May 1, 2010
Global Warming, Continued I am extremely distressed by the profound ignorance and arrogance exhibited by the authors (from Marion, Ill., and Dedham, Mass.)

Global Warming, Continued

I am extremely distressed by the profound ignorance and arrogance exhibited by the authors (from Marion, Ill., and Dedham, Mass.) of two letters published in the April 2010 edition of HPAC Engineering (Sounding Board, “Global Warming,”

The first of those authors states, “As professionals, our focus must be on factual information and bottom-line benefits to our clients.” The author attacks the scientific basis for global warming as “fraudulent justification” for carbon taxes. The author also writes, “We know the latest warming cycle ended during the last decade,” and that concepts such as “carbon saved” are “invented claims.”

The second of the authors attacks David Sellers, PE, for his “perversion of the concept of pollution,” which, he says, “is typical of the extremes to which enviro-activists can go.” He then states with absolute certainty that, “Carbon dioxide (CO2) is not a harmful substance” because it “already is in the air” at concentrations of “about 0.035 percent.” He then states with similar certainty that the effect of doubling or tripling the CO2 concentration “would be negligible” and perhaps cause “greater plant growth.”

Unbelievable. I hope you published those letters to make the point that neither writer understands the science of global warming. It is tragic that so many skeptics who express such strong beliefs about climate change make statements that repeatedly demonstrate they have absolutely no understanding of the physical, chemical, or biological forces that control climate, let alone the nature and existence of life on this planet.

The earth's climate is driven by heat flow, but it is not a machine we understand well enough to control. We ignore the thermodynamics of climate at our own peril.

The letter from William Bishop, EIT, LEED AP, in the same issue is right on the money. But I do not share his optimism about the ability of our engineering peers to understand the science of climate chaos. It is painfully obvious that while some may understand a psychometric chart, they don't have a clue about applied physics, chemistry, and biology on a macro scale. The uncertainty associated with oceanographic and ecological science, not to mention climate science, is daunting.

There are very few absolute facts. What is tragic is that the “facts” stated by these writers and virtually every skeptic of Intergovernmental Panel on Climate Change data are irrelevant to the documented problem. Climate science is fraught with uncertainty; so is medical science, driving a car, and every other aspect of life. That is why prudent people buy life insurance, health insurance, and auto insurance. That is why engineers develop safety factors and best management practices.

The civilized response to greenhouse-gas emissions and concerns about climate change should be no different than our response to any other aspect of life fraught with uncertainty: prevent catastrophe with education, laws, codes, standards, regulations, and insurance.

Personally, I have infinite tolerance for immediate and collective action to reduce greenhouse-gas emissions because I do not totally understand what is happening and why. But I do know something is happening. The evidence is overwhelming. If we do not reduce greenhouse pollution to levels at or below historic levels in a timely fashion, we are endangering the continued stability of our relatively hospitable climate.

We know humans are capable of using technology to exploit and eventually destroy resource bases that have sustained and nurtured many civilizations. It has happened many times. If concentrations in the upper atmosphere continue to increase at current rates, climate patterns as we know them could change not only drastically, but at a rate faster than our ability to adapt.

I do not think it is prudent to continue this experiment in climate modification simply because ignorant and arrogant skeptics choose to act on their beliefs and use irrelevant “facts” to support those beliefs.

It would be tragic if willful ignorance or thoughtless arrogance destroyed the resource base — our stable climate — supporting the 6 billion people alive today. If we continue to exploit land and water using available fossil-fuel resources, atmospheric levels of CO2 will soar.

A preponderance of scientific evidence suggests we have a serious problem.

What belief system gives any of us the right to object to measures that might mitigate, if not solve, the problem?

What belief system gives any human the right to place the lives of 6 billion other people at risk?
David E. Bruderly, PE
Bruderly Engineering Associates
Gainesville, Fla.

LEED Credentials

There are four types of Leadership in Energy and Environmental Design (LEED) credentials. You missed LEED Accredited Professional (AP) without specialty in your article (Engineering Green Buildings, “What's New With LEED Professional Credentials,” March 2010,
Kin (Mike) Wu, PE, LEED AP
U.S. Coast Guard, Civil Engineering Unit
Oakland, Calif.

Author's response:

LEED AP without specialty is a valid designation. However, the credential no longer is offered by the Green Building Certification Institute and has been replaced by the LEED AP with specialty and LEED Green Associate credentials. Those with the LEED AP without specialty designation will never lose their credential, but they will have the option to add a specialty by enrolling in testing or prescriptive credential maintenance. For more information, please visit
Erin Emery
U.S. Green Building Council
Washington, D.C.

Pressurization Control

Editor's note: The February 2010 article “Pressurization Control in Large Commercial Buildings” by Dave Moser, PE, ( has generated a good deal of discussion via the Disqus comment system on Following is a sampling.

“Jim” wrote:

“A way to address inconsistent DP (differential-pressure) readings is to install two DP sensors and average the results. Outdoor air could be sensed at two locations, if desired.”

To which “papaD” replied:

“Multiple DP sensors only compound the errors. How do you average them? Are their positions reflective of the true average building pressure flow? Where do you place outside tap? How do you reduce the volatility of the DP output for control without losing the value of the data? How often do you have to zero and recalibrate the sensors? Is this done regularly in practice?

“Stack pressure and wind pressure both influence net building or space pressure flow. Some walls can show a positive flow, while others could be negative (because of) wind. Trying to overcome anything but a light wind's effects usually is not possible or may damage window seals, windows, or doors. The objective should be to maintain a positive net flow from the area of lower dew-point temperature to higher dew-point temperature. In most climates and seasons, this is inside to outside. In cold climates with higher inside humidity, you can't run the space negative, and you don't want to push humid air into the wall cavity to freeze. Net neutral appears to be the best alternative.

“If not DP direct measurement, then what? Volumetric tracking by zone or AHU (air-handling unit) is much more stable (and) controllable and can manipulate very small increments of DP using differential volume control.”

In response, author Dave Moser writes:

“Indoor- and outdoor-sensor port terminations should be located in as representative a location as possible, with minimal bias to one side of the building or the other, to minimize wind effects. Shielding from wind effects, regular calibration of static-pressure sensors, and proper tuning of control loops are necessary for an active building-pressurization-control strategy to work properly.

“Pressure set point can be adjusted to suit project conditions. If the climate is cold and there are concerns about humid air condensing and freezing in a wall cavity, 0 in. may be the best set point, as ‘papaD’ suggests.

“Volumetric tracking is another method of pressurization control, but may be difficult to add to an existing system because of the space requirements of airflow-measuring stations.”

“javed_rizvi” wrote:

“The article does not address issues with reduced OA (outside air) with (a) reduction (in) VFD (variable-frequency-drive) speed, especially during cold weather. Normally, exhaust fans and kitchen exhaust fans are constant speed, and (a) reduction in OA with (a) reduction (in) VFD speed … reduces load in cold weather. This and stack effect causes negative pressure in (a) building.”

In response, author Dave Moser writes:

“The variation of outside-airflow rate with fan speed/supply-air volume is indeed an issue with air-handling systems that use fixed-position minimum-outside-air dampers. The intent of the article was to discuss building pressurization. When outside-airflow rates change because of variations in supply-fan speed and air-side economizer operation, active building-pressurization systems will respond directly because they measure building pressure directly. If building pressure is not measured, varying outside- and exhaust-airflow rates could indeed be an issue.”

Letters on HPAC Engineering editorial content and issues affecting the HVACR industry are welcome. Please address them to Scott Arnold, executive editor, at [email protected].


I liked Associate Editor Megan White's Views From My Cube editorial (“The Print-vs.-Web Conundrum,” in the April 2010 issue of HPAC Engineering. I don't like online magazines. I rarely read them and never read anywhere near every page. I do look forward to my print versions, though. Some I thumb through all the pages looking for an article to read; some I read cover to cover. I can say I have purchased much more equipment reading about it in a magazine than discovering it online. My magazines get Post-it notes stuck through them waiting for me to pass them along to a colleague or the need to conduct research for a particular project to arise.
Jeffrey Mahaney
Maine Public Broadcasting Network
Bangor, Maine

I'm not ashamed to say I got my PE license in 1977 and have seen many publications come and go. The Web is a good place for a quick fix, but I need to look at something other than my monitor. Give me the news on the screen, but keep the articles in print. I like to carry my magazine with me, even to lunch.
Ernest D. Yonkers, PE
Harrison French & Associates Ltd.
Bentonville, Ark.

I fully agree with Megan White's optimistic view of the long-term survival of the media we've come to know and love. Print lives!

Encouraged by certain manufacturer clients, my firm has become fully immersed in the digital age, including Facebook and Twitter. Am I enamored with or passionate about all of these newfangled forms of communication? To be honest, the jury's still out. But when a stack of magazines or the newspaper arrives, it's a wee slice of heaven. I want to see and feel what I read. I want to be able to easily mark, stash, or set aside something of value when the phone rings.

Sure, I'm the first one to hit the Web when buying that hard-to-find something or other, credit card in hand. And I appreciate robust, easy-to-navigate magazine Websites when I need to find an article fast or see breaking news. But there's nothing that guides me and fills my personal and professional interests like print media.

Magazine Publishers of America just launched a campaign that states in part:

“Barely noticed amidst the thunderous Internet clamor is the simple fact that magazine readership has risen over the past five years. … Even among the groups one would assume are most singularly hooked on digital media, the appeal of magazines is growing.

“… During the 12-year life of Google, magazine readership actually increased 11 percent.

“What it proves … is that a new medium doesn't necessarily displace an existing one. Just as movies didn't kill radio. Just as TV didn't kill movies. An established medium will flourish so long as it continues to offer a unique experience. And as reader loyalty and growth demonstrate, magazines do.”

Thanks again for the affirming editorial.
John Vastyan
Common Ground
Manheim, Pa.

About the Author

Scott Arnold | Executive Editor

Described by a colleague as "a cyborg ... requir(ing) virtually no sleep, no time off, and bland nourishment that can be consumed while at his desk" who was sent "back from the future not to terminate anyone, but with the prime directive 'to edit dry technical copy' in order to save the world at a later date," Scott Arnold joined the editorial staff of HPAC Engineering in 1999. Prior to that, he worked as an editor for daily newspapers and a specialty-publications company. He has a bachelor's degree in journalism from Kent State University.