Impact of High Efficiency Filtration Combined with High Ventilation Rates on Indoor Particle Concentrations and Energy Usage in Office Buildings Michael Waring, PhD Drexel University

Impact of High-Efficiency Filtration Combined with High Ventilation Rates on Indoor Particle Concentrations and Energy Usage in Office Buildings NAFA Technical Seminar 2016 Phoenix, AZ April 7, 2016 Michael S. WARING*, Tom Ben-David, Sheng Wang *Associate Professor Civil, Architectural and Environmental Engineering Drexel University, Philadelphia, PA Indoor Environment Research Group (http://www.indoor-envi.com/) Drexel Air Resources Research Laboratory (DARRL) Building Science & Engineering Group (BSEG) msw59@drexel.edu

Introduction IAQ, building energy, and ventilation People spend 87% of time indoors Indoor exposure to air pollutants is critical Buildings consume ~40% of energy in the U.S. 44% more than transportation 36% more than industry Office stock is a subsector that consumes much energy Higher ventilation rates increase productivity and reduce absenteeism and sick building syndrome in offices However, higher ventilation rates may introduce more PM and ozone, which have health impacts due to exposure Filters may be an effective way to manage PM at higher ventilation How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 3/34

Introduction Cost and benefits of filtration Studies estimate the cost of filtration to be $2.5~$15 /occ/year Depending on filter type and MERV Studies suggest that the cost of filtration outweighs its cost E.g. Azimi & Stephens, 2013; Bekö et al., 2008; Hänninen et al., 2005; Montgomery at al., 2015; Quang et al., 2013 Significant reduction in morbidity and mortality Monetized benefits are estimated $20~$150 /occ/year Interplay of ventilation and filtration affects indoor air quality and building energy consumption How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 4/34

Research Overview NAFA funded research project Question: Can filters protect occupants at high air exchange rates? And is this protection cost efficient? Measurements: Measuring Impacts in Drexel Building Vary filters (MERV 8, 14, 15) and air exchange rates (~1, 2, 3 h-1) Sample outdoor air, supply air, and return air (6 min cycle; 2 min each) PM2.5, ozone (O3), carbon dioxide (CO2), sometimes PM size distributions Determine indoor/outdoor (I/O) ratios of pollutants How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 5/34

Results Experiments: PM2.5 I/O ratios 4 experiments: MERV 8 and 14 each at AER of 1.2 and 2.2 h-1 MERV 8 AER = 2.2 h-1 0.35 (0.089) MERV 8 AER = 1.2 h-1 0.24 (0.04) MERV 14 AER = 1.2 h-1 0.02 (0.03) MERV 14 AER = 2.2 h-1 0.08 (0.18) How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 6/34

Results Experiments: PM number I/O ratios 4 experiments: MERV 8 and 14 each at AER of 1.2 and 2.2 h-1 MERV 8 AER = 2.2 h-1 1.4 (0.58) MERV 14 AER = 2.2 h-1 0.81 (0.44) MERV 8 AER = 1.2 h-1 1.0 (0.33) MERV 14 AER = 1.2 h-1 0.71 (0.31) How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 7/34

Results Experiments: PM2.5 and PM number shown 4 experiments: MERV 8 and 14 each at AER of 1.2 and 2.2 h-1 MERV 8, 2.2 h-1 MERV 8, 1.2 h-1 MERV 14, 2.2 h-1 MERV 14, 1.2 h-1 How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 8/34

Research Overview NAFA funded research project Question: Can filters protect occupants at high air exchange rates? And is this protection cost efficient? Modeling: Impact Ventilation and Filtration have on Building Energy Consumption and Monetized IAQ Exposure in U.S. Offices Model an office in 15 cities in different climate zones across U.S. Vary ventilation rates and filters in the modeled building Monetize costs and assess tradeoffs (i.e., filter cost vs. IAQ protection) How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 9/34

Methodology Modeling: Building simulations Energy simulations using EnergyPlus 15 different cities in the contiguous U.S. Average cost of utilities in each state (2013) Office parameters (1,500 m2) Ventilation at 0, 8.5, 17, 25.5 L/s/person 0, 0.38, 0.77, and 1.2 h-1 Typical construction, occupancy, power density, etc. ASHRAE Standards 62.1, 90.1, 189.1 Constant Air Volume (CAV) system Chiller COP = 3.2 Natural gas boiler efficiency = 0.80 Fan efficiency = 0.70; fan motor efficiency = 0.65 How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 10/34

Methodology Modeling: Air filters MERV 8, 10, 12, 14, 16, and HEPA filters modeled Median efficiency reported in literature (26.0%−99.7%) Azimi et al., 2013 Varied in pressure drop (111−374 Pa) Pressure drop across filter was added to pressure rise by the supply air fan (600 Pa with no filter) How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 11/34

Methodology Modeling: IAQ model Mass balance semi-transient IAQ model Nazaroff and Cass, 1986; Rackes and Waring, 2013; Riley et al., 2012 Only pollutants of outdoor origin Quantify the positive effect filtration has on IAQ Assess how filtration can mitigate negative effects of ventilation Pollutants include: Carbon monoxide (CO); Nitrogen dioxide (NO2); Ozone (O3); Fine particles (PM2.5) Taken from EPA monitoring stations for 6 years Differential model: Iterative solution: How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 12/34

Methodology Modeling: Cost and benefits of filtration What affects the cost and benefits of filtration? Nominal cost Lifespan Installation cost Pressure drop Removal efficiency Affecting filter cost (Jfilter) Affecting energy consumption cost (JE) Affecting IAQ exposure outcomes (JIAQ) How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 13/34

Methodology Modeling: Cost function Cost function includes these costs and benefits of filtration: Total cost Energy cost Filter cost Monetized IAQ exposure How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 14/34

Methodology Modeling: Cost function For a particular building in a particular climate, the function depends on two variables: Ventilation and Filtration Assess the effect of ventilation on total cost function: Assess the effect of filtration on total cost function: How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 15/34

Methodology Modeling: Energy Cost (JE) Increases in ventilation rate and pressure drop require more energy How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 16/34

Methodology Modeling: IAQ monetization (JIAQ) Morbidity and mortality relating to acute and chronic effects Exposure to CO and NO2 reported to cause acute morbific symptoms Exposure to O3 and PM2.5 reported to cause both acute and chronic morbific and mortal symptoms Exponential C-R function to quantify incidences due to exposure Outcomes include mostly cardiopulmonary diseases How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 17/34

Methodology Modeling: IAQ monetization (JIAQ) Quantification of mortality and morbidity Guidelines provided by the EPA Based on either cost of illness (COI) for most acute health effects or willingness to pay (WTP) for most chronic health effects and mortality Outcome Cost per incidence (2013$) Mortality $8,620,400 Chronic bronchitis $462,929 Chronic asthma $52,953 Asthma attack $44 Minor restricted activity days $69 Hospital admission (any reason) $31,640 How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 18/34

Results Modeling: Filter costs (Jfilter) The cost of the filter itself Includes purchase, replacement, and installation $0.5~$8.50 per person per year for MERV 8-16 Up to ~$18 per person per year for HEPA Other studies report similar values (e.g. Azimi & Stephens, 2013) This cost must assessed for each case among filters Highly dependent on manufacturer and type of filter How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 19/34

Results Modeling: IAQ results Pollutant concentrations: NO2 O3 Pollutant concentrations: CO not affected by increasing ventilation NO2 and O3 increase as ventilation rate increases PM2.5 varies with filtration more than with ventilation Absolute concentrations correspond to other studies CO MERV 8 MERV 10 MERV 12 (#1) MERV 12 (#2) MERV 14 MERV 16 HEPA How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 20/34

Results Modeling: IAQ results Monetized results: CO and NO2 have negligible effects, but O3 increases Effects of PM2.5 is highly influenced by filtration CO NO2 O3 MERV 8 MERV 10 MERV 12 (#1) MERV 12 (#2) MERV 14 MERV 16 HEPA PM2.5 How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 21/34

Results Modeling: Combined energy and IAQ results Cost difference compared to BL (0 L/s/occ + MERV 8): Baseline: no ventilation, MERV 8 How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 22/34

Results Modeling: Combined energy and IAQ results IAQ effects are much more expensive than energy cost JIAQ ≈ 5 × JE at low ηPM2.5 Filtration affects total cost function more than ventilation PM2.5 concentration is dominant parameter Cost difference compared to BL (0 L/s/occ + MERV 8): How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 23/34

Results Modeling: Empirical cost function: Energy cost Empirical energy cost function (occupant normalized): Energy cost (US$/occ) Filter pressure drop (Pa) Base energy cost (US$/occ) Ventilation rate (l/s/occ) How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 24/34

Results Modeling: Empirical cost function: Energy cost Empirical energy cost function (occupant normalized): Annual and monthly fits in each location Mean R2 = 0.952 Mean NRMSE = 7.73% Ventilation slope (JE,N /Qv,N) Pressure slope (JE,N /Δpf) Annual JE,0 = 52.2 ~ 85.4 $US/occ Annual mv = 0.64 ~ 2.07 ($US/occ)/(l/s/occ) Annual mf = 2.1×10−2 ~ 4.2×10−2 $US/occ/Pa How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 25/34

Results Modeling: Empirical cost function: Monetized IAQ Empirical IAQ exposure cost function (occupant normalized): IAQ cost (US$/occ) Base IAQ cost (US$/occ) Filter removal efficiency (−) Ventilation rate (l/s/occ) How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 26/34

Results Modeling: Empirical cost function: Monetized IAQ Empirical IAQ exposure cost function (occupant normalized): Annual and monthly fits in each location Mean R2 = 0.987 Mean NRMSE = 4.00% aIAQ, bIAQ, cIAQ are constant model coefficients How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 27/34

Results Modeling: Empirical cost function: Monetized IAQ Empirical IAQ exposure cost function (occupant normalized): Epidemiological uncertainty All parameters were calculated with a confidence interval At the mean of the function: JIAQ,0 = 311 ~ 681 $US/occ aIAQ = 57.5 ~ 143 ($US/occ)/(l/s/occ)1/2 bIAQ = 191 ~ 437 $US/occ cIAQ = 46.9 ~ 94.4 ($US/occ)/(l/s/occ)1/2 How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 28/34

Results Modeling: Effect of ventilation changes Ventilation derivative ($/occ per L/s/occ) A function of both ηPM2.5 and Qv How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 29/34

Results Modeling: Effect of ventilation changes Ventilation derivative ($/occ per L/s/occ) How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 30/34

Results Modeling: Effect of filtration changes J/Δpf is constant Filtration derivative split into two: Pressure drop derivative ($/occ per Pa): Filter efficiency derivative ($/occ per eff): J/Δpf is constant Increasing pressure drop is always unfavorable Maximum potential cost increase: ~$1.0/occ/yr J/ΔηPM2.5 is a function of ventilation, always negative Increasing ηPM2.5 is always favorable Increasing ventilation will increase filtration efficacy How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 31/34

Results Modeling: Effect of filtration Filter efficiency derivative: Compared with VR = 8.5 l/s/occ, filtration is: ~1.20 times more efficacious at 17 l/s/occ and ~1.35 times more efficacious at 25.5 l/s/occ More favorable How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 32/34

Conclusions Ventilation – filtration interaction Coupling high filter efficiency with a high ventilation rate can improve IAQ Benefits of high efficiency filtration significantly outweigh its cost At high filter efficiency, increasing ventilation is favorable At high ventilation rates, filtration is more efficacious The effects of filtration and ventilation can be predicted empirically The framework of this study can aid in determining desirable ventilation- filtration couples How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 33/34

Conclusions Modeling: Limitations and future work Limitations Epidemiological C-R and illness valuation bear large uncertainties Model coefficients are highly variable between different locations and need to be properly characterized Additional effects of ventilation such as productivity increase and SBS are not considered in this study Future work Finish experimental characterizations Fully characterize model parameters Improve framework for minimum filtration recommendations How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 34/34

Acknowledgment Coauthors and special thanks Co-authors for project: Sheng Wang (experiments) Tom Ben-David (modeling) Funding: National Air Filtration Association How well can higher efficiency filtration control particles at high ventilation rates in offices? Slide 35/34

Thank you to our sponsors! Timmy Lott to thank