BuildingAdvice has been analyzing buildings for well over a decade for Carbon Dioxide levels, Temperature, Relative Humidity, and Light among other variables. The results from each building and zone allows us to highlight Trends in the Built Environment like the persistent overventilation of buildings. In fact, according to our research, 77% of all zones in buildings across the United States and Canada are over-ventilated. Of the total population, only 5% are under ventilated, and a modest 18% are acceptable when compared to ASHRAE Standards, U.S. Green Building Council, Indoor Air Quality Association, Health Canada, BOMA, ENERGY STAR, and DOE. Carbon Dioxide levels measured during the occupied times that fall within 700-1000ppm on average are considered acceptable. Those below 700ppm are considered over-ventilated, and those above 1000ppm are considered under ventilated. While results included all building types, the highest concentration of building types experiencing under ventilation were K-12 buildings.
Since 2011 we’ve been supporting hundreds of mechanical and controls contractors as they assess energy performance in facilities. As part of this program they place data logging devices in a building for 7-10 days, and with that data transmitted wirelessly from the building to our cloud-based servers, we run a set of analytics comparing the time resolved data versus Industry Standards. This data is augmented by information gathered in the survey process. The goal is to drive specific building recommendations that drive healthy and comfortable working environments which do not sacrifice operational energy savings from efficiency and maintenance work. In this report example, we can see a Primary Care Facility that has a little of everything going on. Two of the zones fall within the acceptable range overall during the stated occupied times, while one zone is over-ventilated and the other is under ventilated. This example is a great case for demand control ventilation to drive improved air quality for the under ventilated zone, while improving the overall peak levels for the other zones. Additionally, Demand Control Ventilation will also help the zone that is over ventilated by reducing the amount of fresh air delivered to that zone until the carbon dioxide levels rise above the trigger threshold set on the control module.
While there are numerous sources of over ventilation, some common sources we see include but are not limited to: 1) over-sized fans, 2) lower occupancy than design, and 3) economizing/free cooling. Based on field experience and feedback, the predominant source appears to be design and/or commissioning. This could be a function of occupancy fluctuation or a very cautious design that errors on the side of over-ventilation.
In this Carbon Dioxide graph, we see a typical example of facilities that our service provider channel is seeing as a result of their testing, and illustrates the over-ventilation typically seen. Regardless of the source of the problem, it generally represents a great opportunity for correction as part of their Mechanical and/or Controls Service Program. This has been a predictable source of energy savings in almost 8 out of 10 buildings throughout North America.
Why? Because that air, extremely hot, cold, humid or arid, must be reconditioned. That is the equivalent of an energy or utility tax which the owner pays almost daily depending upon conditions. These bills add up and can be a significant source of waste in operating facilities. Correction is relatively inexpensive and has a payback in months, not years.
So, if you are maintaining facilities, you may want to think about taking CO2 measurements to see if your client may be living with a significant source of energy waste that, if corrected, may pay for a portion of your service.