Letters to the Editor
School HVAC Solutions hotly debatedI just completed reading "The Perils of Progress" (June 2001, p. 18) and found it quite interesting. It sounds as if the author is suggesting that designers should willfully ignore the regulations and laws that we are to design upon. If he can ignore ASHRAE's 15 cfm guideline in favor of Wisconsin's 7.
School HVAC Solutions hotly debated
I just completed reading "The Perils of Progress" (June 2001, p. 18) and found it quite interesting.
It sounds as if the author is suggesting that designers should willfully ignore the regulations and laws that we are to design upon. If he can ignore ASHRAE's 15 cfm guideline in favor of Wisconsin's 7.5 cfm, why not ignore Wisconsin's 7.5 cfm in favor of zero cfm?
This is comparable to saying that a ban on left turn on red at a particular intersection does not apply at intersection "X" because there is nobody else present at the intersection.
I wonder if structural loading calculations are ignored as willfully as ventilation rates?
Maybe we also need to look at the building structure for extravagant spending, such as the light fixture/ ceiling/window curtainwall pictured in the "Graduating to Better IAQ" (June 2001, p. 25) story that followed.
While I don't dislike "retro" looks, how are the return to radiators going to help IAQ problems? While I am not a big proponent of new technology solutions, I don't think we can necessarily rule out these solutions.
The author mentions the relatively inexpensive cost of CV systems, yet does not delve deeply into the added costs of building space for these rooms, nor does he appear to factor in the building space costs associated with these systems.
I'm not advocating a "new technology" approach, simply a balanced approach.
Ron Rhoades, Harold L Fox & Associates
No more cookie cutters
I had the occasion to read "The Perils of Progress." Fred Schulz made some accurate observations when he stated many technological advances come with severe cost penalties. Severe reductions in outdoor air create a lengthy list of problems. For example, CO 2 sensors, and for that matter, the entire concept of demand-controlled ventilation, is not about improving IAQ, it's about marginalizing it. But I flat out disagree with many of Mr. Schultz' other conclusions:
"The subject of IAQ is receiving top billing despite the fact that there is no positive solution." Don't bet your license on it Fred! The reality is that the HVAC industry has given lip service to both energy conservation and IAQ. As engineers, we have been so busy mass producing pre-engineered solutions that we have forgotten how to analyze and do not even try to address the challenges anywhere near the extent possible with available technologies.
Typical engineering solutions are predicated on the use of a relatively few, energy-intensive processes that place the objectives of energy efficiency and air quality in conflict. From a fundamental engineering perspective, our solutions are the problem. IAQ problems are the unavoidable end product. Furthermore, as we seek to make our buildings more efficient, IAQ problems will continue to get progressively worse until we learn to correctly identify the deficiencies and begin to develop and apply system strategies that actually address the challenges.
The shame of the situation is that there are no legitimate technological reasons why it has to be this way. There is simply enormous institutional inertia. Fundamental change means significant disruptions affecting design procedures, product development, availability and construction practices.
For example, Mr. Schulz's constant-volume rooftop solution was fundamentally flawed because it failed to correctly identify the nature of the underlying challenges, and because it was technologically regressive.
"There generally has been no problem with IAQ, nor with maintaining satisfactory temperatures in the vast majority of facilities." Wrong! Numerous studies prepared by ASHRAE, state governments and the U.S. General Accounting Office would hold this statement in dispute. More than 70% of all schools have reported IAQ problems. Most school districts are actually afraid to test air quality because of what they think they will find. And since maintenance is usually one of the first budget items to be slashed, temperature control problems are rampant.
"Sick building syndrome occurred almost simultaneously with the introduction of VAV air distribution." VAV technologies date back to the 1950s and preceded IAQ problems by about 30 years. The widespread misapplication of VAV does contribute to IAQ problems, but are not the primary causes. When used in systems employing recirculation, VAV technologies typically reduce total air delivery rates at the space with reduced cooling loads. At the same time, the air-handling unit introduces outside air into the system—also on the basis of thermal control—which is not on the basis of need for ventilation in the space. Ventilation and thermal control are two distinctly different and unrelated needs. Most engineers do not effectively account for this. While this problem can be readily and easily dealt with, the necessary techniques are not widely understood and effectively addressed.
"One can fully expect that mechanical systems will ultimately require 100% outside air to satisfy ASHRAE, the codes and environmentalists." I agree with the content of the statement, but not the context. The usual justification for recirculation is that it saves energy. From a mass-energy balance standpoint, recirculation is the exact thermodynamic equivalent of infiltration. So, why is recirculation "good," but infiltration "bad?" Recirculation is efficient only when outdoor air is used to eliminate the need for mechanical cooling. The concept thermodynamically falls apart for systems serving multiple spaces when steam is used for humidification.
"Demand-controlled ventilation" is nothing more than a band-aid for otherwise bad practices. It reduces energy use by maintaining a marginally acceptable indoor air quality condition. It is interesting that Mr. Schulz refers to the ultimate solution as "outside air overkill," because a correct thermodynamic analysis will show that our unquestioning reliance on recirculation is one of the two major causes of high energy use and is the primary cause of poor air quality. When air quality issues are considered, and there is a valid set of mathematics associated with computing air quality, it can be readily demonstrated that recirculation increases thermally required air delivery rates (and therefore cooling, preheating, and reheat energy use) and air quality is compromised. More importantly, this can be verified both in the laboratory, and in the field. As an engineer, I can easily justify 100% outside air on the basis of energy savings, and do it on a cost-competitive basis with recirculating systems. Furthermore, I can often save enough energy to upgrade a typical school's air quality, returning the entire cost in under eight years.
"How many school districts in this country are financially able to: 1) install heat recovery equipment at $3 per cfm above normal system costs; or 2) install a double mechanical system—one for 100-percent outdoor air and the other for maintaining comfort levels?" All of them! It is not energy-recovery technologies that has the major cost impact on the project, but the manner in which we typically misuse them.
We are not aggressive enough in that we fail to employ the devices in a manner that permits them to contribute over the full range of operational conditions, therefore limiting their thermal and economic contributions. The additional cost of energy recovery/avoidance technologies in the modern school can be more than offset by reductions in other system costs when properly integrated from the beginning. The biggest problem with energy recovery is that engineers, as a rule, do not know how to apply them to best advantage. As for dual-path technologies, the single-duct air delivery system has been obsolete for the past 10 years. Dual-path technologies can eliminate the need for terminal reheat, and the use of new energy resources for terminal reheat should be prohibited. There are literally no applications where this process cannot be displaced with a more efficient approach. Engineers have simply not figured out the advantages they offer and do not make proper use of them.
Mr. Schulz was correct when he said, "there is no positive solution," but only when taken in context with the solutions which have typically been provided for schools in the past. This would include VAV shut-off, fan-powered, and reheat, multi-zone, constant-volume reheat and unit ventilators strategies. Very simply, virtually no HVAC strategies were ever conceived or configured to provide either efficient operation or effective ventilation. Because of this, they can not be controlled to provide these benefits and will continue to produce unsatisfactory results. To provide a positive solution, the system designer must attack the fundamental underlying challenges. In schools, that challenge is completely driven by the need for adequate ventilation. The trick is to efficiently manage ventilation energy while maintaining thermal comfort. Solutions do not have to be complex, but they do have to be different.
Mark S. Lentz, P.E., President, Lentz Engineering Assocs.
The author responds
I appreciate your lengthy, and somewhat surprising, analysis of the engineering profession today, and you are right when you say that your unambiguous positions "are not likely to win many friends."
For more than 50 years I have worked with virtually every school district in Southeast Wisconsin, primarily with the buildings and grounds directors and the business managers. I have provided total energy audits for upwards of 600 educational buildings including all of the buildings in the University of Wisconsin system at all campus locations.
I have produced hundreds of energy-conserving recommendations for industrial and institutional facilities with paybacks of six months to six years, and in almost all cases, these recommendations were implemented only if financial incentives were available from the utilities and governmental agencies. But I conclude these recommendations will be implemented only when the bean counters of this world are replaced by engineers.
As to my statement on ventilation "overkill," there is no question in my mind that 7 1/2 cfm per occupant (not 15 or 20) at design winter conditions—15 cfm per occupant at the average winter temperature of 32°F, and near 40 cfm per occupant at 550 outdoor temperature—is more than adequate to satisfy any environmental requirement. This, of course, is based on a properly operating and fully maintained economizer control cycle.
When it comes to system concepts for elementary schools, I would suggest that you spend some time in the real world of the schools discussed. What you will find is:
—A school district in severe financial straits.
—A business manager whose chief concern is to maintain expenditures within the established budget and lessen the impact of any expenditure on the district tax base. He/she has a lot of projects with a higher priority than conservation.
—A taxpayer who could care less about energy-conserving concepts and favorable paybacks, but cares a lot about increasing the level of educational services and equipment.
—A maintenance man who is constantly reminded to reduce utility bills, regardless of the effect on environmental quality.
—A "breakdown" maintenance and repair program fostered by the excessive charges of outside service companies.
—Faculty members who desired total control of their classroom environment.
As to IAQ, my experience with hundreds of elementary schools with simple constant-volume and economizer controlled systems—not unit ventilators—indicates that less than 5% who were dissatisfied with the air quality. Invariably, the problem was traced to system maladjustment, unqualified tampering or lack of maintenance.
It appears to me that ASHRAE is spending most of its time treating the IAQ "complaint" and not the "cause." I ask you what is being done to eliminate toxic odors of school furniture, carpeting, printed materials, etc.? What is being done to improve the hygienic level of students who no longer believe in showers and who will wear the same clothing Monday through Friday? What pressure is being put on parents? What is being done to "enforce" the ventilation codes in public buildings—codes that we are forced to design to, and for which the owner expends considerable money? When will building inspectors be taught how to quickly inspect and check the quantity of outside air entering a system, not the quality of the end result?
I stand firm on my comments concerning computers. There is no question this equipment has furthered the educational and informational aspects of our lives to a mind-boggling degree. Rather than computing as originally intended, this instrument has become a gigantic reference library which will ultimately destroy our right to privacy, promote a multitude of illegal scams, and be a major contributor to the degeneration of moral and ethical standards. However, unless we immediately take preventive action, the worst impact will be on our children who will avidly seek the monetary rewards of electronics as opposed to becoming proficient in the hands on trades of our construction industry.
When will ASHRAE seriously promote all phases of our industry to counter the glamour industry of electronics?
This may be our most serious challenge for the continued implementation of HVAC systems and equipment.
Fred Schultz, P.E., Enervation, Inc.