There’s some discussion within the industry as to whether or not safing is required in glazed curtain walls. Some of this is based on the belief that a building with sprinklers will contain and limit a fire’s spread. Like most code issues, this one’s a little misleading: sprinklers are meant to suppress a fire, not necessarily put it out, and give occupants a chance to vacate the building. Installing safing does much the same thing. It’s meant to help limit the spread of fire, as well as smoke. And smoke more often kills people before the fire reaches them.
Within this discussion, it’s imperative to check and understand the code and local requirements that come into play. The insulation may be required for thermal performance, but skipping the safing is more of a life-safety issue. If the local code officials don’t know, the fire department inspection people may have some good ideas. And look up members of the Firestop Contractors International Association (FCIA), who live with these issues on a regular basis.
Safing and smoke seal is meant to prevent smoke and fire from going around the floor slab to floors not yet involved in fire. Generally 4” thick, it must be placed into the opening in the same orientation throughout the installation. Different manufacturers will vary with this, but most will require a ½” (nominal) more than the opening dimension to assure a friction fit into the back of the wall-to-slab edge gap.
Support of the safing insulation by some means is needed so it doesn’t fall through. Impaling pins placed a maximum 24” OC in the safing is a must. If the nominal gap is larger than 4”, formed pans of 20-gauge galvanized steel anchored to the slab edge should be required to keep the insulation falling through on wide gaps.
Lastly, applying a smoke seal to the top of the safing is now required by code in many jurisdictions. It is applied at least 1” up on the back of the insulation, and 1” onto the floor.
Underwriters Laboratories and other testing agencies have begun rating and testing whole wall assemblies, including curtain walls, insulation and safing installations. Included in the testing are the miscellaneous taping, supporting clips, and retention devices referenced above. It is truly a “whole assembly” test scenario. Most of the manufacturers have their typical curtain wall insulation/safing installations in the databases; their reps can help you find these should the need arise.
This link will give you the UL rating page, and you can type in either the insulation or wall system manufacturer, then look for a UL 263 rated wall system. Type in “curtain wall” in keyword, and it helps to type in all the info you have: insulation product name or manufacturer. Then browse through the search results to find insulation details similar to what you might propose for a given project. UL can either test a new configuration, or perform an “engineering judgment” to determine if a proposed design is similar in major aspects to an already tested construction, which may alleviate the need for additional or new testing.
The insulation manufacturers and FCIA are also looking at ways to contain fire from “leap frogging” floors around the curtain wall and floor systems. In an unprotected curtain wall, a fire that starts on one floor can break through the exterior wall in vision glass areas, and the flames could damage the glass on the next floor up, thereby “leap frogging” around the floor perimeter and giving the fire an opportunity to spread to the next floors above.
As with most products, the insulation manufacturers are a great resource. It’s one more part of the trade to master, and to have a passing knowledge about. Because if it’s not part of your scope, you’ll have to coordinate it with the trades that will furnish and install it.