Bringing the Outside In:
Ventilation for Your Health
Henry Slack
U.S. Environmental Protection Agency Region 4
Introduction to Air
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We breathe 20-30 lbs air/day !
90% indoors – homes 70%, other bldgs 20%
Indoor air: chemicals, mold, bacteria, dust
Maybe high levels of radon, pesticides,
tobacco smoke, combustion gases
• How can we improve out household air?
Ventilation!
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Cleans your air
Lowers levels of every pollutant
Health, productivity gain > energy $
Exploring ventilation, research
Informational, but no firm conclusion
U.S. EPA does not recommend
ventilation quantities or delivery methods
How We Built Homes Long Ago
• Stone, wood, metal materials
• Open windows half of year
Outdoor Air = Indoor Air
• Lathe and plaster walls (high pH)
• Asbestos and lead-based paint
• No central heat or A/C - unaffordable!
Homes for the past 50 years
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Carpets, wallboard, Particleboard
Finishes, glues, foam insulation
Computers, printers, copiers (toner)
Cleaning, personal, pesticide chemicals
Central A/C and heat, filters
Yes- shut windows, added chemicals
Attached Garage
• Storing gasoline, paint, pesticide, other
chemicals
• Autos (and if on, combustion gases)
• Water heaters, even furnaces
• No caulk or weather stripping between
garage and kitchen = fumes come in
Ventilation Recommendations
• Florence Nightingale – 1860’s
• She + others: around 60 cubic feet of air
per minute per person (CFM/p)
• Post-1973 energy crisis, the American
Society of Heating Refrigerating, and
Air-Conditioning Engineers (ASHRAE)
recommended only 5 CFM/p in nonsmoking offices
Ventilation 1980’s - now
• A few years later, ASHRAE raised their
recommendation to 15 CFM/p.
• The present recommendation in office
buildings is around 13 CFM/p, but the
actual figure is calculated on the
building size as well as occupancy, so it
is not directly comparable.
• The U.S. EPA does not set ventilation
standards.
ASHRAE Standard
• ASHRAE’s recommendations were
originally made as Standard 62,
“Ventilation for Acceptable Indoor Air
Quality.” In 2005, this standard was
split into 62.1 for most buildings and
62.2 for residential buildings
• Based on best science and “engineering
judgment” so new science will change
LEED
• Leadership in Energy and
Environmental Design (LEED) buildings
could get extra credits for 30% more
outside air than ASHRAE 62
Tight Homes
• ASHRAE 62.2 recommends 0.3-0.35 air
changes per hour (ACH)
• Some new residences being built tighter
without outside air ventilation
• Multi-family as low as 0.03 ACH
• Average across two studies: 0.10 ACH
Three Key Ideas
• CO2 may be a pollutant in ways
not previously recognized
• Meta-analysis shows health benefits of
more OA level off around 50 CFM/person
• More ventilation would pay for itself in
offices and schools
Meta-analysis of Ventilation Studies
• Team of leading scientists reviewed
27 papers on health effects and
ventilation written through 2005
• Higher ventilation rates in offices, up to
about 25 l/s/person [50 CFM] are
associated with reduced prevalence of
Sick Building Syndrome symptoms
How Much Outside Air Do We Need?
• 2011 Meta-analysis reviewed 27
separate studies shows health benefits
from delivery of more outside air.
• Higher ventilation rates in offices are
associated with reduced prevalence of
Sick Building Syndrome symptoms
(mostly respiratory).
• The effect goes up to about 50 CFM/p
(Sundell et al, Indoor Air 2011: 21; 191-204)
50 CFM/person is 3x Current Rates!
• Consistency was found across multiple
investigations and different epidemiologic
designs for different populations
• Suggests that lowering existing minimum
ventilation rates inappropriate, but offered
no support for any specific level of
increase
More on the Meta-Analysis
• Consistent across multiple
investigations, different countries,
different research designs, so strong.
• 50 CFM/p is 3-4x higher than ASHRAE
Standard 62 recommends. This study
did NOT recommend any particular
amount of outside air
• They also didn’t discuss using outside
air when local air pollution is bad.
CO2
• We all breathe out carbon dioxide (CO2)
• CO2 levels may affect our ability to
make decisions.
• Typical levels have been viewed as
harmless, although more CO2 makes
our blood more acidic.
• Outdoor air has around 400 parts per
million (PPM) CO2 right now. A typical
office building may see levels go up to
More on CO2
• Outdoor air has around 400 parts per
million (PPM) CO2 right now.
• Offices may go up to 1,000 PPM (or
0.1%) during the day
• Buildings without ventilation may go
much higher
• Submarines and space capsules may
be 10,000 PPM or more
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Decision Making Tests
• Decision-making tests correlate with
leadership skills.
• Reliable: Tested on thousands of people
• 22 subjects took tests. Same people,
same room, same day, but the air held
different levels of carbon dioxide (CO2)
each time: 600 PPM, 1,000 PPM, and
2,500 PPM
CO2 and Decision-making
• 22 subjects completed tests of decisionmaking performance at 600, 1000, 2500
ppm CO2 , all the same day, but in
different order
• Validated decision-making tests (SMS)
Satish, U., et al. Enviro Health Perspect 120: 1671-1677
Result
• Result : statistically significant consistent
downward trends on 7 of 9 decision scales
Slides
• Tests were double-blind: neither the
subjects nor the technicians giving the
tests knew what CO2 levels were
present.
• They even changed the order of the
CO2 concentrations tested, so that the
subject’s level of alertness would not be
a factor.
Is Our Children Learning?
• Many school classrooms
are over 1,000 ppm; in TX,
21% peak CO2 levels were
>3,000 ppm
• Office CO2 levels may be higher in
meeting rooms, where decisions are
made
Does it Pay?
• Many studies: more ventilation leads to
greater productivity in schools, offices
• 1% increase in vent: $3-10,000/year
• Doubling ventilation yields productivity
gains of $37 B (energy cost =$0.13 B).
Economizers gain $33 B, saving energy
but paying $0.28 B for equipment.
(Fisk, Building and Environment, 2011 )
More on These Studies
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So What About Ventilation?
• Ventilation air can solve or improve
almost any indoor air problem,
• Cost: equipment and energy
• Outdoor air must be better than indoors
• Particulates, ozone concerns
Humidity an Issue
• Moisture from ventilation may change
indoor moisture levels and comfort
• Mold grows with moisture, too.
• Brand new southern coastal school
added outside air without moisture
control. School closed within a year to
dry and clean
Bringing The Outside In Our Homes
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Deliver outside air in and push out IA
Exhaust inside air and draw in OA
Balanced methods do both
No single choice
Exhaust –Only Fans
• In most bathrooms, many kitchens
• Reasonable price, but…
• Where does make-up air come from?
– May draw in radon, mold, garage fumes
– May bring in high-humidity air, grow mold
– Does this air go to every room?
Exhaust-only House
• Shows fans on, bringing in outside air
Supply-Only
• Air source is known, air delivered into
HVAC system to filter, dehumidify,
change temperature
• Pushes some air out, no problem.
• More expensive, for equipment and for
energy to treat the air
• More complicated
Supply-Only: CARB Study
• Measured chemicals in newer homes
• Homes had no OA system, supply-only
system, or balanced systems
• None of the 8 supply only systems was
working properly
• Chemical levels in these homes
mirrored homes with no ventilation.
Supply-only House
• Shows fans on, bringing in outside air
Balanced ventilation systems
• Exhaust indoor air, deliver outdoor air
• Heat exchangers transfer heat, save $
– Heat Recovery Ventilator (HRV) – heat
only
– Energy Recovery Ventilator (ERV) – heat
and moisture, humid climates
• More $
• CA : ERV homes= lower chemicals
ERV/HRV House
• Shows fans on, bringing in outside air
Maintenance
• HVAC requires maintenance.
• Recommended 2x/year
• Not always done, and not done on
ventilation equipment
Filtration
• Filtration –needed on outside air
intakes?
• San Francisco Code 38 requires that
outside air delivered to residences near
freeways (which have high PM) must
use a high grade of filter (MERV 13) to
remove some of the PM.
Other Issues
• If air is mixed well, less ventilation?
– Experts on both sides
• Adjustable system? We set
temperatures up and down – why not
ventilation? Will we set too low?
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Conclusion
• Air quality is crucial to breath and health
• Research suggests greater outside air
ventilation would reduce chronic disease
• “Best” system depends on location and
equipment maintenance
• U.S. EPA does not recommend
ventilation quantities or delivery methods