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An Animation...
The following is an animation of how dirty ventilating systems cause harm. While this is provided by a company with a product to sell, we can tell you that exactly that sort of problem existed in the first school our director became ill in - in fact, dirty strings of filth were hanging out of the vents, which also were covered with dirty particles and globs - the air the school occupants were breathing came out of these! The particles would float in the air - one could see them, at times! http://www.classroomiaq.com/
The following is an essay re: Problems With Ventilation Systems, by a prominent engineer, Mark Lentz, ASHRAE Technical Committee TC 9.7 - Educational Facilities, Member (Founding), (2005-Present), of Wisconsin.
Problems With Ventilation Systems
The mold issue has become serious. Architects, engineers and insurance companies are frightened of the issue. A lot of schools can no longer even obtain, much less afford, mold insurance coverage.
Microbiologists have the best understanding of mold. It is their business, their profession, their avocation. However, this is not true of architects, engineers, building inspectors, and even of most health inspectors who between them will have little or no formal education in what contributes to mold growth, and what needs to be done to control it. Since the building codes have yet to even address the issue, building inspectors typically don't know what to look for and have no guidance as to what to do if they find mold. In short, the construction industry doesn't have a very good handle on the problem, and this is aggravated by the fact that neither do health officials.
However, with the passage of time and study of problem buildings, a few things are beginning to come to light.
We know that the threshold of sensitivity to the toxins produced by molds varies substantially between individuals, and that young children are most susceptible due to the fact that their immune systems are still developing. We know that sensitivity increases with time and exposure. We also know that depending on the types of molds (and myco- and endo-toxins involved) certain types of reactions are more or less predictable.
We know that mold needs three things to bloom and grow: nutrients, moisture, and the right range of temperatures. Wherever we find all three, we typically find active mold. We also know that by taking any one of the three away, we will see mold go dormant. Mold can live on almost anything organic, so it is all but impossible to eliminate nutrients. The temperatures molds like are similar to those we like ourselves. So the most effective control strategies are typically constructed around humidity control, air filtration, and dilution ventilation. There are a few active control strategies which employ chemicals and ultra-violet light for use in air handling systems, but these are typically polishing processes and can themselves carry risks.
We also know that people do not typically respond to mold, itself. What they respond to are the myco- and endo-toxins molds produce. We also know that mold spores are tough little organisms. Bleach will not kill most spores or destroy the myco- and endo-toxins. And this is why cleaning up mold infested properties can be so terribly difficult and expensive, and why simply cleaning up a school will not correct the problem.
We know that an extremely high proportion of buildings with mold problems are relatively "new" structures built in the past 5-30 years during which time the construction industry has actually been building much better buildings with well insulated envelopes and roofs.
Most, but not all, of these buildings are also air conditioned.
So, how can this be? I think that the best way I can describe the situation is as an unanticipated consequence of our efforts to reduce energy usage. I will also be frank in stating that it is an issue for which not all of the answers are known at this time.
Wall and roof systems are also typically be build to be relatively impervious to migration of air through the wall and roof systems. This is done to reduce the amount of energy required to support the envelope. It also means that they don't breathe, so when moisture gets into them, it is very difficult to get that moisture out.
Air conditioning can actually create the kinds of conditions necessary for mold and mildew to grow and florish, particularly in hot and humid weather. What's more, many of the most common HVAC system types not only creating conditions conducive to the growth of mold and mildew, but also actively serve to spread infestations throughout schools and homes.
....the role of the HVAC system in this problem ...:
One of the consequences of building well insulated wall and roof systems is that they reduce heating and cooling loads.
This results make the heating, ventilating and air conditioning (HVAC) systems smaller.
Tight building construction limits the amount of air passing through building construction. Since the amount of air delivered by an HVAC system is usually dictated by cooling loads, this means that they will also move less air.
Ventilation is needed to dilute and flush contaminants generated by people, furnishings and building materials from buildings. And, good ventilation is particularly important in previously infested facilities.
Our need for ventilation is completely independent of what is needed to maintain thermal comfort.
Unfortunately, the way ventilation has been historically provided is very energy intensive, and most HVAC systems base the rate at which they provide ventilation in a building to the need of the space for cooling. This creates a built-in mismatch between what ventilation is needed and what is delivered, and this mismatch is usually most severe under extremely cold weather conditions, and in hot and humid weather.
Furthermore, since the amount of air passing through construction is reduced by making construction tighter, the amount of air which must be provided through the HVAC system must be increased to provide the same level of ventilation actually achieved in old, leaky buildings. This means that the amount provided through ventilation must be greater than provided in the past, not less.
This, unfortunately, runs counter to prevailing engineering wisdom. What's more, there is strong anecdotal evidence over the past 20 years from humid areas of the country, like the Gulf Coast and much of the Old South, that merely bringing in more outdoor air causes even greater air quality problems due to the humidity control issues resulting from providing more outdoor air. We've seen school buildings in Florida become unoccupiable in less than 12 months.
I think one of the root cause of this is found in the fact that the classical "tried and true" HVAC solutions are unable to efficiently and effectively process or provide the ventilation air required without violating federally mandated building code requirements. In short, bringing in the necessary amounts of outdoor air requires a great deal of energy which means high operating costs with these strategies. Under these circumstances, the "tried and true" become the "tried and truly awful," and we end up making ourselves sick with the very solutions that are supposed to keep us healthy.
The solution to this problem is not to return to building shabby buildings with obsolete building systems, but to employ new solutions which effectively address the problems.
The bad news is that it takes the HVAC industry about 30-years to respond to a need by developing new solutions and changing the way they approach a problem. At this time, they are at best only about half way through that curve. I say "at best" because the new strategies I am talking about literally change the way buildings must be designed. And that frightens a lot of people.
The good news is that effective solutions have been developed. Some, but not all, in the public domain. Most are cost effective to construct. The problem is getting architects and engineers to employ them. Anyone who wants to read about some of them should do a Google Search on "DOAS Radiant." This will take you to a web site belonging to Penn State University, put up by Dr. Stanley Mumma, PhD, PE, ASHRAE Fellow, which contains literally hundreds of peer reviewed technical articles on new high performance HVAC systems. These articles are not intended to address the mold issue directly, but they do deal with the kind of building design techniques necessary to accomplish this objective.
Mark S. Lentz, P.E., CDT, President
Lentz Engineering Associates, Inc.
511 Broadway, Suite 4
Sheboygan Falls, WI 53085
(920) 467-1075
AREA OF SPECIALTY
Primary: Heating, Ventilation and Air Conditioning. Special emphasis has been placed on systems
analysis, control theory and application, air-side processes, mechanical refrigeration and
primary heat generation, energy conserving processes, and indoor air quality.
Expertise in multiple subject areas is recognized at the Society level by the American Society
of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. (ASHRAE) through active
participation on multiple engineering technical committees and task groups, and through the
Society Honors and Awards Program.
ASHRAE Program Committee (Society Standing Committee), Past Member, Presidential
Appointee, (1989-1992):
* Liaison to Section 9 - Engineering Applications
* Member, Policy Subcommittee
* Member, SPO 4.3 Subcommittee
ASHRAE Technical Committee TC 5.7 - Evaporative Cooling.
* Current Status: Member (1992-present)
* Vice Chairman (2000-2002, 2002-2004)
* Corresponding Member, (1990-1992, 1996-1997, 2001-2002)
ASHRAE Task Group TG 9.MMB - Moisture Management in Buildings
* Current Status: Member (2001-Present)
ASHRAE Technical Committee TC 9.1 - Large Building Air-Conditioning Systems.
* Corresponding Member, (2006-Present)
ASHRAE Technical Committee TC 9.2 - Industrial Air-Conditioning
* Member, (1986-1990), (1992-1996),(1998-Present)
* Corresponding Member, (1990-1992)(1997-1998)
* Subcommittee Chairman for Standards, (1987-1989)
* Revisor, Chapter 14, Laboratories, 1991 ASHRAE Handbook, HVAC Systems and
Applications.
* Revisor, Chapter 17, Data Processing, 1995 and1999 ASHRAE Handbook, HVAC
Systems and Applications.
* Primary Author, W ater, Waste Water, and Hazardous Materials Handling Facilities,
2003 ASHRAE Handbook, HVAC Systems and Applications.
* Member of Laboratory Systems Subcommittee until upgraded to Task Group status.
ASHRAE Technical Committee TC 9.7 - Educational Facilities.
* Member (Founding), (2005-Present)
ASHRAE Technical Committee TC 9.8 - Large Building Air-Conditioning Applications.
* Chairman, (1994-1997)
* Member, (1985-1989, 1993-1997, 2003-Present)
* Corresponding Member, (1989-1992, 1997- 2003)
* Revisor, Chapter 20, Places of Assembly, 1987 ASHRAE Handbook, HVAC
Systems and Applications.
* Revisor, Chapter 4, Places of Assembly, 1991 ASHRAE Handbook, HVAC Systems
and Applications.
* Coordinator and Revisor, Chapter 6, Educational Facilities, 1991 and 1999 ASHRAE
Handbook, HVAC Systems and Applications.
* Liaison to SSPC 62.
ASHRAE Task Group TG-LS - Laboratory Systems.
* Member, (1993-1997)
ASHRAE Technical Committee TC 9.10 - Laboratory Systems.
* Member (Founding), (1993-1997)
* Corresponding Member, (1992-1993), (1998- Present)
ASHRAE SSPC 90.1 - Standard 90 Committee.
* Consultant, (1991-1993)
ASHRAE SSPC 62 - Standard 62 Committee.
* Member, Editorial Changes Subcommittee.
* Liaison from ASHRAE TC-9.8
Seminar Chairman, "Dynamics of Laboratory HVAC Systems," 1988, ASHRAE Winter
Meeting, Dallas, Texas.
Seminar Chairman, "Trends in Laboratory HVAC Systems," 1987 ASHRAE W inter Meeting,
New York, New York.
(first posted on School Mold Forum, Darlington, WI School Mold - WI schools , message # 2.15
http://forums.delphiforums.com/schoolmoldhelp/messages)
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