1. Impact of High-Efficiency Filtration Combined with High Ventilation Rates on Indoor Particle Concentrations and Energy Usage in Office Buildings
National Air Filtration Association (NAFA)
Friday, August 28, 2015
Michael S. Waring
Associate Professor
Director of Architectural Engineering Program
Civil, Architectural and Environmental Engineering at Drexel University
Indoor Environment Research Group (
Drexel Air Resources Research Laboratory (DARRL)
Building Science & Engineering Group (BSEG)

2. Introduction Motivation
Introduce upcoming NAFA + ASHRAE funded research project
Examine the impact of using high efficiency filters at the same time as using high ventilation rates (VRs) in offices
Why do this work?
ASHRAE minimum for VRs in offices is ~17 CFM/person
Yet, increased VRs, particularly in offices, may have many positive effects on occupant wellbeing
Lower infection risk, less Sick Building Syndrome (SBS), reduced absenteeism, better productivity and decision making
However, higher VRs will increase particulate matter (PM) indoors
PM exposure = reduced health!
Impact of High-Efficiency Filtration + High Ventilation Rates in Offices
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3. Introduction Motivation
E.g. Impact of CO2 exposure on human decision making:
Experiments:
Mock office
Clean air
CO2 added to:
600, 1000,
and 2500 ppm
Aptitude testing
Satish et al. (2014) EHP
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4. Methodology Filtration impact field and modeling study
Conduct field experiments to demonstrate ability of filters of different efficiencies to mitigate indoor PM concentrations with varying VRs
Third floor of Drexel University campus building
Measure in ambient air, supply air, and return air:
Fine particles (TSI DustTrak DRX 8533)
Ozone (2B Technologies 205)
Nitrogen oxides (2B Technologies 405)
Carbon dioxide (PP Systems, WMA-4)
Fan energy determined with installed sub-meters
Other energy used with building automation system (BAS) reporting
Model impacts for 14 cities in U.S. climate zones
Impact of High-Efficiency Filtration + High Ventilation Rates in Offices
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5. Methodology Filtration impact field study
Conduct three weeks of testing, at three times in one year:
3 weeks in
Winter
3 weeks in
Spring
3 weeks in
Summer
At least
63 days
of testing
Week 1
Week 2
Week 3
MERV 8
MERV 11
MERV 15
Day
VR High Low High Med High Low High
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6. Methodology Filtration impact field study
Air handling unit (AHU) and sampling schematic:
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7. Methodology Filtration impact field study
E.g., PM2.5 sampling at three locations:
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8. Methodology Filtration impact field study
E.g., PM2.5 indoor/outdoor (I/O) ratios as a function of OA/SA:
1.0
MERV 8 pre-filter + MERV 11 V-filter, Supply flow = ~5500 cfm
0.8
I/O ratio
0.6
0.4
0.2
0.3
0.4
0.5
0.6
Fraction of Outdoor Air (OA) / Supply Air (SA)
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9. Future Impacts Deliverables
Literature review on the impact of high efficiency filtration at mitigating exposure to indoor PM of outdoor origin at different VR conditions
Description of Quality Control/Quality Assurance (QA/QC)
Full time series of all measured data over 63 days of experiments
Measured I/O ratios at the different VRs and filtration efficiencies
Results of the modeling study over the 14 U.S. cities
Cost-benefit analysis of using higher efficiency filters in terms of filter cost and fan energy requirements for a typical year of operation, placed in context of energy needed to supply higher VR
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10. Future Impacts Benefit to NAFA and society
Demonstration of ability to control PM, even at high VRs
Improve work performance and health in offices by using higher VRs, with least negative side effects
Contextualization of energy needed for PM control at high VRs
Influence building design/operation of healthy indoor spaces
Advance NAFA mission to:
“educate end-users about the importance of air filtration”
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11. Questions? Acknowledgments Special thanks to:
National Air Filtration Association (NAFA)
American Society for Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE), New Investigator Award
Questions?
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