Reopen with Confidence Series
Fact or Fiction? Has Covid–19 Killed Customer Concerns About Controlling Operating Costs?
Covid-19 Solutions: Increasing PM 2.5 filtration
We know that adding or increasing filtration increases fan pressure, filter pressure drops, and ultimately power consumption. But how much filtration is enough, and how much is it going to cost? Building owners want to reopen in a safe, healthy and cost-effective way – the question is, what’s the new balance? With ASHRAE and CDC recommending increased ventilation and filtration to mitigate Covid-19 exposure, building owners are now placed in a new situation to determine the best solution for them. Balancing these factors is a great opportunity for you to show your expertise and win their confidence. Read on!
Why filtration is important right now
Over the summer, New York State Governor Cuomo raised the stakes by stating that “Any malls that will open in New York, large malls, we will make it mandatory that they have air filtration systems that can filter out the Covid virus,” at a press briefing on June 29th. Both ASHRAE and CDC are recommending higher MERV filtration to eliminate fine particles and even filter out viruses.
ASHRAE recommends, “that mechanical filter efficiency be at least MERV 13 and preferable MERV 14 or better to help mitigate the transmission of infectious aerosols. Many existing HVAC systems were designed and installed to operate using MERV 6 to MERV 8 filters. While MERV 13 and greater filters are better at removing particles in the 0.3-micron to 1-micron diameter size (the size of many virus particles) the higher efficiency does not come without a penalty.”i
Filtration comes at a cost; or does it?
OK – so we know that higher MERV filters remove smaller particles and both ASHRAE and CDC are clear about this. What about the cost to operate these more capable filters? It’s not as steep as you would expect, given the new objective of balancing safety, health, and cost of operations.
In a study presented at an ASHRAE conference in 2013, 14 rooftop units ranging from 8.5 to 20 tons were fitted with MERV 8, 11, and 14 filters and evaluated for system airflow, filter and coil pressure drop, fan pressure rise, and power draw.ii The median power increase across all systems was only 3.5%, while airflow was reduced 12.5%. Interestingly, the study determined that moving from MERV 8 to MERV 11 did not increase the clean air delivery rate enough to outweigh increased energy costs, while moving to MERV 14 did.
So, it's safe to say that while energy costs will definitely increase, the median fan power consumption will increase only 3.5%. What makes a greater impact is the operating schedule. Paying attention to the before/after operating and occupancy schedules is what is really going to make the difference. For example, if buildings are operating on a reduced fixed schedule, perhaps 800 am to 500 pm, with reduced occupancy to say, 50%, try adjusting the operating schedule to 9 hours instead of 12 hours. (Remember when people would work late to 8 pm?) The real power consumption on units would drop 25% because of the reduced operating schedule, and increase only 3.5% during 9 hours of runtime – for a total energy savings of 20.2%.
So, it's possible to both increase filtration and reduce energy consumption through better analysis and control.
What can you do to help your customers?
It might be a good time to run a Building Scorecard as part of a Building Assessment. We can’t emphasize enough that it is really important to complete a Building Scorecard first before making any recommendations. You can download a sample Building Scorecard here:
Establishing an energy consumption baseline helps you understand what the current energy situation is – and as you complete your walk-thru building assessment, you will be able to highlight which areas will benefit the most. Combining this with an IEQ Assessment will help you balance Health, Comfort, Safety with Cost objectives.
You’ll also be able to point out that increased filtration will not be as expensive as expected, and by optimizing the operating and occupancy schedule, there’s opportunity to actually save money in the process while meeting their goals.
- Log into your BuildingAdvice Account and familiarize yourself with the inputs to create a customized Building Scorecard.
- Develop a target list of buildings to approach.
- On your next sales call, offer to complete a Building Scorecard to help owners and operators understand their building's energy consumption compared to a similar peer set.
- Next, when making service, repairs or upgrades, you will have a baseline to use in comparing before/after scenarios for your proposals.
- Follow up with an IEQ assessment to illustrate what's happening inside the building from an air quality perspective -- useful when discussing ventilation, filtration, and outside air concerns.
Be safe, and get out there!
Referencesi) ASHRAE - https://www.ashrae.org/technical-resources/building-readiness#ecip, 2020
Ii) ASHRAE - ”The Relationship between Filter Pressure Drop, Indoor Air Quality, and Energy Consumption in Rooftop HVAC Units“, Jeffrey Siegel, PhD, Member ASHRAE; Atila Novoselac, PhD, Member ASHRAE; Marwa Zaatari, Student Member ASHRAE. Presented at ASHRAE, 2013.
Filtration Quick Reference Guide