• 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.

  • Can I impose and off-load something that really irks me? A suggestion to the airlines to lower their ticket prices instead of playing so many games. Please stop sending credit card applications from your frequent flyer programs. I must get at least one a week, if not more. If I wanted your (fill in the blank) card, I would have applied for it by now. That’s all any of us need. By not applying for (and accepting) another 30% interest rate, there’s a part of me that thinks it’s my patriotic duty NOT to get more into debt. Heaven forbid the US of A Government should take a similar approach. OK, I feel better… 

    A recent presentation to another trade organization brought home that there are other people out there with just as many smarts in their respective trades as we have in the glazing industry. What knowledge they have in relation to what they do day-in, day-day out, simply amazes. It’s one of the things that makes the construction biz so much fun, and getting to see it all come together in real projects is what continues to float this boat.   

    The group was the Firestop Contractors International Association (FCIA), whose members usually deal with sealing penetrations through either floors or walls to help contain fire. On occasion, they also deal with the curtain wall insulation and particularly the fire safing at the perimeter edge. And while it’s one of the bodies of knowledge we deal with least, some concepts keep coming back again and again. So, some basic insulation and fireproofing concepts seemed proper for this and the next blog.

    • Insulation or safing should NEVER be installed if it’s wet, nor should it be installed (or stored for that matter) where it can get wet. Installation should only occur when the building is mostly dried in, or in areas where insulation is installed that can be protected from the elements. If it’s installed wet, it will eventually need to be replaced, and it’s possible the interior finishes may be in the way when it’s discovered it was wet. Voice of experience:  Insulation was installed wet in the fall in a cold climate and then froze over the winter. When the weather turned warm in the spring, the “leak” was reported and found to be wet insulation.   
    • Coordination with adjacent trades is a must. The insulation and safing have to be installed prior to the interior trades, so getting with the general contractor and working this out is a must. 
    • How the HVAC consultant or engineer wants the wall to perform thermally will likely set the insulation’s thickness. More is better as it relates to R-values (but that’s already something you knew, right?). Now, if we can just get the NFRC folks to include this in their CMA (he said, editorializing a bit).   
    • The wall insulation should be cut to fit the nominal DLO, usually between frame members. Most insulation installations should be foil faced. Not because it performs better thermally, but so that humidity in the treated air doesn’t reach colder glass or metal framing surfaces, which could result in condensation. Because HVAC equipment is now putting more humidity in the air to cut down on energy requirements/size of the mechanical systems, humidity levels are rising as compared to just a few years ago. 
    • Wrapping the mullion in insulation in the spandrel area probably is a good idea from a condensation standpoint. Whether it serves the purpose of insulating the mullion isn’t as clear-cut, since the mullion spanning into the vision area probably short-circuits the thermal benefits. But keeping the mullion protected from possible sources of condensation in the spandrel helps reduce thermal transfer as well.  
    • And because it’s foil faced, the perimeter and any joints of the insulation need to be foil-taped to the perimeter. Joints and perimeters not taped negate any benefit from the foil facing in the first place. Single piece insulation for the openings is preferred (joints are ok, but carry their own problems). Mechanical retention is required; the insulation must stay where it’s designed to be placed.
    • If the horizontal member nearest the safing is more than 8” distant, then a backer bar needs to be added to the insulation inside the curtain wall to support the insulation and prevent it from bowing and widening the gap between insulation and slab edge when safing is installed. 

    Glass and metal frames require insulation to help with thermal performance. But it has to be installed correctly to perform as intended. In the next blog post, I’ll address issues with installing safing. In the meantime, I have a few credit card applications to throw out … or should I just mark them “Return to Sender” and send the Post Office further into the red?

USGlass Magazine

USGlass Magazine