(PDF) Thermal comfort in commercial kitchens (RP-1469): Procedure

This article was downloaded by: [DTU Library] On: 09 December 2013, At: 05:30 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

HVAC&R Research Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/uhvc20

Thermal comfort in commercial kitchens (RP-1469): Procedure and physical measurements (Part 1) a

a

b

Angela Simone , Bjarne W. Olesen , John L. Stoops & Amber W. Watkins

b

a

International Centre for Indoor Environment and Energy (ICIEE), Department of Civil Engineering , Technical University of Denmark (DTU) , Nils Koppels Allé, Building 402, DK-2800 , Kgs. Lyngby , Denmark b

Sustainable Use Consulting at DNV KEMA Energy & Sustainability , Oakland , CA , USA Accepted author version posted online: 10 Oct 2013.Published online: 27 Nov 2013.

To cite this article: Angela Simone , Bjarne W. Olesen , John L. Stoops & Amber W. Watkins (2013) Thermal comfort in commercial kitchens (RP-1469): Procedure and physical measurements (Part 1), HVAC&R Research, 19:8, 1001-1015, DOI: 10.1080/10789669.2013.840494 To link to this article: http://dx.doi.org/10.1080/10789669.2013.840494

PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions

HVAC&R Research (2013) 19, 1001–1015 C 2013 ASHRAE. Copyright  ISSN: 1078-9669 print / 1938-5587 online DOI: 10.1080/10789669.2013.840494

Thermal comfort in commercial kitchens (RP-1469): Procedure and physical measurements (Part 1) ANGELA SIMONE1,∗, BJARNE W. OLESEN1, JOHN L. STOOPS2, and AMBER W. WATKINS2 1

Downloaded by [DTU Library] at 05:30 09 December 2013

International Centre for Indoor Environment and Energy (ICIEE), Department of Civil Engineering, Technical University of Denmark (DTU), Nils Koppels All´e, Building 402, DK-2800 Kgs. Lyngby, Denmark 2 Sustainable Use Consulting at DNV KEMA Energy & Sustainability, Oakland, CA, USA

The indoor climate in commercial kitchens is often unsatisfactory, and working conditions can have a significant effect on employees’ comfort and productivity. The type of establishment (fast food, casual, etc.) and climatic zone can influence thermal conditions in the kitchens. Moreover, the size and arrangement of the kitchen zones, appliances, etc., further complicate an evaluation of the indoor thermal environment in commercial kitchens. In general, comfort criteria are stipulated in international standards (e.g., ASHRAE 55 or ISO EN 7730), but are these standardized methods applicable to such environments as commercial kitchens? This article describes a data collection protocol based on measurements of physical and subjective parameters. The procedure was used to investigate more than 100 commercial kitchens in the United States in both summer and winter. The physical measurements revealed that there is a large range of kitchens environments and confirmed that employees are exposed to a warm-to-hot environment. The measured ranges of activities and temperatures in many cases were outside the range recommended by ASHRAE 55 and ISO EN 7730. The study showed that the predicted mean vote/percentage people dissatisfied (PMV/PPD) index is not directly appropriate for all thermal conditions in commercial kitchens.

Introduction The restaurant industry in the United States is the nation’s second largest private sector employer, with its workforce of 12.8 million projected to increase by 1.3 million positions in the next decade (National Restaurant Association [NRA] 2012). As nearly one in ten of all employed Americans worked in a restaurant in 2011, the NRA expected restaurants to add jobs at a 2.3% rate in 2012, a full percentage above the projected 1.3% gain in total U.S. employment. In the last year, restaurant job creation continues to outpace that of other industries, resulting in 3% more restaurant positions compared to 1.4% for overall U.S. employment. An additional 2.4% increase in restaurant jobs is expected in the United States in 2013, which will result in 13.1 million of restaurants employees equal to 10% of the U.S. workforce (NRA 2013). For countries such as the United States, where one of the largest employee sectors is in the restaurant industry, the wellbeing of the employees is becoming one of the main issues. The commercial kitchen is a unique space where many different HVAC applications must operate within a sin-

Received February 4, 2013; accepted August 22, 2013 Angela Simone, PhD, Associate Member ASHRAE, is Researcher. Bjarne W. Olesen, PhD, Fellow/Life Member ASHRAE, is Professor and Centre Director. John L. Stoops, PhD, Member ASHRAE, is Senior Principal Consultant. Amber W. Watkins is Consultant. ∗ Corresponding author e-mail: [email protected]

gle space. Those different applications can be designed and determined by the appliance line and should follow the guidelines in the kitchen ventilation chapter of the 2011 ASHRAE Handbook—HVAC Application (ASHRAE 2011b), ASHRAE Standard 154 (ASHRAE 2011a), and in prEN16282 (ISO 2011). In the context of energy-saving strategies, ASHRAE/IES Standard 90.1 (ASHRAE 2010b) contains more restrictive requirements for transfer air, demand-controlled ventilation (DCV), energy recovery devices, and high performance hoods. Recent studies and developments have attempted a total kitchen HVAC (TKHVAC) system approach and DCV for commercial kitchens, which are expected to become a standard energy efficient practice (Fisher et al. 2013). However, an acceptable thermal environment must also be provided for kitchen occupants. The appliances, size and arrangement of the kitchen zones, number of employees, variable environmental conditions during business hours, etc., further complicate an evaluation of the indoor thermal environment in kitchens. Previous studies in commercial kitchens have focused mainly on air-conditioning and ventilation systems. When considering thermal comfort, such studies as Pekkinen and Takki-Halttunen (1992) and Livchak et al. (2005) dealt mainly with the acceptable ranges of physical parameters reported in standards, values that were established for indoor environments in which there was a low activity level. Thermal comfort criteria are defined in international standards such as ASHRAE Standard 55 (ASHRAE 2010a) or ISO Standard EN 7730 (ISO 2005), but it is questionable whether these standardized methods are applicable to environments like commercial kitchens.

Downloaded by [DTU Library] at 05:30 09 December 2013

1002 Today there are no specific regulations or even parameters to determine whether thermal conditions in commercial kitchens are comfortable or cost effective. General evaluation criteria for thermal comfort may be inadequate and unsuitable for practical application. Based on standardized methods (ASHRAE and ISO) and on pre-tested pilot measurements, Simone and Olesen (2012a and 2012b) introduced a procedure for collecting data on the physical environment and subjective perceptions in commercial kitchens. The procedure was applied in a large study involving more than 100 commercial kitchens in the United States in order to obtain enough of data to be able to evaluate thermal comfort. Different kitchens types (fast food, dining, etc.) and different kitchens zones, in both summer and winter, were investigated. Part 1 of this series presents the results obtained from physical measurements. Differences between kitchen types (fastfood, casual, and institutional kitchens), seasons, and climatic region are analyzed in terms of the measurements using existing comfort evaluation indices, such as the predicted mean vote/percentage people dissatisfied (PMV/PPD) index, and the applicability in commercial kitchens is evaluated. The subjective evaluations were analyzed and used to define a thermal comfort range in a warm environment in which the occupants have high activity levels. These results are presented in Part 2 of this series.

Evaluation of the thermal environment in commercial kitchen For many years the International Organization for Standardization (ISO) and ASHRAE have been developing standards for the indoor thermal environment. ASHRAE has mainly developed standards for moderate thermal environments (e.g., ASHRAE 55/2010 [ASHRAE 2010a]), while ISO standards cover the entire range from cold stress to comfort to heat stress (e.g., ISO EN 7730/2005 [ISO 2005], ISO EN 7933/2004 [ISO 2004a], and ISO EN 11079/2007 [ISO 2007b]). Thermal comfort is one of the four elements that influence the indoor environmental air quality (IEQ) of a given space, with the other three being lightining quality, acoustical quality, and air quality. It is defined as a “condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation” (ASHRAE Standard 55/2010 [ASHRAE 2010a, p. 4]); this definition has been converted into specifications in terms of physical parameters. PMV is the most widely used index for evaluating indoor thermal comfort, but it is recommended only for values between ±2 on the 7-point PMV-scale (ISO EN 7730/2005 [ISO 2005]). In commercial kitchens, it is also necessary to consider thermal dissatisfaction that can be caused by an overall thermal sensation that is too warm or too cold (i.e., the percentage dissatisfied, PPD) or the percentage dissatisfied by local thermal discomfort (PD) due to draught, vertical temperature gradient, radiant asymmetry, or warm or cold floors (ISO EN 7730/2005 [ISO 2005]). The main activity in a commercial kitchen is the cooking process, which generates heat and effluents that must be

HVAC & R Research captured and exhausted in order to control and guarantee thermal comfort and good air quality for the employees. Previous studies in commercial kitchens have mainly focused on air-conditioning and ventilation systems. They indicate that kitchens are not typical of general spaces, and that thermal comfort conditions in commercial kitchens are determined by envelope heat gain and loss, people, lighting, and miscellaneous equipment. Thermal comfort in a commercial kitchen environment is mainly driven by the radiant heat that directly impacts the comfort of the workers, and by convective loads from both hooded and un-hooded cooking appliances. One published study of the commercial-kitchen environment indicates that the areas on the body that have the greatest exposure to temperature differences are the chest and facial areas, situated between 1.5 and 1.8 m (59 and 71 in.) height above the floor (Livchak et al. 2005). Additionally, it was found that the greatest heat loads are encountered at the cooking line, which produces the largest heat gains in the space, and where the workers are exposed to the highest temperatures. As described in many studies, thermal comfort has a large impact on the performance and productivity of the employees. In particular, Wyon (1996) and later Livchak et al. (2005) reported that an increase of temperature of 10◦ F (5.5◦ C) above the thermally neutral level may result in a 30% loss of productivity. In a commercial kitchen environment, there can be large differences between the type of kitchen space (casual restaurant, institutional restaurant, or quick-service restaurant [QSR]), kitchen activities (preparation, cooking, dish washing), building and type of HVAC system (insulation, windows, air conditioning, natural ventilation), and kitchens that are situated in many different climatic zones. The kitchen environment presents a much broader range of conditions than those that occur in offices, schools, and homes, and the question is whether the methods described in existing thermal comfort standards are applicable. To determine whether they do apply, ASHRAE Research Project RP-1469 was initiated. As part of the project, a measuring procedure was established, focusing in particular on the processes characterizing kitchen spaces and kitchen activities (ASHRAE 2012). The procedure used to establish a database for the thermal environment in commercial kitchens obtains both physical and subjective values. Two types of questionnaire based on the ISO Standard 10551 (ISO 2001) were developed and adapted to the kitchen environment and to kitchen workers in order to achieve the highest possible participation by the employees in the study. They were used in combination with weekly recording of physical parameters supplemented by detailed measurements on a particular day.

Method As the commercial kitchen environment now includes conditions that differ from those studied earlier, a measuring procedure was established to focus on the different processes that take place in a commercial kitchen. For example, employees facing high-energy appliances, such as an under-fired

Downloaded by [DTU Library] at 05:30 09 December 2013

Volume 19, Number 8, November 2013

1003

Fig. 1. Schema of procedure of data collection (color figure available online).

charbroiler, ovens, steamers, or deep-fat fryers, or subjected to bursts of very humid hot air are subject to higher radiant conditions than employees working on a preparation line with their backs some distance from such appliances. A general view of the procedure, from the recruitment of kitchens to the data collection, is summarized in the flowchart in Figure 1. Recruitment of kitchens Commercial kitchen spaces differ by type (casual, institutional, or QSR), kitchen activities (preparation, cooking, dish washing), building and HVAC system types (insulation, windows, air-conditioning, natural ventilation), and locations in different climatic zone. For this reason, measurements of thermal parameters were recorded in different types of kitchens,

in different cities, and in different climatic zones throughout the United States, as shown in Table 1. Site data were collected in nine metropolitan areas located in different climatic zones, according to ASHRAE Standard 169 (ASHRAE 2006) climate zone classifications. In all, 105 commercial kitchens in summer and 104 in winter participated in the thermal comfort evaluation of the kitchen environment, from which over 90% participated in both seasonal study phases. A “casual” dining restaurant is considered to be a restaurant that provides table service, a franchise, chain, or privately owned restaurant. A particular example of a kitchen classified as “casual” is a small privately owned restaurant with a single kitchen. The owner may often be the administrator or part of the kitchen staff. Restaurants grouped as “institutional” are those typically located within a school, an office, a government building cafeteria, or as part of a

Table 1. Number of measured kitchen types in United States. Summer (Phase I) kitchen type sample, August–October 2010 Climate zone (ASHRAE Standard 169 [ASHRAE 2006]) 1—Moist 2/3—Moist 2/3—Dry 4—Marine 4—Moist 4—Moist 5/6—Moist 5/6—Dry 7—Moist Sum by kitchen type

Winter (Phase II) kitchen type sample, January–February 2011

U.S. city

QSR

Institutional

Casual

Sum

QSR

Institutional

Casual

Sum

Miami Atlanta Phoenix Seattle Nashville Washington DC New York Las Vegas Minneapolis

9 7 6 5 2 5 4 8 7 53

3 5 4 9 3 5 4 2 3 38

0 0 2 0 4 0 3 2 3 14

12 12 12 14 9 10 11 12 13 105

9 7 6 5 2 5 4 8 7 53

3 5 4 9 3 5 5 3 3 40

0 0 2 0 3 0 1 2 3 11

12 12 12 14 8 10 10 13 13 104

1004 hotel. Institutional restaurants in general had a more robust ventilation system and a larger food-preparation area and cooking line. Last, QSRs, such as those providing expedited service or “fast food,” are typically owned and operated by franchisees, corporations, or, in some instances, privately held companies. The differentiation between kitchen types has resulted in some overlapping, but the on-site visit during the measurements improved the classification of the kitchen data.

Downloaded by [DTU Library] at 05:30 09 December 2013

Data collection Data collection included several types of measurement: outdoor air temperature and humidity, HVAC system (supply and make-up air temperature and relative humidity [RH]), indoor (thermal) environment, physiological, and subjective evaluation. The intention was to collect data describing the physical environment and personal factors, such as clothing and activity, to be able to calculate existing indices of thermal comfort and/or heat stress. In order to be able to characterize adequately the HVAC systems performance and to obtain some idea of the air quality in each kitchen, the supply and exhaust airflows should have been measured as well. However, supply and exhaust airflow rates measurements were not technically feasible in most of the kitchens. Carbon dioxide concentrations and indoor air quality subjective evaluations were used as indicators instead. Data were recorded in summer and winter and in the three identified kitchen zones (cooking, food preparation, and dish washing) shown by the area inside the dashed line in Figure 2, these being considered likely to have different thermal conditions in the commercial kitchen. During the visit to the kitchens, a sketch of each kitchen and its different zones was

HVAC & R Research made (e.g., Figure 2), including the location of the measuring devices that have been installed, the location of the supply and exhaust of the HVAC system, the exhaust hood and other details (e.g., type of supply device and exhaust grill, use of free-standing fans, etc.), and other notes. The data recorded during the measurements are listed below according the grouped tasks listed in the schema of Figure 1. The following parameters were measured. 1. Long-term measurements (LM) (first to third walkthrough; during a typical week, normally Monday to Saturday): air temperature (ta ), operative temperature (to ), and RH for a whole week in time intervals of 15 min; examples of the measured spots, representative of kitchens zone, are shown in Figure 2 as a rectangular green spot. 2. Short-term (or spot) measurements (SM) (second walkthrough): subjective parameters, such as estimated activity level (met) and clothing insulation (Icl ), globe temperature (tg ) and ta at 0.1 m and 1.7 m (4 and 67 in.) height above the floor, air (ta ), operative (to ), radiant temperature (tr ), air velocity (va ), and RH at 1.1 m (43 in.) above the floor and at 0.3 m (1 ft) distant at the workstation (where the employees were working during the peak operating hours of a working day [breakfast, lunch, and/or dinner time]) during on-site SM. All physical parameters were recorded for 15–20 minutes, having 30–40 equally spaced points over time (30-s time-interval), with an exception for air velocity and directional operative temperature. The air velocity was recorded for 15–20 min with a minimum interval time of 1 s, while the directional operative temperature was recorded in a time interval of 30 s for a minimum of 5 min for each direction (up–down, right–left, front–back).

Fig. 2. Cooking, food preparation, and dishwashing areas of a kitchen sample (color figure available online).

Volume 19, Number 8, November 2013 Physical parameters collected at each representative worker location are shown in Figure 2 by a red arrow. 3. Short-term questionnaire (SQ) (second walk-through): onsite survey of occupants’ subjective reaction to the indoor environment obtained while recording the physical measurements. 4. Long term questionnaire (LQ) (first to third walk-through): general survey of background information on the employees and their overall evaluation of the working conditions.

Downloaded by [DTU Library] at 05:30 09 December 2013

From the average of the physical data recorded at 1.1 m (43 in.) height and the estimated individual parameters (clothing and activity), individual PMV/PPD indices and weighted averages for climate, kitchen type, and zone were calculated. In particular, by using the ASHRAE thermal comfort tool (Huizenga 2011) a PMV value was assigned to each of 364 employees encountered during the on-site SMs. Instrumentation for physical measurements The physical environmental parameters were measured with the instruments shown in Figure 3. RH was measured and recorded using a small data logger (Figure 3a) with an accuracy of ±2.5% (Hobo). The air, globe/operative, and flat radiant temperature sensors were built based on ISO Standard 7726 (ISO 1998) descriptions and as described by Simone et al. (2007). In the measurement range of 50◦ F to 104◦ F (10◦ C to 40◦ C), these temperature sensors have an accuracy of ±0.5◦ F (±0.3◦ C). The air temperature sensors (Figure 3b) were built by enclosing a temperature sensor within an open-ended radiation shield (the cylinder) that enabled a free flow of air to come in contact with the sensor. A grayish globe sensor of 4 cm (1.6 in.) diameter was used to measure the globe temperature (Figure 3c), which, at 1.1 m (43 in.) height above the floor, is an estimate of the operative temperature (to ) for a standing person and thus closely related to the global thermal perception of the occupant and to calculate the mean radiant temperature, from the difference between air and operative temperature, in the minimum temporal average of 12 min with 24 equally spaced points over time. A flat sensor, having two opposed faces with a matte gray finish, each 7 cm (2.8 in.) in diameter (Figure 3d), was used to measure the directional operative temperature (to,i ) and to evaluate the radiant asymmetry that occurred when an employee was facing a high-temperature radiant surface, such as appliances in the cooking zone. The sensor records two values

1005 of operative temperature at a time in the same point in space, equal or different according to the direction of the plate that faces the opposite hemisphere in the same room volume. The average value of the temperature was taken as the temporal average over at least 5 min with 10 measurements that were equally spaced in time. The plane radiant temperature (tp,i ) in six directions and the mean radiant temperature (tr ) were calculated according to Equations 1 and 2: tp,i = tr =

to,i − a · ta 1−a

(1)

0.08 · (tp,up + tp,down ) + 0.23 · (tp,right + tp,le f t ) + 0.35 · (tp, f r ont + tp,back ) 2 · (0.08 + 0.23 + 0.35) (2)

with i representative of the direction 1, 2, 3, 4, 5, or 6 of the sensor facing up, down, right, left, front, or back, relative to the direction the employee was facing. An omnidirectional anemometer was used for measuring air velocity (Figure 3e). This sensor can measure in the range of 0.005 to 5 m/s (9.8 to 984 ft/min) with an accuracy of 0.02 m/s (4 ft/min) ±1% of readings. The portable data logger connected to the anemometer recorded air velocity with a minimum interval time of 1 s (1-Hz frequency). The average air velocity over 12–15 min was used in the analysis. The above sensors yielded a voltage that was directly recorded by a small logger (Figure 3a) and afterward converted to the relevant units by the calibration equations. This way of storing data was very convenient for measurements in kitchens, avoiding any hindrance for the workers, and disturbing them and their work as little as possible. As shown in Figure 4a, the data loggers recorded kitchen temperatures, humidity, and carbon dioxide (CO2 ) concentrations. In addition to what was described above in the “Data Collection” section, loggers to record LMs (Figure 4a) were installed for the duration of one week, or slightly less. The loggers referred to short-term recorded data (Figure 4b) only during the peak operation time (or rush time) of the kitchen, i.e., during the busiest working hour(s). Monitoring a period of 15–20 min during that peak period was performed, as it may be considered to provide the worst thermal environment for the employees. Recording devices were used for more detailed SMs of thermal parameters (air temperatures, humidity, air velocity, and radiant temperatures) and, as earlier explained, at different heights during the peak operating hours in one working day (breakfast, lunch, and/or dinner time).

Fig. 3. Equipment of sensors for measuring thermal parameters (color figure available online).

Downloaded by [DTU Library] at 05:30 09 December 2013

1006

HVAC & R Research

Fig. 4. a. LM devices. b. SM stand placement (color figure available online).

Evaluation of clothing and metabolism During the SMs (second walk-through), the items of clothing worn were noted, how often and how much the clothing insulation was changed, and an evaluation of thermal resistance and vapor diffusion resistance (when possible). Later, the thermal insulation value of each worker’s clothing was estimated as stipulated in ISO 9920 (ISO 2007a). The activity level in a kitchen changes considerably during a working day, so a time-weighted average over each 1-h period was calculated. The employees’ activity level was estimated by observation and by analyses, recording the heart rate of one or more individuals within each kitchen, together with their age, weight, and sex, as stipulated in ISO Standard 8996 (ISO 2004b). Subjective evaluation measurements (SM and LT) Subjective evaluation is a very important component of any procedure for evaluating the thermal comfort condition of an indoor space. The methods used for the collection of occupants’ perception data are described in the present article, but the results obtained and an analysis of the subjective measurements will be reported in a second article (Part 2). Two questionnaires, one on long-term general effects (LQ) and one on occupants’ immediate reactions (SQ), each as described in ASHRAE Report RP-1469 (ASHRAE 2012), were used to evaluate thermal and working conditions, to support physical data monitoring, and to analyze the relationship between the physical parameters of the environment and subjective aspects

of the occupants’ perception of thermal comfort in the kitchen environment. The subjective evaluation of the thermal conditions was conducted using the standard ASHRAE 7-point thermal sensation scale (see Figure 5) during the physical SM. Several other questions adapted to the kitchen environment, but based on ISO 10551 (ISO 2001), were asked in the LQ and consisted of eight parts: background characteristics, personal comfort, personal control, work conditions, work area satisfaction, health characteristics, environmental sensitivity, and clothing (ASHRAE Report RP-1469 report [ASHRAE 2012]).

Statistical analyses All statistical analyses were conducted with SAS software (SAS Institute Inc., Cary, NC, USA) with a type I error rate of α = 0.05. In addition to the descriptive statistical analyses, comparisons between kitchen types, climatic zones, and working areas were analyzed using a one-way ANOVA MEANS procedure in SAS. The effect due to different seasons, summer and winter, on the thermal environment was also evaluated.

Results and discussion SMs were performed in a total of 74 commercial kitchens. Table 2 shows the numbers of kitchens where the detailed Table 2. Number of detailed measured kitchen.

Fig. 5. Seven-point thermal sensation scale (color figure available online).

Kitchen type

Summer

Winter

QSR Casual Institutional Sum

11 6 22 39

11 6 18 35

Downloaded by [DTU Library] at 05:30 09 December 2013

Volume 19, Number 8, November 2013

1007

Fig. 6. Operative temperature data from all kitchen zone SMs in summer and winter (color figure available online).

SMs were carried out in the summer monitoring phase I and in the winter phase II for each kitchen type. An overview of the measured physical parameters in commercial kitchens, in summer and in winter, is shown in the psychometric diagram in Figure 6. The operative temperature and air humidity data were estimated from all SMs at 1.1 m (43 in.) height. The highest temperature values were found in the cooking zones (up to 41.2◦ C (106◦ F)) and the highest RH in the dish-washing area (up to 76%); in particular, 22 cooking zones had a measured to higher than 31◦ C (88◦ F), while similarly high humidity levels were recorded in food-preparation and cooking areas. Operative temperatures to lower than 20◦ C (68◦ F), and as low as 15.9◦ C (61◦ F) in winter, were recorded in a number of different kitchens zones. Those values show that even if all kitchens were provided with AC systems, the recorded temperatures were widely spread over a range that was much larger than expected. The reason for such big differences in temperatures is likely to be not only poor performance of the AC systems but factors such as the big differences in

exposure (cooking, dish washing, and preparation), keeping food warm, etc. From the detailed SMs, the average values of the measured thermal parameters by type and kitchen zones were calculated from time-averages of the SMs and then from the averages over kitchen types or work place, and are shown in Tables 3 to 6. Table 3 shows the yearly averages of all thermal environmental parameters measured/estimated obtained from the average of SMs as a function of the number of occupants, kitchen type, and working areas. The data show that for casual and institutional kitchens the cooking zone is the warmest; however, for QSRs, the differences between cooking and preparation are very small. This is due to the cooking zone and preparation areas being close to each other in these smaller kitchens and also due to a presence of more appliances in the preparation zone for keeping the cooked food warm. Commercial kitchens have air-conditioned indoor environments that are often isolated from the outdoor environment. This is not always true for dish-washing areas, where a door or

Table 3. Average of measured physical parameters by kitchen type and zone. Kitchen type

Kitchen zone

to , ◦ C (◦ F)

ta , ◦ C (◦ F)

tmr , ◦ C (◦ F)

RH, %

va , m/s (ft/min)

Icl , clo

Activity, met

Casual

Cooking Preparation Dish washing Cooking Preparation Dish washing Cooking Preparation Dish washing

31.3 (88.3) 23.9 (74.9) 21.8 (71.3) 30.9 (87.6) 23.6 (74.5) 24.8 (76.6) 26.3 (79.4) 25.9 (78.6) 19.8 (67.6)

29.2 (84.5) 23.5 (74.4) 21.8 (71.3) 28.5 (83.4) 23.2 (73.8) 24.2 (75.6) 25.3 (77.6) 25.4 (77.7) 19.1 (66.5)

35.2 (95.4) 24.4 (75.9) 21.9 (71.4) 34.6 (94.2) 24.0 (75.3) 25.4 (77.8) 27.8 (82.1) 26.5 (79.6) 20.4 (68.7)

36 34 42 30 36 44 39 38 42

0.41 (81) 0.29 (57) 0.25 (49) 0.39 (77) 0.27 (53) 0.26 (51) 0.28 (55) 0.22 (43) 0.14 (28)

0.7 0.7 0.7 0.7 0.7 0.6 0.6 0.6 0.6

4.0 3.4 3.5 3.9 2.9 3.2 3.1 2.6 2.4

Institutional

QSR

1008

HVAC & R Research

Table 4. Representative values of physical measurements by climatic zone and season.

Summer

Downloaded by [DTU Library] at 05:30 09 December 2013

Winter

Climate zone

Number of employees

PMV (±SD)

to (±SD), ◦ C (◦ F)

RH (±SD), %

va (±SD), m/s (ft/min)

1—Moist 2/3—Moist 2/3—Dry 4—Marine 4—Moist 5/6—Moist 5/6—Dry 7—Moist 1—Moist 2/3—Moist 2/3—Dry 4—Marine 4—Moist 5/6—Moist 5/6—Dry 7—Moist

32 36 14 15 45 24 15 13 25 22 21 13 47 22 12 8

2.7 ± 0.9 2 ± 0.7 2.1 ± 2 2.5 ± 0.7 2.9 ± 1.9 2.9 ± 1.1 2.1 ± 1.7 2.7 ± 0.9 0.4 ± 1 0.3 ± 1.4 0.8 ± 0.9 0 ± 0.6 0.7 ± 1.1 –0.8 ± 1.3 0 ± 1.2 –0.2 ± 0.9

29.0 ± 2.8 (84 ± 5) 27.1 ± 4.2 (81 ± 8) 28.3 ± 6.2 (83 ± 11) 23.9 ± 1.5 (75 ± 4) 26.6 ± 5.3 (80 ± 10) 30.3 ± 5.3 (87 ± 10) 24.9 ± 6.1 (77 ± 11) 29.7 ± 3.9 (85 ± 7) 25.4 ± 3.3 (78 ± 6) 26.8 ± 5.2 (80 ± 10) 26.3 ± 4.2 (79 ± 8) 20.5 ± 2.7 (69 ± 5) 25.8 ± 5.1 (78 ± 9) 23.1 ± 4.5 (74 ± 8) 24.0 ± 4.2 (75 ± 8) 24.3 ± 2.5 (76 ± 5)

50 ± 9 44 ± 8 37 ± 4 51 ± 5 45 ± 15 52 ± 12 30 ± 12 31 ± 4 49 ± 10 20 ± 6 24 ± 8 38 ± 4 29 ± 9 26 ± 10 22 ± 8 18 ± 2

0.26 ± 0.16 (52 ± 31) 0.25 ± 0.08 (49 ± 15) 0.40 ± 0.23 (79 ± 45) 0.31 ± 0.20 (61 ± 40) 0.28 ± 0.21 (54 ± 42) 0.49 ± 0.19 (96 ± 38) 0.46 ± 0.24 (90 ± 47) 0.29 ± 0.12 (58 ± 24) 0.34 ± 0.16 (67 ± 32) 0.25 ± 0.09 (50 ± 17) 0.16 ± 0.10 (32 ± 19) 0.19 ± 0.13 (36 ± 25) 0.20 ± 0.10 (40 ± 19) 0.26 ± 0.11 (52 ± 22) 0.40 ± 0.31 (79 ± 61) 0.41 ± 0.20 (80 ± 39)

Table 5. Representative values of physical measurements by climatic zone and season. Summer Climate zone

Winter

Number of SMs

To (±SD), ◦ C (◦ F)

Number of SMs

To (±SD), ◦ C (◦ F)

12 13 7 8 22 5 9 8

29.8 ± 4.0 (86 ± 7) 27.6 ± 4.9 (82 ± 9) 27.1 ± 5.8 (81 ± 10) 24.0 ± 1.7 (75 ± 3) 26.5 ± 4.7 (80 ± 8) 30.8 ± 5.5 (87 ± 10) 28.8 ± 5.8 (84 ± 10) 29.0 ± 4.0 (84 ± 7)

11 9 11 5 20 7 11 5

25.4 ± 3.3 (78 ± 6) 25.7 ± 5.5 (78 ± 10) 25.6 ± 4.7 (78 ± 8) 21.3 ± 2.6 (70 ± 5) 24.5 ± 4.8 (76 ± 9) 23.7 ± 5.6 (74 ± 10) 23.3 ± 3.8 (74 ± 7) 24.1 ± 3.1 (75 ± 6)

1—Moist 2/3—Moist 2/3—Dry 4—Marine 4—Moist 5/6—Moist 5/6—Dry 7—Moist

Table 6. Representative values of physical measurements by kitchen type and zone. Summer Kitchen type Casual

Kitchen zone

Cooking Preparation Dish washing Institutional Cooking Preparation Dish washing QSR Cooking Preparation Dish washing

Number of employees PMV (±SD) 15 5 2 38 59 25 12 37 1

4.9 ± 0.8 2.4 ± 0.8 2.0 ± 0.4 3.7 ± 1.4 1.7 ± 0.9 2.1 ± 1.1 2.8 ± 0.6 1.8 ± 0.5 1.2 ± n.a.

Winter To (±SD), ◦ C (◦ F)

Number of employees

PMV (±SD)

To (±SD), ◦ C (◦ F)

34.9 ± 1.7 (95 ± 6) 28.7 ± 1.6 (84 ± 6) 28.7 ± 0.1 (84 ± 0) 30.9 ± 5.3 (88 ± 19) 24.0 ± 3.7 (75 ± 13) 24.7 ± 2.6 (76 ± 9) 29.1 ± 2.8 (84 ± 10) 26.6 ± 2.6 (80 ± 9) 21.4 ± n.a. (71 ± n.a.)

14 10 6 30 46 23 12 25 4

1.0 ± 1.2 –0.2 ± 1.1 –0.2 ± 0.7 1.6 ± 0.9 0.2 ± 0.7 0.3 ± 0.8 –0.2 ± 1.0 –0.4 ± 0.9 –2.3 ± 1.5

27.4 ± 3.5 (81 ± 13) 21.4 ± 2.8 (71 ± 10) 19.5 ± 3.1 (67 ± 11) 30.4 ± 4.8 (87 ± 17) 23.1 ± 3.1 (74 ± 11) 24.9 ± 2.8 (77 ± 10) 23.6 ± 3 (74 ± 11) 24.8 ± 2.9 (77 ± 10) 19.4 ± 3.3 (67 ± 12)

1009

Downloaded by [DTU Library] at 05:30 09 December 2013

Volume 19, Number 8, November 2013

Fig. 7. Average of PMV and operative temperature (to ) for climate zones with 95% confidence interval (color figure available online).

a window to the outside can be opened for by the employees. Regardless of the season, the average data in Table 3 is likely to be representative of most kitchen environments. More detailed data analyses are given in what follows. Table 4 and Figures 7 and 8 set out the calculated PMV index and measured operative temperature averages for each climatic zone during the summer and winter. The values are averages over the climatic zone and weighted by the numbers of occupants that took part in the thermal comfort evaluation. Even if the average PMV values are within the PMV range ±3 (see Table 4 and Figure 7a), several individual values are

outside this range (see Figure 8), indicating that the PMV index is not really applicable; ISO Standard EN 7730 (ISO 2005) recommends using the PMV-index only in the interval ± 2, meaning that most of the measured conditions are outside the range, indicating a high percentage of dissatisfaction. In Figure 8, from the lower line up, the 10th, 25th, 50th (the median), 75th, and 90th percentiles of PMV values are displayed, with dots representing the outliers. The figure shows that the PMV differences between climatic zones during summer or winter are not significant. Within each climatic zone, a high percentage of calculated variables fall into the gray area, which was not studied in the thermal

Downloaded by [DTU Library] at 05:30 09 December 2013

1010

HVAC & R Research

Fig. 8. Median of PMV with percentile variables for climate zones in summer and winter (color figure available online).

comfort model, indicating once more that the PMV model should not be applied to commercial kitchens. In Figures 7a and 7b, where the variability of PMV and to around the means are reported, it is evident that the operative temperatures show larger differences between the climatic zones during summer and winter. Working conditions in climate zones 1—moist, 5/6—moist, and 7—moist were significantly warmer than in climate zones 4—marine and 5/6—dry (p < 0.02). During winter, the PMV index was significantly lower in kitchens in climate zone 5/6—moist (p < 0.01), while the operative temperature was significantly lower for kitchens in climate zone 4—marine. In all climatic zones, the PMV index was significantly lower during winter than during summer. This is not the same for operative temperature. For climate zones 2/3—dry, 2/3—moist, 4—moist, and 5/6—dry, there were no significant differences between winter and summer. When comparing the differences in temperature and PMV, in particular between climate zones 4—marine and 2/3—moist, it should be noted that in 4—marine, the temperature was much lower than in 2/3—moist, but the PMV was much higher. This discrepancy was due to the effects that the other physical parameters (reported in Table 4), the clothing insulation (Icl = 0.6–0.7 clo) and the activity level (on average equal to 3.2 met ± 0.9 of standard deviation), have on the PMV index. In this study, the ANOVA analysis shows a significant effect on the PMV of the combination of to , RH, Icl , and metabolic rate together (F = 8.3 and p = 0.004), with the single highest effect being that of operative temperature (F = 7.4, p = 0.007, and R2 = 0.52) and the second highest that of the activity level (F = 6.6, p = 0.01, and R2 = 0.21). The actual average values of operative temperature (SM) are shown in Table 5 for each climatic zone during summer and winter. The unweighted values of the operative temperature in

each climatic zone were higher in summer and slightly lower in winter than the values weighted for occupancy. However, they are still representative of hot kitchen environments in summer and warm in winter with an exception for 4—marine climate zone, where commercial kitchens tended to provide the most thermally comfortable environments. In Table 6 and Figure 9, the PMV index and operative temperatures for the three kitchen types and for three working areas are reported as an average of all the values within each kitchen type. When looking at the results for summer and winter in Table 6, it is clear that the PMV index for the cooking zone in summer is well above the range where the index is applicable. For casual and institutional kitchens, the cooking zone had a significantly higher PMV index and operative temperature (p < 0.01) than other work zones. The PMV index for winter was within the range of application of the index. For all kitchen types and work zones, the winter kitchen temperatures were colder than the summer. As may be seen in Figure 9, the PMV of QSRs was significantly different from that of the other types of kitchens. In the institutional and casual kitchens, there was no significant difference between the preparation and dish-washing zones, while for QSR kitchens, there was no difference between the cooking and preparation zones. The dish-washing zone was colder, but as very few data points were obtained, the confidence interval is very large. The method applied showed that the procedure to be used in commercial kitchens must differ from what is used in offices, as more detailed measurements (different zones and more vertical points) are required. The measured vertical air temperatures, globe temperatures, and vertical air temperature profiles, for summer and winter, are given in Tables 7 and 8 and in Figure 10. The

Downloaded by [DTU Library] at 05:30 09 December 2013

Volume 19, Number 8, November 2013

1011

Fig. 9. Average of PMV and operative temperature (to ) for kitchen type and kitchen zones with 95% confidence interval (color figure available online).

Fig. 10. Vertical profiles of average temperature distribution at the cooking line in summer (left) and winter (right) (color figure available online).

1012

Cooking Preparation Dish washing Cooking Preparation Dish washing Cooking Preparation Dish washing

Casual

29.2 (85) 26.8 (80) 26.8(80) 26.6 (80) 24.2 (76) 24.6 (76) 25.4 (78) 24.5 (76) 23.4 974)

0.1 m (4 in.), ◦ C (◦ F) 34.5 (94) 27.8 (82) 27.9 (82) 30.6 (87) 24.6 (76) 25.2 (77) 28.6 (83) 26.1 (79) 24.2 (76)

1.1 m (43 in.), ◦ C (◦ F) 37.9 (100) 28.4 (83) 28.8 (84) 33.3 (92) 24.9 (77) 25.6 (78) 30.4 (87) 27.1 (81) 24.9 (77)

1.7 m (67 in.), ◦ C (◦ F)

Cooking Preparation Dish washing Cooking Preparation Dish washing Cooking Preparation Dish washing

Casual

23.7 (75) 20.8 (69) 19.1 (66) 26.1 (79) 22.5 (73) 22.9 (73) 20.8 (69) 21.5 (71) 19.2 (67)

0.1 m (4 in.), ◦ C (◦ F) 26.4 (79) 22.1 (72) 20.3 (68) 29.6 (85) 23.6 (75) 24.3 (76) 23.9 (75) 23.7 (75) 20.9 (70)

1.1 m (43 in.), ◦ C (◦ F)

Bold indicates high vertical temperature differences in the cooking line.

QSR

Institutional

Kitchen zone

Kitchen type

Globe temperature

30.5 (87) 22.6 (73) 20.7 (69) 33.0 (91) 24.5 (76) 25.0 (77) 27.2 (81) 24.8 (77) 22.1 (72)

22.4 (72) 20.5 (69) 18.9 (66) 24.9 (77) 21.9 (71) 22.1 (72) 20.1 (68) 20.9 (70) 18.4 (65)

24.6 (76) 21.7 (71) 20.1 (68) 27.0 (81) 23.1 (74) 23.5 (74) 23.1 (74) 23.2 (74) 20.4 (69)

1.1 m (43 in.), ◦ C (◦ F)

27.7 (82) 22.4 (72) 20.3 (68) 28.8 (84) 24.4 (76) 24.9 (77) 26.5 (80) 24.3 (76) 21.9 (71)

to

8.6 1.6 2.1 6.7 0.7 1.0 5.0 2.6 1.5

6.8 (12) 1.9 (3) 1.6 (3) 6.9 (12) 2.0 (4) 2.1 (4) 6.4 (12) 3.3 (6) 2.9 (5)

(head–feet level), K (◦ F)

to

16 3 4 12 1 2 9 5 3

(head–feet level), K (◦ F)

1.7 m (67 in.), ◦ C (◦ F)

36.3 (97) 28.1 (83) 28.9 (84) 29.3 (85) 24.5 (76) 25.5 (78) 29.0 (84) 26.8 (80) 24.8 (77)

1.7 m (67 in.), ◦ C (◦ F)

Air temperature

32.6 (91) 27.4 (81) 27.9 (82) 28.4 (83) 24.2 (76) 24.8 (77) 27.3 (81) 25.9 (79) 23.9 (75)

1.1 m (43 in.), ◦ C (◦ F)

Air temperature

0.1 m (4 in.), ◦ C (◦ F)

28.1 (83) 26.5 (80) 26.6 (80) 24.9 (77) 23.4 (74) 23.9 (75) 24.2 (76) 23.7 (75) 22.5 (72)

0.1 m (4 in.), ◦ C (◦ F)

1.7 m (67 in.), ◦ C (◦ F)

Table 8. Average of temperatures by kitchen type and zone in winter.

Bold indicates high vertical temperature differences in the cooking line.

QSR

Institutional

Kitchen zone

Kitchen type

Globe temperature

Table 7. Average of temperatures by kitchen type and zone in summer.

Downloaded by [DTU Library] at 05:30 09 December 2013

ta

15 3 4 8 2 3 9 6 4

5.3 (10) 1.9 (3) 1.4 (2) 3.9 (7) 2.5 (4) 2.7 (5) 6.4 (12) 3.4 (6) 3.5 (6)

(head–feet level), K (◦ F)

8.1 1.6 2.3 4.4 1.1 1.6 4.7 3.1 2.3

(head–feet level), K (◦ F)

ta

1013

Downloaded by [DTU Library] at 05:30 09 December 2013

Volume 19, Number 8, November 2013

Fig. 11. Air and operative temperature (ta and to ) variations in the three kitchens zones in summer and winter; shaded area indicates time of occupancy (color figure available online).

Downloaded by [DTU Library] at 05:30 09 December 2013

1014 conditions in the food-preparation and dish-washing zones were uniform and within normal comfort criteria, providing a vertical temperature difference between head (1.7 m (67 in.)) and feet (0.1 m (4 in.)) of 3–4 K. Due to the high level of thermal radiation falling on a worker’s upper body and head, the vertical temperature differences in the cooking line were very high, as shown by the bold numbers in Tables 7 and 8, up to 16◦ F (8.6 K) for the casual kitchen type in summer and up to 12◦ F (6.9 K) for institutional kitchen in winter. The warm/hot environment in the cooking area exposed the workers to temperatures higher than the 88◦ F (31◦ C), limiting exposure temperature as suggested by Weihe (1987). This may have negative health consequences (ASHRAE 2009). As the food-preparation and dish-washing zones would not be expected to cause any thermal discomfort for the kitchen staff, the vertical temperature profiles shown in Figure 10 are only the actual average values for the cooking zones in summer and winter. The casual and QSR kitchens show different temperature distributions in summer and winter, unlike the institutional kitchens, which were found to have a similar thermal environment at both times of year, most probably due to the different type and use pattern of the HVAC systems installed in them. However, the cooking line in the institutional kitchens seems to be the environment where the occupants may complain more of radiant asymmetry (as indicated by the larger difference between globe/operative and air temperature). The large difference in the thermal environment between summer and winter in casual kitchen types was probably due to more frequent use of natural ventilation for cooling. The present results indicate that casual kitchens provide the worst environment for kitchen staff, although this remains to be corroborated by the forthcoming analysis of their subjective evaluations.

LMs An example of the LMs that were obtained is shown in Figure 11 for a QSR kitchen located in Miami, FL. Figure 11 shows the air and operative temperatures recorded, as broken and solid lines, respectively. During the 24-h data-recording period, the temperature variation that directly influenced employees’ thermal comfort occurred during assumed operating hours from 10:00 a.m.to 10:00 p.m., represented by the shaded areas. During the summer, considerable diurnal temperature variations in the cooking line occurred, rising from 79◦ F to 98◦ F (26.1◦ C to 36.7◦ C), and detailed measurements were recorded (Figure 11a) during peak operating periods. The temperature in the food-preparation line and dish-washing area had a daily temperature variation in the range of 72◦ F to 92◦ F (22.2◦ C to 33.3◦ C) and 75◦ F to 90◦ F (23.9◦ C to 32.2◦ C), respectively during working hours. Thermal radiation from the hot appliances raised the operative temperature by an additional 10◦ F (5.8◦ C). At night, the temperatures decreased but were still high; the air and operative temperatures in the food-preparation and dish-washing areas were similar. As shown in Figure 11b, the temperature increase in winter was the same in all kitchens zones: 9◦ F (4.9◦ C) during operating hours.

HVAC & R Research Conclusions A method and procedure for evaluating the indoor thermal environment in commercial kitchens was developed. This method consisted of: • LMs of radiant temperature, air temperature, and humidity over 1 week in three kitchen workspaces: cooking, dish washing, and food preparation. • on-site SMs of air temperature and operative (radiant) temperature at different heights, along with air velocity and humidity in three work areas: the cooking, dish-washing, and food-preparation zones; • an on-site survey of occupants’ subjective evaluation of the indoor environment, performed at the same time as the SMs are made; • a general survey of background information about the occupants and of their general evaluation of the working conditions. The proposed procedure was validated during on-site measurements performed in more than 100 kitchens located in 9 states of the United States during the summer and winter seasons. The procedure can be recommended for data collection in future studies and for evaluating future kitchen appliances. The results obtained in the validation study establish a benchmark database for the thermal environment in commercial kitchens. Differences due to climatic zone, summer and winter, and type of kitchen were found. The most critical environment for kitchen staff is the cooking zone, where temperatures and vertical temperature differences that were too high for comfort and health were measured. The calculated PMV index values did not differ between climatic zones in either summer or winter, while the operative temperatures differed greatly. The thermal environment in casual kitchens varied seasonally, and kitchen staff in such kitchens are very likely to be exposed to uncomfortable thermal environments. Only the physical measurements are reported in the present article, so these conclusions are restricted to them. They must be corroborated by the subjective evaluations that were obtained at the same time, and this will be reported in a subsequent article. It is the view of the authors that the general evaluation criteria for thermal comfort often used in office environments cannot be applied in commercial kitchens. The PMV index values obtained were often above +3 and significantly outside the upper limit reccommended in international standards for the applicability of the PMV index (+2). The standard PMV-PPD index is thus not suitable for application in commercial kitchens, due to the combination of high activity levels and high air and radiant temperatures. The present study indicates that it will be necessary to establish a method (and a standard) for assessing the acceptability of working environments providing conditions that range between thermal comfort and heat stress.

Acknowledgments This project was supported by ASHRAE RP-1469 “Thermal Comfort in Commercial Kitchens” and the International

Volume 19, Number 8, November 2013 Centre for Indoor Environment and Energy at the Technical University of Denmark (DTU). The Culinary Institute of America (CIA) provided additional and substantial support.

Downloaded by [DTU Library] at 05:30 09 December 2013

References ASHRAE. 2006. ANSI/ASHRAE Standard 169-2006, Weather Data for Building Design Standards. Atlanta, GA: ASHRAE. ASHRAE. 2009. ASHRAE Fundamentals Handbook—Heating, Ventilating, and Air-Conditioning Applications, SI Ed. Chapter 10, Indoor environmental health. Atlanta, GA: ASHRAE. ASHRAE. 2010a. ANSI/ASHRAE Standard 55-2010, Thermal Environmental Conditions for Human Occupancy. Atlanta, GA: ASHRAE. ASHRAE. 2010b. ANSI/ASHRAE Standard 90.1-2010, Energy Standard for Buildings Except Low-Rise Residential Buildings. Atlanta, GA: ASHRAE. ASHRAE. 2011a. ANSI/ASHRAE Standard 154-2011, Ventilation for Commercial Cooking Operations. Atlanta, GA: ASHRAE. ASHRAE. 2011b. ASHRAE Applications Handbook—Heating, Ventilating, and Air-Conditioning Applications, SI Ed. Chapter 33, Kitchen ventilation. Atlanta, GA: ASHRAE. ASHRAE. 2012. Thermal comfort in commercial kitchens. Report RP1469, ASHRAE, Atlanta, GA. Fisher, D., R. Swierczyna, and A. Karas. 2013. Future of DCV for commercial kitchens. ASHRAE Journal 55(2):48–54. Huizenga, C. 2011. ASHRAE thermal comfort tool. CD, version 2. Atlanta, GA: ASHRAE. ISO. 1998. ISO Standard 7726:1998, Ergonomics of the Thermal Environment—Instruments for Measuring Physical Quantities. Geneva, Switzerland: International Organization for Standardization. ISO. 2001. ISO Standard 10551:2001, Ergonomics of the Thermal Environment. Assessment of the Influence of the Thermal Environment Using Subjective Judgment Scales. Geneva, Switzerland: International Organization for Standardization. ISO. 2004a. ISO Standard 7933:2004, Hot Environments—Analytical Determination and Interpretation of Thermal Stress Using Calculation of Required Sweat Rate. Geneva, Switzerland: International Organization for Standardization. ISO. 2004b. ISO Standard 8996:2004, Ergonomics of the Thermal Environment—Determination of the Metabolic Rate. Geneva, Switzerland: International Organization for Standardization.

1015 ISO. 2005. ISO Standard 7730:2005, Moderate Thermal Environments— Determination of the PMV and PPD Indices and Specification of the Conditions for Thermal Comfort. Geneva, Switzerland: International Organization for Standardization. ISO. 2007a. ISO Standard 9920:2007, Ergonomics of the Thermal Environment—Estimation of the Thermal Insulation and Water Vapor Resistance of a Clothing Ensemble. Geneva, Switzerland: International Organization for Standardization. ISO. 2007b. ISO EN Standard 11079:2007, Ergonomics of the Thermal Environment—Determination and Interpretation of Cold Stress When Using Required Clothing Insulation (IREQ) and Local Cooling Effects. Geneva, Switzerland: International Organization for Standardization. ISO. 2011. ISO Standard prEN16282—part 1-8:2011. Kitchen ventilation. Geneva, Switzerland: International Organization for Standardization. Livchak, A., D. Schrock, and Z. Sun. 2005. The effect of supply air systems on kitchen thermal environment. ASHRAE Transactions 111(1):748–54. National Restaurant Association (NRA). 2012. Restaurant industry forecast, 2011. www.restaurants.org. National Restaurant Association (NRA). 2013. Restaurant industry forecast, 2012. www.restaurants.org. Pekkinen, J.S., and T.H. Takki-Halttunen. 1992. Ventilation efficiency and thermal comfort in commercial kitchens. ASHRAE Transactions 98(1):1214–8. Simone, A., and B.W. Olesen. 2012a. Investigation of subject perceptions of the environment in commercial kitchens. Proceedings of Healthy Buildings 2012, July 8–12, Brisbane, Australia. Simone, A., and B.W. Olesen. 2012b. Thermal environment evaluation in commercial kitchens: Procedure of data collection. Proceedings of Healthy Buildings 2012, July 8–12, Brisbane, Australia. Simone, A., B.W. Olesen, J. Babiak, M. Bullo, and G. Langkilde. 2007. Operative temperature control of radiant surface heating and cooling systems. Proceedings of Clima 2007, June 10–14, Helsinki, Finland. Weihe, W.H. 1987. Social and economic values of applied human climatology. Proceedings WMO/WHO/UNEP Symposium Climate and Human Health, September 22–26, 1986, Geneva, WMO-WCAP No. 1, pp. 233–50. Wyon, D.P. 1996. Individual microclimate control: Required range, probable benefits and current feasibility. Proceedings of Indoor Air ’96, Tokyo, 1:1067–72.