Thermal and Air Quality Acceptability in Buildings that Reduce Energy by Reducing Minimum Airflow from Overhead Diffusers

There is great energy-saving potential in reducing variable air volume (VAV) box minimum airflow setpoints.In the past, setpoints have been maintained at high levels because of three concerns: 1) low flows might cause the occupants draft discomfort from insufficient mixing of diffuser discharge air, 2) inability of VAV boxes to control at low flows, and 3) poor air quality resulting from a combination of poor control and insufficient diffuser mixing. It is worth examining these concerns to see whether they are justified. The controller accuracy and stability have recently been addressed by RP 1353, in which VAV boxes were found to control well at very low flow levels. The diffuser mixing issue and impact on comfort are addressed in this research project, RP 1515.RP 1515 is a combined field and laboratory study, in which occupants’ thermal comfort and air quality satisfaction is evaluated in the field under reduced minimum VAV flow rate setpoints, and the mixing performance of diffusers is measured in the laboratory. The laboratory portion was performed with co-funding from Price Industries. Additional co-funding from the California Energy Commission’s PIER program allowed us to quantify the HVAC energy savings resulting from the reduced flows in the field study buildings.

Effects of diffuser airflow minima on occupant comfort, air mixing, and building energy use (RP-1515)

There is great energy-saving potential in reducing variable air volume (VAV) box minimum airflow setpoints to about 10% of maximum.  Typical savings are on the order of 10-30% of total HVAC energy, remarkable for an inexpensive controls setpoint change that properly maintains outside air ventilation. However, there has long been concern whether comfort and room air mixing are maintained under low flows through diffusers, and this concern has prompted VAV minima to be typically set at 20-50% of maximum.RP 1515 evaluated occupants’ thermal comfort and air quality satisfaction in operating buildings under both conventional and reduced minimum VAV flow setpoints, and measured the air diffusion performance index and air change effectiveness for typical diffuser types in the laboratory.  The hypotheses were that lowered flow operation would not significantly reduce comfort or air quality, and that HVAC energy savings would be substantial. The hypotheses were almost entirely confirmed for both warm and cool seasons.  But beyond this, the reduction of excess airflow during low-load periods caused occupants’ cold discomfort in the warm season to be halved, a surprising improvement.  It appears that today’s widespread overcooling of buildings can be corrected without risk of discomfort by lowering conventional VAV minimum flow setpoints

Time-averaged ventilation for optimized control of variable-air-volume systems

Typical Variable Air Volume (VAV) terminals spend the majority of time at their minimum airflow setpoints. These are often higher than the minimum ventilation requirements defined by code, resulting in excess energy use and a risk of over-cooling the spaces. We developed and tested a Time-Averaged Ventilation (TAV) control strategy in an institutional building on the UC Berkeley campus to address this issue. Whenever a zone does not require cooling, TAV alternates the VAV damper between partially open and fully closed so that the average airflow matches a predefined ventilation setpoint. Compared to the existing, base case scenario using single-max VAV logic, this strategy reduced the mean zone airflow fraction from 0.44 to 0.27 during the intervention period. The corresponding reductions in average heating, cooling, and fan power were 41%, 23%, and 15% respectively. In addition to being programmed directly in a native control system, TAV may be applied via sMAP as a low-cost retrofit strategy in any building that has a BACnet network and direct digital control (DDC) to each VAV terminal

A Usability Study of a Social Media Prototype for Building Energy Feedback and Operations

This study explored the potential for using a web-based social network to promote energy awareness and influence energy-conserving behavior in the workplace. The research team developed a social media application prototype and conducted usability testing with 128 subjects as proxies for typical office building occupants. The key findings presented are: 1) the influence of highly personalized energy information; (2) the influence of normative energy information; (3) the potential for sharing personal energy goals and energy data; (4) the effects of incentives such as self-selected goals or reward “badges,” and (5) the implications of using social media for improving communications between building occupants and operators.Findings suggest that highly personalized energy information, at the level of individual workstations or offices, offers benefits for engaging and informing people about their energy use. The cost of energy was found to be the most useful energy metric, a finding supported by previous research. Social aspects of sharing energy use information and personal energy goals were also viewed favorably by the usability test participants. Although a laboratory study may not account for the many complexities of the workplace context, results show considerable promise for using social media to engage commercial building occupants in energy conservation, and to improve communications between occupants and building management around issues related to building operations. The findings conclude with recommendations for the design of energy feedback interfaces, and for incorporating social media characteristics into such systems

Evaluating a Social Media Application for Conserving Energy and Improving Operations in Commercial Buildings

Compared to the wealth of studies on residential energy behavior, studies on the energy attitudes and behaviors of commercial building occupants have been few. However, occupants exert significant control and influence over energy use in commercial buildings, and it has been estimated that 20% to 50% of total building energy use is controlled or impacted by occupants. This study explores the potential for using a web-based social network to promote energy awareness and influence energy-conserving behavior in the workplace. The research team developed a social media application prototype and conducted usability testing with 128 subjects to understand the perspectives of typical office building occupants. The key findings presented are: 1) the influence of personalized energy information; (2) the influence of normative energy information; (3) the potential for sharing personal energy goals and energy data; (4) the effects of incentives such as self-selected goals or rewards, and (5) the implications of using social media for improving communications between building occupants and operators.Findings suggest that highly individualized energy information, at the level or individual workstations or offices, offers benefits for engaging and informing individuals about their energy use, and that the cost of energy is viewed as the most useful energy metric, a finding supported by previous research. Social aspects of sharing energy use information and personal energy goals were also viewed favorably by the usability test participants. Overall the study found considerable potential for using social media to engage commercial building occupants in energy conservation, and to improve communications between occupants and building management. The paper concludes with recommendations for the design of energy feedback systems including those with social media characteristics

A Usability Study of a Social Media Prototype for Building Energy Feedback and Operations

This study explored the potential for using a web-based social network to promote energy awareness and influence energy-conserving behavior in the workplace. The research team developed a social media application prototype and conducted usability testing with 128 subjects as proxies for typical office building occupants. The key findings presented are: 1) the influence of highly personalized energy information; (2) the influence of normative energy information; (3) the potential for sharing personal energy goals and energy data; (4) the effects of incentives such as self-selected goals or reward “badges,” and (5) the implications of using social media for improving communications between building occupants and operators.Findings suggest that highly personalized energy information, at the level of individual workstations or offices, offers benefits for engaging and informing people about their energy use. The cost of energy was found to be the most useful energy metric, a finding supported by previous research. Social aspects of sharing energy use information and personal energy goals were also viewed favorably by the usability test participants. Although a laboratory study may not account for the many complexities of the workplace context, results show considerable promise for using social media to engage commercial building occupants in energy conservation, and to improve communications between occupants and building management around issues related to building operations. The findings conclude with recommendations for the design of energy feedback interfaces, and for incorporating social media characteristics into such systems

Time-averaged ventilation for optimized control of variable-air-volume systems

Typical Variable Air Volume (VAV) terminals spend the majority of time at their minimum airflow setpoints. These are often higher than the minimum ventilation requirements defined by code, resulting in excess energy use and a risk of over-cooling the spaces. We developed and tested a Time-Averaged Ventilation (TAV) control strategy in an institutional building on the UC Berkeley campus to address this issue. Whenever a zone does not require cooling, TAV alternates the VAV damper between partially open and fully closed so that the average airflow matches a predefined ventilation setpoint. Compared to the existing, base case scenario using single-max VAV logic, this strategy reduced the mean zone airflow fraction from 0.44 to 0.27 during the intervention period. The corresponding reductions in average heating, cooling, and fan power were 41%, 23%, and 15% respectively. In addition to being programmed directly in a native control system, TAV may be applied via sMAP as a low-cost retrofit strategy in any building that has a BACnet network and direct digital control (DDC) to each VAV terminal

Time-averaged ventilation for optimized control of variable-air-volume systems

Typical Variable Air Volume (VAV) terminals spend the majority of time at their minimum airflow setpoints. These are often higher than the minimum ventilation requirements defined by code, resulting in excess energy use and a risk of over-cooling the spaces. We developed and tested a Time-Averaged Ventilation (TAV) control strategy in an institutional building on the UC Berkeley campus to address this issue. Whenever a zone does not require cooling, TAV alternates the VAV damper between partially open and fully closed so that the average airflow matches a predefined ventilation setpoint. Compared to the existing, base case scenario using single-max VAV logic, this strategy reduced the mean zone airflow fraction from 0.44 to 0.27 during the intervention period. The corresponding reductions in average heating, cooling, and fan power were 41%, 23%, and 15% respectively. In addition to being programmed directly in a native control system, TAV may be applied via sMAP as a low-cost retrofit strategy in any building that has a BACnet network and direct digital control (DDC) to each VAV terminal

Effect of a heated and cooled office chair on thermal comfort

A heated/cooled chair was evaluated for its effect on thermal sensation and comfort. Thirty college students participated in 150 1.75-hour tests. Two heated/cooled chairs were placed in an environmental chamber resembling an office environment. The chamber temperatures were set at 16, 18, 25 and 29 °C (60.8, 64.4, 77, 84.2 °F). During the tests the subjects had full control of the chair surface temperature through a knob located on the desk. An additional 64 tests with sixteen subjects were conducted at the same four temperatures but with regular mesh or cushion chairs in order to provide reference results for comparison.  Subjective responses about thermal sensation, comfort, and temperature satisfaction were obtained at 20 minute intervals and eight times before, during, and after a break period. The chair’s energy consumption was monitored continuously. The results show that the heated/cooled chair strongly influences the subjects’ thermal sensation and comfort, providing thermal comfort under all tested conditions, both warm and cool. The average power draw is 27 Watts at 16ºC (60.8 °F), and 45.5 Watts at 29ºC ambient conditions (84.2 °F).&nbsp

Effect of a heated and cooled office chair on thermal comfort

A heated/cooled chair was evaluated for its effect on thermal sensation and comfort. Thirty college students participated in 150 1.75-h tests. Two heated/cooled chairs were placed in an environmental chamber resembling an office environment. The chamber temperatures were set at 16°C, 18°C, 25°C, and 29°C (60.8°F, 64.4°F, 77°F, 84.2°F). During the tests, subjects had full control of the chair surface temperature through a knob located on the desk. An additional 64 tests with 16 subjects were conducted at the same 4 temperatures but with regular mesh or cushion chairs in order to provide reference results for comparison. Subjective responses about thermal sensation, comfort, and temperature satisfaction were obtained at 20-min intervals and eight times before, during, and after a break period. The chair's energy consumption was monitored continuously. The results show that the heated/cooled chair strongly influences the subjects thermal sensation and comfort, providing thermal comfort under all tested conditions, both warm and cool. The average power draw is 27 W at 16°C (60.8°F), and 45.5 W at 29°C (84.2°F) ambient conditions. Copyright © 2013 Crown copyright