Sidelighting

From eLADwiki
Jump to: navigation, search

Contents

One Side

Banner Bank Building, Boise, ID; HDR Architects: Image courtesy Kevin Van Den Wymelenberg, University of Idaho
Pioneer Tent and Awning Building, Boise, ID: Image courtesy Kevin Van Den Wymelenberg, University of Idaho

In order to daylight a space from one side, one needs to understand the limits of the relationship between window head height and section depth. The effective distance that daylight can penetrate from one side is no more than two times the head height of the perimeter window. In buildings with traditional floor to ceiling heights (~10’) this translates to about 20’-0” of section depth that can be daylit from one side. It should be noted that the configuration and size of interior furnishings, and the presence and use patterns of blinds might substantially reduce this distance.

If a room exceeds about 25’-0” from perimeter to core (assuming traditional ceiling height) the contrast increases substantially. Since the human eye tends to adjust to the brightest location within a space this can cause the perception of darkness and glare due to the lack of luminous uniformity across the section.

There are two primary strategies to address this condition. Section depths can be kept narrow to ensure relative uniformity. Alternatively, additional sources of daylight can be added to provide supplemental illumination.



Section Key Resources
  • New Buildings Institute, University of Idaho, University of Washington; Daylighting Pattern Guide, 2011
  • Heating, Cooling, Lighting 2nd Edition: Design Methods for Architects. 2001 John Wiley & Sons. Inc.
  • Concepts and Practice of Architectural Daylighting, Moore, 1985, Van Nostrand Reinhold. Lechner, Norbert.
Links

Lead Author(s): Kevin Van Den Wymelenberg


Multiple Sides

NBBJ Offices: New York, NY: Image courtesy Kevin Van Den Wymelenberg, University of Idaho

Norbert Lechner discusses the concerns related to having daylight from one side only and presents a list of alternatives below; “…the illumination is greatest just inside the window and rapidly drops off to inadequate levels for most visual tasks. The view of the sky is often a source of direct glare, and direct sunlight entering the window creates excessive-brightness ratios …To overcome these negative characteristics…, designers should keep in mind the following strategies:

  1. Windows should be high on the wall, widely distributed, and of optimum area.
  2. If possible, place windows on more than one wall.
  3. Place windows adjacent to interior walls.
  4. Splay walls to reduce the contrast between windows and walls.
  5. Filter Daylight
  6. Shade windows from excess sunlight in summer
  7. Use movable shades”



Section Key Resources
  • New Buildings Institute, University of Idaho, University of Washington; Daylighting Pattern Guide, 2011
  • Heating, Cooling, Lighting 2nd Edition: Design Methods for Architects. 2001 John Wiley & Sons. Inc.
  • Concepts and Practice of Architectural Daylighting, Moore, 1985, Van Nostrand Reinhold. Lechner, Norbert.
Links

Lead Author(s): Kevin Van Den Wymelenberg

Overhangs

Ash Creek Elementary School, Monmouth, OR; BOORA Architects: Image courtesy Kevin Van Den Wymelenberg, University of Idaho
Environmental Services Building, University Place; Miller Hull Partnership: Image courtesy Image courtesy Kevin Van Den Wymelenberg, University of Idaho

The purpose of exterior overhangs is to shade window in order to minimize direct sun penetration and the components of heat gain and glare. Several different design strategies and technologies can be used to accomplish these objectives. Sometimes multiple strategies are required to adequately address these concerns.

A good place to start is to use an exterior overhang that is about as deep as the window it is shading is high (1:1 ratio). For much of North America, this strategy will shade a south-facing window during the hottest times of the year. It will also block direct sun from entering the space between March 21st and September 21st. This will reduce solar gain through the glazing significantly during these times of the year.

In areas where it is cloudy much of the year (i.e. west of the Cascades), this strategy will provide sun control during most clear sky days. Overcast skies diffuse direct sun during the low sun angle days of winter.

Additionally, in building types such as schools and offices where occupancy times are limited to mornings through early afternoons (until 3PM), this strategy can be used very effectively on the west elevation as well. By the time the sun comes around enough to begin entering the space, many of the occupants will have left the space. Heat gain incurred in the afternoon can be flushed out during the night and the space will be cool at the beginning of the occupancy cycle the next morning.

It is important to understand that during winter months and early in the morning and late in the afternoon year round, low angle sun will ‘defeat’ almost any fixed shading system. Therefore, some time of dynamic system is necessary to eliminate all direct sun. This may be in the form of simple interior mounted louvers or blinds, or as motorized exterior shading systems.


Section Key Resources
Links

Lead Author(s): Kevin Van Den Wymelenberg

Lightshelves

Center for Advanced Energy Studies, Idaho Falls, ID; GSBS Architects: Image courtesy Kevin Van Den Wymelenberg, University of Idaho and Chris Meek, University of Washington
Ash Creek Elementary School, Monmouth, OR; BOORA Architects: Image courtesy Joel Loveland, University of Washington

Interior light redirecting elements can be used to minimize glare and direct sun penetration as well as to push light onto specific surfaces. In a sidelit architectural interiors, lightshelves can help to diffuse perimeter daylight, block direct sun from penetrating deeply into the space from ‘daylight’ windows, and reduce occupants’ line of sight to the disc of the sun. Furthermore, lightshelves serve to reduce light levels at the perimeter, creating a more evenly distributed illuminance across the section of a room. They can improve the perception of a balanced interior by reflecting diffuse light onto the ceiling plane and vertical surfaces adjacent to windows, reducing contrast near the perimeter. When designing a lightshelf, it is important to consider that a bright white (or translucent) matte finish surface will provide the most light diffusing quality, and will have less contrast with the light source it is obscuring. When detailing lightshelves it is prudent to use lightweight materials that do not encourage users to place light obscuring objects upon them.



Section Key Resources
  • New Buildings Institute, University of Idaho, University of Washington; Daylighting Pattern Guide, 2011
  • Refining the Window, University of Washington, Meek http://www.lightingdesignlab.com/ldlnews/Refining_the_Window.pdf
  • Concepts and Practice of Architectural Daylighting, Moore, 1985, Van Nostrand Reinhold. Lechner, Norbert.
Links

Lead Author(s): Kevin Van Den Wymelenberg

Page Key Resources
  • No publications general to this page have been listed.
Links
  • No links general to this page have been listed.
Citations
70px-Cc att share.png Except where otherwise noted, content on this site is licensed under a         
           Creative Commons Attribution-ShareAlike 3.0 License
Personal tools
Namespaces

Variants
Actions