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SS Credit: Light Pollution Reduction

Good lighting lets you see—great lighting lets you see without being seen.

 What is the Intent of this Credit?

The goal is to:

👉 increase access to the night sky
👉 improve nighttime visibility
👉 reduce negative impacts on people and wildlife

🎯 Big Picture

Light should go where it is needed—not into the sky or neighboring spaces.

🌍 Why This Matters

Poor lighting design causes:

  • skyglow (loss of night sky visibility)
  • disruption to wildlife (especially nocturnal species)
  • glare and discomfort for people
  • light trespass into neighboring properties

🧩 Three Core Requirements

✅ 1. Uplight Control

👉 Prevent light from:

  • escaping upward into the sky

✅ 2. Light Trespass Control

👉 Prevent light from:

  • spilling into adjacent properties

✅ 3. Exterior Signage Control

👉 Limit brightness of:

  • internally illuminated signs

💡 Key Concept: Light Trespass

👉 Defined as:

unwanted light spilling beyond the intended area

⚠️ Impacts

  • annoyance
  • distraction
  • reduced visibility
  • ecological disruption

⚙️ Two Compliance Methods (For Uplight + Trespass)

🔵 Option 1: BUG Rating Method

❓ What is BUG?

👉 Luminaire classification system:

  • B = Backlight
  • U = Uplight
  • G = Glare

📊 What It Does

👉 Limits:

  • uplight (sky pollution)
  • backlight (light trespass)
  • glare (visual discomfort)

📌 Requirement

👉 Luminaires must:

👉 not exceed BUG rating limits

(based on lighting zone)

🎯 Exam Insight

BUG = fixture-based control
(not site calculation)

🟢 Option 2: Calculation Method

❓ What Does It Do?

👉 Limits:

👉 total light emitted above horizontal plane

📊 Requirement

👉 Must not exceed:

  • allowed % of lumens directed upward

🎯 Exam Insight

Calculation method =
👉 overall site lighting performance

🪧 Exterior Signage Requirement (VERY TESTABLE)

🌙 Nighttime Limit

👉 ≤ 200 cd/m²

☀️ Daytime Limit

👉 ≤ 2000 cd/m²

🎯 Memorize These Numbers

  • 200 (night)
  • 2000 (day)

🌌 Good vs Bad Lighting (Conceptual)

❌ Poor Design

  • light in all directions
  • uplight to sky
  • glare
  • spillover

✅ Good Design

  • fully shielded fixtures
  • directed light
  • minimal glare
  • no uplight

🧠 Where People Get Confused

❌ Misconception 1:

“More lighting = better safety”

👉 Not always
👉 Poor lighting creates:

  • glare
  • reduced visibility

❌ Misconception 2:

“Uplight is harmless”

👉 No
👉 Causes:

  • skyglow
  • ecological disruption

❌ Misconception 3:

“BUG and calculation methods must both be used”

👉 No
👉 Choose one method

❌ Misconception 4:

“Signage brightness is not regulated”

👉 No
👉 Strict luminance limits apply

Official FAQs

What does BUG stand for?
👉 Backlight, Uplight, Glare
What are the luminance limits for exterior signage?
• 200 cd/m² (night)
• 2000 cd/m² (day)
A project uses lighting fixtures that emit light upward into the sky. Does it comply?
No.
👉 Violates uplight control
A project controls uplight but causes glare affecting pedestrians. Does it comply?
No.
👉 Must address:
• uplight
• trespass
• glare
Why does LEED require both uplight and light trespass control?
Because:
• uplight affects sky and environment
• trespass affects neighbors and occupants
👉 Both must be controlled for full impact
Why is BUG method preferred in many projects?
Because:
• easier to apply (fixture-based)
• standardized ratings
• reduces calculation complexity

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