aperture placement & area. aperture refers to any daylight source – windows – skylights –...
TRANSCRIPT
Aperture Placement & Area
Aperture
• Refers to any daylight source– Windows– Skylights– Openings– Transparent or translucent surfaces
• Placement and area are important because use of windows and skylights helps achieve thermal and visual comfort passively, saving energy and money
Area
• Side Light – Bigger not necessarily better as it can cause to
much heat lost or gain– Window to wall ration (wwr)– 40% or lower for adequate
insulation in cold climates– Higher R-values raise the ratio
Window to Floor ratio
• Window to floor ratio (wfr)• For side lighting thresholds wfr x tvis– 0.15 < VLT • WFR < 0.18
Area
• Top Light – much brighter than sidelighting, less area is required
• Skylight to roof (SRR) net glazing area divided by gross roof area
• Should be between 3% and 6%, tubular skylights 1-2%
• Area of one skylight = (Floor to Ceiling Height x 1.5)2 • target SRR
• 12' ceiling and 5% skylight to roof ratio the right size skylight would be approximately: (12 x 1.5)^2 x 5% = 16.2sf. Therefore the project should use 4'x4' or 8'x2'
Placement for Daylighting
• Facing the path of the sun receive more direct sunlight than those facing away
• Evenly distributed light is critical for daylighting
• Continuous strip apertures are even better, often best is apertures on multiple sides
• Without careful planning hotspots can occur
Placement for daylighting
• Horizontal bands of windows placed high (avoids glare and bounces light off ceiling) can help as well as evenly spaced vertical windows
Side Light
• Coming from the side light can only reach so far into a building
• One reason for shallow floorplans in multi-story buildings
• At most latitudes the light reaches into the room roughly 2.5x the height of the top of a window
Side Light
• Windows facing away from the sun’s path rather than towards the equator provide the most even illumination, but not the brightest
• East and west facing windows can provide very bright light in the morning or evening but is often insufficient at other times of the day, also prone to glare
• Facing the sun’s path provides the brightest light but can also have a glare, easier to control the glare though
Top Light
• In middle latitudes and those closer to the equator skylights can provided the best illumination
• In latitudes closer to the poles they are less bright and much less seasonal consistency
• Higher apertures are most efficient at bring light deep into a building (glazing on/in roofs)
• Skylights are not the only choice
Top Light
Top Light
• Much brighter than side lights per unit area– Vertical monitor – 2x– Angled monitor – 3x depending on the angle– Horizontal skylight – 5x
• Splayed openings can help spread the light more broadly
Daylight Apertures vs. View Windows
• Good daylighting design considers daylighting apertures separate from view windows
• Daylighting apertures are best located high on the wall so the light reaches deeper into the space
• View windows are at eye level for occupants• Daylighting diffuses light• Often shades and/or light shelves are placed
between the two
• Shades the view while diffusing and redirecting light
Placement for Heating & Cooling
• Can pull in lots of heat but might allow lots of heat loss if located elsewhere
• In many climates east windows can warm spaces early in the day after a cool night
• Warmer climates, west facing windows can be prone to overheating
• Passive solar heating comings solar heat gain with thermal mass inside the building