A blueprint for quality sleep center architecture.
Sleep centers focus on one of the most critical health problems of the current age; this is the failure of a significant portion of the population to get adequate, high-quality sleep. This can have a profound impact on general health, safety, and well-being. The proliferation of centers in both medical and office settings has clearly shown the growth and importance of sleep studies and sleep management.
Unfortunately, patients who participate in sleep studies often report that they could not sleep during the study like they do at home due to activity level, noise, thermal comfort problems, ergonomics of the beds, indoor air quality, lack of windows and views, etc. Somehow, for many patients, the sleep center accommodations don’t seem to satisfy the same requirements as the bedroom, or even a hotel room, which often provides a perfectly adequate sleep experience.
OCCUPANCY QUALITY IN ARCHITECTURE
The architects and designers of sleep centers are quite familiar with the typical layout of a sleep center, and they can usually design a center that meets the physical requirements quite well.
But these same firms have had little training or education in perceptual comfort in architecture, one half of the design equation. Perceptual comfort is formally called the science of building performance, and it includes comfort science related to daylighting, lighting, acoustics, thermal comfort, and indoor air quality. Numerical standards can be applied to all these disciplines, specified on a project, and measured prior to final occupancy.
Perceptual preference is the other half of the design equation, and it describes what kind of an environment might be most satisfying for the occupant (patient). The process of applying these two aspects of research-based design scientifically is now being called “evidence-based design” or EBD, and is practiced by few design professionals, as it is not comprehensively included in their education in architectural or design schools. These two aspects of design, building performance and occupancy research, establish “occupancy quality,” the real goal that most architecture should embody.
BUILDING PERFORMANCE AND THE SLEEP CENTER
As we look at the sleep center performance, there are a number of issues that need to be the focus of good design practice:
Acoustics: Before the site of the sleep center is selected, potential sites should be evaluated for environmental background noise. It is far less expensive to select a quiet site than to remediate a noisy one. Most hospitals and most office buildings have significant interior and exterior environmental noise and are not suitable without remediation.
The patient room should provide the same type of noise environment as the typical home. This means that the HVAC (heating, ventilation, and air conditioning) systems should have a noise criteria (NC) value no greater than that of the home bedroom. The reverberation time should be similar to that of the home bedroom, being no greater than .25 second. And impact noise from walking should be mitigated via floor coverings.
The walls making up the patient room should have a high STC (Sound Transmission Class) to ensure control of adjacent noise, and the floor-ceiling assembly should be high performance enough to control noise above and below the patient rooms. The entry door should be an STC-rated sound door assembly, installed and tested for sound transmission. Windows in the patient room should be sound-rated to deal with outside noise and to reduce it to the room’s NC value.
The adjacent corridor, if present, should be low in reverberation time to control the transfer of noise. All sources of noise in the corridor or rooms along the corridor should be silenced to the level of the NC value selected. All systems within the room should have noise characteristics below the NC value of the room; they should not include impulsive noise or pure tones. The patient should not be able to detect their presence. Patient devices, such as television, sound masking, or fans, should be technically planned for nondisturbance.
Daylighting: Windows should be placed in patient rooms, with a view that is typical of residential views, wherever possible. Window controls (shades, blinds) should be in place to control any light coming in through these windows. The visual reflectance values in the room should be typical of those in the home, and specular (glossy) finishes should be avoided, as they often support glare. Exterior daylight controls (light shelves, louvers, etc) can be helpful in buffering the outside brightness. There should be no view of commercial outdoor illumination through the windows, other than that typical in a residential area. Ideally, windows should be operable.
EVIDENCE-BASED DESIGN AND THE SLEEP CENTER
A project for a sleep center would have all these elements:
- A baseline preoccupancy study of the space and the users to measure both spatial performance and user response.
- A set of sleep center building performance standards that must be met in the design process.
- A set of design processes for each building performance discipline to assist the design team in meeting these requirements.
- A set of quantitative subjective design juries to measure the preverbal response of the user to new design options.
- Completion and commissioning of the center, including remediation of any performance failures.
- A postoccupancy study of the space and the users to measure spatial performance and user response.
Lighting: Lighting in the patient room and corridors should be residential in character, with no in-ceiling commercial fluorescent lighting used, and with all patient room lighting meeting a strict glare criterion for the most sensitive patient. Lighting control should be reachable from the bed for dimming or shutoff. To meet the glare criterion, no light sources should be exposed, and all major surfaces should have reflectance and gloss values near residential values. The corridor lighting should also be noninstitutional lighting, which mainly provides low-level wall and floor illumination, and the reflectance values should be similar to those of the patient room.
Low level lighting should be available for use by staff during the night, and any video recording should be by means of infrared or low light cameras that do not require lighting in the patient room during sleep.
Thermal Comfort: The comfort of the patient is very important, and thermal comfort criteria should be in place in lieu of temperature criteria. It is important to understand that most thermal comfort complaints derive from problems with air velocity or radiant asymmetry (radiant balance between surfaces of different thermal values), such as the floor and ceiling. It is also important to note that clothing type and activity levels need to be accommodated in thermal control. The patient, in sleep clothing, will require an entirely different control of HVAC from the working staff, and the patient criterion must be the overriding one. Control of thermal comfort should be available from the bed, and a fan (which meets the noise standards) in the room is often a reasonable part of the thermal comfort control.
Indoor Air Quality: Since the comfort of the patient is very important, indoor air quality (IAQ) must be well controlled. This can be accomplished by reasonable IAQ standards, by adequate fresh air (ideally, operable windows), and by an exterior environment that does not measure any significant air pollution. To ensure that this requirement is met, low VOC (volatile organic compound) paints, finishes, and furniture should be used, as in sustainable projects.
OCCUPANCY PREFEReNCE AND THE SLEEP CENTER
As we look at sleep center performance, there are a number of issues that need to be the focus of good occupancy quality practice. This process must begin at the schematic phase of the design of the center.
This is normally accomplished by first doing an inventory of considered visual design solutions that rules out solutions that do not meet the metaphor of a home bedroom or other sleep-friendly site.
As the firm begins the informal design of the room, a series of options should be developed, all of which meet the needs of the client’s program. These options should be applied to a visual computer model, and a series of room finishes and textures should be overlaid to the model, so there are at least five room design plans and at least 10 finish and color palette plans.
These options and images should then be applied to a visual POP (Perceptual Occupant Programming) jury. In this jury process:
- Designs are prepared;
- Color and finish schedules are prepared;
- Models are constructed with these options;
- These models are content-mapped (a matrix is developed of what is in the image);
- A set of semantics is selected for ranking these images, using semantics such as “relaxing,” “comfortable,” “low stress,” “restful”; and
- Subjects of the appropriate demographic are selected and tested to find their preverbal feelings and associations, as they view the images.
These data are then analyzed in order to understand which of the design options best meet the preverbal metaphors for satisfaction by the patients.
In order for sleep centers to be successful in engaging the subjects of sleep studies, they must be comfortable and preferred spaces. While comfort and preference are the intent of the design team, few designers have formal tools to deal with these issues. And they don’t realize that occupants cannot self-report on their preferences, as these preferences are preverbal or unconscious. In order to have comfort and preference, evidence-based design (scientific design) must be employed. The upside of this effort will produce a generation of sleep centers that produce predictably more positive responses, because the design of the facilities was as rigorous as the diagnostic sleep studies themselves.
Steven J. Orfield is the president of Orfield Laboratories of Minneapolis, the nation’s first multidisciplinary perceptual consulting lab, certified by NIST (National Institute for Standards and Technology) for acoustic testing. In 2008, OL founded a collaborative architectural research organization, the Architectural Research Consortium, which was developed as a vehicle to bring evidence-based design to architectural firms in support of their efforts to design buildings with better occupancy quality. The author can be reached at firstname.lastname@example.org.