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

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