Green Schools Attributes for Health and Learning (2007) / Chapter Skim
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4 Indoor Air Quality, Health, and Performance
4 Indoor Air Quality, Health, and Performance
Pages 54-79
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From page 54... ...
thermal comfort for building occupants by heating or cooling outside air coming into occupied spaces. Ventilation can be supplied through mechanical systems, which draw air into and push air out of a building, or "naturally," through the opening and clos
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From page 55... ...
People themselves can carry pollen and allergen sources, such as dust mites and pet dander, into a school on their shoes, skin, and clothes. Internal sources include but are not limited to combustion products; building materials and equipment; educational materials; cleaning products; biological agents; and human activity.
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From page 56... ...
GREEN SCHOOLS: ATTRIBUTES FOR HEALTH AND LEARNING Indoor Ventilation Pollutants Natural, Moisture mechanical, or Structural/building Sources hybrid materials External Furnishings Operable Internal Cleaning products windows Pesticides Occupants Chemicals Biological agents Combustion products Indoor Environment Odors Outdoor Pollutant Thermal comfort Sources Relative humidity Operations Ambient air pollution & Airflow and Local point sources Maintenance Traffic Combustion products Biological agents Particulate matter Ozone Pollen Development Comfort Comfort Health Health Student learning Students Teacher Teachers absenteeism FIGURE 4.1 Relationships between pollutants, moisture, and ventilation and human comfort, health, and development. sources of pollution can contribute to indoor air pollutant concentrations when outdoor air is drawn into a school building through air intakes 4-1 located at the rooftop, at ground level, or from below-grade "wells." Outside air also enters the building through doors, windows, ventilation shafts, and leaks in the building envelope.
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From page 57... ...
and semivolatile organic compounds (SVOCs) are chemical compounds used extensively in building materials such as adhesives for wood products and structural materials, paints, and carpet adhesives.
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From page 58... ...
, and indoors (humans, building materials, fibers, bioaerosols, mold, pet dander) (Afshari et al., 2005)
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From page 59... ...
. • Sites of reported contamination include outside air louvers, mixing boxes (where outside air mixes with recirculated air)
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From page 60... ...
Ventilation effectiveness is based on the ability of the system to distribute conditioned air within occupied spaces to dilute and remove air contaminants. The principal standard for ventilation rates is American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE)
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From page 61... ...
. When reduced temperature was with new box outline combined with increased ventilation rates, task completion increased in a test of logical thinking (p < .03)
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From page 62... ...
No studies on the impact of increased ventilation rates and/or effectiveness on teacher health and productivity were identified. However, multiple studies have looked at the effects of increased ventilation rates in office buildings and call centers on adult health and productivity (Milton et al., 2000; Seppänen et al., 1999; Seppänen and Fisk, 2004b, 2005; Fisk et al., 2003; Wargocki et al., 2002; Wyon, 2004)
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From page 63... ...
Some studies found that increasing ventilation rates up to 20 L/s per person was associated with significant decreases in the prevalence of building-related symptoms or with further significant improvements in perceived air quality. The ventilation rate studies reported relative risks of 1.1 for building-related symptoms at low ventilation rates and 6 at high ventilation rates.
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From page 64... ...
Overall their literature review indicated that ventilation has a significant impact on several important user outcomes, including: • Communicable respiratory illnesses,2 • Building-related symptoms, • Task performance and productivity, • Perceived air quality among occupants and sensory panels, and • Respiratory allergies and asthma. Overall, these studies strongly indicate that although compliance with ASHRAE standards for ventilation rates may be the minimum acceptable 2See Chapter 7.
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From page 65... ...
However, the research conducted to date has not established an upper limit on the ventilation rates, above which the benefits of outside air begin to decline. THERMAL COMFORT Human perception of the thermal environment depends on four parameters: air temperature, radiant temperature, relative humidity, and air speed (Kwok, 2000)
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From page 66... ...
discusses perceived air quality and ventilation requirements in the context of indoor sensory pollution loads from occupants and materials. Exhaled breath, skin, sweat, dirty clothing, perfume, deodorants, and other body odors make the occupants themselves a source of the sensory pollution load degrading perceived indoor air quality.
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From page 67... ...
. These and other studies show that sensory pollution loads indoors are perceived by occupants and that dissatisfaction with perceived indoor air quality may have subtle effects on performance.
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From page 68... ...
used previous studies (primarily in office buildings) to develop a model relating building ventilation rates, perceived air quality, and temperature
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From page 69... ...
They estimated that increasing the average ventilation rate from 0.45 to 1.0 exchange per hour 4 would reduce the sick leave used by office workers from 5 days per year to 3.9 days per year. 4Air exchange per hour is a ratio between the quantity of air delivered to a space in an hour divided by the volume of that space.
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From page 70... ...
humidity in winter in cold climates; high humidity during humid weather; noise generated by forced air flow and fans; draft caused by forced air flows. Systems with ducts, fans, Additional risk factors from cooling coils: very high and cooling coils (air relative humidity or condensed moisture (e.g., in cooling conditioning systems)
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From page 71... ...
After initially lowering ventilation requirements in response to the early 1970s energy crisis, ASHRAE Standard 62-2001, "Ventilation for Acceptable Indoor Air Quality," now requires substantially higher ventilation rates for schools and other buildings. ASHRAE Standard 90.1-2001, "Energy Standard for Buildings Except Low-Rise Residential Buildings," and other energysaving measures such as more efficient motors, office equipment, and lighting, along with better thermal insulation for building envelopes, have systematically reduced the sensible heat loads of buildings.
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From page 72... ...
Ensuring that the air supplied is as clean as possible requires controlling the sources of pollutants and moisture within the ventilation system itself, cleaning the incoming outside air as much as possible prior to mixing it with the return air (most commonly this is going to be particulate filtration only, but where the outside air is very contaminated, gas-phase air filtration may also be used) , effectively and continuously maintaining the hygiene of the HVAC system, and controlling indoor pollutant sources to minimize the spread of airborne pollutants.
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From page 73... ...
Throughout much of the United States, ventilation systems need to control humidity as well as temperature and ventilation rates throughout the year. This is particularly true where schools are used year-round.
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Cleaning Although to date no systematic research has examined the relationship of cleaning effectiveness to student and teacher health, student learning, or teacher productivity (Berry, 2005) , a few studies have related methods for source reduction or control in schools to exposures to pollutants.
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From page 75... ...
CURRENT GREEN SCHOOL GUIDELINES Current green school guidelines contain many measures intended to improve indoor air quality. They typically endeavor to manage outdoor pollution in a number of ways.
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From page 76... ...
Finally, current green school guidelines contain numerous measures to reduce indoor pollutant sources: Two up-to-date industry standards are cited to ensure indoor air quality: ASHRAE 62.1-2004 IEQ (design guidelines) and the SMACNA IAQ Construction Guidelines.
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From page 77... ...
Despite emerging studies showing that thermal comfort may play a role in student performance, thermal comfort standards in green school guidelines are few. Typically they rely on compliance with the industry standard ASHRAE 55-2004 and do not address the control of humidity.
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From page 78... ...
Few studies have looked systematically at changes in exposures, health, or productivity based on changes in building materials, cleaning products, or cleaning practices. Recommendation 4a: Future green school guidelines should ensure that, as a minimum, ventilation rates in schools meet current ASHRAE standards overall and as they relate to specific spaces.
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From page 79... ...
INDOOR AIR QUALITY, HEALTH, AND PERFORMANCE Recommendation 4c: Additional research should be conducted to document the full range of costs and benefits of ventilation rates that exceed the current ASHRAE standard and to determine optimum temperature ranges for supporting student learning, teacher productivity, and occupant comfort in school buildings. Recommendation 4d: Studies should be conducted to examine the relationships of exposures from building materials, cleaning products, and cleaning effectiveness to student and teacher health, student learning, and teacher productivity.
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