Fire safety overview, sprinklers, fire areas, construction types and occupancy
Introduction
Proposition: Many important things about architecture are in motion.
People: this activity generates what is called a circulation system of doors, hallways (corridors), stairs, elevators, and so on.
Air: without movement of air, breathing within buildings would become dangerous, instead of healthy. Traditionally, natural ventilation (or leakage) through windows provided fresh air. Increasingly in modern buildings, air is provided mechanically through ducts, and is conditioned as required.
Water: provided for drinking, cleaning, and for removal of wastes. So it enters the building through pipes, and leaves the building through a different set of pipes. The two sets of pipes can never come in contact with each other.
Heat: inside and outside air are separated by an enclosure system (envelope, skin, etc.) that has, to varying extents, the ability to conduct heat and transmit radiant energy, so heat is always moving from inside to outside, or from outside to inside, whenever there is a temperature difference.
Vapor: inside and outside air are separated by an enclosure system (envelope, skin, etc.) that has, to varying extents, the ability to limit the diffusion of water vapor, so vapor (moisture in a gaseous form) is always moving from inside to outside, or from outside to inside, whenever there is a vapor pressure difference.
Light: whether it originates from the outside or inside of a building, light bounces off (or is absorbed by) surfaces in various ways and to various degrees.
Sound: whether it originates from the outside or inside of a building, sound bounces off (or is absorbed by) surfaces in various ways and to various degrees, and is blocked by assemblies in various ways and to various degrees.
Fire: "Carbon-based materials… may enter into a state of rapid combustion. Fire is not something external to such materials, but rather an alternative state of being triggered by ignition and sustained by heat, in the presence of oxygen. Where carbon-based materials are used (ubiquitously in buildings), and where sources of ignition are plentiful (candles, matches, lightning, gas lamps or stoves, fire places and chimneys, boilers and furnaces, faulty electrical connections, and so on), it is not surprising that rooms, buildings, and entire sections of cities often burn." (Ochshorn, What Sustainability Sustains)
A. Historical context.
1. Urban conflagrations were common, devastating entire sections of cities.
2. Trend in fire safety strategy has been shift from limiting fire to:
building of origin; then
floor of origin; then
room of origin.
B. Concerns.
1. life safety
2. protection of property
C. Strategies.
1. alert occupants (fire detecting devices, call boxes, alarms). Based on smoke or heat.
2. provide protected means of egress.
need enough time to escape or places of refuge.
need to protect escape route from fire, heat, and smoke.
need normal -- i.e., not confusing -- circulation patterns so that occupants can find exits easily, marked with exit signs.
3. compartmentation: provide barriers to keep fire isolated. Concept shows up in numerous ways, at different scales:
a) prevent vertical spread (avoid open shafts, stairs, etc.)
b) prevent horizontal spread with fire separation (area separation) walls
c) protect the means of egress
d) protect structural elements
e) how is this compartmentation accomplished? using assemblies with various fire-resistive ratings (specified number of hours of protection, e.g., a 2-hour fire-resistive rating).
4. ventilation: vent smoke, toxic gases.
Windows, skylights, mechanical equipment, roof hatches, etc.
5. Suppression:
Manual. Fire departments (require building, floor access; availability of water; standpipes)
Fire extinguishers.
Fire departments (note use of standpipes; fire-dept. connections outside of building; hydrants)
Automatic. refers primarily to automatic sprinkler systems, as shown below:
Aside from specialized non-water based systems, there are four variations on the theme:
wet pipe system: most common; water under pressure with closed heads. Heads open individually when subjected to high heat, so only those sprinklers actually over the fire will operate in any given case.
dry pipe system: same as above, except pipes filled with air (or other gas) under pressure. When a sprinkler head opens as a result of exposure to high heat, the gas pressure in the pipes is reduced, which triggers a remote valve to open, filling the pipes with water, which is then discharged only through the open heads. Useful for conditions where water might otherwise freeze in pipes (i.e., unheated spaces).
preaction systems: "Pre-action fire sprinkler systems employ the basic concept of a dry pipe system in that water is not normally contained within the pipes. The difference, however, is that water is held from piping by an electrically operated valve, known as a pre-action valve. Valve operation is controlled by independent flame, heat, or smoke detection.
"Two separate events must happen to initiate sprinkler discharge. First, the detection system must identify a developing fire and then open the pre-action valve. This allows water to flow into system piping, which effectively creates a wet pipe sprinkler system. Second, individual sprinkler heads must release to permit water flow onto the fire." (source)
deluge system: sprinkler heads are permanently open; a fire-detecting system (e.g., heat or smoke detector) opens the water valve, so that water is released simultaneously through all the open heads. Used where there is danger of fire "flashing" in advance of closed sprinkler heads (e.g., severe fire hazard areas, e.g., storage facilities with flammable liquids).
Sprinklers discharge in the direction of the deflector, which spreads the water over a larger area. In some cases, the water is directed upward, to wet the ceiling; in other cases downward directly over the source of the fire.
Non-water-based fire suppressants (where damage to electronic equipment or paper records is unacceptable):
HALON was traditional fire suppressant, but production ended in 1993 (ozone depletion concerns — Montreal Protocol)
HFCs have been promoted as a substitute with zero ozone depletion potential (ODP). However, they have high global warming potential (GWP)
One new possibility is the use of fluoroketones, with zero ODP and low GWP.
IBC Chapter 9 sprinkler standards (referencing National Fire Protection Association, or NFPA standards)
Section 903.3.1.1 NFPA 13 sprinkler systems: these are the default, basic sprinkler standards unless otherwise allowed.
Section 903.3.1.2 NFPA 13R sprinkler systems: These are less expensive systems that are permitted (required?) in Group R occupancies of 1–4 stories (not exceeding 60 feet in height)
Section 903.3.1.3 NFPA 13D sprinkler systems: These are the cheapest systems to install, but are only allowed (required?) in one- and two-family dwellings (Group R-3, Group R-4 Condition 1, and townhouses).
While such residential sprinklers are required in the model IBC, they are most often NOT required in codes actually adopted in the various states.
Status of residential sprinklers in U.S. (as of April 2019), per NFPA
States/regions requiring fire sprinklers in new, one- and two-family homes: CA, MD, Washington, D.C.
States prohibiting statewide and new, local adoptions of fire sprinkler requirements in new, one- and two-family homes: AK, AL, AZ, CT, DE, GA, HI, ID, IN, KS, KY, LA, MA, MI, MN, MO, NH, NJ, NY, NC, ND, OH, PA, SC, TX, UT, VA, WV, WI
States allowing local adoptions of sprinkler requirements for new, one- and two-family homes: AR, CO, FL, IL, IA, ME, MS, MT, NE, NV, NM, OK, OR, RI, SD, TN, VT, WA, WY (*Note: In MA and NY, homes of a certain size must be sprinklered)
Using "fire areas" to avoid sprinklers
IBC Chapter 9 requires that sprinklers be used in certain occupancies, unless the "fire area" is limited or other criteria are met. One can create these fire areas using fire barriers or horizontal assemblies (described in a subsequent lecture).
Example 1: For occupancy Group A-1 and A-3, sprinklers are required where the fire area exceeds 12,000 square feet (1115 square meters) OR the fire area has 300 or more occupants OR the fire area is above the ground floor (level of exit discharge).
In other words, if the criteria are not met, then sprinklers are REQUIRED.
Example 2: Sprinklers are required in all group R occupancies. However, NFPA 13R sprinklers can be used in certain subgroups, as can NFPA 13D sprinklers in certain subgroups. And, of course, many states do not require sprinklers in 1- and 2-family residences.
6. site planning issues:
access (best if fire departments have access to all sides of a building, although that is not always possible).
parapets: these are building elements (extensions of the non-combustible wall above the plane of the roof), but have site-planning implications since they protect the building's roof from fires originating off site.
blank walls, or walls with limited "unprotected" openings are required at or near property lines.
fire hydrants
Some images and videos:
But can real architecture catch on fire?
Fire on 50th floor of the John Hancock Building in Chicago (S.O.M. architects), 2015
Both building codes and zoning ordinances are state (governmental) interventions that restrict the freedom of property owners. In the US context, such restrictive acts by the state have been controversial, but ultimately have been upheld by supreme court rulings over the years. The US constitution gives limited powers to the federal government; states then have the ability to impose building code and zoning restrictions.
In the recent past, many states had adopted their own building codes, many — but not all — based on model codes such as the "BOCA code" (Basic National Building Code promulgated by Building Officials and Code Administration, International), the "Southern Building Code" (Standard Building Code promulgated by the Southern Building Code Congress, International), or the "UBC" (Uniform Building Code promulgated by the International Congress of Building Officials).
Image from Jim Rossberg and Roberto Leon, "Evolution of Codes in the USA," (manuscript) National Earthquake Hazards Reduction Program.
These separate model code agencies have gotten together to produce a national model code under the auspices of the International Code Council (ICC). The International Building Code (IBC) has now been adopted by all 50 states, finally giving the US a de facto national code, even though each state may well modify it in its own way. See this interactive adoption map.
Zoning is still generally a municipal, county, or state function, and varies considerably from place to place. Where building codes cover issues like fire safety, accessibility, and structural safety, zoning generally deals with property limitations such as minimum property size, allowable property use (occupancies), building height, bulk, massing, floor-area-ratio, parking, setbacks (yards), and so on.
Fire safety per building code:
Watch this 6-minute video to get a sense of the destructive power of fire, the speed with which it develops, and the incredible quantity of fuel supplied by ordinary domestic objects. Our discussion of fire safety is based on the IBC (International Building Code). Follow online links to "course readings" and "internet sources" or just go directly here.
And yet is is still unusual for municipalities to require residential sprinklers in new construction: "'When you start mandating a fire sprinkler system, you are going to price a lot of people out of these new homes,' said Ned Munoz, vice president of regulatory affairs for the Texas Association of Home Builders, which lobbied heavily for anti-sprinkler legislation." (New homes burn faster, but states resist sprinklers) See this website for state-by-state data on residential sprinkler requirements.
Introduction: Building code fire safety issues
How high (number of stories, height in feet)?
How much floor area (on one floor; on multiple floors)?
How far from property line, and how many windows?
What materials can it be constructed from?
How many means of egress (exits)? How wide?
How many "hours" fire-resistive rating on various elements?
Most answers determined as follows (IBC 2018):
Occupancy group: chapter 3
Construction type: Table 601
Other specific questions are based on:
Exterior wall fire-resistive ratings and openings: Table 602 and Table 705.8.
For each element, the required fire-resistive rating (number of hours) is given.
Table 601 footnotes are not shown; see IBC for complete details.
Exterior wall fire-resistance based on distance from property line:
See Table 602 NYS 2020 Building Code (based on IBC 2018) for "fire-resistive rating requirements for exterior walls based on fire separation distance." This table tells you the required rating (number of hours) for exterior walls based on their distance (frontage) from the property line. See Table 705.8 for percentages of allowable openings in exterior walls.
Graphic interpretation of exterior wall requirements:
Table 602 footnotes are not shown; see IBC for complete details.
Disclaimer: Students are responsible for material presented in class, and required material described on course outline. These notes are provided as a tentative outline of material intended to be presented in lectures only; they may not cover all material, and they may contain information not actually presented. Notes may be updated each year, and may or may not apply to non-current versions of course.
first posted Aug. 29, 2007 | last updated: Sept. 4, 2020
2007–2020 J. Ochshorn. All rights reserved. Republishing material on this web site, whether in print or on another web site, in whole or in part, is not permitted without advance permission of the author.