CHANGES When considering the word change and applying it to the fireground, the definition from Webster’s dictionary is probably more applicable today than it has been in recent times. Webster’s defines change as “to put something in place of something else," and “to exchange, to make different.” Over the course of the past year, this definition has taken on a whole different meaning when it is applied to the enemy of the modern fireground – time (or the lack of it)! By now, every firefighter should be aware that fireground time has slowly been reduced by the building industry as the need for speed, cost reductions, and the lack of some building materials that were common several years ago are no longer used. An example of how building materials have changed:
Most firefighters are well aware of these changes, and because they are not new, there is a tendency to assume it is “business as usual.” However, during the past year or so, the building industry has taken the “alternative building methods” approach to a new level. Let’s look at several examples that are relatively new and should be evaluated from two basic fireground perspectives:
Truss Construction As soon as someone says the magic word truss construction, the immediate reaction is to think “been there and done that.” Although truss construction and the venerable 2" x 4” sized truss member has been around for about 40 years, a major change is slowly being introduced that will change your perspective of the truss that is the staple of residential construction. That change is glue and the removal of gang nail plates. Let me restate that from another viewpoint. Trusses in residential occupancies and moderate sized commercials, are beginning to use 2" x 4" trusses that are glued together, and do not use gang nail plates. Yes, you read that right. From the perspective of the building industry, why not glue the truss members together and eliminate gang nail plates to save a few dollars per truss? From the perspective of the fire service, how will this subtle change affect fireground time? As this type of construction is relatively new, the answer is not new. As the glue that is presently being used reportedly softens and melts at 250 degrees (yes, that is 250 degrees F), the question from the fire service perspective is relatively easy to answer. As 250 degrees will be reached at the ceiling in the early stages of a fire, your fireground time has just been significantly reduced to the point that as you arrive at a typical residential structure fire (remember that NFPA says that most of our structure fires are in residential structures), depending on the extension of fire, you may not have time for an interior attack, if fireground safety is a primary consideration. Reflective Board If you thought glued trusses were worthy of consideration, try this one! You are probably well aware that plywood replaced 1" x 6" sheathing, and today, OSB (oriented strand board) has replaced plywood. When a typical home is constructed, the exterior and roof is normally is covered with OSB. Why? Cost! OSB is cheaper than plywood. So, what is wrong with OSB? It fails at a significantly faster rate than plywood. So, how has the building industry attempted to solve this problematic dilemma? The current solution is to put a reflective foil on one side of the OSB and the OSB is installed with the reflective foil towards the interior of the structure. The foil is designed to reflect heat away from the OSB and allow it to last longer before failing. Now, just for a moment, think about the consequences when this material is exposed to fire. If it does its intended job, what will the consequence be? The answer is relatively simple if tests that have been conducted in Texas are correct. The buildup of heat within the interior of a structure is faster than the normal rate, as heat from the fire is reflected back into the interior! This will have a dramatic affect on one of the major fireground problems of 2006 – flashover! If flashover is a current fireground problem, and it is, this material has the potential to enhance the frequency of flashovers. Note: Reflective is also used in a different manner in hot areas such as Palm Springs. the foil side of the OSB is reversed (the foil is on the exterior side of the OSB) so heat from sunlight is reflected away from the structure, resulting in cooler interior temperatures. Structural Insulated Panels (SIP) Although this list of “alternative" building materials could be longer, we will look at one more gem that is also a positive for the building industry, and a huge negative for the fire service. This one is a prime example of why the increasing scarcity of wood is resulting in some interesting building material combinations – such as SIP. Structural Insulated Panels are pre made at the factory and then shipped to the job site, and are ready to be installed as walls. As an example, an SIP exterior wall would consist of a ½-inch sheet of OSB (this sheet would be on the exterior), bonded to 8” of Styrofoam, that is also bonded to another sheet of ½-inch OSB (this sheet would be on the interior). The beauty of this combination is:
Although this construction method is relatively new and it does not have a history of how it reacts in a fire, I think what it is capable of doing in a fire takes little contemplation. High-impact Wallboard Most firefighters are aware that several years ago, the building industry started to use drywall that had an imbedded layer of Lexan that was designed to make breaching walls more difficult. Although this type of wallboard was successful at accomplishing this goal, it had low sales because of its high cost. As a replacement, it appears that a new type of high-impact wallboard is replacing the older type of wallboard, but instead of an imbedded layer of Lexan, the new wallboard features n imbedded layer of fiberglass mesh that accomplished the same goal at a lower cost. Note: See the October, 2006 issue of Fire Engineering magazine, pg 117, for an overview of this new product that will make forcible entry and exit more difficult for fireground personnel. So, although the preceding overview of a few changes in building construction may not be new news, how does the “rubber meet the road?” In our next article, let’s use this article as the introduction to consider the following viewpoints regarding change to your fireground office:
Chief Mittendorf is the author of “Truck Company Operations” and “Facing the Promotional Interview.” To purchase, return to the Main Page and scroll down to Fire Engineering Books. © Copyright Firenuggets.com 2006 • Click here for Terms and Conditions of Use
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