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Heating, ventilation, and air-conditioning (HVAC) systems consume more than 40% of a building's total energy use. Several strategies have been developed to decrease the energy consumption of HVAC systems. But few energy reduction strategies also impact indoor air quality (IAQ). Providing a risk-free indoor environment is crucial for the occupant's comfort and safety, especially in the post-pandemic scenario. The CO2 concentration significantly impacts indoor air quality (IAQ) complaints and health symptoms in buildings, while ventilation levels are below the recommended rates. In a typical all-air HVAC system, a fraction of return air is recirculated into the space to reduce the system load. The recirculated air containing metabolic carbon dioxide (CO2) generated by the occupants is mixed with the outdoor air to dilute the CO2 concentration before being supplied into the conditioned space. This return air ratio plays a vital role in balancing the energy demand and providing acceptable IAQ. For spaces fitted with individual split AC systems without a fresh air duct option, 100% of the return air is recirculated into the conditioned space. The IAQ is highly affected in such space as it relies entirely on infiltration. There is a need to study methods to reduce energy demands while maintaining indoor air quality (IAQ) requirements. Computational Fluid Dynamics (CFD) simulation of indoor environments can help analyze different CO2 concentration reduction strategies, thus improving the HVAC design to provide a healthy, code-compliant indoor air quality. In this study, a CFD model is developed to compute the CO2 concentration at the supply considering the recirculation ratio of return air. The developed model estimates the optimum return air ratio that minimizes the energy cost of the system while maintaining acceptable IAQ. [ABSTRACT FROM AUTHOR]

Indoor air quality is increasingly recognized as a serious health hazard in many international environments. During the recent pandemic, this concern was amplified as Covid-19-related mortality closely correlated with poor air quality. Even a comparatively small decline in the Air Quality Index (AQI) can be linked to a sharp mortality increase. Worsening air quality levels are compounded by distinct air-quality issues in different geographical areas. In the face of this serious and wide-ranging threat, the common solutionâ€"introducing a high MERV-rated filterâ€"comes up short, as these filters create back pressure that often exceeds the capacity of the HVAC systems in which they are installed. High-backpressure filters also use more energy and require frequent filter changes, making them more expensive to maintain and bad for the environment. This paper describes a new form of electrostatic filtration that is ideal for international markets since it has a uniform performance, low back pressure, is energy efficient, and can be tuned to perform at a range of filtration levels depending on demand. This is accomplished by varying voltage applied to the ionization stage of the filter. In this study, we operate an electrostatic filter with a variable power source set to vary filtration level according to a variety of operating algorithms and compare the resulting energy use to standard air filters. [ABSTRACT FROM AUTHOR]

Measuring air infiltration through the external building envelope as well as between adjacent zones within a building is important since air leakage is related to increased energy use and poor indoor air quality (IAQ). State of the art methods can determine both leakages, however it can be both time consuming and labor intensive as it requires running both guarded and compartmentalization tests. This paper presents our work on developing a simplified testing procedure to determine power law flow equation leakage parameters of both external and internal boundaries of tested zones. The proposed Zonal Multipoint Pressure Test (ZMPT) method modulates airflow in the zone using a variable airflow measurement panel (mounted in either a window or the door), and solving the mass balance equations for the leakage parameters. ZMPT results were compared to conventional test results and found to correlate to within +/-7%. [ABSTRACT FROM AUTHOR]

There is a compelling body of evidence calling for a reduction in the amount of carbon dioxide (CO2) that mankind is emitting into the atmosphere. A segment of climate science community contends that we will be required to actively “reduce” the magnitude of our atmospheric CO2 content, not merely reduce mankind’s contribution to the increase. Five methods of CO2 mitigation are briefly mentioned, followed by the description of a sixth, innovative method of using chemical or adsorption scrubbing techniques to remove indoor air CO2 from building HVAC systems for the purpose of reducing the required outdoor air (OA) ventilation to provide energy and CO2 reductions. The reduced OA ventilation will correspond to a reduced source energy consumption while simultaneously scrubbing other indoor air contaminants, improving indoor air quality (IAQ). A building HVAC energy model is presented in which an indoor air CO2 scrubbing technology is incorporated. Although the scrubbed indoor CO2 is merely vented and released into outdoor air, the resulting reduction in source fossil fuel energy related CO2 emissions is calculated for the analysis of the net CO2 reduction potential. An eQuest building model is utilized for three different locations in the USA (Atlanta, Detroit, and Los Angeles) and the 2016 USEPA eGrid database is used to calculate the local electric powerplant source CO2 emissions. The results indicate that regions in the United States with both high HVAC loads for heating and/or cooling coupled to a carbon intense local electric supply will benefit the most by utilizing the proposed HVAC / CO2 mitigation system. Of the three sample areas, Detroit had the highest CO2 source emissions saving potential from this application at 66,560 lb/yr (30,255 kg/yr) followed by Atlanta with 46,149 lb/yr (20,977 kg/yr). The mild southern California weather coupled with the less carbon intense electric grid only produced 2,340 lb/yr (1,064 kg/yr) source CO2 reductions. The addition of other energy conservation measures or site renewable energy generation would obviously increase these source carbon reductions. If the human occupant respiration CO2 were captured and permanently sequestered from this same office building’s indoor air, 55,600 lb/yr (25,300 kg/yr) would be sequestered. Ultimately, the hypothesis of this paper is that a more lucrative market for these emerging CO2 scrubbing techniques may first find a beneficial use in the HVAC product and/or energy efficiency space. This application may create a viable business model in which these technologies are deployed, tested and refined as profitable HVAC products, and then hopefully deployed in future years for direct atmospheric CO2 mitigation. Further study of this concept seems warranted, and the author invites future discussion and critical review of this papers concepts and conclusions. [ABSTRACT FROM AUTHOR]

In order to reduce energy consumption while maintain high indoor air quality (IAQ), CO2-based Demand controlled ventilation (DCV) has been investigated a lot and become trend of the future ventilation system. Among different advanced sensors, the real-time occupancy estimation (people counting) sensor has played an important role in CO2-based demand control ventilation (DCV) systems. However, since particle diffusion indoors is slower than dynamic changes of occupant presence in transient conditions, the actual CO2 concentration will generally lag behind actual number of occupants while dynamic infiltration may mitigate the lag effect. Therefore, simulations were conducted in this paper to provide insight into the application of occupancy estimation sensors for CO2-based DCV and dynamic infiltration in the real world. Two different stochastic occupancy profiles for two different space types have been investigated, which were generated based on Markov-chain model and Gaussian model with high variance, respectively. It has been observed that due to the lag effect, the actual CO2 concentration with Gaussian occupancy model is more likely to exceed the set-point value than that with Markov-chain occupancy model. Fortunately, the simulation results showed that dynamic infiltration owing to dynamic operation of building envelopes such as operable windows eliminated the lag effect. Therefore, for the space with variant occupancy profile, it is suggested to operate DCV by integrating the system with dynamic operations of building envelopes in order to improve the indoor air quality. [ABSTRACT FROM AUTHOR]

Air-conditioning is simultaneous control and maintenance of dry bulb temperature, relative humidity, cleanliness, odor, noise and pressure inside a conditioned area. Air-conditioning is required for a product or process or for comfort. Indoor Air Quality (IAQ) is the quality of air which affects our comfort and health. In a good indoor environment, work efficiency of occupants gets enhanced, learning results are better amongst students and absenteeism is lower. This in-turn increases workplace productivity and test-scores in schools, which is supported by research. Research has shown that the pollutants, often present in indoor air, have a clear link with productivity, sense of wellbeing and occupant health. In long term, they lead to health hazards like asthma, allergies, headaches and respiratory diseases. Furthermore, temperatures that are too high or too low, continuous high noise levels, or excessively bright or inadequate lighting level increase the stress levels in the human body, thus creating health issues like sleep disorder, digestive problems, and memory and concentration impairment. We inhale Oxygen and exhale carbon-di-oxide. The Outdoor air which is drawn by the air-conditioning unit provides oxygen. As such the quality of outdoor air is highly significant. There is a difference between outdoor air and fresh air as outside air may not be always fresh and may not be of acceptable quality. Indoor Air Quality (IAQ) is considered to be 'healthy' when the air does not contain contaminants in harmful concentrations and is acceptable when the majority of people feel satisfied. Exposure to hazardous airborne agents present in many indoor spaces cause adverse effects such as respiratory and cardiovascular diseases, allergy, and irritation of the respiratory tract and possibly lead to cancer. That is why our responsibility is to provide healthy indoor environment for occupants. We breathe about 12000 litres (3170 gallons) of air every day and it is vital for our health to make sure that the air we breathe is clean. [ABSTRACT FROM AUTHOR]

This conference paper is based on Standard 90.1 to provide several selected energy efficiency measures (EEMs) in existing buildings for energy efficient operation and management. The examples of the EEMs are presented to explain the convergence of Standard 90.1, 62.1 and 55 - to provide acceptable indoor air quality and thermal environmental conditions for human occupancy while optimizing energy efficiency in built environment. These concepts of the EEMs can be also applied to new construction and major renovation. [ABSTRACT FROM AUTHOR]

This research investigates the potential of the Biowall to reduce energy while effectively improving Indoor Air Quality. Data acquisition systems were used to measure VOC, CO2, temperature, and relative humidity levels of the air before and after passing through the Biowall. This data was used to calibrate a mathematical model of the heat and mass transfer of air flowing through the Biowall and HVA C system. The model provides an accurate representation of Biowall performance over a range of operating conditions. The model suggests that the Biowall does not require extra dehumidification and thus uses the equivalent amount of energy to that of an energy recovery ventilator. The modeling results also show that by improving the irrigation system for the Biowall it has the potential to use 25% less energy than the ERV. Results from this research demonstrate that the Biowall, integrated into the central HVAC system of an energy efficient home, can improve indoor air quality and reduce energy consumption resulting in an appealing ventilation system that could be used in many applications in the future. Further integration of Air Quality measures into the current energy model developed by this research will provide the grounds for an optimal system design for future development. [ABSTRACT FROM AUTHOR]

Gas-phase air cleaners are used to remove a wide variety of contaminants from the air. However, it is often difficult to judge which air cleaner works for which contaminants and, further, to determine which air cleaner is best for a given application. Most gas-phase air cleaners use sorbents (e.g., activated carbon) to remove the contaminants from the air. Since sorbents vary in which contaminants they can remove and air cleaners contain different sorbents in various configurations, it is critical to have test data to document the performance of air cleaners. To meet this need, ASHRAE has published a new laboratory test standard giving the HVAC market its first gas-phase test standard for air cleaning devices. This method is ASHRAE 145.2-2011 "Laboratory Test Method for Assessing the Performance of Gas-Phase Air Cleaning Systems: Air Cleaning Devices." Five different air cleaners were tested for efficiency and capacity per ASHRAE 145.2 for three different contaminant gases. The air cleaners were chosen to cover a wide range of the capabilities of currently available devices and include two residential and three commercial units. All of the air cleaners are sorbent-based, but the sorbents are designed to apply best to different contaminants. Three contaminants were chosen to include compounds that are undesirable in air but are commonly found in indoor air or in outdoor air that is entering buildings. These compounds also serve to highlight the capabilities of the test method and the differences across types of air cleaners. The compounds selected for these tests were toluene, sulfur dioxide, and ozone. The test results are presented in comparison tables and presented graphically where appropriate. These results include low concentration 'initial efficiencies,' breakthrough curves for high concentration exposure, and capacity measurements for the five air cleaners for each of the three contaminants. [ABSTRACT FROM AUTHOR]

Concern over providing acceptable indoor air quality (IAQ) while minimizing associated energy consumption has raised attentions toward optimizing HVAC equipment. Energy recovery ventilators (ERVs) transfer energy between conditioned exhaust air and outdoor ventilation air to reduce the energy demand of HVAC system. An ERV may operate in (1) full-load, (2) part-load, or (3) full bypass (no energy transfer) condition. In this paper, based on minimization of HVAC system energy consumption, an optimal strategy to control the operation of an ERV is concluded and compared to other control alternatives in the literature. The paper explains the dependency of the optimal control strategy to the ERV's latent-to-sensible effectiveness ratio and outdoor conditions. Potential energy savings with an optimized system is investigated by TRNSYS simulation of an office building in four North American cities as representatives of major climates. The results show that an ERV can lead to significant annual heating energy saving (about 35% in cold climate) and annual cooling energy saving (up to 20%), provided the ERV has the capability to transfer moisture and is properly controlled. Also, it is shown that IAQ can be improved during the winter, since employing ERVs humidifies cold-dry outdoor air. [ABSTRACT FROM AUTHOR]

Mankind has known the Evaporative Cooling Technology for a long time. However, Direct Evaporative Cooling (DEC) systems have been greatly under utilized by the HVAC industry, in part because of the concerns regarding the negative effects of these systems on the Indoor Air Quality (IAQ). On the contrary, the IAQ in buildings can, in fact, greatly benefit from the design and installation of DEC systems through the introduction of 100% Outdoor Air. DEC rigid media further improves IAQ by acting as a good filtration device and also as a sound-attenuating device in noise-sensitive applications. In addition to IAQ benefits, the DEC can help achieve energy savings by providing both free sensible cooling and beneficial winter humidification. DEC can also be combined with Indirect Evaporative Coolers (IEC) to provide further energy savings by increasing the refrigeration free cooling hours in hot and dry North American climates. This paper will analyze the annual DEC system performance for different climate zones in various cities across North America. [ABSTRACT FROM AUTHOR]

Stratified air ventilation systems such as displacement ventilation can provide better indoor air quality with enhanced ventilation effectiveness compared to the traditional overhead mixing systems. In the case of displacement ventilation systems the higher supply air temperatures combined with the low supply airflow rates can also provide higher energy efficiency. However, the size and locations of displacement diffusers as well as the strength, location, and type of the sensible heat loads can affect the performance of the displacement ventilation systems. This paper with the help of Computational Fluid Dynamics (CFD) simulations describes comparative performance of the displacement ventilation with the traditional overhead mixing system for a two-story lobby of a healthcare facility with identical winter heating and summer cooling heat loads. CFD results reveal three-dimensional airflow patterns, resulting temperature distribution along with the occupant thermal comfort parameters for each case. [ABSTRACT FROM AUTHOR]

The 2005 Energy Policy Act Requires that federal facilities be built to achieve at least a 30% energy savings over the 2004 ASHRAE Standard 90.1-2004. The Construction Engineering Research Laboratory of the U.S. Army Corps of Engineers, in collaboration with U.S. Army Corps of Engineers Headquarters and centers of standardization for respective building types, the U.S. Department of Energy (DOE), the National Renewable Energy Laboratory, and the ASHRAE Military Technology Group have developed design guides to achieve 30% energy savings over a baseline built to the minimum requirements of ASHRAE Standard 90.1-2004 for new buildings to be constructed under the Military Transformation Program. The building types included barracks, administrative buildings (e.g., a battalion headquarters and a company operation facility), a maintenance facility, a dining facility, a child development center, and an Army reserve center. This paper presents the results of the energy analysis for tactical equipment maintenance facilities (TEMFs). It provides a definition of the baseline building selected for the analysis and the modeling assumptions. As a result of a computer analysis using EnergyPlus version 2.0, baseline and target energy budgets are clearly defined for all 15 DOE climate zones. Finally, a recommended set of energy efficiency solutions for each climate zone is presented that enable at least 30% energy savings in addition to improved and more productive work environments that provide better thermal conditions and indoor air quality for soldiers and workers. Results of this study were implemented through the Army's standard design/build process in late 2007 by incorporating the target energy budgets by climate zone and the recommended sets of technologies to meet these budgets into the Army standard Request for Proposal for TEMFs. [ABSTRACT FROM AUTHOR]

Indoor air distribution is a major concern in designing indoor thermal environment of a large space, which is different from normal buildings. Today, stratified air conditioning is a common choice for large-space buildings. Indoor air distribution with the stratified air conditioning is affected by many design parameters. These parameters have direct effects on thermal comfort, environment noise and energy consumption. Selection of these parameters thus becomes the key problem in design of indoor thermal environment in a large space. In this paper, a large-space building is taken as the study object. It was found that the cooling load varies linearly with the stratified height. The calculations of the air distributions were performed under the conditions of different stratified height, diameter and quantity of the blast nozzles. Based on calculated results, the alignment charts were plotted in an effort to determine the design parameters such as the height, the diameter and the number of blast nozzles and their selection range for a large-space building. According to the charts, the relationship of design parameters and their optimized selection are analyzed. It is clear that the lower the height, the less the energy consumption demand is, however, the noise level would be higher. Based on above results, an optimized and practical methodology is formulated for the design of the air distribution in a large space. [ABSTRACT FROM AUTHOR]

Whereas in the past, ventilation was automatically linked to indoor air quality control, there is nowadays more interest in ventilation as an energy efficient strategy to achieve thermal comfort and good indoor air quality. To reach these targets and manage hybrid ventilation systems, simples and advanced control strategies are therefore needed. This paper presents examples of developed and a numerically and experimentally assessed control strategy architectures of hybrid ventilation controllers. In order to carry out a choice of control parameters and evaluation techniques, we have first developed and numerical tool (HYBCELL1.0) and an experimental device (HYBCELL test cell). As a first approach, simple control strategies have been tested. More complex control strategies based on hierarchical fuzzy controllers have then been developed. To allow an objective evaluation of the controllers using comfort, indoor air quality, energy and stability criteria, fitness functions have been used to compare the relative performances of developed control strategy architectures. [ABSTRACT FROM AUTHOR]

Indoor moisture and temperature conditions and equipment operation were measured and analyzed for 43 homes in warm-humid and mixed-humid climate regions of the United States. A range of house and mechanical system types were evaluated, including standard building enclosures and cooling systems and high-performance building envelopes with enhanced cooling or supplemental dehumidification systems. Conventional cooling systems in standard houses usually provide reasonable humidity control (below 60% RH) in midsummer However, high humidity levels are observed at times when cooling loads are modest. The addition of continuous mechanical ventilation to standard houses in humid climates did not consistently increase indoor humidity levels. Indoor humidity levels were highest in high-performance, low sensible heat gain homes with mechanical ventilation. In these homes, the temperature balance point is higher so there are many hours when sensible cooling is not required yet there are still significant moisture loads from internal sources and ventilation. These homes often require a separate dehumidifier to maintain space humidity in the swing seasons and at night when the thermostat is satisfied. The use of supplemental dehumidification in a high-performance house enables the implementation of efficiency improvements that significantly reduce sensible cooling demand while still maintaining proper humidity levels. [ABSTRACT FROM AUTHOR]