Wednesday, February 22, 2012

A home is comfortable when temperature and humidity is controlled.

 Comfort Cooling Controlling Humidity and Temperature.
An air- conditioner ability to remove moisture increases when the equipment runs for longer periods of time. At the beginning of every cycle in hot moist climates, the air conditioner puts moisture into the house as water is evaporated off the inside coil. Since a smaller air conditioner runs longer to keep the house at the temperature set point, it removes more moisture than a larger unit would be able to achieve.
A 5-ton unit, running for five minutes would remove 1.4 pounds of water. A 2.5-ton air conditioner, in the same house, running for ten minutes would remove 1.7 pounds of moisture. This is an increase in moisture removal of 21%.
The amount of moisture removed is not only a function of how long the air conditioner runs, but also it’s Sensible Heat Ratio (SHR - the percentage of the total capacity delivered as lower house temperature).
A low Sensible Heat Ratio will result in more moisture removal. For hot wet climates where moisture removal is important, air flow across the coil should be reduced slightly to increase the SHR and the air conditioner condensing unit and indoor coil combination should be chosen to have a low SHR. Please note, if you don't use the outdoor unit manufacturer's indoor coil, you cannot use their published SHR.
Typical matched units from major manufacturers have Sensible Heat Ratios in the 68% to 80% range when it is 95¡F outside and 75¡F with 50% relative humidity inside. Even Temperatures are Necessary for comfort. Some people don’t experience problem with moisture, but  have problems with uneven temperatures when the air conditioner was on
The following describes two methods contractors can use when attempting to get proper distribution and mixing of the air.
An old method is to use a large air handler fan to circulate air all or most of the time. This is sometimes effective in mixing the air but at a high price. There is an old rule of thumb that between four and six house volumes of air must pass through the air handler in an hour. At six air changes this means a 1400 sf. home would have to have a continuously running fan that delivers 1120 CFM (equivalent to almost 3 tons) regardless of the cooling load of the house.
The common practice is to install an air conditioner (inside and outside unit) with the capacity to meet those flow requirements.

  • There are many disadvantages to this scenario:
  • the need for a larger and more expensive duct system to handle the increased flow
  • increased duct conduction due to constant circulation and the larger surface area of duct system
  • reduced latent capacity due to constant circulation and short compressor cycles (caused by the oversized outdoor unit)
  • increased cooling load due to duct leakage effects and fan energy delivered as heat
A better solution is, to design and install a delivery system that properly distributes the cooling to each room, then to select and place supply grilles that promote mixing by "throwing" the delivered air into the right places in the room. Air Conditioning Contractors of America has produced manuals to guide contractors in this process (Manual D-Duct Design and Manual T-Terminal Design).These Manuals lead the installing contractor through the process of selecting the proper size duct and type of register based on the location of the register, size of the room, restriction the duct run, and the dimensions and heat gain of the room. Unfortunately, only the best contractors and builders ever pay attention to these critical details.
The problems of stagnation and overheating can be reduced by proper implementation of ACCA procedures. These problems can be further reduced by ensuring that the assumptions built into these manuals are not violated. For example, it is assumed that there is no duct leakage in the system. Any long time reader of Home Energy will immediately note that this assumption is violated in nearly all homes (including new ones). Proper installation of the duct system and leakage testing are essential to obtain comfort.
Another assumption is that the conduction losses are the same percentage of the delivered cooling regardless of the length of the duct run. This would be an insignificant assumption in a heavily insulated system (and R-4 is not heavily insulated). Long duct runs through the attic loose over 15% of their cooling capacity before the conditioned air reaches its destination. Long duct runs need additional insulation to deliver the proper amount of cooling to the distant rooms.
Uneven temperatures have become more common due to the "modern" practice of severely reducing overhangs above the windows. Without overhangs, rooms with west facing windows will overheat in the afternoon since their need for cooling can easily double Drafts Destroy Comfort
A draft exists when unwanted air movement causes cooling on one part of your body. The colder the air and the faster it is blowing, the more offensive drafts are. Air conditioning drafts are characterized by cold, high velocity air striking your body. Studies show that these drafts are even more offensive if they are intermittent.
Oversized air conditioners are a major contributor to drafts. An oversized air conditioner is almost always married to a duct system that is unable to deliver the amount of air necessary for proper air conditioner performance (more on this later). The result is a poor compromise air flow that is too low for the air conditioner and too high for the duct system. The low air flow across the oversize coil produces colder delivery temperatures and the high air flow through the ducts and grilles produce high pressures, noise, and high velocities at the grilles. When low delivery temperatures are coupled with high velocity discharge through inappropriately selected (small and without proper throw or spread - often the cheapest) and poorly placed grilles, occupants experience drafts.
Bigger is not Better, Quiet is Better
We all know how noisy forced air cooling systems can be. These noises can come from the grilles, the ducts, and from the fan. Our perception of noise is affected by both the frequency and the level of the sound. Higher frequency sounds (the sounds generated by high discharge velocities at grilles) are more offensive than lower frequency sounds (the sounds generated by the fan). For grilles there is a Noise Criteria (NC) rating that mimics the human perception of sound. The NC for a particular grille increases as more air is forced through it.
When an air conditioner and duct system are properly is sized to meet the cooling load it is easier distribute the cool air without being noisy. When a duct system is being designed, the NC level and face velocity of every supply grille should be considered and held below NC-25 and 700 fpm for a quiet system.
Grilles with dampers are invariably noisier than equivalent grilles without dampers. When the dampers are partially closed, the pressures and leaks in the ducts increase and the air flow across the coil is reduced. Occupants generally close dampers to redirect air to another room that they believe needs more delivery. If the system is designed correctly dampers, either at the register or in line balancing dampers should not be needed.
Bigger is not Better, Efficient is Better
There is a lot of emphasis on the rated efficiency of air conditioners. Unfortunately, this necessary emphasis on equipment design has overshadowed efforts to improve the selection and installation of the entire air conditioning system. It is incorrectly assumed by builders, contractors, and the buying public that if you spend the money on a high efficiency air conditioner you have gotten all the efficiency you can. But common problems such as over sizing, improper installation, and low air flow, and leaky duct systems mean that customers don't get the efficiency they paid a premium for.
A System with Correct Air Flow Helps Make an Efficient System Most air conditioners are designed to have 400 CFM per ton of air flow across the inside coil. When the air conditioner is coupled with a duct system that meets Manual D criteria, the proper flow is achieved.
However, since air conditioners are commonly oversized for the heat gain of the home and the duct systems are not designed to Manual D even new systems are usually deficient in air flow. This situation only gets worse as the inside coil picks up dirt. In a recent laboratory test of a high efficiency air conditioner, Proctor Engineering Group found a 7 % drop in efficiency when the air flow was reduced by 30%. In order to ensure that the design air flow is being achieved, the installing contractor must measure the air flow across the inside coil.
An Air Conditioner with Proper Charge Helps Make an Efficient System A new split system air conditioner comes from the factory with the proper amount of factory installed charge for a standard length set of refrigerant lines. When the unit is installed, the contractor needs to evacuate the lines and indoor coil and weigh in any additional charge needed for the line set length increase over the standard length. Most of the time this is not done. This results in, leaks not being detected, air and moisture being captured in the line set and coil, and the unit ends up undercharged. In many cases the amount of undercharge is severe.
In the summer of 1995, Proctor Engineering Group and Arizona Public Service Company monitored a group of twenty two newly constructed homes.
Nearly all of those homes had undercharged air conditioners. One of the worst units had 62% of correct charge (and 79% of proper flow). The homeowner complained to the builder that the air conditioner was not working right. She was told that the wrong amount of insulation had been installed in her attic and an insulation contractor was called in to apply additional insulation.
Shortly thereafter the true problem showed itself when the air conditioner compressor failed. Eliminating Duct Leaks Helps Make an Efficient System The evidence against leaky and under insulated ducts continues to mount. Leaky ducts are a large contributor to system inefficiency and the negative effect increases with outdoor temperature. The Arizona Public Service Company test found that sealing a 13% supply leak saved 22% of the cooling energy consumption in the 100¡F to 105¡F temperature range.
To ensure a tight duct system the installing contractor will have to do a test of duct integrity using specialized tools. (See the Sept/Oct Î93 issue of Home Energy for more information on duct testing.)
A Smaller Air Conditioner Helps Make an Efficient System Air conditioners are very inefficient when they first start operation. It is far better for the air conditioner to run longer cycles than shorter ones. The efficiency of the typical air conditioner increases the longer it runs. For example, increasing the run time from 5 minutes to 9 minutes resulted in a savings of 10% for the unit described in "Bigger is not better" HE May/June 1995.
Because of the inefficiencies associated with the start up of the air conditioner, under most conditions, a smaller air conditioner will produce the same amount of cooling with lower energy consumption.
Bigger is not better.
An air conditioner sized to ACCA Manuals J and S is big enough. Industry specialists who design and sell air conditioners have long used Manual J as a standard method for determining the amount of cooling needed to deliver thermal comfort to single family residences. The procedure is used to calculate room-by-room loads for duct design purposes and whole house loads for equipment selection. It was jointly developed by the Air Conditioning Contractors of America (ACCA) and the Air-Conditioning and Refrigeration Institute (ARI) and it is based on a number of sources including the ASHRAE Handbook of Fundamentals.
Despite the widespread use of this procedure, many contractors have been reluctant to accept the ability of Manual J to deliver adequate cooling under design conditions. One reason for this reluctance has been the lack of information about how actual cooling loads compare to Manual J estimates. While many who have used Manual J extensively have long suspected it has an over sizing margin, field studies had not been performed to verify this anecdotal evidence.
New data show that Manual J overestimates the sensible cooling load in hot dry climates. It is likely that the same is true of the sensible load in hot moist climates. Proctor Engineering Group, Electric Power Research Institute, Nevada Power, and Arizona Public Service monitored air conditioning systems installed in new homes in Phoenix, Arizona and Las Vegas Nevada. By testing the actual cooling capacity required to maintain comfort under severe conditions, these tests have yielded the first measurements that confirm and quantify the overestimation present in Manual J.
The studies showed that even when faced with an extraordinarily hot summer when almost 200 hours exceeded design conditions (design conditions are exceeded only 73 hours in a typical summer), the actual sensible cooling loads of the houses were less than Manual J estimates.
At the most intensively monitored sites in the studies, the data acquisition equipment recorded air flow, temperature drop and moisture removed from the conditioned air. The research team calculated the actual capacity delivered by the air conditioner for every air conditioner cycle.
The systems were monitored from July 30 through September 25, 1995. Occupants were free to adjust their thermostat settings to any value, but most kept a constant thermostat setting. Most of the systems monitored were typical installations (including leaky ducts that increase the cooling load that the equipment needed to deliver).
One typical house illustrates the overestimation contained in Manual J. System 26 had an 11.6% return leak and a 6% supply leak Figure 2 displays the hourly sensible cooling load against the outdoor temperature.
Outdoor temperatures at this house ranged as high as 116¡F (according to ASHRAE Fundamentals the mean extreme temperature for Phoenix is 112.8¡F.) Even though this time period was extra ordinarily hot, the sensible load requirements for all but 3 hours (0.2%) of the 1316 monitored hours the load was less than Manual J estimated cooling load. Manual J over predicted the design load for this house by almost 50%.
These data illustrate that there was no need to oversize the air conditioner beyond the Manual J cooling load because Manual J already overestimates that load.
In fact the air conditioner installed in this house had a design sensible capacity 24% larger than Manual J and that excess capacity was not useful. Because of the over sizing however, the homeowners paid approximately $330 in additional first costs and they will pay additional unnecessary operating costs every summer month for the life of the system.
Using Your Foot for Target Practice
We know designers who determine the system air flow based on floor area (this oversize’s the air conditioner in energy efficient homes), and then try to squeeze down the size of the duct system so that it can be installed in the house. They explain that they can’t use a higher insulation level on the ducts because there is no room, and, when faced with poor performance, increase the size of the air conditioner. If the goal is comfort or efficiency, they are shooting themselves in the foot.
It is not uncommon for poor cooling performance to be attributed to insufficient equipment size when in fact there is more than enough cooling capacity. Usually, in a residential system, this situation is caused by poor design and installation that: reduce the capacity of the system by incorrect charge, low air flow, and duct leakage, cause noise, drafts, and uneven cooling by using an oversized air conditioner relative to the cooling load and undersized ducts relative to the oversized unit. Most household air conditioning problems will be eliminated when the capacity of the air conditioner is reduced to ACCA Manual J and Manual S standards, an appropriately designed, insulated, and leak-proof distribution system is used, and the system is installed to meet the manufacturers standards These systems will have higher efficiencies because they will run longer cycles and will circulate air as needed a larger percentage of time. Properly designed and installed air conditioners are reliable and will deliver comfort to each room of the house for less cost.
Recommendations Summary List
  • Wherever possible reduce the cooling load of the house. Overhangs above east and west windows are particularly effective in reducing cooling load...
  • Perform Manual J for all installations and select equipment using Manual S.
  • Insure that the system installed never exceeds the capacity of the equipment suggested by Manual S.
  • Size duct systems based on Manual D. If in doubt size upwards.
  • Determine the grille location and characteristics using Manual T.
  • Confirm proper evacuation of the line set and indoor coil with a micron gauge.
  • Confirm proper charge using the manufacturers suggested method.
  • Confirm proper airflow by test. The flow can be determined from the coil pressure drop when pressure/flow data is available from the coil manufacturer or can be determined with a duct test rig or flow hood.
  • Increase the duct insulation above R-4 (at least on long runs in the attic).
  • Confirm that the duct leakage is less than 3% of coil air flow for a new system and less than 6% of coil air flow for an existing system
Jules Williams.

Wednesday, February 15, 2012

One of the most cost effective ways to obtain home and business Heating.

Jules Williams    Date 2/15/2012.


An Engineering  marvel that gets very little mention:

It is not common with today’s technologies to find an operation that provides more out- put compared to the energy necessary to initiate a  process. The HVAC heat pump produces  out levels  much higher than the energy needed for its operation.

We all know that heat flows from a warmer to a cooler condition. How is it possible to obtain  enough heat  from outdoors when the  temperature  is 35 degrees Fahrenheit  or lower in order to heat an indoor space?
OPERATION OF A TYPICAL HEAT PUMP: The heat pump uses a refrigeration cycle identical to a conventional air-conditioner. A typical air-conditioner circulates a gas that has a low temperature boiling point through a coil located in the inside of a home or business. The gas being colder than the indoor air picks up heat from the space, and carries the heat to the outside where  air passing through the out -door coil removes heat from the gas. The cycle is repeated until the air reaches a desired temperature.
The Heat pump operates in an identical way except it is designed to heat and cool by reversing the coils automatically. The indoor coil becomes the outdoor coil, in-order to obtain cooling or heating.
WHY WOULD I NEED SUCH A CONTRAPTION: Considering the unpredictable cost for electrical energy, locations with no natural gas has to heat homes and business with electrical heaters. Electric heating is expensive and there are other issues associated with resistance heating.
Last week I operated a test 3 ton heat pump when the outdoor temperature was 40 degrees Fahrenheit  using refrigerant 410A. The discharge air temperature  to the house was 75 degrees Fahrenheit . The unit was consuming 2400 watts to operate, and was delivering 27000 BTU of heat. A typical heat pump can provide 3.29 BTU’s for every watt that it consumes for operation. Compared to using electric heating , the input compared to the output would be 1 to 1. The heat pump  provides more than 2 output  to 1 input. In fact at 17 dry bulb and 15 wet bulb the heat pump performs at 2.6 output compared to input energy. However at 47 dry bulb and 43 wet bulb which is about normal winter for most of Texas, the heat pump operates at 3.6 times its input consumption.

Energy savings using a heat pump compared to using electricity to heat a building is between 2.5 and 3.5 time greater using a heat pump to produce heating. Indoor comfort condition is easier to obtain using a heat pump  when compared to using electric resistance heating.

The heat pump operates for more hours than a conventional condenser when the condenser is sized and installed correctly.
The life expectancy of the heat pump may be less than the condenser; however considering the cost savings associated with operating a heart pump compared to resistance electrical heating the heat pump should be considered for  its economic operation.
My recommendation to home and business owners  is to seriously consider replacing condensers with heat pumps when access to natural gas is not possible. The cost for operating the heat pump will be 2.5 to 3.5 times lower with the heat pump  when compared to electric heating.

Thursday, February 9, 2012

Acceptable Carbon Monoxide levels for residential applications.

Acceptable Levels of Carbon monoxide in Homes.

Standard for Action Levels:
The following action levels have been defined as minimums for BPI certified Carbon Monoxide Analysts. Analysts may work for a government agency or business entity that has adopted more stringent standards than the ones defined in this document. As such, CO Analysts may enforce those higher standards. Under no circumstances shall a BPI certified CO Analyst recognize less stringent standards or ignore conditions in excess of the defined action levels. The action levels are considered net indoor ambient readings - i.e. - indoor ambient minus outdoor ambient readings 0 to 9 parts per million (ppm)
Normal - No Action: Typical from: outdoor sources, fumes from attached garages, heavy smoking, fireplace spillage and operation of unvented combustion appliances. With ambient conditions in this range, analysts may continue testing sequences 10 to 35 parts per million (ppm) .

Marginal: This level could become problematic in some situations.  Occupants should be advised of a potential health hazard to small children, elderly people and persons suffering from respiratory or heart problems. If the home has an attached garage, document CO levels in garage. Accept this level as normal for unvented appliances but not for vented appliances. If unvented appliances are in operation, recommend additional ventilation in the areas of operation. With ambient conditions in this range, analysts may continue testing to locate the CO source.

36 to 99 parts per million (ppm) Excessive: Medical Alert. Conditions must be mitigated. Actions: Ask occupants to step outside and query about health symptoms. Advise occupants to seek medical attention. If occupants exhibit any symptoms of CO poisoning, have someone drive them to a medical facility. Enter the building, open doors and windows to ventilate the structure. Turn off all combustion appliances until the CO level has been reduced to safe levels. If forced air equipment is available, continuous operation of the air handler is recommended at this time. If the home has an attached garage, document CO levels in garage. Test combustion appliances one at a time to determine the source of CO production. If an appliance is determined to be the source of CO production, it should be shut off and not used until a qualified technician with proper test equipment can service it.

100 - 200 parts per million (ppm)
Dangerous: Medical Alert. Emergency conditions exist. Actions: Evacuate the building immediately and check occupants for health symptoms. Advise all occupants to seek medical attention.
Occupants should have someone else drive them to a medical facility. If occupants exhibit symptoms of CO poisoning, emergency service personnel must be called. Evacuation is important, but Analysts must not subject themselves to excessive conditions. Maximum exposure time is 15 minutes. Open all doors and windows that can be done quickly. If the home has an attached garage, document CO levels in garage. Disable combustion appliance operation. Continually monitor indoor ambient levels while moving through the building.
 Once the atmosphere within the structure has returned to safe levels and the appliances have been turned back on, locate the source of CO production for corrective measures.

Greater than 200 parts per million (ppm)
Dangerous: Medical Alert.

 Jules Williams

Thursday, February 2, 2012

IAQ concerns for schools.

THE PROBLEM OF POOR INDOOR AIR QUALITY IN SCHOOLS (Research Advantix Systems.)Jules Williams.
 Parents worry about many things when they send their children off to school each morning, but the quality of the air their children breathe throughout the day is likely the last thing on their minds. Most parents assume that schools provide a clean, healthy and safe environment, and that their children will have an opportunity to learn in a setting that fosters growth and creativity, without undue distraction.
Most parents in the United States may believe their children’s schools are safe, but they are wrong. A June 2000 U.S. Department of Education study found that, in the mid-1990s, one in five U.S. schools (about 25,000) reported unsatisfactory indoor air quality (IAQ). Today, millions of children attend schools plagued by poor IAQ due to the presence of molds, toxins, chemicals and other unhealthy environmental factors. These potentially harmful conditions dramatically impede the performance of both students and teachers (Healthy Schools Network (HSN), Who’s In Charge? 2006). Poor IAQ has also been documented to cause serious, long-lasting and life-threatening health problems. The Environmental Protection Agency (EPA) recommends various steps be taken to improve the problems which include diligently monitoring and regulating moisture in schools, implementing programs to oversee good air quality maintenance and utilizing new technology to improve ventilation and dehumidification in facilities.
The problem of poor indoor air quality in schools is widespread and its health risks are too important to ignore. The following is intended to outline the problem, its detrimental impact on the health of students and teachers, and provide recommendations for how poor IAQ in schools can be addressed.

The Prevalence of Poor Indoor Air Quality in Schools
Half of the nation’s 120,000 public and private schools are estimated to have polluted indoor air (HSN, Who’s In Charge? 2006).These affected schools enroll 55 million children each year, who on any given day are at risk for developing health symptoms related to poor IAQ. Despite the high number of children at risk, there is no outside public health agency tasked with regulating and enforcing guidelines with regard to unsafe indoor air environments in schools. The nation’s public school system also employs six million individuals who are exposed to unhealthy indoor air. Many have documented being aware of poor IAQ within their facilities (HSN, Who’s In Charge? 2006). A survey of school nurses conducted in 2010 found that 40 percent of respondents knew children and staff who had been adversely affected by pollutants in schools (HSN, NASN Survey, 2010). More than 75 percent of surveyed nurses said their schools had no indoor air quality team or coordinator. Needless to say, there are far too few resources and organizations actively working to resolve the problem of poor IAQ in schools, which has been called “America’s largest unaddressed children’s health crisis” by teachers (HSN, Who’s In Charge? 2006).

Causes of Poor Indoor Air Quality in Schools
 According to the EPA, levels of indoor air pollutants may be two to five times higher, and in some cases, more than 100 times higher than outdoor levels. The quality of air is influenced by a number of factors, including:

 Number of particles and contaminants present – Called “indoor air pollutants,” these include mold, bacteria, dust mites, animal dander, second-hand smoke and chemicals from cleaning products.

 (EPA, Indoor IAQ and Student Performance, 2003). Many of these also serve as triggers for asthma (EPA, Managing Asthma in Schools, 2010).

 Level of relative humidity and temperature – Both humidity and heat influence the growth of bacteria and mold, some species of which contain toxins that are particularly hazardous to humans.

 Effectiveness of heating, ventilation and air conditioning systems (HVAC) – Poorly operating HVAC systems can cause indoor air pollutants and carbon dioxide to become concentrated to levels that are harmful to humans. HVAC systems that do not effectively control relative humidity can promote the growth of bacteria and mold. Moisture, dirt, bacteria and build-up of other harmful contaminants in HVAC systems also degrade the quality of the air.

 Building repair – Older school buildings present a maintenance challenge for many school districts across the country. Aging buildings that suffer from leaks, water damage and excess moisture significantly contribute to poor air quality (EPA, Indoor IAQ and Student Performance, 2003).

Current Regulations on Indoor Air Quality in Schools
Laws regulating IAQ in schools are highly variable and difficult to categorize. Some are driven by action steps and processes (for example: create an IAQ monitoring committee), outline specific procedures for building inspections, instruct how employee complaints should be filed or require explicit steps for conducting safe renovations. These laws might be addendums to existing state laws regarding other issues that affect IAQ, such as pest control, the use of pesticides or regulation of hazardous materials (HSN, Sick Schools, 2009). The Environmental Law Institute publishes an annual database of state IAQ Laws, which include a comprehensive listing of state guidelines (HSN, Sick Schools, 2009).

Health Risks Associated with Poor Indoor Air Quality
A growing body of research continues to link student performance to the quality of the air that they breathe. It has been shown that illnesses and frequent absences have a negative impact on overall student performance as well. Short-term physical health effects of poor IAQ on students include fatigue, nausea, inability to concentrate and impaired memory and focus. These problems are often caused by poor air ventilation (EPA, Indoor Air and Student Performance, 2003).
School ventilation systems are put in place to remove or dilute airborne contaminants (from people breathing, cleaning agents, pathogens and other agents) by increasing circulation of fresh air. In certain concentrations, these contaminants can be harmful. They are also used to decrease levels of carbon dioxide, which in high levels has been documented to decrease student concentration and performance on tests and increase the number of student complaints of health problems compared to classes with lower carbon dioxide levels (NCEF, Do School Facilities Affect Academic Outcomes? 2002).

One EPA study found that students in classrooms breathing higher rates of cleaner, outdoor air scored up to 15 percent higher on standardized tests compared to students in classrooms with lower rates of outdoor air ventilation.
Other adverse health effects from exposure to poor IAQ include asthma and respiratory illnesses. Asthma, a chronic respiratory inflammatory disease that causes the airways to constrict and leads to wheezing, breathlessness, and coughing is one of the leading causes of absenteeism for children in the United States and is exacerbated by many triggers found in schools with poor IAQ (EPA, Managing Asthma in Schools, 2010). Millions of children suffer from asthma and the disease collectively accounts for more than 14 million missed school days a year (EPA, IAQ in School Performance 2003). 4 |  
The amount of moisture found in buildings has been called an issue of public health by the Institute of Medicine as there is a significant association between damp indoor spaces and asthma attacks (IOM, Damp Indoor Spaces and Health, 2004). It is widely accepted that improved IAQ reduces asthma related absenteeism (HSN, Sick Schools, 2009).
Poor indoor air quality caused by dampness and mold, has also been shown to cause a significant increase in health problems. Their presence can induce coughing, throat irritation, tiredness, headaches and wheezing. People with compromised immune systems, or who are more susceptible to infections, are more likely to suffer the ill effects from mold and other products of damp, indoor environments (EPA, How does IAQ impact student performance? 2010 and IOM, Damp Indoor Spaces and Health, 2004).
The health risks associated with poor indoor air quality can be dangerous and in severe cases, deadly. Both children and adults exposed to these toxic air environments in schools are at risk for developing physical symptoms related to poor IAQ. However, the impact of polluted air on children’s health may be far greater than it is it to adults, as their bodies are still developing and are therefore more vulnerable (EPA, How Does Indoor Air Quality Impact Student Health and Performance? 2010). Also, while there are legislative mandates and systematic protections in place for adults with regard to their safety in the workplace, there are fewer protections in place for children in schools (HSN, Who’s In Charge? 2006).

A Vicious Cycle: The Impact of Improved Ventilation on Humidity and Mold
It would seem that the answer to these problems is to simply increase the level of fresh air circulating in classrooms – to dilute the levels of harmful pollutants and carbon dioxide. In theory, this is a logical solution. However, with increased fresh air there is also an increase in air moisture in humid climates which conventional HVAC systems have difficulty in controlling. Increased moisture and humidity contributes to the growth of mold and bacteria in the air which can be extremely hazardous to humans. It is therefore important to recognize that the seemingly obvious course of action to improve school air is a vicious cycle, because improving ventilation heightens the potential risk of mold and bacteria growth.
The key to mold control is humidity control. A more effective solution to this cycle is to effectively end the cycle by increasing ventilation and removing humidity. By keeping the air dry, it would also be free of mold and bacteria.

The Dangerous Impact of Poor Indoor Air Quality in Schools
Florida is one of the nation’s warmest and most humid states. Buildings are frequently affected by air quality problems due to increased heat and humidity. During the school year, 2.6 million children and hundreds of thousands of teachers and other employees spend at least six hours a day in Florida's public schools. Yet, there are still no universal laws or enforcements in place to govern how schools should monitor, detect and handle mold buildup and other indoor air-quality issues. In 2010, in an effort to uncover the full extent of the problem in Florida schools,

The Orlando Sentinel reviewed thousands of maintenance work orders, school district reports and complaints from parents and teachers across five counties, which revealed numerous instances of dangerous air quality conditions that were improperly addressed by school administrations, or in some cases, ignored altogether