Entering the new year is an ideal time to reflect on our engineering practice, its history and its future. Professional design disciplines constantly balance the desire for innovation with the reliability of established practices. We sometimes lean towards innovative solutions, and other times favor tried and true methods. Our engineering work must result in the highest level of safety and reliability, yet be adaptable to changing needs. 

While prescriptive codes dictate our lessons learned, performance-based codes allow for flexibility in our evolving built environment. We will only find balance between the cutting edge and the reliable through contemplation of our past, present and future. As the world changes at an ever-increasing pace, the necessity of design flexibility will be all the more justified.

As an ancient trade, plumbing logically relies on proven materials and methods. A discipline studied and practiced for almost three millennia, its roots can be traced back to Rome’s “plumbus” (translating as “those who worked with lead”) and Syrian civilization beyond. Modern plumbing systems are an evolution of our ancestors’ work, with each generation improving upon the achievements of the last (see Figure 1). 

Plumbing systems have evolved and modern installations would be unrecognizable to our Roman ancestors. Imagine the ancient plumbus witnessing our accomplishments in state-of-the-art systems, never mind the discovery of the toxic properties of their widely used lead piping. 

However, progress in the field tends to be incremental, with little incentive for design innovation. This is not without good cause, as plumbing design is critical to the health and safety of occupants in all buildings. When newly discovered threats to health have emerged, design solutions have been developed and scaled to the industry. We’ve recently seen this with bacteria control in hot water systems, for example. 

There is no doubt that established practices have provided reliable and robust results. Our established practices are memorialized in plumbing regulations, detailing prescriptive requirements for design and installation.

Code Evolution

Alternatives to prescriptive construction regulations exist, in the form of performance-based building regulations. For example, the International Code Council has published the International Performance Code, which includes plumbing design criteria in Chapter 12. 

The approach is not a new concept and again brings us back to ancient civilization. Hammurabi, the sixth king of the First Babylonian Dynasty, is known for the Code of Hammurabi, one of the earliest and most complete legal codes (see Figure 2). Hammurabi’s code stated in 1754 BC that “if a builder builds a house for someone and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death.” 

Although our legal process has evolved somewhat from Hammurabi’s time, one could argue this is our civilization’s first performance-based design and construction regulation. Our primary design goal is always to protect health and life safety, which is not a new concept.

Today’s performance-based codes speak of design goals without explicitly listing prescriptive requirements. The International Code Council’s performance code provides baseline objectives for building systems and presents a framework for their implementation. A definition of design objective is provided as “what is expected in terms of societal goals or what society ‘demands’ from buildings and facilities.” 

These objectives are refined into functional statements and further as performance requirements. “What society demands” is an evolving concept, with new challenges in building construction changing public perception. 

Performance-based design regulations are easily adaptable for present-day needs as their fundamental goals do not necessarily require constant modification. We have protected, and always will protect, life safety as a fundamental design goal, for example. The International Performance Code should be more widely adopted by local authorities to improve design innovation.

Internationally, flexible design regulations are widespread while prescriptive design is more common in the United States. Performance language has been employed around the world for some time, similarly structured to ours though with slightly different nomenclature. In England, building regulations list similar performance-based requirements, with further guidance on design criteria given. 

For example, requirements for cold water supply include providing “wholesome water to any place where drinking water is drawn off,” and “wholesome water to any sink provided in any area where food is prepared.” The use of the word “wholesome” is interesting, defined as water supply meeting certain water supply regulations. 

Fire Protection Design

While other nations have provided greater design freedom, a lack of regulatory oversight can be catastrophic. Energy-efficient, but combustible, exterior systems were installed, for instance, at the Grenfell Tower in West London in 2016. Though the cladding provided improved energy efficiency for the renovated building, when ignited it allowed for rapid vertical fire spread, resulting in 72 deaths. It was the deadliest structural fire in the United Kingdom for almost three decades. 

A system similar to the International Performance Code from the Society of Fire Protection Engineers outlines the process for project stakeholders to develop performance-based solutions. Fundamental design goals are defined, with design objectives and criteria providing further detail. The various definitions and procedures are similar to the International Performance Code in that basic needs are determined, either by a written standard or by project stakeholders, and further detailed with specific requirements. 

The process begins with basic statements not so different from Hammurabi’s goal of protecting life safety in the ancient world. Our ancestors’ ideas of protecting life safety and property are still in use today.

The performance-based model fits fire protection design well, as architectural design can challenge traditional prescriptive systems. It is common in the restoration of historic buildings. Recently, Goldman Copeland’s conversion of a historic church to multi-use office building presented significant design challenges. 

A performance-based methodology was employed, resulting in the development of a fire model to simulate smoke conditions. Automated smoke control systems were designed, based on the results of the fire model, to meet goals and criteria related to life safety. 

Plumbing system design flexibility will not often be required for architectural design features but it will be for innovations in infrastructure. Prescriptive methods for stormwater management, for example, may not adequately address flood mitigation in areas with rising sea levels and increasingly frequent storms. Performance-based methodology would benefit our adaptability to the changing environment. 

Design Flexibility

It is worth noting that prescriptive codes and standards often include an equivalency clause. The International Plumbing Code allows for alternative materials and methods when approved by the Authority Having Jurisdiction. So even prescriptive building regulations allow for alternative designs, though they require the designer to follow defined methods and materials as the primary design procedure.

Performance-based methods allow professionals to meet the intent of regulations while maintaining design flexibility. This alternative approach is not to be without structure and oversight. The methodology must include all project stakeholders and include robust regulatory oversight and peer review. Building code officials will need to be supported by a peer review process, as keeping up with new technologies will sometimes require expert oversight from the private industry. 

The opportunities for performance-based methods to enhance our plumbing design work will allow for more efficient and innovative installations. However, they must be balanced with adequate regulatory oversight and enforcing prescriptive requirements where appropriate. 

In addition to regulatory oversight, education of all project stakeholders will be critical to implementing performance-based methods to their maximum potential. Design professionals will require a fundamental understanding of the code’s intent. Prescriptive methods also require this knowledge. However, the burden of developing unique designs demands professionals who understand not only the intent of the code but also how that intent achieves project goals and objectives.

The path to a future of quality innovation is found through respect for the past. As an ancient trade, the plumbing industry has had thousands of years to learn. We have cataloged the whole of our acquired knowledge in regulations and design literature, which have been guiding our drafting pens. 

Let us recognize that building regulation started with Hammurabi’s very basic, yet comprehensive goal of life safety. The present precisely divides our past and future. Let us keep an eye on both to achieve balanced innovation in our practice.