Commercial Roof Insulation: An Old Headache Gets Worse
DEPARTMENTS
Training Notebook
Think back to the last time you were operating on the roof of a taxpayer or factory building. You finally got the saw started, cut a 4 X 8 hole, peeled back the roof, and NOTHING! You hadn’t even penetrated the roof deck itself!
Sound familiar? If you haven’t experienced this situation yet, it probably won’t be too long until you do. For those of us who have run into these problems and were left shaking our heads and wondering why, this article will attempt to provide some answers.
The biggest part of the problem described above is the type of roof insulation applied to the roof in question., Cutting a flat roof used to be somewhat simple. You had a horizontal surface to work on, and, as long as the fire had not done too much damage, you could expect reasonably firm footing.
An axe and/or a saw penetrated the deck easily. Most of these structures were wood frame, usually tongue and groove planking laid over the wooden rafters. Later, plywood sheathing was used. On top of the deck, the roof membrane was laid. It could be a simple one of tar paper and cold asphalt, or the more complex one constructed of hot asphalt and numerous layers of felt, finished off with slag or gravel.
When the building needed reroofing, depending on the condition and age of the old roof, only the stone might be removed and the new roof laid over the old one. Eventually, we might encounter two-inch thick layers of asphalt. Even under these conditions, the saw had very little trouble penetrating the roof through the deck, except for occasional gumming.
With the development of steel decks, insulation was used to smooth out the “Q” decking to receive the roofing membrane. While there were only a few types of insulations available at this point, it was probable that more would be developed and that their use would be expanded. Even as you read this article, someone, somewhere is developing a new type of insulation. There are several forms on the market today, all made of different materials and intended to be used with different types of roof systems. They will all cause some sort of problem.
The most commonly used insulation is a dense fiberboard. Ranging in size from 1/2-inch and up, it can be found anywhere. Its low cost makes it very attractive to the economical roofer. It is often used to smooth out an old roof after the stone or slag is removed, resulting in a sandwich effect, where two or more layers of roofing may be found. In such cases, several sets of cuts, cutting one layer at a time, will be necessary to complete the vertical artery. Also be wary of flame impingement on the core of insulation. Spot fires and/ or smoldering insulation can be expected.
When this fiberboard substance is used over steel decks the transfer of heat through the deck may ignite the insulation. The combination of this and the air flow through the channels of the “Q” deck itself can cause major problems.
Another form of insulation growing in popularity is the foam type. Sold under different trade names and for different uses, they all present some common problems. While some, such as Styrofoam, are very flammable, other types are denser and may not readily ignite. However, as they are exposed to flame and heat they do emit toxic smoke and by-products. Although it is cumbersome to use while cutting roofs, self-contained breathing apparatus (SCBA) is highly recommended here.
With some of the foams, spot fires in the core is a very real possibility and should be watched for, especially when removing roof covering. Of greater significance, though, is the difficulty of penetration with the saw or axe. The insulation’s resilience and thickness make the axe practically useless. Several sets of cuts may be needed, even with a saw. In the case of a gypsum deck, one can readily expect to make at least two sets of cuts, one through the insulation and one through the deck. Spare saws and blades should be kept handy to facilitate the operation.
A variation of the foam system is the canted or graded system. Using pieces of various sizes and shapes, a flat roof can be given one or more pitches to shed water. The result is best described as resembling a moonscape. The insulation is graded outward from drains or scuttles and may be as thick as 12 inches or more, plus the roof deck.
Vertical ventilation will be difficult, to say the least, on a canted system. Due to the system’s unique design, drain pipes, normally found close to parapets or other perimeters, can now be placed anywhere on the structure. As such, the fastest penetration can be achieved around the drains where the insulation is thinnest.
If this area suits your primary purpose for effective vertical ventilation, then cut in the area of the drain as it will provide the area of quickest penetration. Be careful that the “freed” pipe does not fall on the firefighters operating below. Look, in this case, for natural openings: skylights, ventilators, scuttles, etc. Choose your cuts carefully and beware of hidden dangers.
A variation of the foam systems that was recently introduced is best described as an upside down roof. In this system the roof membrane is laid directly over a smooth deck. In the case of steel, a fiber or gypsum board will usually be laid first. On top of the membrane a Styrofoam insulation, bonded to a layer of 1/2-inch concrete, is laid, concrete side up. The concrete serves to weigh down the Styrofoam and helps protect the roof from vandalism and weather conditions. In some cases, large stones set in an adhesive are used in place of the concrete.
As the insulation is not fully adhered, the roof team may be able to pry up one or more of the boards. However, the boards are very heavy, and two or more men may be needed to lift and move them. Once the insulation is removed, the deck will be exposed and penetration can be attempted. As before, watch out for spot fires and core exposure. Also be wary of open burning of the roof, as the entire core is exposed.
The greatest hazard with a majority of insulations is their susceptibility to fire. The core will be exposed in various ways: by our vent holes, pipe chases and ducts, and heat conduction through the roof deck itself. Many roof fires have started as a result of overheated exhaust ducts passing through the insulation. Roof teams should watch for telltale signs of fire extension into the core. Smoke wisping out around vents far from the fire, bubbling tar, and spot fires can indicate a possible core fire. Good overhaul practices can go a long way towards preventing a major problem.
There is another hazard inherent to the design of the insulation itself. Because it is intended to retain heat, we can fully expect higher interior temperatures, leading to quicker flashover conditions. In the case of a possible backdraft condition, where vertical ventilation becomes the primary task, the engine company must move slowly and carefully and wait for the roof crews to accomplish their task.
Some of the thicker insulations will actually hide the warning signs of collapse from the roof personnel by absorbing telltale sign and movement. When wet, the extra weight will add to the collapse potential. Whenever possible, an officer or firefighter should be assigned as safety man to monitor conditions. If the integrity of the roof becomes questionable, GET OFF!
As previously mentioned, ventilating these roofs will be very difficult, maybe even impossible. Several saws and teams of men will be needed just to get one or two holes. A defensive operation, such as a trench cut, may prove to be futile. Because rapid vertical ventilation is important in a commercial structure, it may be more effective if the first crews to the roof remove hatches, skylights, ducts, etc. As additional crews arrive, a coordinated effort at cutting the roof, if still necessary, can then be attempted. Members should be aware of the type of joist and deck system below them. (Preplanning goes a long way in this type of operation.) Remember, don’t cut those cords on the open web bar joists.
Stretching a handline to the roof will control spot fires in the core and keep smoldering insulation from bursting into flame. Overhaul and remove all suspected insulation from the roof as soon as possible. Exposing the core can be avoided by cutting the insulation back from the edge of the vent holes.
When dealing with this type of structure, preplanning and inspection are important steps in developing your operational techniques and fireground decisions. Information as to the type of insulation and its hazards can be obtained from the builder, architect, or maybe even the local roofing outfit. Supply yards and distributors are also a great source of knowledge.
The problems associated with these types of insulation materials can compound an already difficult fire situation if you are not prepared to deal with it. Given the heavy fire load of most commercial occupancies, early roof failure should be anticipated. If this insulation is going to put you in physical danger by prolonging your roof operation unnecessarily, abandon it. CAUTION IS THE WATCHWORD! A building can be replaced, lives can’t.
