The Hennepin Healthcare Clinic and Specialty Center (CSC) in Minneapolis is making an impression with its aesthetic use of natural lighting, wayfinding, convenience, and life/safety photoluminenscent (PL) egress path markings.
Designed by BWBR, CSC is a six-story glass façade with a 58-m2 (190-ft) glass and steel skyway. The 30,379-m2 (327,000-sf) facility is expected to receive Leadership in Energy and Environmental Design (LEED) Gold certification.
The project’s general contractor (GC) installed 914 m (3000 ft) of linear cast-in nosings to protect the stairwells’ concrete stair edges from damage, help prevent slippage via a built-in abrasive tread surface, and provide PL illumination with embedded aluminum strips permanently coated with a rechargeable phosphorescent chemical.
According to Pete Haag, AIA, LEED AP, CDT, a senior job captain at BWBR, PL previously was not code-mandated and used only voluntarily in a handful of building projects. The CSC is one of the first PL specification compliances under the 2015 Minnesota Building Code (MBC) Section 1024–Chapter 10, Means of Egress, which was adopted from the Washington, D.C.-based International Code Council’s (ICC’s) 2012 International Building Code (IBC).
How rechargeable PL works
The stair nosings’ PL strips are energized continually by light-emitting diode (LED) fixtures and natural light from a wall of glass windows spanning the entire height of the stairwells. According to MBC, the PL is required to glow for a minimum of 90 minutes when energized by 60-minutes of exposure from a minimum 11-lux (1-footcandle [FC]) light source as per Underwriters Laboratories (UL) 1994, Standard for Luminosity Egress Path Marking Systems, or ASTM E2072, Standard Specification for Photolumination (Phosphorescent) Safety Markings. In the event that power and emergency lighting fails, the stair nosings’ PL strips, combined with PL demarcation tape applied to all steel railings, handrails, stair landings, and exit doors outlines will expedite safe occupant egress.
The stairwells have drywall and other aesthetic interior finishing features, such as color coding each floor for easy wayfinding.
Other life/safety architectural designs
There is a 25-mm (1-in.) expansion joint between the free-floating second-story skyway and the buildings it connects to. The floor-to-floor mechanism expands/contracts from 50 to 100 percent and is protected with an aesthetic 76-mm (3-in.) stainless steel linear cover offering a seamless, solid walkway between the structures’ joint. Expansion joint assemblies are also employed in the skyway/building joint’s ceiling and walls with a stainless steel cover matching the doorway finish. The joint also includes two-hour-rated firestop consisting of 63.5-mm (2 1/2-in.) expansion foam with an internal intumescent layer that swells in the presence of extreme heat to prevent fire, smoke, and toxic gas infiltration through the joint.