Resilience in Adopting Green Building Design - Natural Lighting for Indoor Swimming Pools

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‘Veil Reflection’ in Indoor Swimming Pools can Impair the Vision of Lifeguards and Affect Life-rescue. The Author Illustrates the use of ‘Resilience and Adaptive cycle theory’ in a study to develop new design guidelines for indoor swimming pools in Hong Kong.


Under the aegis of environmental protection and corporate responsibility, there are concerns being raised on different sustainable design concepts in buildings. In the last decade, there have been green building tools/assessment schemes made available which set standard protocols for green buildings. These protocols are good for building professionals and enable building designers to follow concrete guidelines instead of abstract concepts. However, such guidelines have their limits and once the limits are exceeded, a sequence of unexpected events may be the outcome.

In this article, the author illustrates the use of ‘resilience and adaptive cycle theory’ on a project studying the natural light design practices for indoor swimming pools in Hong Kong to improve the sustainable design process. Applying adaptive cycle theory, Parsons Brinckerhoff (now part of WSP | Parsons Brinckerhoff) was able to identify points of weakness and to develop comprehensive design guidelines.

Safety in Swimming Pools

Swimming is one of the most popular recreational activities and an important survival skill, and swimming pools have existed for centuries. Safety is of primary concern for most stakeholders, and many of the safety aspects of indoor pools, such as the filtration systems, non-slippery floors, and appropriate water temperature, are related to building design. It has been well documented that safety measures are useful in minimizing fatal accidents.

The adoption of ‘green’ building design introduced new challenges to safety in swimming pools by promoting large openings and windows for light and ventilation, which in some cases result in ‘veil reflection’ on the water surface of the swimming pool. These reflections may impair the vision of lifeguards and affect life-rescue.

Risk Assessment Through ‘Resilience and the adaptive cycle’ concept

WSP | Parsons Brinckerhoff utilized the ‘resilience and adaptive cycle’ framework for their study on veil reflection, and to develop new design guidelines. There are four phases in an adaptive cycle: growth or exploration (r), conservation (K), release or collapse (Ω), and reorganization (α). As systems move along the adaptive cycle they gain and lose connectivity, capacity, and resilience to disturbance (see Figure 1).

resilience adaptive cycle processFigure 1 – Resilience and the Adaptive Cycle Concept, showing possible changes between phases.

Growth or Exploration (r) Phase

In the early stage of ‘green’ building design, large openings and windows for admitting more daylight and providing natural ventilation were promoted. Experienced designers and specialists spent time investigating the possible impact of adding such features. In this phase, project teams tend to take precautionary measures and to use prototype design as well as limiting the area of application. There is no major report on the occurrence of veiling reflection (reflected glare on the water surface of the swimming pool which can impair the vision of the lifeguard). The shortcomings are that highly intensive coordination and mature understanding of theory are required and the efficiency of the design process is relatively low and not able to satisfy all best practices and guidelines.

Conservation (K) Phase

After sufficient experiences were gained from various projects, several design practices and rules of thumb were established. In this phase, most professionals can carry out the design. The design processes become smooth and mature. Each component, such as the use of openings for natural lighting and ventilation, is well integrated into different design considerations and responds to various local code requirements and is accredited with several green building certifications. The stakeholders benefit from the high efficiency of the design process in the meantime; and the different authorities and certification bodies are familiar with the design approach. The trade-offs are the reduction in flexibility of design and less room to identify and solve project-specific problems by an alternative method. After the mass production of “green” swimming pools, dramatic increases in the observation of veiling reflection were reported by the operation teams. Worse still, veiling reflection becomes one of the reasons for delay in several life-rescue cases.

Release or Collapse (Ω) Phase

Drowning is one of the top three leading causes of unintentional death worldwide1. In Hong Kong, approximately seven fatal incidents of drowning in swimming pools are reported per annum. The increase in delay of rescue and near-miss rescue cases raised the concern of the public and government operating authorities. Furthermore, lifeguard associations have sometimes refused to staff these “green” swimming pools due to an unacceptable level of veiling reflection. Hence, abortive work and delay in handover is found in new swimming pools.

resilience adaptive cycle processFigure 2 – Vulnerability study on effect of green building design on veiling reflection in swimming pools

Expressed in terms of vulnerability (see Figure 2), new green building design raised veiling reflection from crisis management (rarely occurs but serious consequence) to a challenge that must be mitigated (veiling reflection occurs several hours a day). Since veiling reflection might cause drowning and death, and “green” swimming pools increase the occurrence of veiling reflection, its consequence is considered to be severe. When relevant government authorities gave serious consideration to veiling reflection in project implementation, many ideas were generated by stakeholders such as: using CCTV instead of lifeguards, using high-quality (low-e) glazing, adding shading devices to the pool area, installing more underwater lighting, and providing polarized sunglasses to lifeguards.

Reorganization (α) Phase

In the release or collapse phase (Ω), many new ideas were proposed and applied to new swimming pools. As these innovative ideas were tested, it enabled stakeholders to sort out major key factors and constrain the dynamic. A series of studies were conducted to identify the key design parameters, the challenges of natural and artificial lighting design in swimming pool design, and major mitigation measures. The first design guidelines worldwide on this specific topic were developed - reorganization (α) phase - and the arrangement specifically addressed the weakness of the design process in the growth or exploration (r) and conservation (K) phases.

swimming pool roof lights

Ideal model of 25m x 50m indoor swimming pool with rooflights

Design Examples

Case 2 - With Rooflight

  1. Pool Basin finish to have min. reflectance of 0.7.
  2. Swimming Pool to be north /south oriented. 25m short sides facing north & south. 50m long sides facing east & west.
  3. Lookout Post for Lifeguards
    • At middle 1/3 zone of pool length
    • Not to be opposite windows
  4. Window at north & south ends of pool to reduce exposure to low altitude sunlight.
  5. Pool Deck Width and Window Height - Pool deck width to be twice the window height to reduce veiling reflection.
  6. Building Height - The height of ceiling is governed by artificial lighting system.
  7. Spectator Stand not to directly face windows and the resultant veiling reflection.
  8. Ventilation Consideration - Louvres recommended for natural ventilation.
  9. Rooflight
    • Area should be at least 50% of the pool deck area.
    • Internal shading recommended to block out direct glare by sunlight.
    • Light transmittance value of the glazing should be greater than that of the glazing for the windows by at least 0.2.
Figure 3 - Arrangement of an ideal swimming pool

WSP | Parsons Brinckerhoff’s Role

WSP | Parsons Brinckerhoff was appointed by the government of Hong Kong as lead consultant in reviewing the existing design and developing a new design practice of natural and artificial light in indoor swimming pools in the reorganization (α) phase.

Apart from research study, the team also needed to identify the point of weakness through different tools, including the adaptive cycle framework. The major objective is to absorb disturbances (green building design practices, etc.) and still retain the basic function and structure (a safe and enjoyable swimming environment).

In the development of these guidelines, a study based on resilience and the adaptive cycle theory found the following:

  • There is no principle on the design for swimming pools related to lighting and water body in existing documents [growth or exploration (r) phase].
  • There is no conceptual guidance outlining the relationship between different design criteria and veiling reflection [growth or exploration (r) phase].
  • There is a need to demonstrate how the above principles and theories can be applied in building design to prevent a misunderstanding of principles [conservation (K) phase].

The design guidelines shall do the following:

  • Highlight the induced lighting problems in swimming pools and bridge the missing link between artificial and natural lighting design for swimming pools.
  • Transform the physical/biological rules and conceptual relationships into concrete design guidelines that most building professionals can follow.
  • Provide work examples (Figure 3) with renderings (Figure 4) for building professionals to study in order to avoid any misunderstanding of the proposed guidelines.
renderings of an ideal swimming poolFigure 4 - The renderings of an ideal swimming pool used as a reference by stakeholders


New design concepts create new opportunities for design professionals but can also create challenges. Developing a system that can accommodate any change in design practices without deviating from the original principle is not easy. Using resilience assessments in different new sustainable designs help to identify potential problems at an early stage but, due to the one-off nature of building projects, applying complete assessments is not yet affordable. This project illustrates that several weaknesses in the design process can be identified through applying the concept of resilience and the adaptive cycle, and innovative measures were proposed to handle these issues. The first design guidelines would undergo other resilience and adaptive cycles, but the uncertainties between veiling reflection and other design practices have been reduced.

1World Health Organization, 2004, The World Health Report: 2004: Changing History, World Health Organization, Geneva, Switzerland.

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