Pattern 13: Atrium and Adjacent Floorplate

An atrium can serve as an excellent daylighting resource in multi-story buildings, however to be successful, several steps are critical. First, the size and shape of the atrium must be designed in relationship to the floor area where daylight is required. Second, the daylight apertures must be designed in terms of size, orientation, and configuration to provide daylight to the critical interior surfaces. Third, the spaces where people spend the most time must be located directly adjacent to the atrium, or within the atrium, so that daylight can reasonably reach these areas. And fourth, several other details must be coordinated so that daylight is provided in a sufficient and comfortable fashion to people in these spaces, including the size and proximity of perimeter daylight sources, location of circulation ways, solar shading and glare control, and light redirecting devices. 

It is of paramount importance that a sober attitude is brought to the design of atriums intended to be a daylighting resource so that the size and shape of the atrium is commensurate with the daylighting task at hand. It is far too easy for atriums to be squeezed down in size (narrow throat) by economic or floor area pressures and be expected to solve the daylighting problem for far too great a floor area. With atria design, rules of thumb quickly become inadequate due to the complexity of design interactions discussed above. However a designer must begin somewhere, and a safe (although primitive) rule of thumb to achieve comprehensive daylighting from an atrium is that the atrium should be as wide as it is tall with substantial aperture area in the roof. 

Before a meaningful discussion of atria design is possible, it is important to understand that the success of an atrium for daylighting can be considered in two distinct ways. The first manner in which atria can be measured with regards to daylighting is in their ability to provide brightness on vertical surfaces deep within a floor section to help balance the brightness from perimeter windows. Measured in this way, it is relatively easy to have a successful atrium. However, most often designers expect atria to not only increase the perception of brightness in the spaces adjacent to them but to provide functional illumination on vertical and horizontal surfaces in the spaces within and adjacent to them. Measured in this way, it is far more difficult to achieve a successful atrium. It is this ‘comprehensive’ approach to daylighting design that the rule of thumb above is derived from. It is important to note that both of these goals are important and it is possible to have either one without the other. While the most successful atria meet both goals, it would be unfair to say that if only one of these two goals were achieved that the atrium was unsuccessful. 

This pattern analysis explores the size and shape of atria design for multistory buildings including the relative height and width of the atrium, width of adjacent floor plates, the design of the daylight apertures and light redirecting elements, and the role of perimeter light sources and how they interact with the daylight provided from the atrium. The case study used to examine these design alternatives is the Great River Energy Headquarters in Maple Grove, MN. It is a four-story office building designed by Perkins+Will Architects. This pattern sequence highlights simulations under sunny sky conditions during September at noon with workplane illumination data represented in lux. Office lighting criteria range from 300-400 lux and 300 lux was selected as one of the daylighting design criteria examined herein. The percentage of floor area above this value is presented for each permutation.