|Meeting Sustainability Goals through Integration of Fire Alarm and Building Controls|
Issue 66: Meeting Sustainability Goals through Integration of Fire Alarm and Building Controls
By Paul Turnbull
Building owners are increasingly focused on the "green" aspects of
their buildings and operations. They have replaced standard light bulbs
with CFL or LED bulbs, they recycle office paper, and they use Energy
Star compliant computers and appliances. But they probably haven't
considered the sustainability impact of their life safety systems. This
article looks at ways that integration between a building's fire alarm
system and its building control system can be used to help achieve
sustainability goals while still complying with code requirements for
the life safety systems.
The first question to be answered is why someone would want to
integrate their fire alarm and building control systems. There are many
benefits from this integration, including the ability to monitor the
status of both systems from one location, or to utilize features of the
building control system that may not be available on the fire alarm
system, such as remote notification, trending, or maintenance
management. But the biggest advantage is that both systems will
cooperate to provide appropriate responses during emergency situations.
These responses could include avoiding detrimental responses, like
adding air to a fire, or providing beneficial responses, such as
supplying or exhausting air from parts of the building to remove smoke
and/or create pressure differences – in other words, to perform smoke
Unfortunately, the life safety benefits of a smoke control system can
conflict with the goal of operating the building in an energy-efficient
manner. The International Building Code1 (IBC)
requires smoke control systems to be activated weekly to verify they are
ready to operate when needed. During this code-required test, large
quantities of conditioned air are exhausted to the outside, while nearly
equal quantities of unconditioned air are drawn from the outside.
After the test is completed, additional energy is required to condition
the air that was drawn in during testing. From an energy-efficiency
standpoint, that weekly smoke control system test is a waste.
Since testing of smoke control systems is mandated, there is not much
that can be done to avoid its associated inefficiencies. However,
sustainability goals go beyond energy-efficiency considerations to
include material resource management, which takes into account energy
and resources required to produce and transport products to the building
site; air quality considerations such as toxins in air exhausted from
the building; and waste disposal. With this broader scope in mind,
there are a number of design choices that can be made to provide
sustainability benefits that help counteract the negative impact of the
The first sustainability benefit from integrating fire alarm and
building control systems is a reduction in the amount of equipment
used. Building control systems include control equipment and control
circuits to operate fans and dampers for comfort purposes. Fire alarm
systems often include control equipment and control circuits to override
these fans and dampers to provide the intended life safety function.
If the building control system has the appropriate life safety listings,
these systems can be integrated, making it unnecessary to duplicate
these controls and control circuits. Instead, a signal from the fire
alarm system can cause the building control system to operate the fans
and dampers in a manner appropriate for life safety. Since less
equipment is required, less energy and resources were used to produce
the products and transport them to the building site compared to what
would have been required if the systems had not been integrated.
By sealing construction cracks, painting walls, making sure doors fit
well, and caulking doors and windows, the stairwell pressurization fan
could be reduced by over 80%. This means less electricity is used to
run and/or test the smaller fan, less material is used to create the
smaller ductwork, and less conditioned air is exhausted and less
unconditioned air is brought in during testing.
Some sustainability benefits can be achieved through modification of
the smoke control system itself. Pressurizing a stairwell with
unconditioned air, or air conditioned just enough to keep it safely
above freezing, provides an energy savings from not conditioning the
pressurization air. This approach also reduces the pressure difference
between the top and bottom of the stairwell relative to the outdoors due
to stack effect, leading to a reduction in the amount of air needed to
pressurize the stairwell. Using the equations found in NFPA 92,2
an analysis of an 8-story stairwell using loose construction techniques
in a location with a 10°F (-12°C) winter design temperature was shown
to require 3800 cfm (1.8 m3/s) using 72°F (22°C) air for pressurization, but only 3200 cfm (1.5 m3/s) using unconditioned air; a reduction of approximately 15%.4
While the reduction in pressurization air is not as large as in the
previous example, the sustainability benefits from reducing equipment
size are the same as previously described.
Another change to the smoke control system that can lead to
sustainability benefits is to divide large spaces into smaller spaces
during an emergency, using deployable barriers. When many floors are
connected together using open stairs, the smoke exhaust system must be
sized for the combined volume of all connected floors. Use of
deployable barriers reduces the size of each protected space, leading to
a corresponding reduction in fan and ductwork sizes for each space.
Operation or testing of these smaller systems uses less energy and
exhausts less conditioned air to the outdoors compared to systems using
One last approach for making smoke control systems more sustainable
may be unpopular because it requires modification to the building
design, but this approach can lead to substantial gains. In building
designs where little volume exists above the highest walking surface,
smoke exhaust fans would have to be sized for the inefficiencies of a
system that includes plugholing (drawing clean air up through the smoke
layer). Increasing the volume of space above the highest walking
surface allows a deeper smoke layer to form, which can reduce the number
of exhaust inlets needed to prevent plugholing, and can also reduce the
size of the smoke exhaust fans.
The volume above the highest walking surface could be increased by
providing additional building height at the top of the atrium, but other
methods that do not affect the building shell can also be used, such as
separating the highest floors from the atrium by glass walls or other
barriers. Increasing the building height or adding glass walls will
require additional construction materials, which will offset some of the
gains made from increasing the efficiency of the smoke control system,
but this is a one-time tradeoff, where the efficiency gains are realized
every year over the life of the building.
Increasing the volume above the highest walking surface to extreme
proportions can result in the greatest sustainability benefits. If the
volume is sufficiently large that all building occupants can be
evacuated before the volume fills with smoke, a passive smoke-filling
approach is all that is required. A passive system is certainly the
most sustainable system of all, because it completely removes the need
for fans, ductwork, exhaust grilles, etc., and the electricity that
would have powered it all. And because there are no operational parts,
the weekly tests that dump conditioned air to the outside and require
the associated reconditioning of make-up air are also eliminated.
The previous paragraphs have described methods that can make a smoke
control system more sustainable, but it should be pointed out that any
smoke control system is more sustainable than no smoke control system. A
smoke control system reduces migration of smoke within a building.
This prevents smoke from damaging building finishes and contents in
parts of the building that are not directly involved in the fire, so
these finishes and contents do not need to be replaced after the fire.
Protecting something for continued use is much more sustainable than
allowing it to be damaged and then having to replace it.
Paul Turnbull is with Siemens Industry, Inc.
4th Quarter 2011 - Fire Safety: An Integral Part of Sustainability -- Christopher J. Wieczorek, Ph.D.
2nd Quarter 2010 - Fire Protection Engineering and Sustainable Design - Simon Dent
2nd Quarter 2010 – Green Construction and Fire Protection - Dominick G. Kasmauskas
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