In HVAC systems, ducts distribute more than air; they also distribute noise produced by fans. Duct liners were developed in part to absorb noise before it emanates from ductwork; designers apply different thicknesses and lengths of duct liner to reduce noise to various levels. In this January 2012 article, Stephanie Ayers, Jeffrey L. Fullerton, INCE Bd. Cert., LEED AP BD+C, and Steven H. Miller, CDT, discuss acoustical benefits of duct liners and available choices in liner materials.
The retrocommissioning of two office buildings served by central-station variable-air-volume air handlers in California revealed substantial opportunities for optimizing pressurization-control systems in large commercial buildings. In this February 2010 article, Dave Moser, PE, discusses two such opportunities: outside-air-static-pressure-measurement termination and control sequences.
Each year, grease fires in U.S. commercial kitchens result in more than $100 million in property damage. In this May 2004 article, Peter C. D'Antonio, PE, examines the ins and outs of grease removal in kitchen exhaust systems.
Chilled beams are cooling (and optionally heating) units located in or above a conditioned space that utilize a ventilation-only primary air stream from a remote air handler to induce larger recirculating room flows, effectively heating, cooling, and ventilating the space without the use of an in-room fan and with reduced overall airflow from the central air-handling unit. In this November 2013 article, Craig R. Buck, PE, LEED AP, HFDP, discusses benefits and challenges related to the use of active chilled beams in health-care settings.
HVAC design engineers face many choices throughout the planning process, perhaps few as crucial as that of fan equipment, a principal consumer of energy. In this August 2010 article, Brian Mleziva discusses options for improving energy efficiency when designing a HVAC system and selecting a fan.
Hospital-acquired, or nosocomial, infections have proven to be a persistent and sometimes tragic problem. In this January 2007 article, Wladyslaw J. Kowalski, PE, PhD, examines the epidemiology and aerobiological pathways of airborne nosocomial infections and reviews air- and surface-disinfection technologies, including ultraviolet germicidal irradiation.
The first step in most HVAC design projects is to calculate heating and cooling loads. These calculations become the basis for sizing equipment and, when required, projecting energy use. While energy-use projections can be data- and calculation-intensive, even the most sophisticated procedures consist of little more than calculating the heating or cooling load at each outdoor temperature of interest, multiplying by the number of hours of each outdoor-temperature occurrence in a year, and summing. In this September 2013 article, Kenneth M. Elovitz, PE, Esq., explains how engineers can apply the process in reverse: use historical energy-use and weather data to infer building heating or cooling loads and understand how a building uses energy.
Though vital to maintaining good indoor-air quality, outdoor air can be expensive to temper and, if not conditioned properly, cause humidity problems in a building. In this December 2009 article, Mike Wolf, PE, and Jackson Smith discuss dedicated outdoor-air systems, which supply cooled, dehumidified outside air to buildings during summer and heated outside air during winter.
Selecting a fan can be fairly complex. In this April 2011 article, Molly Rehwaldt and Tim Mathson outline the basic process for matching a fan to a system.
One of the simple truths of building operation is you need to measure what you want to manage. Of primary concern to most building operators is energy use. As David W. Bearg, PE, points out in this July 2014 article, however, employee costs easily are 100 times energy costs (i.e., $200 to $300 per square foot vs. $2 to $3 per square foot). With a mere 1-percent increase in worker productivity equaling all that is being spent on energy, Bearg says, it behooves building operators to better manage—and measure—two aspects of building operations that directly impact worker health and productivity: ventilation and moisture.
When designing a cooling system for a large open space with a high ceiling, such as an open-floor-plan office, auditorium, casino, restaurant, or theater, one should consider a displacement-ventilation (DV) system, Mark Costello says in this September 2013 article. In a DV system, cool supply air displaces warm room air at very low velocities, offering energy efficiency, indoor-air-quality benefits, and low maintenance costs compared with traditional mixed systems.
The 2013 version of ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, includes a fan-efficiency requirement based on ANSI/AMCA Standard 205-12, Energy Efficiency Classification for Fans. In this May 2013 article, Michael Brendel, PhD, explores the role fan efficiency plays in Standard 90.1, with specific attention paid to how the new fan-efficiency requirement works with the standard’s fan-power limitation.
Condensation occurs when duct-surface temperature is equal to or lower than the dew-point temperature. When condensed moisture mixes with dust or dirt in ducts, mold and microbial growth occurs. In this December 2009 article, Ken Forsythe discusses the role fiberglass duct insulation can play in mold prevention.
When it comes to deciding whether to repair or replace an older rooftop unit, it is important to consider a number of factors, including current condition, age, efficiency, maintenance/repair history, and associated utility costs. In this February 2014 article, David Negrey discusses the process of making an informed decision.
Traditionally, sizing UV-C lamps for the purpose of irradiating HVAC cooling coils depended on trial and error and rules of thumb. That changed with the publication of the 2011 edition of ASHRAE Handbook—HVAC Applications, which provides a quantitative approach to lamp sizing resulting in systems meeting performance requirements at the lowest initial and long-term operating costs. In this article, Forrest Fencl summarizes that guidance and offers a method to simplify future designs.
The issue of “toxic mold” first hit the news during the mid-1990s, with several high-profile cases of severe illness and irreparable building damage. Soon after, the phrase, “Mold is gold,” was coined to reflect the growing industry of mold testing, remediation, and litigation. Since then, untold millions have been spent to rid properties of mold, with millions more paid to claimants for mold-related illnesses and economic losses. In this April 2014 article, Tony Fedel, PE, addresses the issue of mold—specifically, mold spores—as an indoor-air pollutant that can be minimized through an effective HVAC air-filtration strategy.
Hospital-acquired infections (HAIs) are a leading cause of death in the United States, killing more people than AIDS, breast cancer, and automobile accidents. In 2010 alone, HAIs contributed to more than 99,000 deaths—one death every 6 min—and costs of up to $57,000 per patient, with an increase in length of hospital stay of about 10 to 15 days. In this February 2013 Managing Your Facilities column, Robert Scheir, PhD, discusses ultraviolet germicidal irradiation as a method of inactivating mold, bacteria, and viruses, reducing many airborne microorganisms.
In this February 2006 article, James Livingston provides suggestions for maximizing louver performance and ensuring louvers are equipped to meet the needs of their specific application.
Humorist Will Rogers once said, "It's not what we don't know that hurts; it's what we know that ain't so." As engineers, how much of what we know "ain't so"? We rely on information and calculation methods we assume have a firm foundation in reality only to sometimes find they do not. That is what happened in 2005, when, asked by an attorney to investigate the failure of a HVAC system to provide the owner's expected comfort conditions, William Allen, PE, reviewed design drawings and calculations and built a mockup of a flexible-duct system, described in this December 2010 article.
Air infiltration long has been a little-understood or even ignored factor when it comes to energy efficiency in commercial buildings. Engineers understand it exists, but tolerate its existence by simply accounting for it in heating- and cooling-system design. Fixing the problem at its source can be complicated and span beyond a designer’s scope of work. In this April 2013 Engineering Green Buildings column, Nate Gillette, AIA, LEED AP, CEM, says addressing air infiltration no doubt will become a best practice in the green-buildings industry.
In this August 2009 article, Ron Wilkinson, PE, LEED AP, CPMP, discusses how owner-controlled base-building improvements and tenant-controlled space improvements can save energy in a high-rise office building without negatively impacting one another or violating terms of lease agreements. Specifically, it discusses a process of transitioning from constant-volume to variable-air-volume control with the intent of reducing overall energy consumption and carbon-dioxide emissions and earning recognition through certification programs such as the U.S. Green Building Council's Leadership in Energy and Environmental Design (LEED).
Within large industrial corporations, facility maintenance often is viewed as no more than an operating expense. In northern Colorado, however, one manufacturer is working hard to change the way the economic benefits of energy efficiency are perceived and accounted for, recognizing facility energy-cost savings as a key contributor to the overall profitability of an organization. In this February 2014 article, Peter D’Antonio, PE, CEM, LEED AP, details a public-private partnership between the manufacturer, a commissioning provider, and local utilities to reduce HVAC energy costs.
While the principle of diversity as it applies to the mechanical systems of buildings—simply put, the variation of occupant location throughout the day—is an often-discussed topic among engineers during design, its benefits and applications often go unquantified. As such, neither the building owner nor the design professional truly appreciates the energy and cost savings realized by the application of this simple principle. In this December 2010 article, Jack L. Burton, EIT, LEED AP, discusses one of many scenarios in which the application of diversity principles can yield energy and cost benefits.
In this July 2010 article, Michael West, PhD, PE, explains how engineers can achieve performance equal to or better than that of a reheat coil and controls without the complexity and cost using a dedicated outdoor-air system (DOAS) equipped with heat-pipe coils and/or a direct-expansion DOAS based on refrigerant runaround and coil bypass. Both techniques are mature, with more than a decade of successful application, use readily available components, and can be cost-efficient in a well-designed system, West says.
Light-commercial facilities have been a largely cost-driven market, with only passing concern for efficiency and life cycle, Chad Senger says in this article. He discusses how the latest technological advances have made control and system-integration capabilities available and affordable for small and mid-sized buildings while providing functionality similar to that of large building automation systems.
In this April 2008 article, Francis (J.R.) Babineau examines the two primary HVAC air-handling insulations—duct wrap and duct liner—as well as acoustical silencers, a common noise-control product.
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• Innovative HVACR Solutions, January 2014.
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