Courtesy of Amy Stalbosky, National Corporate Architect, Major Ind., Inc.
Designing natural daylighting in a building can be difficult if the building is an existing structure or if the property has a difficult orientation. There are a few things to consider when working with difficult building layouts.
Windows facing north offer the best building orientation for reducing heat gain and glare. This orientation should be the key location for using clear vision glazing. True north glazing, at or above the Tropic of Cancer (23.4 degrees north of the Equator), will receive no direct sun. Therefore, northern light into a building is considered indirect. While you still need to consider building adjacencies and reflections, northern windows can be clear glass with minimal overhang, and blinds or shades may not be needed.
Southern glazing can often be an equally good orientation for proper daylighting, though in many cases it should be protected by building overhangs (computerized daylighting analysis can evaluate how low the sun’s angle will be in the winter months). That said, direct sunlight into a building from south facing glazing isn’t necessarily a bad element. Sunlight is often psychologically lifting to the spirit, and with southern exposure, sunlight angles will travel across an interior space, creating drama and adding intrigue to design elements. There are, however, particular spots like circulation areas, stairwells, and intersections where direct sunlight can create glare and hot spots and can make life uncomfortable for people maneuvering within the building. In these spaces, diffuse daylighting materials are recommended.
Sometimes a building’s orientation cannot avoid or reduce eastern and western exposures. East and west facing spaces will receive the most direct sun glare of any direction, and even building overhangs and horizontal sunshades cannot reduce glare into windows. Evergreen trees are often the easiest natural solution to reduce direct sun glare. Rooms facing east and west should be daylit using diffuse daylighting materials, instead of clear glass, as much as possible. Diffuse daylighting materials will not only reduce light, but most importantly bend the light, spreading out the quantity of light to a larger space. This can certainly be a benefit when designed properly! Breakfast rooms with diffuse daylighting are best oriented to the eastern side of a building, while evening sitting rooms work well with diffuse daylighting on the western side of a building.