In addition to an increase in greenhouse effect emissions the intensive use of air conditioning in the retail sector can eventually carry implications on the health of some of those directly exposed to sudden cooling particularly in hot summer days. This paper reports the results of an experimental study conducted in the summer of 2005 in the United Kingdom investigating air conditioning frequency of use and the indoor air temperatures of air conditioned premises. It was found that in some large retail stores indoor air temperatures could be set higher improving thermal comfort and contributing towards the environment

Bruhns, H

Caeir, JAJ

Summerfield, AJ

English

UCL Discovery

A Study on the Intensive Use of Air Conditioning in Large Retail Stores  Jorge A.J. Caeiro1, Harry Bruhns, Alex J. Summerfield  1University College London, Bartlett School of Graduate Studies, Torrington Place Site, Gower Street, London, WC1E 6BT, United Kingdom Email: j.caeiro@ucl.ac.uk http://www.bartlett.ucl.ac.uk  Summary:  In addition to an increase in greenhouse effect emissions the intensive use of air conditioning in the retail sector can eventually carry implications on the health of some of those directly exposed to sudden cooling particularly in hot summer days. This paper reports the results of an experimental study conducted in the summer of 2005 in the United Kingdom investigating air conditioning frequency of use and the indoor air temperatures of air conditioned premises. It was found that in some large retail stores indoor  air  temperatures  could  be  set  higher improving  thermal  comfort  and  contributing  towards  the environment.   Keywords:  Air  conditioning  use  in  shops,  indoor  environmental  quality,  indoor  environmental  factors  1 Introduction Increasingly, there is evidence that the global climate is changing quite considerably and that such change is in part due to anthropogenic emissions of greenhouse gases,  a  significant  proportion  of  which  are  a consequence  of  burning  fossil  fuels  for  electricity generation.  Nevertheless,  and  as  in  most  developed countries, there has been in the UK a steady increase in the air conditioned area and intensity of use of Air Conditioning (AC) in the retail sector.  The  UK  has  a  temperate  climate  without  large seasonal  extremes  of  temperature,  i.e.  summers  are cool and winters are mild. However, eight out of the ten warmest years recorded in England happened in the  last  16  years  [1].  AC  usage  in  the  UK’s  retail sector  is  a  relatively  recent  phenomenon  but  as climate is globally warming up the sudden growth of air conditioners usage is something to be concerned about. It is known that AC use in some sectors of the UK's  non-domestic  building  stock,  is  increasing rapidly but statistical data is scarce. Since the early 1970s the rate of growth in UK energy consumption in  the  service  sector,  i.e.  commercial  and  public buildings,  has  increased  by  approximately  30% compared with a 25% increase in the domestic sector [2].It is important to know if rising AC use is one of the  reasons  for  such  an  increase  and  if  energy efficiency measures are being used effectively to limit the  power  required  by  AC  systems.  These  systems exist primarily for the comfort of customers and staff, also for stock in case of food, but the same effect can be achieved with much less energy use, particularly in temperate  climates  such  as  in  the  UK.  Typical measures  in  the  retail  sector  may  include  more efficient  use  of  display  lighting,  more  and  non-arbitrary  setting  of  cooling  temperatures  combined with self closing doors or air curtains.  A  broad  survey  with  comparatively  low  data  depth has  been  carried  out  of  700  retail  premises  to determine  the frequency  of  AC  use  and  the  rate  of growth. The street surveys involved walking around areas  which  contained  significant  numbers  of  non-domestic  buildings  and  noting  HVAC  systems  by visual  inspection  of  the  accessible  parts  of  the building  and,  where  possible,  by  casual  internal inspection.  In addition, to assess the intensity of cooling energy use a sub-sample of about 20 retail premises was also probed for temperature and relative humidity on a hot summer’s  day  (outdoor  temperatures  ranging  from 25-27 0C).  2. Research approach  The  street  surveys  were  all  carried  out  in  a  busy commercial district in central London. The capital of the United Kingdom is located in the Thames Valley region  where  the  greatest  concentration  of  air-conditioning  is  found.  Being  in  the  South  East  of England  its  climate  is  largely  influenced  by  the continental proximity and the added urban heat island effect. Summer temperatures can occasionally climb up  to  more  than  30 0C.  The  shops  surveyed  were either part of a chain or local and were selected based on their size; location and type of activity (see Table 1).  Shop  Type of shop  Size  Survey duration (minutes) A  Household Furnishing Large  7 B  Department Store Large  7 C  Department Store Large  12 D  News Agent  Medium  6 E  Supermarket  Large  12 F  Supermarket  Large  7 G  Electrical Supplies Medium  11 H  Department Store Large  12 I  Household Furnishing Large  5 J  Multimedia Centre Medium  6 K  Multimedia Centre Large  5 L  Supermarket  Large  10 M  Designer Clothes Large  11 N  Pharmacy  Large  8 O  Record Store  Very Large 6 P  Book Store  Very Large 8 Q  Sports Store  Large  5 R  Gifts  Medium  6 S  News Agent  Medium  5 T  Multimedia Centre Large  5  Table 1- Shops’ description data  Medium  to  very  large  size  shops  were  elected  not only  because  of  the  greater  likelihood  of  being  air conditioned but also because the surveyor could probe the environmental conditions for longer time without being too conspicuous.  Dry- bulb temperature is perhaps the most practical and simultaneously the most revealing environmental index in judging indoor comfort under cold conditions and thus was considered a good indicator of cooling intensity.  To  record  Temperature  and  Relative Humidity  (RH)  two  portable  environmental dataloggers were used. These were carried inside of a well ventilated bag hanging from the surveyor’s hand. The probing time was dictated by the response time of the loggers. As it took about 3 minutes for the loggers to record 90% of the actual temperature reading the surveys had to be conducted for at least 5-10 minutes. The  response  time  for  RH  was  much  faster  which revealed to  be very  useful in determining the exact period of time the surveyor was indoors. The loggers were programmed to record readings every 5 seconds.  3 Analysis of experimental results Figures 1.a and 1.b show the evolution of indoor air temperature  and  RH  over  time  for  half  the  shops surveyed. The survey started just after the surveyor left  an  air  conditioned  room  hence  the  low temperature recorded before shop A being surveyed followed by an increase when indoors. As should be expected,  periods  indoors  of  intensively  air conditioned premises are generally characterized by a sharp drop of temperature and RH. By contrast, the periods  spend  outdoors  are  also  generally characterized  by  a  rise  of  temperature  as  might  be expected. For ease of interpretation of the results the periods spent indoors are labeled with an uppercase letter  on  top  of  the  two  delimiting  vertical  lines, designation  which  has  correspondence  with  that  in Table 1.  Figure 1.a - Air temperature and RH variation23242526272812:00 12:10 12:20 12:30 12:40 12:50 13:00 13:10 13:20 13:30 13:40 13:50 14:00 14:10 14:20Time (Hours)Temperature (0C)323742475257Relative Humidity (%)Dry Bulb Temperature RH %A B C D E F G H I JFigure 1.b - Air temperature and RH variation(cont'd)2223242526272814:24 14:34 14:44 14:54 15:04 15:14 15:24 15:34 15:44 15:54 16:04 16:14Time (Hours)Temperature (0C)32374247525762677277Relative Humidity (%)Dry Bulb Temperature RH %K L M N O P Q R S TThe chart analysis shows that in some shops there is not a very marked temperature change from outdoors. This  is  primarily  due  to  not  all  shops  being  air conditioned, having air conditioners set for ventilation only  or  having  doors  wide  open  without  using  air curtains.  In  others  though  there  is  a  noticeable temperature  drop, like in shop  E.  Recorded  shop  E temperature shows no signs of stabilizing during the period the surveyor stayed indoors suggesting that it would eventually drop still further. It should also be noted that of all those surveyed only four shops kept the cold in using automatic doors. Eleven shops had air curtains installed but actually only three had them operating. An assumption can thus be made that the recorded temperatures  could  even  be  lower  if  these facilities  were  in  use.  Interestingly  the  continuous downtrend of indoor and outdoor temperatures, seen in Figure 1.b, is due to the fact that all shops after shop N were located in a different street, which due to its  orientation  received  much  less  direct  solar radiation throughout the day than the former one.    4 Conclusions and future work  Thermal  comfort  is  perceived  in  different  ways  by different subjects and a vast amount of literature has already been published throughout the years on this subject. However, there are no known studies on the issue of people walking out from a warm into a much cooler environment, or vice versa, as often happens. Also the health implications of a sudden exposure to a much cooler environment are still pretty unclear but anyhow out of the scope of this paper. Yet, it is well known  and  documented  that  symptoms  of  patients with  chronic  respiratory  diseases,  e.g.  bronchitis  or emphysema,  increase  in  colder  environments. Moreover a study performed in the USA [3] revealed evidence of cold sensitivity in asthmatics.  The  study  carried  out  had  the  primary  aim  of investigating  the  level  of  indoor  air  temperatures existing in air conditioned premises. As a result it was also  found  that  some  supermarkets  registered  the lowest  indoor  air temperatures relatively  to  outdoor temperature presumably due to the combined cooling effect of the AC system and of open display fridges. This may  be eventually  designed to slow  down the decay  of  perishable  goods  like  vegetables  and  fruit ensuring  a  longer  shelf  live  whilst  retaining  ready access to the displayed goods.  The study carried out in the summer of 2005 was a fairly  small  survey  of  UK  retail  premises  therefore much  larger  follow-on  surveys  are  to  be  conducted during the next few years. Of additional interest, are the  longitudinal  possibilities  of  such  a  survey, whereby once most of the database is populated the same sites can be re visited in the next years, and the frequency and intensity of AC use examined year on year. Future research will investigate the implications to energy consumption of the practices observed. So as  well  as  examining  this  growth,  the  energy efficiency  measures  applied  will  also  be  assessed. This work will include obtaining floorspace data for the  surveyed  premises  and  modeling  energy  use  to estimate  incremental  energy  consumption.  Logging equipment  with  enhanced  features  will  be  used  as well  as  Infrared  Imaging  which  is  already  being tested. Acknowledgements This  research  project  is  part  of  the  wider  Carbon Reduction  in  Buildings  (CaRB)  project  which  is developing  computer  models  that  will  make  it possible to pinpoint effective ways of cutting carbon emissions arising from energy in buildings. CaRB has 5  UK  partners:  De  Montfort  University,  University College  London,  The  University  of  Reading, University  of  Manchester  and  The  University  of Sheffield. CaRB is supported by the Carbon Vision initiative which is jointly funded by the Carbon Trust and  Engineering  and  Physical  Sciences  Research Council, with additional support from the Economic and  Social  Research  Council  and  Natural Environment  Research  Council.  The  partners  are assisted  by  a  steering  panel of  representatives  from UK  industry  and  government.  See http://www.carb.org.uk for further details.  References [1]  M.Hulme,  J.Turnpenny,  G.Jenkins,  Climate change  scenarios  for  the  United  Kingdom:  The UKCIPO2 briefing report, Tyndall Centre for climate change research, School of Environmental sciences, University of East Anglia, Norwich, UK, 2002, 14 pp [2]  C.H.  Pout,  F.  MacKenzie,  R.  Bettle,  Carbon dioxide emissions from non-domestic buildings: 2000 and  beyond,  BRE  Report  442,  Building  Research Establishment, Watford , UK, 2002 [3]  L.  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A study on the intensive use of air conditioning in large retail stores

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