Building Orientation

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Introduction

Orientation of the building generally used to refer to solar orientation which is the siting of building with respect to solar access. Although any building will have different orientations for its different sides, the orientation can refer to a particular room, or to the most important facade of the building.

The building orientation can have an impact on heating, lighting and cooling costs. By maximizing southern exposure, for example, one can take optimal advantage of the sun for daylight and passive solar heating. This will result in lower cooling costs by minimizing western exposures, where it's most difficult to provide shade from the sun.


Brief Description

Energy conservation strategies relating to building orientation:

• Maximizing north and south façade exposure for daylight harvesting to reduce lighting electrical loads

• Using southern exposure for solar heat gain to reduce heating loads in the heating season

• Using shading strategies to reduce cooling loads caused by solar gain on south façades

• Turning long façades toward the direction of prevailing breezes to enhance the cooling effect of natural ventilation

• Turning long façades in the direction parallel to slopes to take advantage of cool updrafts to enhance natural ventilation

• Shielding windows and openings from the direction of harsh winter winds and storms to reduce heating loads

• Orienting the most populated building spaces toward north and south exposures to maximize daylighting and natural ventilation benefit

• Determining building occupant usage patterns for public, commercial, institutional, or residential buildings, and how occupants will be affected by the building orientation, by time of day, on different exposures


Application: Designing for Building Orientation:

• The designer must consider and prioritize all factors and site conditions affecting building orientation. For example, a building might have to take heed of multiple orientation factors depending on functional requirements: designing for cooling load or heating load. To take advantage of north–south daylighting, the building may be oriented along an east–west axis. But this may be counter to street lines and other site considerations. Orientation of the building entrance may have to respect street access, activity zones, and local urban design guidelines.

• For most regions, optimum façade orientation is typically south. South-facing glass is relatively easy to shade with an overhang during the summer to minimize solar heat gain. Light shelves also can work well with the higher sun in the southern exposure. North-facing glass receives good daylight but relatively little direct isolation, so heat gain is less of a concern.

• East and west window orientations and horizontal orientation (skylights) all result in more undesired heat gain in the summer than winter. East and west sun glare is also more difficult to control for occupant comfort because of low sun angles in early morning and late afternoon.

• Wind will affect tall buildings more than low structures. Design for wind direction—admitting favorable breezes and shielding from storms and cold weather winds. Wind information is often available from airports, libraries, and/or county agricultural extension offices. In cold climates, locate pedestrian paths and parking lots on south and east sides of buildings to enable snow melting, but in southern climates locate these on the less sunny east or north sides of the building.

• In temperate and northern climates, locate deciduous trees for south-side shading in the cooling season; in the heating season, the dropped leaves will permit desired solar gain. In urban settings, orientation may be strongly determined by local regulation, view easements, and urban design regulations. Be aware of unique local and site-specific conditions, such as lake or coastal exposures, effect of mountainous conditions, and special scenic easements.

• To minimize heat losses and gains through the surface of a building, a compact shape is desirable. This characteristic is mathematically described as the “surface-to-volume” ratio of the building. The most compact orthogonal building would be a cube. This configuration, however, may place a large portion of the floor area far from perimeter daylighting. Contrary to the cube, a building massing that optimizes daylighting and ventilation would be elongated along its east–west axis so that more of the building area is closer to the perimeter. Although this may appear to compromise the thermal performance of the building, the electrical load and cooling load savings achieved by a well-designed daylighting system will more than compensate for the increased surface losses.


References:

http://www.efficiencyvermont.com/pages/Business/BuildingEfficiently/TypicalEnergyEfficiencyAppr/BuildingOrientation/

http://wiki.aia.org/Wiki%20Pages/Building%20Orientation.aspx

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