Daylighting and Electric Lighting Integration in the Retail Sector

English. The retail sector represents 11% of the GDP and employs 15% of the workforce in the European Union. To tackle growth of e-commerce, physical retail stores need to be reviewed; both to decrease operating costs, increase productivity and to make the shopping experience more appealing. Energy use for lighting accounts for 50% of the total energy use in non-food retail stores, which is consumed primarily during daylight hours. Therefore, designing for daylighting and electric lighting integration is fundamental to obtain energy savings, as well as keeping occupants healthy and satisfied. This thesis describes field monitoring and supplementary building performance simulations of an existing daylighting and electric lighting integrated design for a furniture store. The store includes several areas of the showroom equipped with abundant daylighting. For the monitoring, the areas of the Living Room and Home Decoration exhibitions were selected. They include wide glazed areas, daylight harvesting systems, and tunable lighting. The monitoring procedure assesses four aspects: energy use, objective or measurable lighting conditions, circadian potential, and subjective evaluation of lighting. This study introduces an assessment based on the customers' path, which proved particularly informative in a retail setting. The results suggest that the integration project was successful in terms of energy saving, as well as customers and staff appreciation. Observations allowed a critical view on some of the objective photometric measures. Surprisingly, limited glare which simulations showed to occur, seems not to be a problem for users, rather an opportunity in a retail scenario. The customers were more attentive to daylighting and observing objects under natural light, and having a (good) view to the outside was the most positively evaluated. Clients also reported a better shopping experience compared to equivalent shops. Staff members showed satisfaction with the electric lighting solutions, such as LED panels with automatic tuning of correlated colour temperature. For future projects, the study argues that daylighting in furniture shops may be an asset. In addition, for the methodological part, the monitoring suggests that objective and subjective evaluations should be always combined for a full understanding of the integrated project.

English. The retail sector is an important part of the global economy and is a major influence on our leisure time and quality of life. With the massive introduction of online commerce, many physical stores have seen their sales drop dramatically. The big retail chains are faced with large stores that do not invoice as much as they used to. In an effort to attract customers again, big retail players are exploring new ways to make their stores more attractive and enjoyable for customers and employees, as well as more sustainable. Daylight and natural ventilation were widely used in old industrial and commercial buildings, but with the cheapening of electric light and air conditioning systems, retail stores evolved into closed boxes. Now we realise the mistake of abandoning natural light, as science proves that it improves not only lighting conditions but also mood, health and can even reduce energy use. Daylight, therefore, is a great tool to improve the shopping and work experience in a store, and that is why in new stores or renovations, the integration of daylight in the design is, luckily, being reconsidered. In this thesis, a peculiar case study is presented; a pilot IKEA furniture store opened in Kaarst (Germany) in 2018 with the aim of testing daylight integrated design as a new strategy for the new chain store openings and retrofits. The solutions include skylights, wide windows and electric lighting that adjusts its intensity and colour with natural light. The results of the case study revealed that customers enjoyed the shopping experience much more compared with other chain stores, especially appreciating the fact that they could observe the products under natural light and have views of the outside. The latter was also highly valued by the employees, as the visual connection to the surroundings made working hours more pleasant. In fact, the integration of daylight was listed by all workers as the most positive improvement of the shop compared to the old one. Other interesting findings were also revealed by the research carried out in the different areas studied in the shop, such as the larger the windows were the more satisfied that customers were with the interior temperature. It was also found that certain control systems for lighting were saving much less energy than expected and that most of the knowledge, standards reference and methods commonly used for the evaluation of daylight integration were judged as a less than perfect fit for a furniture store. Consequently, the author had to devise alternative methods for the correct evaluation of the lighting in the different spaces. One of them was the collection of data based on the main route taken by the customers when walking through the store, instead of using the typical horizontal measuring grid for the entire surface. This saved a lot of time as the number of points was on average 80% lower and the results proved to be more useful and representative, as the height of the exhibitors and products varies greatly between departments. Therefore, the horizontal grid generated confusing values at certain points, which affected the average values; values that were not reliable with what the customer was perceiving. One of the most revealing parts of the study was the combination of measured or simulated technical evaluations with the reality perceived by customers and employees. For example, some simulations resulted in a very high level of discomfort due to daylight glare in some areas, while the customers interviewed in that very same position and time did not seem to be disturbed since they only experienced it for a few seconds. Quite the opposite was true in reality, as some clients affirmed that those rays of sun were pleasant and less annoying than certain electric spotlights in some areas of the store. As one of the main conclusions, the monitoring suggests that objective and subjective evaluations should always be combined for a complete understanding of the project as a whole. The author's fieldwork during the three weeklong store visits included a wide variety of measurements of the quantity and quality of lighting, as well as light and temperature tracking, customer surveys, and interviews with store staff. Nearly 150 customer responses were collected and processed together with a total of six interviews that were conducted with different employees of the store, with different roles. A close collaboration with the facility management team of the store was also necessary to obtain the necessary data and documentation, as well as to share benefits and problems that the introduction of the new lighting control systems generated. As an anecdote, thanks to this thesis, many of the lighting systems that did not work properly were finally correctly adjusted by the manufacturer. The monitoring protocol was defined in collaboration with a research project of the international energy agency (SHC-IEA Task 61, subtask D) of which this thesis was the first case study, so the defined method will be reused in the following buildings to be surveyed. IKEA expressed great interest in the monitoring method used, as well as in the results and findings obtained. These were presented to the design and marketing teams, so they could be taken into account in future projects.