Residential Filtration - NAFA– Cleaning – Candles – Smoking – Incense. What particles do we care about? ... – Not well demonstrated health impact • Big stuff we can see

Residential FiltrationNAFA Conference 2018

Dr. Iain Walker

Air pollutants in homesPM has biggest health impact – focus on particle filtration

Disability Adjusted Life Years: DALYs

Logue, J. M., Price, P. N., Sherman, M. H., & Singer, B. C. (2012). A Method to Estimate the Chronic Health Impact of Air Pollutants in U.S. Residences. Environmental Health Perspectives, 120(2), 216–222

Where do indoor particles come from?• Outdoors

– Combustion – ICE’s– Agriculture– Industry– Atmospheric chemistry, e.g., ozone reactions– Wildfires

• Indoors– Cooking– Cleaning – Candles– Smoking– Incense

What particles do we care about?• Primarily PM2.5

– Demonstrated health impact

• Maybe ultrafines (sub-micron)– Not well demonstrated health

impact

• Big stuff we can see– Heat exchanger/blower

fouling

Focus on MERV 11/12/13To remove PM2.5

Particles: PM2.5

…causes increased cardiovascular morbidity and mortality;

…is associated with and likely causes respiratory illness.1

www.epa.gov/pm-pollution/particulate-matter-pm-basics#PM

PM2.5 BenchmarksStandard Annual mean

g /m324-h meang /m3

US Ambient Standard(2012) 12 35

WHO Guideline Values(2005) 10 25

Canadian Ambient Standard2015 10 28

Canadian Ambient Standard2020 8.8 27

Standards only set for outdoor “ambient” air - no indoor standardsIAQ standards focus on specifying filters NOT measured

Stephens, Brennan & HarrimanASHRAE Journal, September 2016

PM2.5 in the Residential Environment

Active Filtration

Filters in Residential Standards: ASHRAE 62.21. MERV 6 – to protect equipment2. 20% ventilation credit for better filtration:

• Need a minimum flow rate through the filter:

Average flow ratethrough filter

Filtration factor 62.2 ventilation rate

A better filter requires less airflow to get the 20% credit

EPA Indoor Air Plus

MERV 8 minimum for central forced air systemsRecommend MERV 13 for supply air

USGBC LEED for Homes

Good: MERV 8Better: MERV 10Best: MERV 13

American Lung Association

• Once upon a time: MERV 11, changed every three months

• Currently…?

State of the air 2018 – no mention of filters or filtration

California Air Resources Board• Regulation for outdoor air• Certifies Portable Air Cleaners• Evaluating near roadway exposure• Evaluating cooking exposure• Studies showing improved health (asthma) with better filters

California Building Standards

Currently refer to ASHRAE 62.2: MERV 6 minimum

From 2020:

• MERV 13 filters in forced air systems

• Two inch filter depth

2019

Recent Research• Focus on filters in central forced air systems

– Interaction with HVAC performance• Change in airflows, static pressures, duct leakage,

heating/cooling energy use• Energy impacts of upgrading filters• Different filtration approaches

– Indoor and outdoor sources• Performance over time

– Particle removal– Fouling rates

Do better filters kill residential systems?Proposals to improve filtration get the same HVAC contractor feedback:Extra flow resistance will1. Lower flow resulting in lower heating/cooling efficiency2. Increase static pressures and overload blowers3. Make systems too noisy4. Increase duct leaks

California MERV 16 swap-out• LBNL field study 10 homes monitored for a year for California Energy

Commission

• Swapped in MERV16 filter for MERV 5- 11

Included some 4 in. filters:

A smorgasbord of filters

.. Even more filtersDirty Filters Thin Filters

Deep filters

Filter static pressure changes and loading rates

• Fan power reduced by 100 W PSC , increased by 70 W ECM• 1 or 2 in. filter loading rate: 10 Pa/million kg• 4 in. filter loading rate: 5 Pa/million kg

1 million kg = 2.2 million lb = 29 million ft3 = 29,000 minutes @ 1000 cfm = 20 days @ 24/7

Note – typical residential blower max pressure difference is 125 Pa (0.5” H2O)

Figure 5: Fan flow and power changes from House 1. The vertical lines show when the filter was changed from MERV 8 to MERV 16. Cooling and heating modes can be seen for both filters.

Figure 6: Pressure across the filter for House 1.

Figure 7: Pressure across the fan for House 1.

Figure 8: Supply plenum pressure (relative to inside the house) for House 1.

Figure 9: Return plenum pressure (relative to inside the house) for House 1.

Figure 10: Supply side leakage for House 1.

Figure 11: Return side leakage for House 1.

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MERV 8 CoolingMERV 8 Heating


Plenum Pressures [Pa]

Cumulative Mass Flow [10

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Supply Plenum Pressure, House 1

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Return Plenum Pressure, House 1

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Supply Leakage Flow [% of Fan Flow]


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Supply Leakage Flow, House 1

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Return Leakage Flow [% of Fan Flow]


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Return Leakage Flow, House 1

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Flow: MERV 8 CoolingFlow: MERV 8 Heating

Flow: MERV 16 CoolingFlow: MERV 16 Heating

Fan Power

Fan Power [watts]

Fan Flow [cfm]


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kg ]

Filters: MERV 8 | MERV 16

Fan Flow and Power, House 1

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Pressure [Pa]


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Filters: MERV 8 | MERV 16

Filter Pressure, House 1

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Pressure [Pa]


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Fan Pressure, House 1

Figure 8: Supply plenum pressure (relative to inside the house) for House 1.

Figure 9: Return plenum pressure (relative to inside the house) for House 1.

Figure 10: Supply side leakage for House 1.

Figure 11: Return side leakage for House 1.

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Return Leakage Flow [% of Fan Flow]


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Return Leakage Flow, House 1

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0.511.522.5





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Supply Plenum Pressure, House 1

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Return Plenum Pressure, House 1

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Supply Leakage Flow [% of Fan Flow]


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Supply Leakage Flow, House 1

LBNL MERV 16 Field Study Summary• HUGE system to system and filter to filter variability • Everything < MERV 16 very small impact (

University of Texas Field Study

• ASHRAE RP 1299

• 17 homes and light commercial systems

• Short –term measurements

• Swapping low “MERV 2*” for MERV 11/12– Small changes in fan power and air flow– No measureable change in daily energy use

* Glass fiber “rock catcher”

But what about filter effectiveness changes?

MERV12MERV7

New

“Used”

MERV vs. Flow resistance - DEG

More variability between MERV 8 filters than between MERV 8 and other filters

MERV vs. flow resistance – IIT

Are high MERV filters system killers?No… but

… Some systems lots of air flow resistance already

… Advise against using 1” MERV 16 filters in residential systems

… bigger (2” or 4”) filter slots are a really good idea

… there is a huge range of filter flow resistance – even for the same MERV rating

Comparing filtration/ventilation optionsCalifornia Air Resources Board/LBNL Study• Field Study near freeway in

Sacramento, CA for California Air Resources Board

• Unoccupied – focus on outdoor particles• Compare eight enhanced filtration

systems to common, “reference” system– ASHRAE 62.2 Exhaust ventilation +

MERV 6 on central forced air system• Operate each system 5-7 days in

summer & fall/winter• Key metric is indoor-to-outdoor ratio

Test House: Impacted by I-80, Sacramento

~300 m N of

Test House

Particle Instrumentation

• Parallel systems switching indoor and outdoor

Particle Measurements

Ex M6 RTS M13 A+ESP Sup M16Cont

CFIS M16MRT

Ex+M13MRT

Ex+M13CONT

HEPA MRT Bypass

Indoor Particles – from cooking

Recirculation with M13/M16 filters

Outdoor Particle Filter Field Study Conclusions

• You need a good filter –MERV 13

• You need to operate continuously or at least a minimum runtime

• Central systems can have good performance if they do the above PLUS they get the indoor particles!

• HEPA bypass & ESP not very effective

• Room air cleaners are great for the room they are in

Residential Filtration Recommendations Consider the quality of your outdoor, “fresh” air

Highways and other major roadways, Industry, Agriculture

Supply ventilation (includes HRV/ERV) should be: Minimum MERV 13

Central forced air system required to address indoor sources Be aware of systems already at capacity for retrofitting At least MERV 13 preferably greater 2” (or 4” for MERV 16) filters are highly recommended Operate central systems continuously or minimum run time Consider stand-alone filtration in non-forced air homes or homes with

inefficient blower motors

What’s next in residential filtration?• Gas-phase filtration

– Targeting formaldehyde, acrolein

• What to do for non-forced air homes?

• Better forced air system design to accommodate better filters

• Get contractors to install wider filter slots

• Integrate with pollutant sensors & smart IAQ systems

AnyQuestions?

Swapping to MERV 16 problematic

Swapping to MERV 16 problematic

Residential FiltrationAir pollutants in homesWhere do indoor particles come from?What particles do we care about?Particles: PM2.5PM2.5 BenchmarksSlide Number 7PM2.5 in the Residential EnvironmentFilters in Residential Standards: ASHRAE 62.2Slide Number 10EPA Indoor Air PlusUSGBC LEED for HomesAmerican Lung AssociationCalifornia Air Resources BoardCalifornia Building Standards Recent ResearchDo better filters kill residential systems?California MERV 16 swap-outA smorgasbord of filters.. Even more filtersFilter static pressure changes and loading ratesSlide Number 22Slide Number 23LBNL MERV 16 Field Study SummaryUniversity of Texas Field Study But what about filter effectiveness changes?MERV vs. Flow resistance - DEGMERV vs. flow resistance – IITAre high MERV filters system killers?Comparing filtration/ventilation optionsTest House: Impacted by I-80, SacramentoParticle InstrumentationParticle MeasurementsSlide Number 34Indoor Particles – from cookingOutdoor Particle Filter Field Study ConclusionsResidential Filtration RecommendationsWhat’s next in residential filtration?Slide Number 39Swapping to MERV 16 problematicSwapping to MERV 16 problematic

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Residential Filtration - NAFA– Cleaning – Candles – Smoking – Incense. What particles do we care about? ... – Not well demonstrated health impact • Big stuff we can see