by Lisa May
Whether replacing a dated, inefficient hospital or renovating an historic mental health institution, window selection is an important consideration in creating a modern, healing environment.
Behavioral healthcare facilities must minimize risks to patient safety, while maintaining a therapeutic environment. Windows provide daylighting and views to outside, helping create a more homelike and caring atmosphere for patients, while also contributing to staff health and well-being.
The American Institute of Architects’ (AIA’s) 2006 Guidelines for Design and Construction of Healthcare Facilities notes:
The built environment, no matter how well-constructed, cannot be relied on as an absolute preventive measure. Staff awareness of their environment, and the behavior risks and needs of the patients served in the environment are absolute necessities[.]
To ensure safety, behavioral healthcare facilities must meet comprehensive accreditation standards. A facility’s risk assessment depends on the patient population being served. Patient supervision and policies governing staff intercession, as well as control of patient access to various types of objects, are often site-specific variables. Risk also varies for areas within the building—seclusion rooms, bedrooms, and comfort spaces usually warrant consideration as higher-risk areas.
Selecting windows in patient-accessible areas calls for careful consideration. For behavioral healthcare applications, window products’ evaluation may include resistance to, or restriction of:
- escape attempts;
- patient access to unauthorized areas;
- attack to window components using blunt or sharp objects;
- tampering with, or disabling, locking devices;
- glazing infill exposure to flame or heat;
- chemical or bodily fluid resistance;
- laceration or self-harm by cutting;
- pica behavior (i.e. ingestion of components, materials, or coatings);
- abrasion, prying, or cutting of frame materials, glazing, or hardware;
- weaponization of parts that could be removed from window assemblies; and
- ligature, either intentional or accidental.
Due to site-specific variables, an adequate assessment can only be made through early consultation with the facilities management staff, security personnel, and treatment professionals.
Human impact testing
If a patient runs into the window, or if he or she strikes or throws an object against it, energy must be transferred sequentially through hardware, window frames, anchorage, and substrates. A human impact may impart as much as 2.7 kJ (2000 lb) of energy, based on the shoulder impact of a 90.7-kg (200-lb) person moving at 7.62 m (25 ft) per second.
This can require 12.7-mm (1⁄2-in.) thick polycarbonate or 11-mm (7⁄16-in.) tempered laminated glass for interior glazing. Standard windows fitted with safety glass or polycarbonate are seldom considered sufficient because interior glazing infill deflects on impact and may disengage from the standard window’s frame.
For a body hitting the window system, impact energy (W) can be calculated as:
W = ½ mv2
v = velocity at impact; and
m = mass of impact object
Using potential energy to calculate the energy imparted by a pendulum drop test, it can be calculated as:
W = wh
w = weight of impact object; and
h = vertical height the weight drops (not pendulum length).
When using either of these calculation methods, air resistance is considered negligible and units must be kept consistent.
The need to validate the human impact aspect of the total window system’s security in the laboratory led to American Architectural Manufacturers Association (AAMA) 501.8, Standard Test Method for Determination of Resistance to Human Impact of Window Systems Intended for Use in Psychiatric Applications. It involves using a weighted impact device to apply a force simulating a patient running full-speed into a window. The test window complies when the window frame, glazing, hardware, and locking devices do not ‘fail,’ as defined by the performance requirements therein:
9.1. At the conclusion of testing the window system shall be deemed to pass the test if the following conditions are met:
The impact test load has not breeched or penetrated through the innermost glazing layer.
The innermost glazing remains held in place within the perimeter of the window frame.
Partial disengagement is allowed if meeting the requirements below:
- There is no damage to locking devices which would allow the window system to be opened in a manner not intended by the manufacturer.
- The window system does not disengage from any anchors securing the system within the opening.
- The window anchorage does not disengage from the substrate into which it was anchored during testing.
- The window hinges do not disengage to allow access to the exterior of the window system.
- No pieces may fall off the interior of the window such that they are accessible to the occupant(s).
- Frame joinery may be damaged, but must remain intact.
- No openings outside of the interior glazing infill greater than 5.0 cm (2 in.) diameter sphere created which would allow egress or the passage of large objects, or allow access to the between-glass space.
- No de-lamination or separation of material greater than 322 mm2 (0.5 si) from the interior surface, immediately following the impact.
In certain occupancies, no delamination or discharge of material from the interior surface may be allowed. When this is deemed necessary, the specifier should so note in bid and contract documentation.