Consultant Scott Lynn urges La Crosse to favor warmer, shielded streetlights to cut skyglow

Scott Lynn, a part‑time consultant with Mead & Hunt and president of the Kickapoo Valley Dark Sky Initiative, told La Crosse officials that recent conversions from high‑pressure sodium lamps to white LEDs can unintentionally increase night‑sky brightness and that warmer, shielded fixtures offer a practical alternative.

Lynn opened by describing satellite imagery from 2016–2022 and local ground measurements in his Ontario test area, saying the ground readings rose much more than the satellite data indicated after LEDs were installed. “We installed 3,000 Kelvin instead of 4,000 Kelvin. They reduced the amount of light coming out of those fixtures by 50% … and still our sky got 54% brighter,” Lynn said, using the contrast to explain how blue‑rich LEDs scatter more light in the atmosphere.

The matter matters because, Lynn said, increased skyglow has documented ecological and public‑health effects and uses energy that contributes to climate impacts. He explained basic technical terms for the group — lumens (quantity of light), correlated color temperature (Kelvin; higher numbers mean bluer light), and “0‑up” fixtures (designed to emit no light above the horizontal) — and recommended municipal choices that prioritize low CCT (1,800–2,200 K), shielding, lumen control, and timed dimming.

Lynn cited a parallel study in Chelan County, Washington, where the National Park Service measured a roughly 60% increase in sky brightness after LED conversions, and described local retrofit projects — including work at the Kickapoo Valley Reserve and small municipalities such as Lafarge and Westby — where 0‑up fixtures and dimming produced large reductions in skyglow while maintaining ground‑level illumination. He reported project outcomes from his installations: substantial uniformity gains, energy savings (he cited figures around 75%), and steep drops in skyglow (he cited up to 93% for specific retrofits), with payback timelines he estimated at roughly two to three years when incentives and durable fixtures are considered.

Commissioners asked practical questions about decorative poles, retrofits, and whether redirecting light downward could cause harms. Lynn said he knows of no research showing harms from directing light down; the change keeps the same useful light on ground surfaces while eliminating wasted uplight. He also explained incentive programs (Focus on Energy and Design Lights Consortium lists) that can reduce fixture costs, noting new 2,200 K products recently qualified for incentives.

Council members and staff said the presentation was useful background for drafting a city lighting ordinance. Deputy staff and the chair said staff will work with engineering and public works on standards for public and private lighting, and Lynn agreed to provide model ordinance language he has used elsewhere.

Staff next steps: staff will draft ordinance language for both public and private lighting standards, involve engineering/public‑works, and hold community engagement sessions before returning ordinance language to this body for further review.