Our bodies evolved under natural sunlight, which shifts in both intensity and color temperature throughout the day — from warm reddish sunrise (~2,200K), through neutral midday white (~5,500K), and back to warm amber at sunset (~2,700K). This natural variation regulates our circadian rhythm, influencing alertness, mood, and sleep quality.
Modern electric lighting, typically fixed at a single colour temperature, disrupts this rhythm. Human-Centric Lighting (HCL) uses tunable white LED technology controlled via DALI-2 to replicate the natural daylight curve indoors.
How It Works with KNX & DALI
A DALI-2 tunable white driver accepts two separate channels: one for warm white LEDs and one for cool white LEDs. By independently varying the intensity of each channel, the system blends the output to any point on the black-body curve between approximately 2,700K and 6,500K.
A KNX time controller or weather station triggers the DALI gateway to adjust colour temperature on a programmed schedule:
- 07:00 — Warm 2,800K at 30% for gentle wake-up
- 09:00 — Cool 5,000K at 80% for focus and productivity
- 13:00 — Neutral 4,000K at 70% for post-lunch alertness
- 18:00 — Gradual fade to warm 3,000K at 50% for relaxation
- 21:00 — Very warm 2,700K at 20% for winding down
Benefits Backed by Research
Studies in schools, hospitals, and offices have shown that HCL systems can improve concentration by up to 15%, reduce error rates, and improve sleep quality scores. In senior care facilities, proper circadian lighting has been shown to reduce agitation and improve sleep consistency among dementia patients.
The Green Wire designs and installs DALI-2 tunable white systems integrated into KNX building automation. Contact us to discuss a human-centric lighting scheme for your project.
