Bringing the Outside In:
Ventilation for Your Health
Henry Slack
U.S. Environmental Protection Agency Region 4
Introduction to Air
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?
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
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
• 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
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originally made as Standard 62,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
• 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
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.
• 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
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 : statistically significant consistent
downward trends on 7 of 9 decision scales
• Tests were double-blind: neither the
subjects nor the technicians giving the
tests knew what CO2 levels were
• 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
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
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
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
• 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
– Energy Recovery Ventilator (ERV) – heat
and moisture, humid climates
• More $
• CA : ERV homes= lower chemicals
• Shows fans on, bringing in outside air
• HVAC requires maintenance.
• Recommended 2x/year
• Not always done, and not done on
ventilation equipment
• Filtration –needed on outside air
• 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?
• 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

Presentation 1 - National Healthy Homes Conference