Aperture Placement & Area

1. Aperture Placement & Area

2. 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

3. 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 adequateinsulation in cold climates • Higher R-values raise the ratio

4. Window to Floor ratio • Window to floor ratio (wfr) • For side lighting thresholds wfr x tvis • 0.15 < VLT • WFR < 0.18

5. 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'

6. 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

7. 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

8. 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

9. 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

11. 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

12. Top Light

13. 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

14. 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

15. Shades the view while diffusing and redirecting light

16. 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