Service G · continued

## Optimizing the façade

19

Glazing ratio, glass specification and shading geometry are usually settled on appearance and capital cost, then defended for the rest of the project. We test them against daylight, glare, cooling load and lighting energy together, and present the trade-off as a set of comparable options.

The four variables

Glazing ratio | More glass admits more daylight and more heat. The useful range is narrower than most schemes assume, and it is orientation-dependent.
Glass specification | Visible light transmittance against solar heat gain coefficient. A high-performance coating can hold daylight while cutting gain.
External shading | Geometry tuned to orientation and sun path: horizontal on south, vertical on east and west. The most effective single measure in this climate.
Interior control | Blinds, light shelves and daylight-linked dimming. Necessary, but no substitute for getting the façade right.

Deliverables

- Daylight simulation report
- sDA and ASE compliance results
- Floor-plate daylight heat maps

- Glare assessment
- Shading and façade recommendations
- Certification credit evidence

Why it pays twice

A well-daylit floor plate reduces installed lighting hours, which reduces lighting energy and the cooling load that lighting creates. Handled badly, the same daylight arrives as glare and solar gain. Occupants close the blinds, the lights go on, and the cooling system carries both.

55%
Typical sDA target for certification credit
sDA

Spatial Daylight Autonomy. The share of floor area receiving 300 lux for at least half of occupied hours.

ASE

Annual Sunlight Exposure. The share of area receiving excessive direct sun, a proxy for glare risk.

Daylight factor

Interior illuminance as a percentage of unobstructed exterior illuminance under an overcast sky.

DGP

Daylight Glare Probability. Occupant discomfort risk evaluated from specific view positions.

G · Daylighting Assessment 19