Last week, we covered bipolar ionization in detail, explaining how it is a very useful HVAC system attachment that can easily be installed to prevent the spread of viruses, bacteria, and other airborne pathogens. This tech has been around for a little while and seems especially useful to prevent the spread of COVID-19. However, bipolar ionization isn’t the cheapest option to prevent to accomplish this goal. That crown goes to a process called air flushing.
What is air flushing?
Every building is required to have carbon monoxide detectors connected to a Direct Open Air System (DOAS). If the parts per million detected in the air rises above normal levels, the DOAS system in your building will open up and let in fresh air; it’s a safety protocol. Air flushing is a version of this process that fully replaces all air in your building. Put simply, air flushing periodically replaces indoor air with fresh air at intervals you can set. How is this done? Well, the process goes like this:
- First, your facility’s building automation system is calibrated to handle air flushing. This will control the use of your building’s DOAS and HVAC systems.
- In the background, your automation system calculates the total volume of the cubic air, taking into account the CFMs your DOAS fans can draw.
- Finally, given all the data collected, all air is flushed out of your building and replaced with new outdoor air.
Air flushing is a much cheaper and less invasive alternative to bipolar ionization because it doesn’t require adding to or replacing any of your HVAC system.
What’s required to set up air flushing?
To properly set up air flushing, your facility should have a DOAS system (which is required by law anyways), a working HVAC system, and, most importantly, a building automation system (BAS). An automation system is required because it’s the initiator for the air flush; algorithms programmed into it control when flushing actually happens, so without it, air flushing would not be possible.
The drawback of air flushing
Integrating air flushing comes at one cost: energy consumption. It takes a fair amount of energy to flush the full air volume out of a building and replace it with new air. The bigger your facility is, the more energy this process will consume. That’s the main drawback.
Bipolar ionization vs air flushing: which should you choose?
The ultimate determinant of which one you choose is cost. Can you afford an investment of a few thousand to tens of thousands (depending on your building size)? If so, bipolar ionization is a good option because it has an immediate cost but doesn’t take extra energy to use. Air flushing on the other hand comes at a very minimal cost upfront, but does consume energy to use, so the ultimate cost of air purification is spread out. Which option you should choose is dependent on your organization’s budget and goals.
How much does air flushing cost?
EnergyLink integrated air flushing for Columbia Independent Schools to make their school as safe as possible for their young students. To install air flushing for this 100,000 sqft. facility, which is single-level, had offices, classrooms, and a gym, it only cost $400. The price will vary based on the size of your building, but this is a good way to measure how much air flushing may cost for your facility.
In terms of the additional energy costs of doing air flushing, CIS chose to flush their facility four times per week, which comes at an energy consumption cost between these two tables:
Annual cost of flushing 3 nights per week
| Season | Additional Cost ($) |
| Summer months total | 638.67 |
| Winter months total | 1,714.67 |
| Shoulder months total | 587.89 |
| Annual months total | 2,941.22 |
Annual cost of flushing 5 nights per week
| Season | Additional Cost ($) |
| Summer months total | 1,064.45 |
| Winter months total | 2,857.78 |
| Shoulder months total | 979.81 |
| Annual months total | 4,902.04 |
