EEWs, Drywall, and Laminated I-Beams
A question for any construction experts out there. Our town has a large number of homes with walk-out basements with living quarters and living rooms in these basements. A preponderance of these are constructed with laminated I-beams as the floor joists, covered with drywall. The windows are typically energy efficient windows. My question is this--does anyone know of any correlation between the time it takes EEWs to fail and the time that heat/fire penetrate the drywall enough to cause a collapse hazard in the laminated I-beams? Or how about regular windows? My question is based upon sizing up a structure, knowing that it is probably built with these features, and seeing fire blowing out of a basement window and deciding whether or not to committ forces for a quick attack/rescue, or just leave them out and drown it. Anyone who has knowledge on these things would be a big help....
Windows vs. Wood I-Joists
I've seen many fire tests through my job regarding the pro's and con's of windows and wooden I-joist when subject to fire. Trying to make a comparision is difficult I best, but I'll give it my best.
Energy efficient windows are designed to stop leakage of the interior conditions to the exterior. This is peformed by stopping the convection of heat through the window. This works both ways (in --> out, out --> in). By the composite (multi-layering) of the window, it takes a greater amount of heat (both intensity and duration) for the exterior window to fail. To that end, the amount of heat contained in the fire compartment (in your case, a walk-out basement) is increased which adds to the second problem....
Wood I-joist is a composite of wood pieces and an adhesive. The industry found out that, since the strength of a dimensional wood member distributes (cross-section) its load in an I pattern (top, bottom, center strip), it is more economical to develop wood members in a simular shape. However, the 'up and down piece' (web) is normaly constructed of OSB-board or so other composite, using wood pieces mixed with glue and pressed together. The problem? The heat of the fire banking at the ceiling with the I-joists coupled with the increased time of an unventilated fire has been tested to show a failure from 20% - 50% compared to dimensional lumber (such as 2 x 10's). At least you have some gyp board to protect a little bit, which is not the case in almost all unfinished basements utilizing this construction.
Conclusion: Window failure should not be used as an indicator to determine the stuctural stability of floor systems! The windows will make it all the way to flashover or until you open the door. Side note: Folks in Hurricane areas that have updated building codes can multiply the issue more with multi-layered window construction.