IAQ In Schools: Problems and Solutions
by: Robert F. Goodfellow
A 2006 national report, Greening America's Schools, concluded that environmentally-friendly school buildings lead to lower operating costs, improved test scores, and enhanced student health. The report, produced by Capital E and co-sponsored by The American Institute of Architects (AIA), concluded that environmentally-friendly schools save an average of $100,000 each year. The study examined 30 green schools built between 2001 and 2006, and determined that the total financial benefits of green schools are 20 times greater than their initial cost difference.
The findings also indicate that there are tremendous benefits from energy efficient school design, not only from an economic standpoint, but also from far healthier environments through enhancements such as improved air quality. Among the study's conclusions:
- On average, green schools use 33% less energy.
- A study of Chicago and Washington D.C. schools concluded that better facilities could add three to four percentage points to a school's standardized test scores.
- Green schools typically have better indoor air quality (IAQ), which contributes to fewer sick days.
It's clear - cleaner air in our schools is a necessary component for students' success. But cleaner, healthier air may not be as simple as A-B-C.
Typical IAQ Problems in Schools
Indoor air contaminants can originate within the school building or be drawn in from the outdoors. If pollutant sources are not controlled, indoor air problems can develop even if the HVAC system is properly designed, operated, and maintained.
Air contaminants consist of particles, dust, fibers, biological agents (e.g., bacteria, viruses, and mold), and gases or vapors. Sources of indoor air contamination include polluted outdoor air and underground sources (e.g., radon, pesticides, and leakage from underground storage tanks).
Indoor air contamination can also be caused by a variety of indoor sources (e.g., equipment, furnishings, and housekeeping supplies). Indoor concentration levels of air pollutants can vary by time and location within the school building, or possibly a single classroom. Pollutants can be emitted from point sources, such as science storerooms, or from area sources, such as newly painted surfaces.
Pollutants can vary with time, such as only when floor stripping is done, or continuously such as fungi growing in the HVAC system. Indoor air often contains a variety of contaminants at concentrations that are well below any standards or guidelines for occupational exposure. It is often difficult to relate complaints of specific health effects to exposures to specific pollutant concentrations, especially since the exposures may be to low levels of pollutant mixtures.
The Key to Cleaner, Healthier Air
The conventional approach to air quality in schools is to introduce fresh, outside air to dilute contaminants. The amount of outside air introduced to the indoor environment depends on the number of building occupants.
Most schools' HVAC systems are designed for 15 CFM per person. This can be costly, in terms of conditioning outside air, and sometimes ineffective, when the outside air is polluted. Cleaning the air, rather than diluting it, can save energy and money and improve IAQ.
Most people are aware that outdoor air pollution can damage their health but many do not know that indoor air pollution can also have significant health effects. EPA studies of human exposure to air pollutants indicate that indoor levels of pollutants may be 2-5 times, and occasionally 100 times, higher than outdoor levels.
These levels of indoor air pollutants are of particular concern since most people spend the majority of their time indoors. Indoor air quality contributes to a favorable learning environment for students, productivity for teachers and staff, and a sense of comfort, health, and well-being.
Failure to respond quickly and effectively to IAQ problems can lead to numerous adverse health, cost, and educational process consequences, as children may be especially susceptible to air pollution. The same concentration of pollutants can result in higher body burden in children than adults because children breathe a greater volume of air relative to their body weight.
Schools are also unique in their environment. The occupants of schools are close together, with the typical school having about four times as many occupants as office buildings for the same amount of floor space.
A variety of potential pollutant sources exist in schools, including art and science materials, industrial and vocational arts, and gymnasiums. In combination with natural ventilation, schools may use many heating, ventilating, and air conditioning systems (HVAC), including unit ventilators and rooftop units. All require appropriate care and maintenance.
Filtration and Ventilation
Historically, increasing filter efficiency meant increasing energy and operating costs. It takes more fan horsepower to push air through denser, more efficient filters. These filters can load quickly and require replacement often. And diluting indoor air with more outdoor air means heating cold, unconditioned outdoor air in the winter and cooling hot, humid air in the summer.
Today, some high efficiency air cleaners, such as polarized-media electronic air cleaners, have low static pressures and high dust-holding capacities that are capable of cleaning air without increasing costs. These air cleaners can be used for cleaning indoor, re-circulated air, and also for eliminating odors and ultrafine particles from incoming outdoor air, such as vehicle exhaust emissions.
ANSI/ASHRAE Standard 62.1-2010, which is the basis for many local mechanical codes, provides three alternative procedures for determining minimum outdoor airflow rates: the ventilation rate procedure, the natural ventilation procedure, and IAQ procedure. The first two are prescriptive methods that are easy to calculate.
The IAQ procedure is more complex and based on performance criteria. It allows HVAC system designers and operators to reduce outdoor air when it has been determined that the air inside the space is clean enough.
Impacting the Bottom Line
So we can see that reduced outside air can save money and pay for the cost of the air cleaning equipment. Here's the breakdown:
Energy Consumption. In a typical building with no smoking and no unusual contaminant sources, outdoor air levels can often be reduced to between 7.5 and 10 CFM per person. For example, a school with a 60-ton rooftop unit can expect annual savings on utility costs in the range of $3,000 to $12,000 depending on the geographic location of the building, the utility rates, and the hours of operation.
Capital Investment. Reduced outside air can favorably impact equipment selection. Lower fan horsepower requirements can translate into smaller tonnage equipment.
Maintenance. Polarized-media electronic air cleaner media pads last longer than conventional passive filtration, extending change-out intervals and saving labor costs. Maintenance personnel like the light-weight pads that are lighter, less bulky than equivalent efficiency bag or cartridge filters, and easier to store and handle.
But Wait, There's More!
High efficiency air cleaning systems offer other benefits for schools, as well:
Improved IAQ. High efficiencyair cleaners remove dangerous airborne particles that other air cleaning systems miss - including odors, VOCs, smoke, bacteria, allergens, fine dust, molds and pollen - without producing any harmful ozone.
Mold Prevention. Air cleaners that collect mold spores reduce the risk of potential mold problems by removing mold spores from the air stream, as well as sub-micron particles, which can provide a food source for mold growth.
Versatility. Few air cleaners offer the same versatility when it comes to application in the types of HVAC equipment used most frequently in schools. Versatile air cleaners can be applied to packaged terminal units, unit ventilators, rooftop units, water-source heat pumps, as well as large custom air handling units.
Increased Attendance. Studies document the correlation in the reduction of student and staff absenteeism to cleaner air in schools. Poorly controlled asthma can more than double healthcare costs and threaten educational achievement.
In the August 2011 issue of The Archives of Allergy, Asthma & Immunology, researchers at National Jewish Health reported that children with "very poorly controlled" asthma missed an average of 18 days of school each year, compared to 2 or less for other asthma patients.
The researchers studied 628 children ages 6 to 12 with severe or difficult-to-treat asthma and evaluated direct medical costs - medications, unscheduled office and emergency visits, and hospital admissions, as well as indirect costs including school/work days lost. Very poorly controlled asthma patients incurred an average of $7,846 in costs compared to $3,766 for patients with well controlled asthma.
Researchers estimated that one parent would have to stay home for each missed school day, at an average cost of $172 dollars per day. Indirect costs for very poorly controlled asthma, $3,078, were more than eight times as great as the costs for not well controlled asthma, $369. With no missed school days among well controlled asthma patients, their indirect costs were $0.
The large variance for missed school days suggested another cost not included in the researchers' calculations - low educational achievement. They cited a study of 3,812 students in Missouri indicating a much higher chance of failure for those absent an average of 12 school days.
Case in Point
Endeavor Elementary School in West Chester, Ohio is an example of reduced ventilation within a school building. As the school building neared completion just prior to the 2007/2008 school year, Endeavor was looking at the possibility of using a heat recovery ventilation system in order to save money on operating costs. It was going to be costly to condition outside air at the 15 CFM per person minimum requirement.
Utilizing the ASHRAE Standard 62 IAQ Procedure and the Ventilation Rate Procedure, a prescriptive method of determining outside air requirements by concentrating on controlling the contaminants of concern within a space, the result was a reduction in the outside air requirement of almost 60 percent. Roughly translated, that's $30,000 on the HVAC equipment capital investment.
A month after the school opened, the air was tested to confirm its quality. Indoor particulate counts were measured in several size ranges, as was CO, humidity and total VOCs. Indoor data was then compared to outdoor conditions. Tests confirmed that indoor air was as clean or cleaner than it would have been, had outside air been brought in at 15 CFM per person.