The LEED standard recognizes the usefulness of CO2 to monitor Indoor Air Quality. But did you know that the LEED standard for new construction includes provisions for measuring CO2 levels outdoors?
EQ1.2 – Outdoor Air Delivery Monitoring, a possible credit in the United States Green Building Council’s LEED Certification for New Construction, calls for either carbon dioxide monitors or outdoor airflow monitors that signal when fresh air is needed. Depending on the configuration of the HVAC system, outdoor CO2 measurements can be used to provide a baseline for indoor air quality.
While ambient outdoor air was historically considered 400ppm, the LEED credit now provides for CO2 levels inside the building to be in proportion to the CO2 level in outdoor air.
Why the change? The 400 ppm standard as stated in ASHRAE 62.1 -2004 and -2007 did not account for generally rising ambient CO2 levels or "CO2 islands” in metropolitan areas. The revised standard enables some new building HVAC systems to take an outdoor CO2 reading in close proximity to the building, then to bring in fresh air when indoor CO2 levels become a percentage higher than outdoor air.
Note that outdoor CO2 measurement is not required for LEED credit, and may only be useful under certain scenarios. Companies seeking LEED certified new buildings should consult a LEED-certified expert for the most recent rules.
Also note that the ASHRAE recommended 800ppm CO2 limit for office buildings still apply, as well as current ASHRAE workplace safety limits.
To monitor outdoor CO2 levels, companies can use our eSense Low-Temperature CO2 Meter with a built-in heating element and IP65 outdoor rating. This meter will transmit the current CO2 levels outdoors, from which a baseline can be derived.