With air conditioning being available for a little more than 100 years now, the ability to provide both heating and cooling to a space has led to our migration to a life with 90 percent of our time being spent indoors. While there have been many improvements to HVAC (heating, ventilation and air conditioning) over recent years, the most overlooked strategy for improvement is what the industry calls DCV (demand control ventilation).
When the first version of the ASHRAE ventilation guidelines (62.1) were published in 1973, this was the first time that controls were really looked at to improve indoor air quality in buildings, with CO2 being used as a means to determine the number of occupants in a space. People breathe out CO2 at a constant rate so using CO2 to determine how much heating, cooling or ventilation to provide to a space allows for both better indoor air quality but also great energy efficiency.
There are however other, often overlooked, indoor environmental factors that make for good triggers to supply more outside air, turn on filtration or supply humidification to a space. It’s therefore time for the building management sector to start thinking, not just about space demand (i.e. how many people are there and therefore just CO2), but to also start focusing on the dynamic ways spaces can be improved.
In addition, there is no lower cost way to save between 10-40% energy in a building (while improving IAQ) than adding DCV to a building.
In many industrial settings, we see huge filtration systems controlled by a simple on/off switch, with motion sensors or perhaps even a work mat that turns on a fume hood. In some instances, the trigger for the manual control of a fan is a physical reaction or an audible alarm.
The first problem with this system is that most of these large fans are variable speed, meaning that they can run at between 20% and 100% speed. The problem with a simple on/off switch is that the fan will always go to 100% with the result that it’s using the most energy and making the most noise. This isn’t ideal for variable speed fans as they generally like to be cycled up slowly with the life of the fan and the associated filters being limited. Using VOCs or perhaps dust (PM1 through 10 is a good trigger for example in a welding facility) tied to a variable speed controller can both lead to better performance and longevity for the fan but also is likely to result in better indoor air quality, and therefore fewer workplace claims and lowered risk for workers.
Print rooms and change rooms
Even in office settings VOCs can be a better trigger for improved exhaust in a building. Print rooms typically have the highest VOCs in an office setting. Best practice is having them both under negative pressure, while also making sure to exhaust them as VOC level increase is important for overall health outcomes.
In a change room, VOCs and humidity are both very good triggers for exhaust. VOCs are often given off by shampoos, perfumes and other products which are used at differing levels by occupants. It could be that just 2 occupants are enough for creating a need to exhaust a change room (making CO2 less effective). The same goes for humidity, as a very steamy space for an extended period of time could lead to mold issues if the ventilation system isn’t doing anything to address extended periods of high humidity.
So while the ASHRAE standard 62.1 for ventilation only focuses on CO2 as a trigger for saving energy and improving indoor air quality, there are many other IAQ factors that, depending on the building use, could be even more effective. It’s good to start thinking in terms of creating dynamic indoor air improvements through sensors and controls, rather than to simply think about DCV as it was conceived in the 1970s. We have the tools to do so much better for occupants.