Sun Control: Daylighting and Efficiency

High-performance window systems are considered by many to be an essential to today’s health care facilities. Multiple studies show that patient recovery, occupant morale and staff productivity are positively influenced by improved ventilation, indoor air quality and daylighting.
In addition, window systems can improve energy-savings and safety, reduce maintenance needs and extend the lifecycle of buildings and materials.
Hospitals are the second largest energy consumer among U.S. buildings, according to the architectural research group at San Francisco-based Anshen+Allen, collaborators on the Green Project Lab, a prototype featured at several national healthcare conferences.
Reviewing and summarizing more than 4,000 reports and surveys, the firm also learned that:
• Patients with views and access to nature recover more quickly, experience less pain and require fewer medications than patients with no view to nature.
• 80 percent of respondents felt that environmentally friendly building materials, energy-conserving light fixtures and increased daylighting are priorities for facilities planning and operations.
• 90 percent of respondents believe the patient benefits from being able to control their environment including lighting, television and privacy windows.
To helping achieve these benefits, window system components should be part of an integrated design. This design approach not only means working with the owner, occupants, facility manager and architect; but also includes working with the lighting engineer, mechanical engineer and HVAC contractor, landscape architect and interior designer.
As part of these early discussions, specialty contractors and window system manufacturers can provide recommendations to accommodate the project’s unique requirements for successful solar management and natural daylighting. Glass, framing, thermal barriers and shading devices are essential considerations in high-performance window systems that help control the solar spectrum.
Glass Options
The solar spectrum consists of ultraviolet light, visible light, and infrared. UV is invisible to the human eye and long-term exposure damages materials, such as sensitive medical collections. UV also deteriorates plastic, a staple in healthcare facilities, and fades furniture, fixtures and artwork. Visible light also can contribute to fading. Like UV, infrared is invisible to the human eye and has a penetrating heat effect.
Typically, solar reflective glass coatings dramatically reduce unwanted heat gain by reflecting and absorbing high amounts of infrared and visible light. Spectrally selective glass coatings allow color flexibility in reflection and transmission, while blocking a large portion of the solar spectrum.
Unlike static glass, electrochromic glass coatings electronically tint to provide dynamic solar control. The Green Patient Lab, version 3.0, uses a high-performance window system with EC glass to demonstrate solar and daylighting control. Strategically positioned within the rooms schematic, the glass reduces glare on the television, while preserving the view to the outdoors.
Healthcare facilities also can strategically optimize glass selection by elevation, using clear substrates and coatings on north-facing façades, and darker glass on south, east and especially west façades. Similarly, darker glass should be considered for large view windows and the use of clearer glass for transom lites. Unless a downward view is important, vision glass below sill height usually can be eliminated, to reduce solar gain that carries no useful daylight.
Pragmatically, floor plan layout should locate rooms with little use for natural daylight, such as washrooms, server rooms, etc., in non-perimeter areas. Activities within a daylit room should be oriented to minimize glare issues, such as facing medical equipment and computer monitors at right angles with incoming sun.
Exterior sunshades intercept unwanted solar heat gain before it can impact a building’s HVAC system load. They also can make a powerful, aesthetic statement in a building’s design, as well as in its performance.
The University of Colorado’s new Health Sciences Center research complex emphasized ventilation, lab engineering, building operations and maintenance, and energy conservation in its designs.
To assist in accomplishing these goals, the sunshades are engineered as an integral component of the high-performance window and curtainwall systems. These systems incorporate polyamide nylon thermal barriers and nine different glass types in various silk screens and colors. The window spans drench the facility’s interior with natural light, while managing solar heat gain and remaining condensation-free at sub-zero temperatures. The extruded aluminum sun shades on south-facing exposures further enhance performance, while ornamental exterior trim covers add visual interest.
Architects are exercising their creativity with sunshades with blades, tubes, catwalk grids, solid panels and louvers. Louvered sunshades can add diffusion to direct natural daylight for south, east and west facades. At the same time, exterior shelves are limited in their daylight re-directing effectiveness for the diffuse sun of overcast conditions.
Remember, exterior shelves or shades act as solar shading only for high sun angles. For high latitudes or east/west facing facades, cut-off angles can be very low for occupied hours. Below this cut-off angle, supplemental interior shading must be employed to reduce glare from direct beam sun.
Interior Shading
Window blinds also act as effective solar shading, especially when coupled with exterior brise soleil sunshades. Between-glass blinds offer excellent thermal performance, as well as privacy and light control.
While reducing overall daylight transmission, between-glass blinds significantly improve daylight distribution through the space. Blind slats can be inverted to direct light upwards, if unconventional aesthetics and light leakage in the closed position are acceptable.
Specified as an integral unit, windows with between-glass blinds contribute to safety and sanitation by minimizing the potential dangers of exposed cords and slats, and reducing the need for cleaning and maintenance.
Large, arched windows with between-glass blinds were chosen for The Villages Regional Hospital in central Florida. Located in a popular retirement community, the hospital’s patient-friendly atmosphere and stylish design encourages many to equate the facility to that of a hotel. Patients and staff both enjoy the plentiful, natural light. In patient rooms, the between-glass blinds allow individual control of sunlight and views. This sense of control can be an important factor in a patient’s healing process.
Patients in brightly lit rooms have a shorter length of stay, according to the Center for Health Design. The Center’s research also shows patients experienced less perceived stress and pain medication costs were reduced by 20 percent when patients were exposed to increased intensity of sunlight.
Green Goals and Guide
A complete daylighting system shades from direct sunlight, minimizes glare and heat gain, and redirects visible light for deeper illumination. Lighting accounts for 40 percent of the energy used in a typical commercial building.
When properly executed, daylighting can reduce HVAC peak loads with corresponding reductions in mechanical equipment capacity and carbon footprint.
In April 2009, the U.S. Department of Energy launched the Hospital Energy Alliance to reduce energy consumption and greenhouse gas emissions. Furthermore, the new 2010 ASHRAE 90.1 Energy Standard will require a 20 percent to 30 percent increase in energy savings above the current standard.
Healthcare facilities look to green building guidelines for potential energy savings and improved safety and health. The most successful facilities accomplish their green design goals using a whole building approach, taking into account building envelope, site, orientation, HVAC and lighting systems. The Green Guide for Health Care addresses all of these aspects and was the foundation for the U.S. Green Building Council’s LEED for Healthcare.
Currently a pilot program, LEED for Healthcare awards a maximum of four points for views and daylight. Separate requirements are given for diagnostic and treatment areas versus in-patient units. In general, these requirements are consistent with those for LEED for New Construction and Major Renovations’ Indoor Environmental Quality category.
Checklist for Success
Solar control and daylighting systems are best-suited for healthcare facilities under these conditions:
• The building team members are brought together early for an integrated design.
• The facility will be constructed on an unobstructed site in mid-latitudes with a clear climate.
• Whole-building energy modeling is planned.
• The design features expansive north- and south-facing façades.
• Atria, courtyards, light wells or high ceilings will be incorporated.
• Dimmable artificial lighting controls are available for critical spaces.
• Task area illumination will be provided.
• Blinds, drapes or shades can be used for glare control.

Lisa May is Healthcare market manager at Wausau Window and Wall Systems. Reacher her at

Wausau Window and Wall Systems

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