III. VERTICAL DAYLIGHT

III. VERTICAL DAYLIGHT

Vertical windows are not the only effective means of daylighting; on the contrary, horizontal glazing seems to be becoming more prevalent in the modern world. Courtesy of advanced technology, glazing and apertures on ceilings and rooftops has more room for design possibilities; clerestory windows, atria, and skylights are among the most common examples.

A major advantage vertical glazing has over horizontal types is its higher levels of daylight penetration. Typically, the range of horizontal illumination is relatively sparse; the deeper the room in question is, the less light is able to reach into the space, necessitating electrical lights that much more. Vertical glazing resolves this, as it can cover any area within any given space, no matter its depth; this enables more even and present daylight in any type of room.

One immediate disadvantage, however, is that they generally lack outdoor views. Unlike their horizontal counterparts, they usually do not offer views with elements such as greenery, which studies have proven as beneficial for physical and mental welfare. For this reason, both glazing types often pair together in the same space in order to combine their benefits. Therefore, instead of shifting focus on outdoor views, building design should magnify the amount of daylighting that apertures can allow into a space.

CLERESTORIES

Clerestory windows are a common type of horizontal fenestration; in fact, they have been since early times in architectural history, helping define several archaic styles of building design over centuries. One example is the Pantheon of Ste. Genevieve in Paris; architect Jacques-Germain Soufflot designed multiple clerestories to admit daylight into a monumental structure (Top Row). The prominence of clerestories has not dwindled over the centuries, however, as they continue to illuminate interiors for more contemporary spaces, such as the Atocha Station in Madrid (Bottom Row).

Their utility attributes to illuminating spaces better than traditional vertical glazing. This is because their greater heights, on the wall or the roof, allow for deeper light penetration with a more even spread across the interior’s floor area. Along with that, clerestories also have the option of translucent glazing since they are outside of the occupants’ eye level and further from peripheral vision; meanwhile, translucent glazing creates disruptive glare for regular windows (Clear glazing is preferable in this case) (Lechner, 417). Lighter-colored roofs with high reflectance can boost their effects as well (Lechner, 414).

One issue, however, is that their light intensity and distribution remain somewhat uneven; for an example, even when clerestories span across all four exterior sides of a given space, the light’s presence and spread are not very sufficient, as shown in the diagram above to the left (Meek, 97). Sun paths are also a crucial factor in designing clerestories, since this type of glazing heavily relies on direction and orientation (IES Daylighting Committee, 38). Barring these potential obstacles, however, clerestory windows are a helpful means for sufficient daylighting.

Meanwhile, sawtooth glazing is a specific type of clerestory that slopes at an angle and gathers daylight from a single direction. The slopes not only help direct and reflect lighting into a given interior space, but they also keep one clerestory from blocking and shading the other (Lechner, 432).

For an example, when facing north, sawtooth glazing does provide sufficient lighting for a given interior space; unfortunately, however, it spreads light unevenly due to the windows’ directionality, as shown in the bottom left diagram above (Meek, 98). Therefore, calculating the sun’s angle of incidence is yet again crucial in their design. Generally, sawtooth glazing is an efficient alternative to regular clerestories, but perhaps would go well with other lighting types for more even daylight distribution. They, along with clerestories, are viable means of admitting daylight, although optimal results show alongside vertical glazing.

SKYLIGHTS

Skylights are a common means of vertical daylighting, as they admit much more daylight and distribute it along the space much more evenly than vertical glazing (Lechner, 413). Multiple skylights can illuminate a single space without limitation, resulting in more prevalent and consistent daylighting. Historic examples include the Labrouste Reading Room in the Labrouste Bibliotheque Nacionale (Top Right) and the main exhibition area of the Musée d’Orsay (Bottom Right), both of which reside in Paris.

In fact, having multiple skylights cover one space is preferable to a single larger one, since they distribute natural light across the room much more easily (Meek, 104-105). In other words, quantity often takes priority over size in terms of aperture design. The diagrams displayed above represent the general rule of thumb for distributing skylights across a given space for efficient and plentiful daylighting (IES Daylighting Committee, 38).

The effectiveness of skylight design depends on a multitude of factors. For an example, the same study of the Seattle gymnasium not only tested sawtooth glazing’s illuminance, but also revealed how skylights fare within the same setting; namely, the resulting measurements showed more potent and equal daylight from skylights than clerestories (Meek, 97). These two glazing types can pair together in the same space for even bolder illumination, however; such is the case with the Musée d’Orsay.

Skylights have their downsides, however; for instance, skylights are very difficult to shade properly (Lechner, 414). Unlike sawtooth glazing or clerestory windows, they lack a certain degree of horizontality for overhangs to comfortably and effectively prevent direct glare and thermal issues. Having structural supports act as passive shading elements could somewhat suffice, such as those in the National Museum of the Roman Arts in Merida (Top Right), or the MAXXI Museum in Rome (Bottom Right), but would still prove a troublesome endeavor. These flaws make the likes of sawtooth and clerestory apertures more preferable, since they are not as susceptible to summer and winter conditions and have more shading opportunities.

On top of that, not only are they much more difficult to shade than regular windows and clerestories, but they also admit much more daylight during the summer than the winter (Lechner, 413). This is very inconvenient, since heat and light from the sun are much more welcome during the winter than in the summer. Despite these shortcomings, skylights are an effective means of providing sufficient illuminance for deeper spaces.

LIGHT WELLS

Comparable to skylights, light wells and shafts are ceiling apertures that admit daylight deep into an interior space. Unlike skylights or atria, however, skyward views are completely obscure, only focusing on gathering as much daylight as possible. Because of this, unlike other horizontal apertures, light wells can pierce through multiple floors at a time (Lechner, 414). Considering these traits, light wells are great for illuminating lower floors of multistory buildings, even if they completely lack outdoor views. Examples include the Riem Center in Munich, Germany (Top Right), as well as Le Corbusier’s La Tourette monastery in Eveux, France (Bottom Right).

Courtesy of modern and advanced building and material technologies, highly reflective or mirrored surfaces can compose the sides of light wells (Lechner, 414). Because of their reflectance, light wells can absorb just a miniscule fraction of penetrating daylight, the rest of which travels downwards into the space, as shown in the left diagram above (Lechner, 414).

Although light wells have an inherent lack of outdoor views, they compensate for this by funneling light deep into a space. What results is a very useful tool for daylighting, providing strong and concentrated illumination for single and multi-story architecture.

ATRIA

Although atria are similar to light wells, they are much larger and inhabitable; in a sense, they act as rooftops for a given space (Lechner, 414). As a result, the illumination atria bring is maximal, as they cover the entire ceiling and admit the most amount of daylight out of all vertical apertures. Their designs can either stretch across a narrow yet lengthy space, such as the Les Passages shopping arcade in Paris (Top Right), or a wider and taller space or channel, such as the Casa Batlló in Barcelona (Bottom Right).

The advantages of atria stretch beyond daylighting for occupant comfort, however. For instance, they have access to more advanced glazing features, including fritted glass “to soften the sunlight and control excessive light and heat flow” (IES Daylighting Committee, 38). They can also act as “solar buffers” for nearby air-conditioned spaces, reducing unwanted heat to increase well-being and lower HVAC costs (IES Daylighting Committee, 38). Not only do atria provide enormous amounts of daylight at a time, but they give substantial thermal comfort as well.

Atria are massive in scale and therefore more practical for larger buildings, but they provide many benefits for building occupants in terms of daylighting and thermal function.

CONCLUSION

Daylighting is one of the most essential resources for sustaining the human body. Its impacts not only reach visual and aesthetic appeal, but also include a multitude of physical and psychological advantages. From decreasing stress to shortening recovery times to improving the mental state, natural light has proven itself to be an extremely potent force in assisting people’s well-being; countless studies have confirmed the quantity and magnitude of these benefits since long ago.

With these benefits in mind, architecture has limitless potential in harnessing them to create healthy and comforting designs. As stated earlier, there is no decisive or clear-cut technique that instantly satisfies every building’s need for proper daylighting; designers have to consider several aspects such as glare, shading, and maintenance. Even outside of the construction itself, other considerations include sun angles and orbit, seasonal changes, and building orientation. Frankly, there are too many variables for there to be a singular and easy solution to addressing sunlight and views in buildings.

Luckily, this is where the art behind architecture begins. Because of all of these variables, there are innumerous possibilities for daylighting in building design. It helps that advanced building technologies expand such capabilities even further, creating a realm in which inhabitants can experience architectural comfort and improve their health.

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

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.