Fire Protection Engineering and Sustainable Design
Why performance-based design will become increasingly important in the future
By Simon Dent | Fire Protection Engineering
In the 21st century, sustainable
building design is an increasingly popular and important client
requirement as well as a growing focus for professional engineering
firms. For the fire protection engineer, integrating sustainable, or
"green," building design aspirations presents the challenge of resolving
conflicts between architectural vision and code expectations for fire
At the heart of fire protection
engineering is meeting the challenges of clients' innovation. It is
often the case that the fire protection engineer contributes to a broad
spectrum of building solutions that significantly affect many other
members of the design team.
By discussing the challenges that fire protection
engineering must overcome to support sustainable building design, this
article seeks to embellish on a simple philosophy " that the fire
protection engineer's use of performance-based design can both liberate
the design team from code restraints, which might other wise hinder the
building's sustainability rating, and serve to address the more holistic
aspects of true sustainability.
SUSTAINABLE BUILDING DESIGN: A MULTIDIMENSIONAL CHALLENGE
In order to understand the implications
of sustainability for fire safety, it is first necessary to understand
what is really meant by "sustainable building design."
In the first instance, a sustainable
building is the physical end product of a design philosophy to improve
the "performance" of the built environment by increasing the efficiency
of the resources used in building during its lifecycle: construction,
operation and demolition. Such performance is typically measured through
a range of international environmental performance-rating systems for
Widely recognized rating systems include:
BREEAM, the Building Research Establishment Environmental Assessment
Method most commonly used in the UK and increasingly internationally;
LEED, The Leadership in Energy and Environmental Design Green Building
Rating System developed in the United States; and Green Star, a similar
rating system used in Australia.
All of the systems are fairly similar in
their approach, with scores for the incorporation of sustainable design
under areas such as energy, water, pollution and waste. The higher the
total building score the more sustainable the design is considered to
In the second instance, a truly sustainable building is also a socially
sustainable one; that has a positive social impact on the local
environment for the duration of the building's existence. Wider issues
such as societal needs, maintenance of heritage, provision of social
amenity, accessibility for all and future-proofing of a building so that
it continues to be useable for a longer lifespan than a more
conventionally designed building can all be considered.
BUILDING SUSTAINABILITY AND THE FIRE PROTECTION ENGINEER
Clients' design aspirations and tenant
demands increasingly lean towards the provision of large open floor
plates, the incorporation of open atria and the interconnection of
spaces and stories. These approaches maximize a building's bright and
airy feel of daylight and natural ventilation while being harmonious
with the principles of sustainability.
This desire for open planning alone
presents the fire protection engineer with a concept design that is at
odds with most international building codes that seek to limit large
open compartments and the interlinking of floors. Achieving a "good" or
"excellent" rating is often required for funding, good corporate
governance, or for attracting tenants and premium rental returns;
therefore, the design team seeks to achieve quantified reductions in the
use of resources such as energy and water. Fire protection engineers,
as part of these design teams, must rise to the challenge of
contributing to these reductions without significantly compromising the
client's aesthetic requirements, or the resulting level of fire safety.
Natural lighting from large open spaces
and glass facades can provide benefits in reducing energy consumption
while increasing population well-being and productivity when compared to
artificial lighting alternatives. Despite the restrictions of building
codes, engineered solutions can make these designs (which also require
less use of fire compartmentation) feasible. Through the assessment of
the fire load within the space, fire protection engineers can assess the
smoke movement through interlinking spaces and develop technical
solutions to address this while also tailoring the solutions towards a
low energy, natural ventilation strategy. Additionally, the engineered
provision of elements such as active smoke or fire curtains can provide
the code-required barrier between, for example, an atria mezzanine and
an adjacent escape route.
In order to quantifiably reduce a building's
resource use, fire protection engineers also need to think about the
resource demands of products necessary to achieve the required fire
Despite refurbishment projects' obvious relationship to
the sustainable philosophy of re-use, recycle, they present the greatest
challenge to providing adequate levels of performance for both fire and
sustainability. These buildings also present a challenge to code
officials, as the buildings rarely comply with the current standards.
For refurbishment, the best approach is performance-based engineering -
understanding how the building currently performs and finding
appropriate solutions working with the building's current provisions to
achieve acceptable levels of safety. Considering embodied energy, it is
far more sustainable to reuse existing buildings. Through good design,
it is possible to do so far into the future.
SOCIALLY SUSTAINABLE FIRE ENGINEERING
Aside from the client-driven challenges,
there are other aspects that relate to sustainability that are likely to
become stronger influencing factors for designs of the future - such as
the actual population of the buildings.
A global trend towards aging populations
and longer working lives means sweeping code assumptions that building
occupants are generally mobile are becoming less appropriate. Typically,
greater provision is made where, for example, it is known that a
building is designed to accommodate a high proportion of wheelchair
The issue of obesity, and the challenges it poses to fire safety are
perhaps felt most acutely in hospitals and treatment centers.
Flexible working and the increased focus
on maintaining a healthy work life balance is also presenting new
challenges and opportunities. As flexible working becomes a more popular
approach, businesses are increasingly designing fit-outs without
dedicated desks, with occupant's hot-desking or using flexible spaces
for their activities. This, combined with the understanding that many
offices are generally only occupied to 70% capacity with people on
leave, out at meetings, etc., provides an opportunity for businesses to
actually lease less space than they would if everyone had a traditional
desk. This may result in more people being allocated to work in a
building than say the exit width can accommodate, although the actual
population at any point in time should be no greater than can be
evacuated safely. The challenge for the fire protection engineer is to
test whether or not that is true and possibly to design for more people
than simple floor area calculations would imply. This is particularly
relevant where a building may cater for trading floors, or changing its
use from an office to education, as is happening in many city centers.
Increasing flexibility and minimizing
business loss also improves sustainability. Sprinkler protection of
buildings, although using resources, can be seen as inherently improving
sustainability both for flexibility and as they reduce the potential
size of polluting fires. Residential sprinkler protection, particularly
in higher risk occupancies, can be argued to be socially sustainable as
they reduce risk of loss to life and property and protect some of the
most vulnerable members of society.
Some of this may appear to lead to overly
conservative designs and hence not be sustainable; however, if future
flexibility can be increased, the lifespan of a building can be
increased and hence its sustainability. All of these decisions should be
made by the client, and the fire protection engineer can help provide
their clients with information and options.
Simon Dent is with Arup.
Building Code of Australia, Australian Building Codes Board, Canberra, 2009.
NFPA 101, Life Safety Code, National Fire Protection Association, Quincy, MA, 2009.
McGrattan, K., et al. Fire Dynamics
Simulator (Version 5) User's Guide, NIST Special Publication 1019-5,
National Institute of Standards and Technology, Gaithersburg, MD, 2009.
Case Study 1: Stockland Head Office Sydney, Australia
THE BRIEF The client's objectives for their new head office were to:
Create connectivity in their business to break down internal silos.
Showcase excellence in
environmentally sustainable design for a tenancy in an existing
Meet time and budget constraints.
Minimize disruption to other tenants in the building.
Stockland's new head office is an
eight-story tenancy on levels 22-29 of an existing 32-story office
building in Sydney's central business district. The original building
was a typical 1980s high rise, with a central core and floors separated
from each other.
To respond to the business and environmental needs
of the client, the architect developed a concept for interconnecting the
eight stories with an open atrium, circulation stairs and two fire
isolated escape stairs.
LIMITING THE VISION To minimize fire and smoke spread, the Building Code of Australia (BCA)1 allowed
the provision of only two stories to be interconnected via open stairs.
The code alternative was to design an enclosed atrium requiring glazing
and wall wetting sprinklers to separate the floors from the void. This
did not meet the desire for real interconnection in the tenancy.
To allow an open atrium and stairs,
as shown in Figure 1, various options were explored using
performance-based design. Options included smoke exhaust and the use of
vertical fire curtains surrounding the atrium on six floors; however,
there were issues with cost and practicality.
It was finally decided that the
design would feature a horizontal fire curtain. The curtain serves to
seal off the atrium in the event of fire by incorporating a fire-rated
flexible fabric that is carried on thin wires across the void. The
concept used curtains at levels 25 and 27, essentially reintroducing the
fire compartmentation given by the previous floors. Figure 2 shows an
elevation view of the design. Vertical curtains were used to close
around the accommodation stair. Risk assessment techniques were used to
demonstrate that a 3-level interconnection achieved an acceptable level
of performance. The risk assessment also addressed failure of the
COMMUNITY, ENVIRONMENT AND SOCIAL CONSIDERATIONS
The project showcased what could be
done with existing building stock, both in achieving an exciting new
work environment and in achieving excellence in environmental
Reuse of a building is far more environmentally
responsible than development of a new one, but it can be a significant
challenge. The environmentally sustainable design for this tenancy, as
well as the business objectives for Stockland, hinges on the creation of
the open atrium. Without the fire protection engineering design to
allow the open atrium, these objectives simply could not be achieved.
Case Study 2: California Academy of Sciences California, USA
THE BRIEF The client's objectives for their Academy were to:
Design a working research facility
with the capability for unlimited storage of specimen samples. The
samples were to be contained within combustible preservative within
movable storage cabinets (compact shelving).
Create a unique rainforest
exhibition, effectively a "building within a building" incorporating
multiple levels of interconnectivity.
Safeguard 18 million samples of
plants, animals, fossils and artifacts - essential tools for comparative
studies on the history and future of the natural world.
PROJECT APPRECIATION The 41,000 m2 sprinklered
building shown in Figure 3, features an undulating 1.01 ha living roof.
Other important architectural features include a perimeter steel canopy
supporting photovoltaic cells, a large glass skylight supported by a
tensile net structure and a 28 m diameter glazed dome, housing a
rainforest exhibition. The new $484 million CAS opened to the public in
LIMITING THE VISION
In the United States,
performance-based fire safety is generally accomplished under the guise
of the prescriptive building codes "alternate materials and methods of
design" clause. In the CAS, more than a dozen such performance-based
design equivalencies were proposed and accepted.
For example, the NFPA suite of codes2 do
not normally permit multiple levels to be atmospherically
interconnected without smoke exhaust. However, interconnectivity between
multiple levels was a client requirement for the rainforest exhibition
dome. Achieving smoke exhaust from the rainforest dome would be
architecturally undesirable and physically difficult to implement, as
the dome itself is located within the larger CAS building.
The ceiling of the main exhibit hall
required special treatment in order to avoid the cavernous echo that
might occur with such large spaces. In this case, 0.5 meter x 0.5 meter
square panels were suspended approximately 2 meters below the concave
main exhibit hall roof to help dampen the echo. Under the curved roof,
the panels needed to appear "free floating" or disconnected from each
other. This resulted in a 12 cm gap (approximate) between each panel. In
the event of a fire underneath, this free-floating collection of
ceiling panels with associated gaps would not permit a normal ceiling
jet to form. The plenum space above them was the entire area of the
exhibit hall, which meant that a hot layer could take significant time
to develop. Because of this geometry, there was a concern that sprinkler
operation would be significantly delayed.
The client's requirements for a
working research facility also provided a great challenge. The required
design has no similar precedents and was therefore not addressed under
generic code guidance.
Normally, due to the hazard type
(preservatives with >70% alcohol content), the code would require an
automatic sprinkler system with secondary containment of combustible
spills and fire suppression water. This would prove a big burden in
terms of drainage implications.
For the research facilities, high
pressure water mist systems were investigated. The design required a
peer review and full scale fire testing. Fire tests were performed to
prove the theoretical performance of the mist system design. The results
were a success.
The proposed suppression system successfully
incorporated a greatly reduced water flow rate - thus the design
precluded the need for special drainage and containment systems.
The client's requirement for a
multilevel rainforest exhibition could not be achieved through the
normal use of smoke exhaust. Using performance-based design tools and
computer-aided fire and egress analysis, the fire protection engineers
were able to verify the safety of the egress strategy within the
rainforest exhibition without smoke exhaust.
Fire Dynamics Simulator3 was
used to model a likely fire scenario - the results of which were
compared to an egress analysis model to ascertain an appropriate
evacuation time within tenable limits. The approving authorities
reviewed the results and approved the rainforest design. The fire
protection engineering analysis saved the architectural integrity and
satisfied the client aspirations for an immersive rainforest experience.
FDS modeling was necessary to
determine whether the sprinklers within the exhibition hall would
activate within a reasonable amount of time. A solid ceiling model was
compared to the proposed ceiling. The resulting strategy included the
spacing of the sprinklers in a more dense arrangement to have the
confidence that they would activate within the same time frame as that
of a standard design. This work saved the architectural integrity of the
The engineering work provided a safe environment,
maximized space savings and benefited the building functionally and
aesthetically. It provided savings with regard to initial installation
costs and future service and maintenance costs projected against the
building's life cycle.