building Operations & Maintenance (O+M) and LEED for neighborhood development (ND). Within these standards, there are several new project variations. For example, in LEED v3, there were project variations under BD+C for new construction, core and shell, schools, retail and healthcare. In LEED v4, new BD+C variations include data centers, hospitality, warehouses, residential homes, and multi-family midrise homes.

What makes this more complicated is that for every project variation, the LEED specification for using CO2 sensors for IAQ is slightly different. However, the most common requirement under the new “Enhanced Indoor Air Quality Strategies” credit category found in most of the projects is:

Monitor CO2 concentrations within all densely occupied spaces. CO2 monitors must be between 3 and 6 feet (900 and 1 800 millimeters) above the floor. CO2 monitors must have an audible or visual indicator or alert the building automation system if the sensed CO2 concentration exceeds the setpoint by more than 10%. Calculate appropriate CO2 setpoints using methods in ASHRAE 62.1–2010, Appendix C.

While the LEED standard continues to evolve, measuring CO2 for IAQ continues to play a part in the overall goal of safe and energy-efficient buildings.


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