20 May 2009

Glazing in Fire Doors

Wired glass is traditionally used in fire doors, not because it survives the fire tests, but because until recently, there has been no viable alternatives that do survive the tests.

Now, however, we have options. Therefore, current codes have eliminated the use of wired glass in most cases. Unfortunately, it’s not immediately obvious when reading the code how severely its use has been restricted.

IBC 715.4.6.1 and 715.5.3 clearly permit wired glazing in doors as long as it meets the size limitations, at least from a fire point of view.

Now let’s turn to chapter 24 to consider impact resistance. According to 2406.3.1, if the glass opening is larger in 3 inches, the glass needs to be safety glazing [2406.3.1]. Since most wired glass does not comply with CPSC 16 CFR 1201, it cannot be used in doors that use the maximum openings allowed in chapter 7.

The options available to us are (in approximate ascending cost):
  1. Safety-Rated Wired glass such as SuperLite I-W and Film-Faced Ceramic glazing such as FireLite NT have a film on one face of the wired or ceramic glazing material to provide safety characteristics, but are susceptible to scratching.
  2. Laminated Ceramic such as FireLite Plus has the safty film laminated between two layers of ceramic glazing material.
  3. Laminated glass with intumescent interlayers such as PyroStop has intumescing safety interlayers between two or more sheets of anealed glass.
  4. Gel-filled, dual glazed units such as SuperLite II are similar in construction to an insulating unit, but filled with an intumescing gel rather than air.

Note that gel-filled units also provides temperature rise control, and can be used to create unlimited-area, transparent, fire-rated walls. (Other glazing assemblies are limited to a maximum of 25 percent of the wall area.)

No comments:

Post a Comment