Information
Daylighting
A short checklist for using windows to light buildings, not just to look out of them.
Windows light buildings. A daylighting strategy uses that light deliberately, and it is inseparable from the thermal design: think about solar heat gain and daylight together.
A short checklist
- Keep it simple. Use intuition and the available analysis tools; daylighting design must include a thermal analysis.
- Control the electric lighting first. Photosensor dimming is what turns daylight into energy savings.
- Use tall windows. Daylight reaches roughly 1.5 times the window head height into a room; clerestories extend it without increasing window-to-wall ratio.
- Think in effective aperture (visible transmittance × window-to-wall ratio). Around 0.30 on north and south façades is a good starting point; minimize east and west glazing.
- Drop vision glass below sill height unless the downward view matters; it adds heat gain without useful daylight.
- Select glass by orientation: clear, high-VT glass on the north; solar-control glass on south, east and especially west.
- Plan for glare: light shelves, louvers and shades are part of the design, not an afterthought.
Where vacuum glass helps
High visible transmittance and low U-factor usually pull in opposite directions: more glass means more heat loss. A ZERO glass package breaks that link. With a center-of-glass U-factor around 0.08 the window area can follow the daylighting need rather than the heating load, which is why passive house designers pair vacuum glass with larger, better-oriented windows.