II. HORIZONTAL DAYLIGHT

II. HORIZONTAL DAYLIGHT

What with daylight’s countless benefits towards physical and mental health, architectural designs for healthcare should adjust accordingly. Namely, buildings should implement systems that maximize and prolong daylight exposure. Bear in mind, strategic design choices go beyond glazing material; on top of that, factors such as shading, glazing area, and aperture placement and distribution bear as much importance. Architects also must make sure to control and prevent lighting flaws including glare, uneven illumination, underexposure, and overexposure to avoid disturbing occupants.

Even with all of these constraints, however, there is no singular or straight-forward method or solution to addressing natural lighting. Taking all of these elements into account, developing windows and apertures for daylighting and views is a complex process. This even goes without addressing more foreign elements such as the dynamic nature of the sun’s orbit or the building’s orientation, making the craft that much more uncertain. Rather, the following types and considerations of vertical glazing should contribute to the thought process behind designing buildings for optimal lighting and views. The result would be a more healthful, invigorating, and satisfying environment.

GLAZING AREA

A case study for the Banner Bank Building in Boise, Indiana (Left Diagrams) tested the effects of window-to-wall ratios on interior illumination (Meek, 67-69). The research unveiled a clear disparity between how much narrow glazing apertures admitted daylight compared to wider ones. Thin slivers of glazing, such as those sprawling across the Jewish Museum in Berlin, courtesy of Daniel Libeskind, only allow minimal sunlight (Top Right). Meanwhile, larger glazing, such as in the Academy of Fine Arts in Nuremberg (Germany) covers significantly more floor area with daylight (Bottom Right). Evidence shows that the larger the glazing area, the more exposure to daylight and outdoor views.

With curtain or window-wall systems, glazing occupies an entire given surface. This makes for the largest possible daylighting aperture for maximized illumination. The result, however, is not necessarily the best possible option, since such widespread devices lack fenestration control or inherent shading to prevent any visual or thermal discomfort (IES Daylighting Committee, 29). Overall, although widespread glazing gives the most outdoor views and light, designers should tread carefully, as such openings can overwhelm and act counterproductively towards occupants needing a relaxing and comfortable space.

WINDOW HEIGHTS

Installing windows at a tall height is a viable method of optimizing daylighting; the higher the ceiling and window height are, the deeper daylight will penetrate a given space (IES Daylighting Committee, 28). In fact, a common rule of thumb for architects is the following: Daylight penetration into a space equals 1.5 times the height of a given window (Lechner, 419). With this equation in mind, windows far above the floor will draw an especially high amount of sunlight into interior spaces. This method is different from installing clerestories, in that horizontal windows can still provide a clear outdoor view to provide additional psychological aid.

Examples include the Sant'Ignazio Church in Rome (Top Right), and the Gare de Lyon Railway Station (Saint-Exupery) near Lyon, France (Bottom Row).

One potential issue, however, is that the extended glazing heights and views may cause occupants to feel phobic. On top of that, from a design perspective, architects would need to design taller spaces to maximize window heights (Lechner, 416). Considering these benefits and downsides, there should exist a balance in which increasing horizontal window heights can optimize daylighting without becoming overwhelming for occupants and cumbersome for designers.

SLOPED GLAZING

The benefits of sloped or angled glazing depend on the direction of tilt. Sloping towards the sky provides high illumination, ideal for spaces such as greenhouses and passive solar designs (Illuminating Engineering Society, 30). One example is the Musée des Confluences in Lyon, France, a building with large sections of upwards glazing, exposing occupants to a significant amount of sunlight (Top Row). Despite these advantages, upwards glazing facing southwards is not desirable, since it can lead to major heating and thermal issues during the summer (Lechner, 181). Overall, glazing sloping upwards is a potent means of introducing daylight to occupants, albeit a risky one.

Meanwhile, designers occasionally build glazing sloping towards the ground in order to provide shading without needing an overhang, since the angle of incidence between the glass and direct solar radiation decreases and creates an inherent shading (IES Daylighting Committee, 30-31). The railway station in Lucerne (Switzerland) demonstrates this, with a concrete overhang and structural skeleton only assisting with shading outdoor views (Bottom Row). Although not that common in architecture, downward-sloping glazing can prove useful for providing occupants with sunlight and comfortable outdoor sights.

LOUVERS

Louvers are blind-like devices that provide shading and control the amount of direct daylight entering a given space. Designers can install them outside or inside of the building’s envelope to block solar radiation before or after passing through the glazing itself (IES Daylighting Committee, 54). Light-colored louvers are especially useful for blocking direct sunlight and glare while allowing diffuse light to illuminate interior spaces (Lechner, 417). The Haus de Architektur (House of Architecture) in Munich is one example in which wooden louvers clad one of its buildings for visual and shading purposes (Top Row).

Horizontal louvers especially benefit east and west-facing walls, as those areas receive the most solar exposure during the summer (Lechner, 419). Meanwhile, vertical louvers, such as those on the Fondazione Prado in Milano, Italy (Bottom Row), are especially useful for shading northern facades (Lechner, 420).

Not only do louvers provide a tool for aesthetic appeal, but they also protect inhabitants against glare and overexposure without compromising daylight entry, although outdoor views may not be as prominent. Factors such as louver thickness, material, and distribution across a building’s facade can vary, making for an advantageous device for daylighting spaces.

ROOM DEPTH

Daylight designs sometimes go beyond glazing or shading; rather, it can involve the room itself. Factors such as the surface area and height of glazing affect the amount of sunlight penetration in a given space, and the aforementioned space’s shape and volume follow suit. In this case, the distance between the glazing and the opposite wall determines how much the daylight covers the room’s floor area; the shorter the distance, the higher the illumination.

One example is a thin corridor in the Tinguely Museum in Basel, Switzerland, courtesy of architect Mario Botta (Top Right). Meanwhile, the deeper a room is, the more difficult it is for sunlight to evenly penetrate it. For instance, an acoustic room in the Casa de Música, a performance building in Portugal by Rem Koolhaas, has notably less sunlight penetration than the previous museum’s corridor (Bottom Right).

Quantitative evidence takes the form of another case study (Left Diagrams) of the Banner Bank Building in Boise, Indiana. It revealed the following: a room with a short section depth (The distance between the window and the opposite wall) of 10’ received total floor illumination (Meek, 73). Meanwhile, a room with a larger depth of 50’ only received a meager 35% of illumination, proving inefficient (Meek, 75). The deeper the room is, the less floor area daylight touches.

SLOPED CEILINGS

Inclining the ceiling facilitates greater window heights, thus increasing the illuminated area without affecting floor-to-floor heights for multistory buildings (IES Daylighting Committee, 28). Because of the higher angle, designers can install glazing further from the floor or ground-level for daylight to better illuminate a given space (IES Daylighting Committee, 28). Much like with adjusting and decreasing room depth, tilting the ceiling of immediately creates more opportunities for daylight-friendly design.

Examples include the Chiesa della Autostrada, or the Church of St. John the Baptist, an ecclesiastical building next to an Italian highway (Top Right). The facade slopes downward towards the glazing with supports to allow more sunlight to penetrate the interior; it is also worth noting the shallow depth of the corridor, promoting even illumination. Another example, once again, is the Casa de Música in Porto, Portugal (Bottom). Helping this case is the pale color palette decorating the ceiling, allowing sunlight to reflect deep into the space much more easily.

Although the dynamicity of these angles may not make for a very meditative environment, inclining ceilings is still a useful technique for inviting more daylight into interior spaces.

LIGHT SHELVES

Light shelves are devices common in horizontal glazing design. They block direct sunlight and glare from outside and inside of the building, preventing the need to apply foreign interior shading devices that could obstruct daylight and views (IES Daylighting Committee, 30). In terms of illumination, reflections ounce off the top of the shelf, providing deeper light penetration for more hours of the year; this allows windows to remain without shades for longer periods of time (IES Daylighting Committee, 30).

Sometimes, designers can also shape custom shelves that optimize daylighting conditions by blocking the sun in the summer and absorbing it during the winter; as a result, they make for an efficient medium for providing views and regulating daylight simultaneously. The diagram above on the left is one such example, provided “Heating, Cooling, Lighting: Sustainable Design Methods for Architects” by Norbert Lechner (424).

Shelves go above eye-level to deliver their effects while preventing glare from atop its surface (Lechner, 419). More specifically, designers normally place them 7 feet above ground level, requiring rooms to be at least 9.5 feet tall (IES Daylighting Committee, 30). Alongside that, shelves and ceilings should consist of a reflective material and color to maximize the effects (Illuminating Engineering Society, 30). Part of this is because lighter-colored louvers allow some diffuse sunlight to enter the building (Lechner, 417).

Architects can also install a second shelf within the building’s interior side, increasing the amount of collected daylight and reflecting it deeper into a given room (Lechner 419). An internal shelf alone will not suffice, however, as this misses the opportunity to shade outdoor views and prevent potential glare. Instead, it is best to install shelves both inside and outside of the building’s envelope simultaneously for optimal results (Lechner, 420).

Despite the benefits, there is still a significant risk of glare. To counter this, the building’s design has to balance between shelves and electrical lighting, or yet another source of glare-free daylight (IES Daylighting Committee, 31). Also, as stated earlier, the room must be tall enough to provide shelving well above eye-level to avoid invasive glare creating visual discomfort. Designers would need to take further care in arranging their constructions accordingly, and rooms and spaces meant to have low heights may not fare well with shelves altogether. Aside from these issues, light shelves prove to be an effective way of maximizing interior lighting while shading outdoor views.

BIBLIOGRAPHY

IES Daylighting Committee. Recommended Practice for Daylighting Buildings. Illuminating Engineering Society of North America, 2013.

Lechner, Norbert. Heating, Cooling, Lighting: Sustainable Design Methods for Architects. 4th ed., Wiley, 2014.

Meek, Christopher, and Kevin Wymelenberg. Daylighting and Integrated Lighting Design. Routledge, 2015.

IMAGE CREDITS

“F-35 Academic Training Center.” U.S. Air Force Civil Engineer Center, United States Air Force, www.afcec.af.mil/News/Photos/igphoto/2001592228/.

Henderson, Julian. “Bronx Library Center, Second Floor Interior.” Wikipedia, Wikimedia Foundation Inc., 25 May 2012, en.wikipedia.org/wiki/File:Bronx_Library_Center_second_floor_interior.jpg.

Header photograph taken by Miguel Choi.

Sketches based on those in “Heating, Cooling, Lighting: Sustainable Design Methods for Architects” by Norbert Lechner and “Recommended Practice for Daylighting Buildings” by the IES Daylighting Committee.