INDOOR AIR QUALITY
IN PORTABLES
Montgomery County Public Schools, Md.
Speaker: Sean R. Yarup, M.P.H.
AASA NATIONAL CONFERENCE
ON EDUCATION
March 4th, 2007
New Orleans, La.
AGENDA
• Provide background on portables at
Montgomery County Public Schools (MCPS)
• Present IAQ findings in portables
• Discuss portable assessment strategy
• Provide recommendations to address IAQ
issues
BACKGROUND
• Montgomery County, Md.
– Suburb northwest of Washington D.C.
– Area: 497 square miles
– Population: 942,000
• Montgomery County Public Schools
– 199 schools
– 129 ES, 38 MS, 25 HS, 7 centers
– Enrollment: 137,798
– National ranking: 17th largest
– Staff: 21,840
– School Operating Budget: $1.85 billion
PORTABLES AT MCPS IN 2006
•
•
•
•
Elementary
High
Middle
Holding
Total
469
83
25
30
607
• 120 portables are over 11
years old
• Average portable is 912
square feet
• Holds 20-25 occupants
• 14,000 attend classes in
portables
NUMBER OF PORTABLES
800
700
600
500
400
Portables
300
200
100
0
2001
2002
2003
2004
2005
2006
2007
Projected
IAQ COMPLAINTS
IN PORTABLES
50
45
40
35
30
25
IAQ Complaints
20
15
10
5
0
2000 2001 2002 2003 2004 2005 2006
IAQ COMPLAINTS
IN ALL BUILDINGS
300
250
200
150
IAQ Complaints
100
50
0
2000 2001 2002 2003 2004 2005 2006
IAQ FINDINGS IN MCPS PORTABLES
• Elevated CO2 and humidity levels due to HVAC
system design, operation and maintenance
issues
• Moisture entry & condensation from building
envelope deficiencies
– Primary factor in mold growth
• Relocation, reassembly and site placement
critical in minimizing moisture entry
• Poor acoustics from loud exhaust fans
• Lack of IAQ awareness / training among staff
INDOOR CO2 – VENTILATION RATE DIAGRAM
HVAC SYSTEM CHALLENGES
Providing sufficient ventilation without
increasing humidity
• Minimum ventilation rate
– ASHRAE Standard 62.1-2004 requires a minimum ventilation
rate of 15 cubic feet per minute (CFM) per person in classrooms
– Carbon dioxide: Less than 700 ppm above outside ambient
levels
• Temperature and humidity ranges
– ANSI/ASHRAE Standard 55-2004, Thermal Environmental
Conditions for Human Occupancy
– 73-79 F, 40-60% in summer
– 68-74 F, 30-50% in winter
HVAC SYSTEM CHALLENGES
• Design
– Limited ventilation and dehumidification capabilities
– Short-circuiting air flow
• Operation
– Supply and exhaust fan operation not balanced
according to occupant load to prevent building
depressurization
• Maintenance
– Lack of preventive maintenance leads to decreased
performance of HVAC system
BUILDING ENVELOPE DEFICIENCIES
MOISTURE ENTRY – EXTERIOR
• Gaps in vertical seams of
exterior siding
• Inadequate flashing
above doors and around
windows
• Physical damage from
vandalism
• Non-gasketed nails
• Lack of vapor barrier
– Condensation
CRAWLSPACE DAMPNESS
• Damp crawlspace air
migrates up through
penetrations in floor
• Wet plywood skirting
becomes moldy and may
wick moisture to subfloor
OVERGROWN VEGETATION
BUILDING ENVELOPE DEFICIENCIES
MOISTURE ENTRY – ROOFING SYSTEM
CANOPY RUNOFF
INADEQUATE DRAINAGE
SITE PLACEMENT
• Proximity to trees
• Low lying areas with
poor drainage
SITE PLACEMENT
LACK OF MAINTENANCE
MCPS ASSESSMENT STRATEGY
MCPS Assessment Team
• Environmental health specialist
• HVAC mechanic
• Construction specialist (e.g, inspector, carpenter, roofer)
• School building service manager
Assessment Tools
• Inspection checklist
• IAQ meter
• Moisture meter
• Infrared camera
• Flashlight
IAQ METER
• Measures thermal
comfort, ventilation &
sources of
combustion
–
–
–
–
Temperature
Humidity
Carbon dioxide
Carbon monoxide
MOISTURE METER
INFRARED CAMERA
MCPS RECOMMENDATIONS
• Replace carpet with vinyl floor tile
• Remotely control HVAC system
• Evaluate improvement options for heat pumps
– Energy recovery ventilator wheel with CO2 stat
– Refrigerant reheat coils and dehumidification cycle
with CO2 stat and humidistat
– Carbon-pleated air filters
• Develop construction specifications for portables
• Replace plywood skirting with vinyl lattice
CARPET REPLACEMENT
WITH VINYL FLOOR TILE
• Improves indoor air
quality
• Removes musty
odors, mold, dust
mites and other
allergens
• Releases less
particles in the air
than carpet
REMOTE CONTROL FOR
PORTABLE HVAC SYSTEM
Allows for flexible scheduling and
temperature control based on
occupancy
Heating Season
• 5 am to 8 am - 700 F
• 8 am to 4 pm - 680 F
• 4 pm to 6 pm - 640 F
• 6 pm to 5 am - 500 F
Cooling Season
• 8 am to 4 pm - 760 F
• 4 pm to 6 pm - 800 F
• 6 pm to 5 am - 900 F
ENERGY RECOVERY WHEEL
HEAT PUMP APPLICATION
• Reduces humidity during
unoccupied periods when
linked to humidistat
• Reduces CO2 levels
during occupied periods
when linked to CO2
sensor
VINYL LATTICE SKIRTING
MCPS RECOMMENDATIONS
• Perform commissioning process
– Balance ventilation rates to provide slight
pressurization
– Screen for VOCs (formaldehyde)
– Screen for carbon monoxide (i.e., if near bus loop or
high traffic area)
– Seal seams to exterior metal siding
– Review canopy design to prevent “waterfall” effect on
portable siding
CANOPY > 3” FROM ROOF
PROTOCOL FOR
RELOCATION & REASSEMBLY
• Relocation
• Reassembly
– Site Selection
– Caulking and
Sealing
• Commissioning
ABS FOUNDATION PADS
MCPS RECOMMENDATIONS
• Train building service staff on HVAC system preventive
maintenance
• Conduct IAQ awareness in portables to teaching and
administrative staff
• Specify low-emitting building materials (Green Seal &
GREENGUARD certified products)
• Continue portable reduction plan through construction
funding increases
HEALTH GAINS FROM
IMPROVED INDOOR AIR QUALITY
100.0%
90.0%
Increased outside air
Pollutant source control
87.3%
flu
Moisture
control
% Improvement/reduction in symptoms
80.0%
85.0%
SBS
72.5%
asthma
67.0%
SBS
70.0%
CBPD / ABSIC BIDS™ 2005
Health Gains from Improved Indoor Air Quality
61.5%
asthma,
allergies
60.0%
46.0%
respiratory
50.0%
35.0%
SBS
40.0%
Individual control /
task air
Average 41.5%
33.6%
SBS
47.0%
SBS
33.0%
SBS
30.0%
20.0%
respiratory
20.0%
23.5%
headache
23.6%
asthma
20.0%
headache
15.0%
colds
21.4%
asthma,
mucosal
13.5%
bronchial
(asthma)
10.0%
0.0%
Drinka et al
1996
Jaakkola &
Miettinen
1995
Brundage et
al 1988
Fisk &
Rosenfeld
1997
Bourbeau et Sundell 1996
al 1997
Fisk &
Rosenfeld
1997
Kaczmarczyk Menzies 1997 Cox-Ganser Husman et al
Beijing
Australian
et al 2002
et al (NIOSH) / National Residences / Residences /
2005
Public Health Liu et al 1996 Garrett et al
Institute 2002
1996
Wargocki
1998
Source: Carnegie Mellon University Center for Building Performance, 2005
Wieslander et Jaakkola et al
Oslo
al 1997
1994
Residences /
Jaakkola et al
1999
PRODUCTIVITY GAINS FROM
IMPROVED TEMPERATURE CONTROL
Productivity Gains from Improved Temperature Control
CBPD / ABSIC BIDS™ 2005
18.0%
Individual temperature control
16.0%
15.0%
14.0%
% Improvement
12.0%
10.0%
8.0%
7.0%
6.0%
4.9%
Desktop temperature control
4.1%
4.1%
Average 3.6%
4.0%
2.8%
2.8%
2.7%
2.3%
2.0%
1.9%
0.8%
0.2%
0.7%
0.6%
0.0%
Bank of America
/ Bauman et al
1992
West Bend /
Kroner et al
1992
Hayashi et al
2003
Wilkinson
Building / Rowe
2002
Niemala et al
2002
Tham et al 2003
Mendell et al
2002
Niemala et al
2002
Number Service
/ Hannula et al
2000
Wyon 1996
Wyon 1996
Pilcher et al
2002
Source: Carnegie Mellon University Center for Building Performance, 2005
Witterseh 2001 Witterseh 2001
SUMMARY
• IAQ issues in portables magnified due to many
factors
• Difficult to achieve ventilation rates and control
humidity with current HVAC system design
• A thorough assessment by school staff can
improve indoor air quality
• School planning and funding critical in limiting
the number of portables
IAQ WEBSITE
http://www.mcps.k12.md.us/departments/iaq