A study by the Eneref Institute found that retail stores with well-designed skylights saw a 40% increase in sales [1]. According to the research, occupants prefer a pleasantly daylit interior space because it creates a more hospitable, engaging and conducive shopping environment. Moreover, as shoppers get more environmentally conscious, natural daylight allows shoppers to appreciate natural resources and the reduction in need for artificial lighting.
Looking at the comparison photos of the two shopping malls below, the retail area with a skylight creates an environment that mimics the outdoor environment and the connection to the natural sky, which can produce a better retail experience for the occupants.
Fig: Comparison of two malls with and without skylights
DESIGN CHALLENGES FOR LARGE SKYLIGHTS
Designing large skylights poses a few challenging aspects, as it is not as simple as just opening up the roof and installing glass panels. Various openings can be designed in large retail malls, as they have an abundance of roof space. Many different types of skylights are seen in the market. They can generally be classified into two different categories, namely skylights with horizontal glazing and skylight with vertical glazing; refer to the picture below.
Fig: Two types of skylights opening, vertical and horizontal
What kind of opening is suitable for the climate, topology and surroundings can be a complex challenge for the building owners and designers.
A few of the design challenges that come with skylights for large retail malls include:
1. Heat penetration and thermal comfort
In a tropical climate, sunlight is abundant. However, if the opening was not designed taking into account the sun's direction and the amount of heat entering the building, it will cause thermal comfort issues with elevated temperatures below the skylight. Moreover, the excessive heat entry also means that the building air conditioning systems will have to work harder, hence, causing an energy consumption penalty to operate the building.
Fig: Measured air temperature at one of the malls with skylights (air temperature is not within ASHRAE 55.1 thermal comfort range)
2. Ineffective daylight design
If the mall were surrounded by mixed development and high rises, a vertical opening might not be able to allow daylight into the mall as the high rise buildings will be blocking the daylight.
Fig: Retail mall with vertical skylight facing high rise buildings
3. Glare problem
Direct sunlight is a double edge sword. In general, too much direct sunlight will create a glare and result in discomfort to the shoppers and a displeasing shopping experience. Ideally, we want mostly soft glare freed diffuse daylight to enter through the skylights together with a controlled amount of direct sunlight that can allow shoppers to have a connection to the sun/sky and be aware of outdoor weather.
Fig: Glare from the direct sunlight from the skylight and direct sunlight in the retail areas
SUMMARY & RECOMMENDATIONS
Designing skylights in the retail malls can be a complex issue where a misdesign can create ripple effects such as thermal discomfort, no or too much daylight, and glare issues, at the same time skylights can be an additional cost to the building. In IEN Consultants, we utilize multiple software to model and analyze the effectiveness of the skylights and ensure thermal/visual comfort to the occupants.
In one of our case studies where we demonstrate the design process of large retail skylights including using IES-VE and various software to achieve the optimum design for the skylights.
Case Study: https://www.ien.com.my/post/daylight-simulation-skylight-designs-for-large-retail-mall
Reference:
[1] Eneref Institute article - https://eneref.org/daylight-in-big-box-retail-stores/