David Faulkner’s research while affiliated with Lawrence Berkeley National Laboratory and other places

To assess cool-roof benefits, the temperatures, heat flows, and energy uses in two similar single-family, single-story homes built side by side in Fresno, California were measured for a year. The "cool" house had a reflective cool concrete tile roof (initial albedo 0.51) with above-sheathing ventilation, and nearly twice the thermal capacitance of the standard dark asphalt shingle roof (initial albedo 0.07) on the "standard" house. Cool-roof energy savings in the cooling and heating seasons were computed two ways. Method A divides by HVAC efficiency the difference (standard cool) in ceiling + duct heat gain. Method B measures the difference in HVAC energy use, corrected for differences in plug and window heat gains. Based on the more conservative Method B, annual cooling (compressor + fan), heating fuel, and heating fan site energy savings per unit ceiling area were 2.82 kWh/m(2) (26%), 1.13 kWh/m(2) (4%), and 0.0294 kWh/m(2) (3%), respectively. Annual space conditioning (heating + cooling) source energy savings were 10.7 kWh/m(2) (15%); annual energy cost savings were $0.886/m(2) (20%). Annual conditioning CO2, NOx, and SO2 emission reductions were 1.63 kg/m(2) (15%), 0.621 g/m(2) (10%), and 0.0462 g/m(2) (22%). Peak-hour cooling power demand reduction was 0.88 W/m(2) (37%).

Abstract This field study of 37 small and medium commercial buildings throughout California obtained information on ventilation rate, temperature, and heating, ventilating, and air-conditioning (HVAC) system characteristics. The study included seven retail establishments; five restaurants; eight offices; two each of gas stations, hair salons, healthcare facilities, grocery stores, dental offices, and fitness centers; and five other buildings. Fourteen (38%) of the buildings either could not or did not provide outdoor air through the HVAC system. The air exchange rate averaged 1.6 (s.d. = 1.7) exchanges per hour and was similar between buildings with and without outdoor air supplied through the HVAC system, indicating that some buildings have significant leakage or ventilation through open windows and doors. Not all buildings had sufficient air exchange to meet ASHRAE 62.1 Standards, including buildings used for fitness centers, hair salons, offices, and retail establishments. The majority of the time, buildings were within the ASHRAE temperature comfort range. Offices were frequently overcooled in the summer. All of the buildings had filters, but over half the buildings had a filter with a minimum efficiency reporting value rating of 4 or lower, which are not very effective for removing fine particles. Most U.S. commercial buildings (96%) are small- to medium-sized, using nearly 18% of the country’s energy, and sheltering a large population daily. Little is known about the ventilation systems in these buildings. This study found a wide variety of ventilation conditions, with many buildings failing to meet relevant ventilation standards. Regulators may want to consider implementing more complete building inspections at commissioning and point of sale.

In demand-controlled ventilation (DCV), rates of outdoor air ventilation are automatically modulated as occupant density varies. The objective is to keep ventilation rates at or above design specifications and code requirements and also to save energy by avoiding excessive ventilation rates. DCV is most often used in spaces with highly variable and sometime dense occupancy. In almost all cases, carbon dioxide (CO) sensors installed in buildings provide the signal to the ventilation rate control system. People produce and exhale CO as a consequence of their normal metabolic processes; thus, the concentrations of CO inside occupied buildings are higher than the concentrations of CO in the outdoor air. The magnitude of the indoor-outdoor CO concentration difference decreases as the building's ventilation rate per person increases. The difference between the indoor and outdoor CO concentration is also a proxy for the indoor concentrations of other occupant-generated bioeffluents, such as body odors. Reviews of the research literature on DCV indicate a significant potential for energy savings, particularly in buildings or spaces with a high and variable occupancy. Based on modeling, cooling energy savings from applications of DCV are as high as 20%. With support from the California Energy Commission and the U.S. Department of Energy, the Lawrence Berkeley National Laboratory has performed research on the performance of CO sensing technologies and optical people counters for DCV. In addition, modeling was performed to evaluate the potential energy savings and cost effectiveness of using DCV in general office spaces within the range of California climates. The above-described research has implications for the specifications pertaining to DCV in section 121 of the California Title 24 Standard. Consequently, this document suggests possible changes in these specifications based on the research findings. The suggested changes in specifications were developed in consultation with staff from the Iowa Energy Center who evaluated the accuracy of new CO sensors in laboratory-based research. In addition, staff of the California Energy Commission, and their consultants in the area of DCV, provided input for the suggested changes in specifications.

Carbon dioxide (CO) sensors are often deployed in commercial buildings to obtain CO data that are used, in a process called demand-controlled ventilation, to automatically modulate rates of outdoor air ventilation. The objective is to keep ventilation rates at or above design specifications and code requirements and also to save energy by avoiding excessive ventilation rates. Demand controlled ventilation is most often used in spaces with highly variable and sometime dense occupancy. Reasonably accurate CO measurements are needed for successful demand controlled ventilation; however, prior research has suggested substantial measurement errors. Accordingly, this study evaluated: (a) the accuracy of 208 CO single-location sensors located in 34 commercial buildings, (b) the accuracy of four multi-location CO measurement systems that utilize tubing, valves, and pumps to measure at multiple locations with single CO sensors, and (c) the spatial variability of CO concentrations within meeting rooms. The field studies of the accuracy of single-location CO sensors included multi-concentration calibration checks of 90 sensors in which sensor accuracy was checked at multiple CO concentrations using primary standard calibration gases. From these evaluations, average errors were small, -26 ppm and -9 ppm at 760 and 1010 ppm, respectively; however, the averages of the absolute values of error were 118 ppm (16%) and 138 ppm (14%), at concentrations of 760 and 1010 ppm, respectively. The calibration data are generally well fit by a straight line as indicated by high values of R². The Title 24 standard specifies that sensor error must be certified as no greater than 75 ppm for a period of five years after sensor installation. At 1010 ppm, 40% of sensors had errors greater than {+-}75 ppm and 31% of sensors has errors greater than {+-}100 ppm. At 760 ppm, 47% of sensors had errors greater than {+-}75 ppm and 37% of sensors had errors greater than {+-}100 ppm. A significant fraction of sensors had errors substantially larger than 100 ppm. For example, at 1010 ppm, 19% of sensors had an error greater than 200 ppm and 13% of sensors had errors greater than 300 ppm. The field studies also included single-concentration calibration checks of 118 sensors at the concentrations encountered in the buildings, which were normally less than 500 ppm during the testing. For analyses, these data were combined with data from the calibration challenges at 510 ppm obtained during the multi-concentration calibration checks. For the resulting data set, the average error was 60 ppm and the average of the absolute value of error was 154 ppm. Statistical analyses indicated that there were statistically significant differences between the average accuracies of sensors from different manufacturers. Sensors with a 'single lamp single wavelength' design tended to have a statistically significantly smaller average error than sensors with other designs except for 'single lamp dual wavelength' sensors, which did not have a statistically significantly lower accuracy. Sensor age was not consistently a statistically significant predictor of error.

Are the carbon dioxide (CO2) sensors in your demand controlled ventilation systems sufficiently accurate? The data from these sensors are used to automatically modulate minimum rates of outdoor air ventilation. The goal is to keep ventilation rates at or above design requirements while adjusting the ventilation rate with changes in occupancy in order to save energy. Studies of energy savings from demand controlled ventilation and of the relationship of indoor CO2 concentrations with health and work performance provide a strong rationale for use of indoor CO2 data to control minimum ventilation rates1-7. However, this strategy will only be effective if, in practice, the CO2 sensors have a reasonable accuracy. The objective of this study was; therefore, to determine if CO2 sensor performance, in practice, is generally acceptable or problematic. This article provides a summary of study methods and findings ? additional details are available in a paper in the proceedings of the ASHRAE IAQ?2007 Conference8.

An assessment of the indoor air quality (IAQ) of the San Francisco Federal Building (SFFB) was conducted on May 12 and 14, 2009 at the request of the General Services Administration (GSA). The purpose of the assessment was for a general screening of IAQ parameters typically indicative of well functioning building systems. One naturally ventilated space and one mechanically ventilated space were studied. In both zones, the levels of indoor air contaminants, including CO2, CO, particulate matter, volatile organic compounds, and aldehydes, were low, relative to reference exposure levels and air quality standards for comparable office buildings. We found slightly elevated levels of volatile organic compounds (VOCs) including two compounds often found in"green" cleaning products. In addition, we found two industrial solvents at levels higher than typically seen in office buildings, but the levels were not sufficient to be of a health concern. The ventilation rates in the two study spaces were high by any standard. Ventilation rates in the building should be further investigated and adjusted to be in line with the building design. Based on our measurements, we conclude that the IAQ is satisfactory in the zone we tested, but IAQ may need to be re-checked after the ventilation rates have been lowered.

An improved HVAC system for portable classrooms was specified to address key problems in existing units. These included low energy efficiency, poor control of and provision for adequate ventilation, and excessive acoustic noise. Working with industry, a prototype improved heat pump air conditioner was developed to meet the specification. A one-year measurement-intensive field-test of ten of these IHPAC systems was conducted in occupied classrooms in two distinct California climates. These measurements are compared to those made in parallel in side by side portable classrooms equipped with standard 10 SEER heat pump air conditioner equipment. The IHPAC units were found to work as designed, providing predicted annual energy efficiency improvements of about 36 percent to 42 percent across California's climate zones, relative to 10 SEER units. Classroom ventilation was vastly improved as evidenced by far lower indoor minus outdoor CO2 concentrations. TheIHPAC units were found to provide ventilation that meets both California State energy and occupational codes and the ASHRAE minimum ventilation requirements; the classrooms equipped with the 10 SEER equipment universally did not meet these targets. The IHPAC system provided a major improvement in indoor acoustic conditions. HVAC system generated background noise was reduced in fan-only and fan and compressor modes, reducing the nose levels to better than the design objective of 45 dB(A), and acceptable for additional design points by the Collaborative on High Performance Schools. The IHPAC provided superior ventilation, with indoor minus outdoor CO2 concentrations that showed that the Title 24 minimum ventilation requirement of 15 CFM per occupant was nearly always being met. The opposite was found in the classrooms utilizing the 10 SEER system, where the indoor minus outdoor CO2 concentrations frequently exceeded levels that reflect inadequate ventilation. Improved ventilation conditions in the IHPAC lead to effective removal of volatile organic compounds and aldehydes, on average lowering the concentrations by 57 percent relative to the levels in the 10 SEER classrooms. The average IHPAC to 10 SEER formaldehyde ratio was about 67 percent, indicating only a 33 percent reduction of this compound in indoor air. The IHPAC thermal control system provided less variability in occupied classroom temperature than the 10 SEER thermostats. The average room temperatures in all seasons tended to be slightly lower in the IHPAC classrooms, often below the lower limit of the ASHRAE 55 thermal comfort band. State-wide and national energy modeling provided conservative estimates of potential energy savings by use of the IHPAC system that would provide payback a the range of time far lower than the lifetime of the equipment. Assuming electricity costs of $0.15/kWh, the perclassroom range of savings is from about$85 to $195 per year in California, and about$89 to $250 per year in the U.S., depending upon the city. These modelsdid not include the non-energy benefits to the classrooms including better air quality and acoustic conditions that could lead to improved health and learning in school. Market connection efforts that were part of the study give all indication that this has been a very successful project. The successes include the specification of the IHPAC equipment in the CHPS portable classroom standards, the release of a commercial product based on the standards that is now being installed in schools around the U.S., and the fact that a public utility company is currently considering the addition of the technology to its customer incentive program. These successes indicate that the IHPAC may reach its potential to improve ventilation and save energy in classrooms.

Carbon dioxide (CO2) sensors are often deployed in commercial buildings to obtain CO2 data that are used to automatically modulate rates of outdoor air supply. The goal is to keep ventilation rates at or above design requirements and to save energy by avoiding ventilation rates exceeding design requirements. However, there have been many anecdotal reports of poor CO2 sensor performance in actual commercial building applications. This study evaluated the accuracy of 44 CO2 sensors located in nine commercial buildings to determine if CO2 sensor performance, in practice, is generally acceptable or problematic. CO2 measurement errors varied widely and were sometimes hundreds of parts per million. Despite its small size, this study provides a strong indication that the accuracy of CO2 sensors, as they are applied and maintained in commercial buildings, is frequently less than needed to measure typical values of maximum one-hour-average indoor-outdoor CO2 concentration differences with less than a 20percent error. Thus, we conclude that there is a need for more accurate CO2 sensors and/or better sensor maintenance or calibration procedures.

Underfloor air distribution (UFAD) is a new method of supplying heated or cooled air throughout a building. Reported advantages of UFAD include energy savings and improved indoor air quality (IAQ). We measured several aspects of the performance of a UFAD system installed in a medium-size office building. The measured air change effectiveness was very close to unity, which is comparable to that measured in buildings with typical overhead air distribution. The pollutant removal efficiency for carbon dioxide was 13% higher than expected in a space with well-mixed air, suggesting a 13% reduction in exposures to occupant generated pollutants. The increase in indoor air temperatures with height above the floor was only 1 to 2 °C. This amount of thermal stratification could reduce the sensible energy requirements for cooling of outdoor air by approximately 10%. The occupants' level of satisfaction with thermal conditions was well above average and this high satisfaction rating could possibly be due, in all or part, to the use of a UFAD system. The results of this study provide some evidence of moderate energy and IAQ-related benefits of UFAD. Before general conclusions are drawn, the benefits need to be confirmed in other studies.