Data centers are essential in today's digital world, supporting everything from cloud computing to artificial intelligence. As digital demand grows, so does the need for data center infrastructure. Despite challenges like limited power supply, North America's data center inventory grew by 24.4% year-over-year in Q1 2024.1 Globally, data storage is expected to double from 10.1 zettabytes in 2023 to 21.0 zettabytes by 2027.2,3 Rapid growth increases HVAC demand for higher heat loads while maintaining efficiency and reliability.
Outdoor air infiltration and return air energy transfer are two building energy consumption paths that are unstable and cannot be accurately modeled over time. These "ghost energy" paths can vary from hour to hour if not by minute and waste significant energy that must be eliminated in real buildings to achieve stable building energy use that can be accurately modeled. In this article, these two paths will be analyzed with a 24-hour model applied to the 26-story office tower as defined by Figure 1 of Reference 1 on the summer design day and typical fall weather.
The coastal climate of Port Arthur, Texas, is hot, damp and makes one appreciate effective dehumidification. The 2023 ASHRAE Handbook-HVACApplications, Chapter 64, "Avoiding Moisture and Mold Problems,"1 frames the challenges facing designers. This article looks at some of them using a well-insulated, tight, 2,400 ft2 (223 m2) four-bedroom Port Arthur, Texas, house with high performance windows as an example.
Refrigerants used in thermal management systems of next-generation military transport vehicles must be efficient and safe for use in harsh environments. Flammability of low-global warming potential (GWP) refrigerants poses significant challenges for military applications due to varied extreme environments and battlefield threats. This study creates new test methodology to evaluate the flammability of selected pure refrigerants and blends to determine their performance under various military-relevant threats-ultimately to identify the optimal low-GWP refrigerant for use in military mobile air-conditioning (MAC) systems.
Infectious disease outbreaks such as COVID-19 have emphasized the need for rapidly deployable isolation facilities that ensure infection control and protect health-care workers (HCW). This study (Part 2 of a two-part series) builds upon-the-design--framework introduced in Part 1 in the February 2026 ASHRAE Journal and focuses on the engineering validation of a modular negative pressure isolation room (MNPIR). A full-scale prototype was tested using SF6 tracer gas, and results were compared with computational fluid dynamics (CFD) simulations.
The value proposition for using building commissioning (Cx) in the HVAC&R industry is more justified now than ever before due to the proven results in return on investment for owners and risk reduction for contractors. This article explores how the work of testing, adjusting and balancing (TAB) professionals combined with building automation system (BAS) information benefits building commissioning. It also offers examples of ways to improve the communication and relationship between these important disciplines.
My first day in the HVAC industry was marked by a disagreement. I began listening after the conversation had already begun. The controls contractor misspoke-"hot gas bypass" inserted itself where "hot gas reheat" should have been. It was too late. The manufacturer's rep scrunched his face and said, "But we aren't talking about hot gas bypass. We are talking about hot gas reheat! Completely different things!"
Climate change and global warming can have adverse effects on the design, use and maintenance of prefabricated structural insulating panels used in cold stores and similar built applications. This article includes discussion of stand-alone single-volume cold stores of all sizes and cold stores built in multistory conventional buildings. It is primarily for those who own, operate or maintain such insulating panel structures for product preservation and storage. It focuses on individuals who are in logistics, especially for refrigerated products, rather than experts in the sustainability movement or in climate change or global warming. It serves to highlight in some detail how they may be affected by climate change and how they could help themselves.
In many world cities, especially in India, high temperature variations are observed throughout the year. For instance, Delhi, India's capital city, has long, scorching summers and short, cold winters.1 Residents use desert coolers and vapor compression refrigeration systems (VCRS) during summer and rainy seasons to cope with the hot, humid environment. In winter, electrical heaters are preferred to combat the cold climate, although they consume a significant amount of electricity. 2Air pollution is also a pressing concern, especially in a densely populated city like Delhi.2 In summer, the air quality index (AQI) in Delhi averages above 200, which falls within the poor range and causes discomfort for people with heart disease and breathing difficulties. It averages above 500 in winter and peaks around 900 (near year end), significantly affecting people with lung and heart diseases.3,4 Delhi residents have no better solution to the air pollution problem; they are restricted to using air purifiers only, which is not a complete solution because these purifiers are sufficient only for a particular room with a high cost. After a literature review, this article shows the experimental investigation of an air conditioner and sterilizer for combined cooling and heating applications that works efficiently throughout a large space.
The increasing frequency of infectious disease outbreaks underscores the urgent need for rapidly deployable medical isolation facilities that can ensure infection control while maintaining health-care capacity. Part 1 of a two-part series presents the conceptual framework and design methodology for modular negative pressure isolation rooms (MNPIR) developed for pandemic response. Beginning with lessons from past outbreaks and evolving infection control strategies, it discusses critical design principles-airflow directionality, pressure differentials and filtration requirements-that form the basis of resilient ventilation systems. The architectural and engineering criteria for temporary but safe mobile isolation units are outlined, with particular emphasis on layout planning, patient-health-care worker flow separation and system integration. This design-based foundation provides the groundwork for validation, which is detailed in Part 2.
Fan energy index (FEI) is receiving significant attention in the wake of United States Department of Energy (DOE) fan regulation. Although the Energy Conservation Standard for Fans and Blowers proposed rule was withdrawn by the current administration on Jan. 17, 2025, the final rule of the Test Procedure for Fans and Blowers was published on May 1, 2023, for compliance in the marketplace. These metrics and regulations do not address noise specifically; however, fans tend to generate less noise when operating at their peak efficiency point. This article provides an overview of fan noise characteristics and general behaviors. Unfortunately, fan regulation alone is not enough to guarantee quieter fan selections. The mechanical engineer and acoustical consultant must work together to find a fan selection that optimizes energy efficiency and meets the project's noise requirements.
In the September issue of ASHRAE Journal, this column started a three-part series on liquid-cooled server processor cold plates. Part 1 concentrated on the history of cold plates used in cooling computers. Part 2 focuses on the technical design of cold plates-to provide HVAC designers and others with a more intuitive understanding of the devices they are (or soon will be) charged with cooling.
Residential air conditioners have often used fan coil units to heat or cool air before returning it to a room. The objective of the research discussed here was to evaluate the performance of a novel chilled beam system for residential air-conditioning applications. Testing was conducted in a mock-up apartment laboratory, assessing the system's performance in cooling, heating, ventilation and dehumidification. Testing focused on indoor environmental quality-including comfort, indoor air quality and noise levels-in compliance with relevant standards like ISO 7730, Ergonomics of the Thermal Environment.
Air changes per hour (ACH) are commonly used in the HVAC community as a metric for specifying ventilation airflow rates. However, a lack of proper understanding regarding the use of ACH can lead to unnecessary penalties in the initial and operating costs of building ventilation systems. ACH combines two key aspects of ventilation: the level of dilution (how much) and the rate of dilution (how fast), into a single metric. The "level" of dilution is determined solely by the volumetric flow rate (q) and does not depend on the volume of the space being ventilated. In contrast, the "rate" of dilution is influenced by the volume of the space, which introduces an inertial resistance to the dilution process. This paper aims to clarify the basis of ACH and its suitable application as a design metric for ventilation.
Wildfires are increasingly overwhelming fire services and severely impacting hundreds of millions globally every year, either through deteriorating air quality or direct exposure to escalating fire events. HVAC filters are essential for maintaining clean indoor air by effectively removing airborne particles. Current testing standards for HVAC filters rely on aerosols such as salt and oil droplets to evaluate performance. Still, wildfire smoke, comprising a mix of solid and liquid particles, presents a more complex challenge. Despite the increasing prevalence of wildfires, research remains limited on their impact on HVAC filter efficiency. In the study discussed in this article, we developed a woodfire smoke generator and conducted loading experiments to evaluate the effects of smoke particles on electret HVAC filter performance.
Ihave always had a love for the outdoors-I would say a real avid outdoor enthusiast. As a boy, I spent long summer days with my friends exploring the woods near our homes building tree forts and primitive shelters using scrap lumber, logs and tree branches. We had all kinds of adventures. I guess you could say that my interaction with the built environment started very early, though I must admit my structures would not have passed code. They were from the "perilous" movement in architecture, and I fell out of a few trees. At least my early structures were net zero energy. Clearly, I was ahead of my time.
How do we quantify building emissions? Performing whole life carbon assessment for both new and existing buildings is essential for achieving net zero cities and mitigating the impact of climate change. Whole life carbon emissions encompass the total carbon produced by any built asset throughout its entire lifespan, including construction, operation and eventual disposal. Understanding their implications is crucial for designing sustainable solutions and making informed decisions about building projects. This article is intended to outline what the Royal Institute of Chartered Surveyors' "Whole Life Carbon Assessment for the Building Environment (WLCA)" is, and updates to its 2nd edition, which includes integrating user carbon.
