Which Existing Openings Need Protection and Why?
With a substantial amount of < a href="https://kraemerdesidev.wpenginepowered.com/work/">KDG’s portfolio consisting of work in existing historic buildings, we come across conditions where it is sometimes difficult to understand what is required by code and how to best achieve the requirements in a building that was constructed before the current code existed.

The Michigan Rehabilitation Code for Existing Buildings is great for bridging the gap, but there are still some situations that it does not address, leaving gray areas and room for interpretation. This is another reason why it is so important that we keep an open dialogue with our local plan reviewers and inspectors, to work through the various interpretations to arrive at the best approach for each issue.
 

• Fire Separation Distance – If the building is in close proximity to another building, the exterior wall may be required to be fire rated, depending on the distance between the buildings. If the exterior wall is required to be fire rated, only a certain percentage of protected or unprotected openings in the wall are allowable. Especially with alley facades, we often end up with a fire rated exterior wall with a percentage of openings that exceeds the code allowance. Some buildings also have an exterior wall on a lot line with a neighboring building right up against it. Current code does not allow openings on lot lines regardless of height. However, a taller existing building may have window openings on the side walls that overlook the roof of the neighboring building.
   
• Pedestrian Bridges – It is often desired to connect an existing building across an alley to a parking garage or nearby building. Where a pedestrian bridge connects two buildings, the exterior walls of the buildings at both ends are required to have a 2-hour fire rating in the area within ten feet of the bridge enclosure. Openings are allowed within this boundary, but they need to have a rated opening protective.

Water Curtains and Window Sprinklers – What are the rules?
Fortunately, there is an exception in the building code that allows for an opening protective to be provided via a “water curtain approved for that use.” Other than requiring that they be approved, the requirements for a water curtain at a window are not described in the building code, so it is understandable that architects may not be clear on what the requirements are.

While the exception is vague, it allows the best of both worlds: the opening(s) can remain and still be protected against fire. There is usually a fire suppression system being installed anyway, so the water curtains can be installed by the fire suppression contractor without the added cost of bringing an additional trade on site. In the past, we have noted the windows that require water curtains on the drawings, and the fire suppression contractor was responsible for installing an acceptable system.

Recently, the local inspectors have become more educated on the requirements for window sprinklers, likely because of the inconsistencies they were seeing in what was being installed. Tested solutions meeting the requirements include not only special sprinkler heads installed by the fire suppression contractor, but also require that the window itself meets specific glass and frame criteria.

It is essential that the architect communicate these window requirements in the drawings and specifications, because it is too late by the time the fire suppression system is getting designed, or worse, during inspections toward the end of the project.

UL tests and engineering judgements dating back as far as 1995 have evaluated the performance of window sprinklers as an alternate opening protective. The general criteria states that the glass, whether a single pane or the individual panes making up an insulating glass unit, needs to be ¼” glass that is tempered.

Window frames must be non-combustible, non-operable and have rubber gasket seals. Horizontal mullions are not allowed. The sprinkler heads themselves are specially-designed for this purpose, and must be exposed, never concealed. They must be positioned within a certain distance from the glass and a certain distance from the top of the window. No window treatments should be located between the glass and the sprinkler head. The requirements specific to the type of sprinkler head should be listed in the product data submittal from the fire suppression contractor.

We have witnessed a lot of window types and sprinkler heads that do not comply with these requirements, and inspectors have rightfully started to challenge projects that are currently under construction. We as architects need to do better to make sure this scope is captured in the drawings and specifications, and keep an eye out to see that the appropriate type of system is indicated in the submittals, and subsequently installed.