Preventing & Solving Mold Problems in Schools
Rich Prill Building Science & IAQ Specialist Washington State University Extension Energy Program Spokane, WA 25 years IAQ Experience Region 10 EPA IAQ Education & Technical Resource > 500 NW School Walk-Throughs Building Operator Certification IAQ Instructor
Indoor Dampness, Molds, and Health
Dry
Surveys find dampness and molds are common in schools and office buildings Causes: – water leakage through roofs and walls – plumbing system leaks – groundwater floods – damp construction materials – high indoor rates of moisture generation – entry of humid outdoor air – water vapor condensation on cold surfaces of windows and walls Based on the available surveys, approximately half of U.S. homes have visible evidence of a dampness problem or mold contamination
Molds & Bacteria
Dry
• Can lead to microscopic airborne particles, containing allergens or chemicals with potential to induce inflammation in the respiratory system • Dampness also increases emission rates of gaseous non-microbial chemicals such as formaldehyde
• High indoor relative humidity can increase house dust mites - - a very important source of indoor allergens
Molds Mold concentrations generally higher outdoors Primarily allergic reactions –Eye, nose, throat irritation –Shortness breath –Dizziness, fever, lethargy –Digestive problems –Skin rash
National Academy of Science Institute of Medicine (2004)
Dry
Extensive study concluded that building dampness and mold represented a public health problem “ Building dampness and mold were associated with 30% to 50% increases in a variety of respiratory and asthma-related health outcomes “ “Steps should be taken to reduce building dampness and mold, including various education efforts, reviews of buildings codes and contracts, and an exploration of financial incentives for reduced dampness.”
Molds & Dampness
Dry
Of the 21.8 million people reported to have asthma in the U.S., approximately 4.6 million cases (~20%) were estimated to be attributable to dampness and mold exposure in the home
The associated annual cost of current asthma attributable to dampness and mold in the U.S was estimated to be $3.5 billion
Mold Exposure and Reaction • Exposure is complex = depends: – Species compete: come and go – Metabolic products produced by each species – Amount of exposure – Duration of exposure – Individual susceptibility
Due to Uncertainties: Practice “Prudent Avoidance” • People should not live in the presence of mold, moldy odors, damp conditions • Dampness, odors and visible mold should “corrected” as soon as possible Damp environments have been shown to be directly related to adverse health effects
Why Mold Problems ?
Mold Growth Spores
Nutrients Temperature o
o
(40 F to 100 F)
Moisture
Mold Just add water …
Some climates are prone to mold problems
Moisture Rules • Moisture flow is from warm to cold
• Moisture moves from more to less • Air transports moisture from
• high pressure to low pressure areas • Gravity pulls water down • Water wicks up • Drainage is critical
Just Add Water From the Outside From the Inside
Water entry from Outside • • • • • •
Roofs and Walls Windows, Doors, Flashings Crawlspaces, Basements, Slabs Where materials meet Plumbing systems Heating/Cooling systems – Leaky ducts Condensate
Patios and decks lower than floors and slope away from building Garage floor lower than main floor and slope away from building Driveway lower than garage door and slope away from building Grade lower than main floor and slope away from building
Building Science Fundamentals • Nature is lazy (path of least resistance) But, molds are NOT lazy!
• The path of least resistance is the path to problems, unless you know your way • It costs about 3 times more to fix it later • Gravity is free: slope to drain flashing are your friends
Avoid Flat Roofs
Gravity always trumps caulking
Another good argument against flat roofs
Mark on floor plan to ensure thorough check from the inside Potential Water Entry Areas
Avoid built-in cabinets at windows
Window leak behind built-in cabinets = mold
Drainage plane ? Flashing ? Weather Resistant Barrier ? Drying potential ?
Diameter (inches)
Capillary Rise (inches)
capillary break
capillary breaks
E.I.F.S.
E.I.F.S.
Block = Rigid Sponge
irrigation system defeating roof over-hang
Ensure proper drainage
the “Best” water leak:
Small enough to not cause problems
Large enough to be noticed
If it gets wet, it must dry quickly 24 – 48 hours is recommended Use your judgment !
If water gets in . . . it must dry out quickly
If can’t stop the water, remove the mold food
temporary solutions
Preventing Biological Growth
Thoroughly dry wet materials within 48 hours
Drying Add heat (vaporize)
+ Aggressive Air Exchange (remove) (outside air)
Note: De-Humidification may be necessary
1 school out of 44 2008-2009
Dehumidifiers Installed
Ensure proper drainage
Warm Air Rises
00
70 F
70 0 F
40
0
F
Portable is damp & smells moldy
“unplanned air flows”
What goes out
Must come in
Open crawl vents often allow more air (+ contaminants) to enter buildings Also: cold floor, frozen pipes, pests
Closed crawl vents can result in build-up of radon, moisture, etc.
Can’t decide ?
Crawlspace Guidance
Exhaust air from under groundcover to prevent entry of radon or other contaminants
Moisture
Fundamentals
Relative Humidity The degree of saturation of the air % of water holding capacity
“Relative” to the temperature If the air is half full = 50% rh If the air is 90% full = 90% rh Most molds will grown at ~85% rh and above
RELATIVE HUMIDITY FACT: Warm Air Can Hold More Moisture Than Cold Air TEMP. R.H.
RELATIVE HUMIDITY Raise the air temperature = lower the relative humidity TEMP.
R.H.
RELATIVE HUMIDITY Lower the temperature = increases the relative humidity TEMP.
R.H.
Moisture Dynamics Lower the temperature enough and the air becomes completely saturated
= Condensation
Moisture Dynamics Temperature at which air becomes completely saturated =
Dew Point Temperature =
100% Relative Humidity
40
0F
100% rh (fog)
40
0F
100% rh (fog)
70
0F = % rh
40 0F 100% rh (fog)
70
0F
=
35 % rh
COLD OUTSIDE
DEW POINT
High Relative Humidity = Mold
COLD OUTSIDE
Areas of High RH
RH% and Dew Point 95 % RH = the dew point is: only 3 degrees below air temp
85 % RH = the dew point is: only 6 degrees below air temp
60 % RH = the dew point is: • 20 degrees below air temp 0
70 F building air temperature
allow air circulation
Vent moisture outside
Mold under sink
Infrared Camera
Energy - Moisture Unplanned Air Flows
Warm
Cold
Optimum Moisture Level ? Depends on Occupants – Sensitivity to “dryness” – Sensitivity to “dampness”
Depends on the Building – Masonry & Plaster – Sheetrock & Wallpaper – Temperature of Materials
Suggest 30% to 50 % for IAQ
Relative Humidity in NW Schools • Properly ventilated schools generally result in lower relative humidity levels compared to many homes • Occupants in schools can experience “drying” effects from these lower relative humidity levels compared to their homes
Dust Mites dine on skin flakes
Mite feces = potent allergen
Require about 45% relative humidity to survive
Is there mold ? • Visual inspection – Indication of water or moisture – Visible mold or “mildew”
• Moldy - Musty odors • Health symptoms suggest exposure
Thorough Investigation Careful examination inside and out: faulty exhaust water leaks inadequate ventilation capillary action combustion cold spots duct leaks activities A thorough investigation also identifies the boundaries & extent of the cleaning & drying necessary for remediation work
Find the water leaks
water leaks = potential molds
Potential Water Entry Areas
Unsealed ducts + wet crawl space = moisture in building
Indoor temperature & relative humidity logger
100% 80% 60% 50% 40% 30% Date and Time
surface temperature
Infrared Camera
energy - moisture - unplanned airflows
calcium chloride vapor emission test: quantify the volume of water vapor radiating from a concrete slab Use this test to model the amount of moisture that emits from 1,000 square feet of slab surface in 24 hours.
result is expressed as "pounds" which is the equivalent weight of water, emitted as vapor, over 1,000 square feet in 24 hours. This test requires the use of a gram-weight scale with a gradation of 1/10th (0.1) gram. The calcium chloride container is weighed before and after exposure to the concrete slab. Vaprecision.com
Evidence of moisture and/or mold may not be obvious
“Blank” switch plate covering inspection hole
leaky windows + built in cabinets
Contain work areas with closed doors or poly sheeting Check pressures between zones Contain debris – do not track through clean zones Turn off air handlers and protect ducts
remove at least 2 feet of material around visible growth
CLEANING: Scrub!
Whoa ! Time to get serious with containment and PPE
note air pressure Maintain a negative pressure zone
Do It Yourself or Contract? • Depends on size of problem • Discuss with occupants • Consider your abilities • Look at cost-benefit
EPA Guidance for Mold Remediation in Schools IICRC S-520 Standard and Reference Guide for Professional Mold Remediation Institute of Inspection, Cleaning & Restoration Certification
Testing for Molds
Currently no meaningful mold exposure standards or thresholds Too many uncertainties: thousands of mold species measurements health impacts occupant sensitivities exposure complexities
Testing for Mold EPA and New York City guidelines
do not recommend airborne mold sampling as part of an investigation or remediation effort But, useful information may be obtained
IAQ Testing “Absence of Evidence . . .
is not Evidence of Absence” Testing can produce “False Negatives” But not “False Positives”
Air Sampling for Molds Compare outside to inside Compare “non-problem” zone with “problem” zone Look for viable and non-viable Look for other pollutants
Airborne sampling is a “snapshot in time” Settled particle sample is a “time integrated test” and provides evidence of other pollutants!
Who is doing the inspection, sampling, and analysis? Interpretation is critical aspect !
Air samples are a “snap shot in time”
Cleaning Mold: Is Bleach Necessary?
Bleach Bleach can kill - does not clean – Not always necessary to kill mold, But must remove mold – Soapy water is less dangerous – If necessary, treat cleaned surfaces with dilute bleach
Replace or Salvage? • Soft, absorbent materials that get moldy should usually be discarded – Paper, textiles, wallboard – “freeze-dry” valuable papers
• Small amounts of obviously superficial contamination may be cleaned with soap and water.
Preventing Mold • • • • • •
Water-resistant buildings Proper drainage Immediate & thorough drying Monitor for leaks & “cold areas” Exhaust “point sources” Ventilate properly