By Ir TL Chen FIFireE, FASHRAE, FIEM, PEng
1.0 The Introduction
The objective of fire engineers is to design fire protection systems to achieve life safety protection and property protection in that order. To venture beyond these two main objectives will require concerted change of mindset.
Fire protection engineering may not be typically considered during a green building design process. However, there are several ways that a green building design may affect related fire protection systems or fire/life safety code requirements. Several examples include fire department access, issues associated with using reclaimed water to supply fire suppression systems, and the use of atria to provide natural light. Underfloor air-distribution systems are commonly employed in many sustainable design projects and may present building code compliance challenges. Additionally, there are aspects of fire protection engineering that may be utilized in an integrated green building approach to support sustainable design. Designing low-water (water mist or fog systems) or no-water consumption (dry chemical or clean agent) fire-suppression systems may be applicable in some design situations. Performance-based design approaches may also be used as a method to meet the intent of the applicable codes when unique green building design methods are employed.
Some of the questions that need to be addressed are:
- Which fire/life safety building code requirements most often come into conflict with application of innovative green building design elements and why?
- How can a design team address these building fire/life safety concerns and satisfy local building and fire authorities while incorporating the desired sustainable design elements into the project?
2.0 Prescriptive Code Compliance Process
Designers, builders, and other stakeholders and practitioners in the built environment face the challenge of providing sustainable design elements while at the same time meeting model building and fire code requirements.
Sustainable design building elements, materials or methods of construction may face questions and concerns from local building and fire authorities. Design teams may need to demonstrate to the fire authority how these innovative sustainable design elements comply with the prescribed code requirements or comply with the intent of the code provisions.
At this point in the project development, designers are often confronted with the challenge of answering the following questions:
1. What are the sustainable design elements that can be shown to be in strict compliance with the prescribed code provisions?
2. Which are the sustainable design elements that may not meet the prescribed code provisions and will need to be demonstrated to be equivalent?
The key for the design team at this juncture is to recognize that all construction projects need to satisfy the building and fire code provisions. It is also vital to understand that innovative approaches to building design elements need to be identified early in the project design. Creative, integrated prescriptive code compliance can be part of a sustainable design project as long as the design team begins to discuss these code compliance issues early in the design process.
This prescriptive code compliance design process requires an integrated, collaborative effort of all project design team members including the owner, architect, M & E engineers, C & S engineers, fire engineer (if appointed for performance-based approach), façade consultant, interior designer, and landscape consultant.
3.0 Integrated Design/Code Compliance Process
Unlike traditional design projects where each design team member often works independently to address their area of design responsibility, an integrated design process relies on combining the team member strengths to collaborate early in the design process to address the sustainable design elements on items such as water usage, energy usage, occupant comfort, public safety/health, and environmental impact. The intent is to answer how each of these elements can be incorporated into a comprehensive design solution for the building that meets the prescribed code requirements or can be shown to meet the intent of the code.
When the prescriptive code approach cannot handle a new/innovative design element, a performance- based design approach maybe needed for certain sustainable design elements of the project. The performance-based design approach builds upon the integrated design process to convince the fire authority that the design element complies with the intent of the code provisions, fulfills its intended purpose, and is shown to be at least equivalent in quality, strength, fire resistance and safety.
Therefore, the performance-based design approach again requires the “blending” of design team disciplines. This integrated design process is critical for sustainable design projects and is often conducted in periodic “design charrette” meetings among the team members. In a design charrette, the collective expertise of the project team is brought together to identify areas of overlap and synergy among the various design disciplines to develop solutions to building efficiencies, including water usage, energy usage, occupant comfort, day lighting and environmental impact.
Each of these elements can have practical impacts on meeting code requirements to “bridge the gap” between the implementation of sustainable design elements and building/fire code requirements, code intent and fire-fighting tactics. Fire authority approval of these innovative materials, systems and assemblies that are often a part of “building green” is a critical part of the design process that risked being overlooked.
4.0 Fire-Suppression Systems
In green designs, rainwater and reclaimed water may be proposed to supply not only irrigation systems, but also fire-sprinkler systems. Industrial sites often have non potable water supplies contributing to a fire- water supply system, but for the most part, residential and commercial urban developments have potable fire-water supplies. When reclaimed water interfaces with potable systems and is proposed as part of a fire-water supply system, back flow requirements need to be reviewed carefully. In addition, there may be sprinkler pipe drop requirements that need to be taken into account to protect sprinkler systems against sediment buildup in their pipes.
Pipe-corrosion potential will need to be evaluated. Microbiologically influenced corrosion may be an issue with the use of reclaimed water supplies. Where present, such corrosion can reduce a sprinkler pipe’s life and require chemical treatment to remediate. Hence, it may not make sense to use reclaimed water as part of a fire-suppression system if chemicals must be added to the system or if a premature failure of the sprinkler system could occur because of poor water quality.
Water mist systems score well in green building designs as an element of fire suppression. In some cases, water-mist use is not the result of a desire to conserve water but of working with the available water supply, especially in adaptive-reuse buildings.
5.0 Natural Lighting
A popular approach in sustainable design is harvesting the use of natural light. Natural light maybe brought to a building’s interior through the use of skylights, light wells and atria. These design elements may impose building, fire and life safety code issues if not coordinated with fire protection engineers during the early stages of design.
Light wells can affect building code requirements. A light well is a shaft located in an interior area of a building. Windows located in this shaft allow light to filter from the roof level to interior areas. A light well designed to bring natural light through a building to lower levels may need to address its impact on horizontal fire compartmentation. Light pipes (a variant of light wells) have similar concerns.
6.0 Underfloor Air-distribution
Underfloor air-distribution (UFAD) systems have become a common element in green building design. The concept utilises the under floor plenum for supply air-distribution and the space above the ceiling as return plenum. Several code issues may need to be addressed when a UFAD system is proposed. The under floor plenum is normally also used for power and data cable distribution.
In a plenum space, power cables need to conform to electrical code requirements and be installed within electrical conduit/raceway enclosures, while data cables not installed in conduit/raceways need to be plenum-rated and comply with electrical code requirements. There can be issues regarding connections between power and data cables which are under and above a floor.
Depending on the floor plenum height, smoke detection may be required. When smoke detectors are installed below floors, they should be installed correctly (below soffit of raised floor panels and not resting on the floor bed) and be made accessible for periodic maintenance and testing.
7.0 Atria
In green buildings, atria are a common method of allowing natural light and air-distribution, sometimes in conjunction with natural ventilation, to assist the air-distribution system in overcoming stack effect. Smoke-control is often required when an atrium is planned. Also, atria generally are required to be served by sprinkler systems that are separate from the
remainder of the floors. Other fire-protection issues, such as an atrium’s size and arrangement, including the location of walking surfaces and exit paths, need to be discussed early in a design process. These issues, in conjunction with design fire size, will affect a smoke-control ventilation system.
Supply and exhaust air requirements also need to be established. These determine the amount of equipment required and the size of the airshaft(s) serving a space. Supply air velocity is important in smoke-control systems, and it affects grille sizing and location. These issues are best determined early in a design process for space requirements and power consumption (normal and emergency) to be established for smoke-control system equipment.
Natural ventilation is sometimes used to supplement or provide supply air to an atrium, both normally and in smoke-control mode. In the event natural ventilation is used, the wind effect may need to be addressed, possibly by modeling, in the design of a smoke- control system. In some cases, natural ventilation and the stack effect may be suitable to ventilate an atrium normally and during a fire.
8.0 GREEN BUILDING INDEX
Under the recently (May 2009) launched Green Building Index (GBI) rating system for Malaysia, there are direct and indirect green credit points allocated for fire design elements.
For the Non-Residential tool, direct credit points are cited for;
1) MR7 – Refrigerants and Clean Agents (2 points)
2) IN1 – Innovation e.g. Recycling of all fire system water during regular testing (1 point)
Whereas indirect credit points can be found under the criteria impacting material reuse and recycling, and reduction in potable water use.
9.0 ACKNOWLEDGEMENT
This article has extensively quoted materials from the paper on “Role and Challenges of the Fire Engineer in Green Building Design” by Ronald J. Mahlman , P.E.- Rolf Jensen & Associates.