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concepts · updated 2026-08-01

Night sky radiant cooling potentials in New Mexico

confidence: medium volatility: cold verified: 2026-08-01fresh

A 2006 state-funded report by Mark Chalom Architect (with Bristol Stickney and Kate Snider) for Governor Richardson's Water Innovation Fund, quantifying the potential of night sky radiant cooling to replace evaporative coolers and air conditioners across New Mexico's 11 climate zones.

A 2006 state-funded report by Mark Chalom Architect (with Bristol Stickney and Kate Snider) for Governor Richardson’s Water Innovation Fund. The report quantifies the potential of night sky radiant cooling (NSRC) to replace evaporative coolers and air conditioners across New Mexico’s 11 climate zones.

Core findings

  • NSRC can cool an efficiently designed 1,800 sq ft home in New Mexico’s hottest climate zones entirely, including Carlsbad; the coolest zones (e.g. Red River) need only nighttime ventilation through open windows.
  • The study tested 10 different radiator/collector types over two summers (2004–2005) in Tesuque, NM, measuring actual BTU output at 5-minute intervals against on-site weather data.
  • Average cooling “U” value across all tested radiators: 1.66 BTU/hr·ft²·°F (the companion calculator uses 1.7 as its default).
  • The executive summary states power savings for cooling range from 25% in Albuquerque to 89% in Carlsbad compared to conventional air conditioning. The companion calculator’s savings-summary sheet gives a different profile — 81% of A/C cooling kWh saved in Albuquerque and 58% in Carlsbad (with ~85% in most milder zones) — the two figures measure savings differently and the sources do not reconcile them.
  • Water savings are substantial on two fronts: evaporative coolers consume water directly (the report puts their water use at ~40× NSRC’s in Carlsbad), and every kWh saved also saves water at the power plant (PNM average: 0.74 gallons per kWh) — 96% power-plant water savings vs A/C in Carlsbad, 73% in Albuquerque. The modeled 1,800 sq ft home saved 4,477 gallons per season in Albuquerque and 7,500 gallons in Carlsbad.

System design assumed

The baseline system uses:

  • A radiant-heated concrete slab floor (already common in NM construction)
  • Unglazed swimming pool collectors on a flat roof, repurposed as night-sky radiators
  • A closed water loop between the slab and the roof panels

This is the same architecture described in the archive’s pool-heater cooling and radiant cooling design brief pages — the report provides independent field data supporting Baer’s claims.

Connection to the archive

The report explicitly cites Steve Baer and Zomeworks:

“Steve Baer of Zomeworks, inspired by Harold Hay’s Skytherm Designs, has been working with the principal of night sky radiation for over three decades and has developed such technologies as the Cool Cell as well as the Double Play Solar Heating and Cooling System.”

It reproduces thermal performance data for Baer’s Double Play system (source: Zomeworks, Double Play Progress Report), notes that “In 2002 Baer held a conference in Albuquerque discussing the promise of heating and cooling using unglazed collectors and related systems,” and gives Baer an “honorable mention” for the white-plate sensor insight — using a plate’s own temperature as an integrated measure of radiant cooling potential instead of correlating individual weather variables. The bibliography lists Baer’s Cooling with Pool Heaters.

Two companion files accompany the report: a slide presentation (Kate Snider, February 2006; image-based .ppt) and an interactive Excel calculator (Bristol Stickney, February 2006) for projecting cooling-energy and water savings for a user-defined house across the 11 climate zones. The calculator’s default sample house is 1,800 sq ft with 400 sq ft of roof radiator, a 120 W pump, and an assumed 10 hours/night of NSRC availability.

Radiator test results

The study tested 10 collector types of various materials and cross-sections at a facility nicknamed “Skylab” in Tesuque, NM (6,800 ft): horizontal insulated 4′×10′ tabletops, a 40-gallon insulated storage tank, a 10 W pump at ½ gal/min, and a white reference plate, all logged at 5-minute intervals. Key variables:

  • Tilt correction factor — flat panels see the most sky, but tilting penalized cooling less than theory predicts: radiators set fully vertical measured only a ~25% drop in cooling rate, about half the loss the “view factor” formula expects, giving designs more flexibility
  • Wind correction factor — wind warms a cold plate by forced convection, reducing net radiative cooling; the reported “U” values already average in the test site’s intermittent wind, with multipliers provided for constantly windy climates
  • Correlation between radiator output, white-plate temperature, and weather data allowed projecting performance across all 11 NM climate zones

Why it matters

This is the only source in the archive that provides government-funded, independently measured field data for the night-sky radiative cooling principle. It validates the claims made in the archive’s concept pages with two summers of actual radiator testing and statewide projections. It also demonstrates that the pool-heater-as-radiator idea works at scale — not just as a Zomeworks experiment, but as a state-level energy strategy.

See also