The SunCooler™ as the Heat Mitigation Strategy for DOT Facilities

The Caltrans Sustainability Roadmap 2022-2023 clearly articulates the mounting operational and human-cost challenges facing departments of transportation maintenance shop ventilation:

“Extreme heat days can cause cooling equipment failures in buildings, leading to an increase in heat-related illnesses and loss of productivity due to building closures. Building maintenance staff might be required to work extended hours to maintain and repair equipment to keep buildings at an acceptable temperature level. Extreme temperatures can cause buildings to deteriorate prematurely, shortening their service life, requiring more frequent maintenance and repair. Maintenance crews might be required to work at night to avoid heatstroke during extreme heat events. Additionally, increased temperatures and extreme heat days may cause wildfires to grow in scale and frequency.” ¹

NWREC has responded to this statement from Caltrans with a publically available proposal on Caltrans.Brightidea, because:

The SunCooler™ is the only fully off-grid industrial-scale solar air handling HVAC system purpose-built to solve exactly these problems for DOT maintenance service centers, equipment shops, high-bay warehouses, administrative buildings, and other high-volume facilities. Rooftop drop-in installation. No wiring. No electrical permits.

• 1/10th the Cost of Conventional HVAC: The SunCooler delivers a complete facility-wide heat mitigation and ventilation solution at roughly one-tenth the cost of traditional HVAC retrofits with zero wiring, no electrical permits, and minimal operational disruption.
• Keeps Maintenance & Repair Operations Running: High-velocity turbulent airflow (up to 15,000 CFM) provides real psychrometric cooling so technicians can continue working safely through heat waves instead of shifting hours or losing productivity.
• Replaces Inadequate Passive Vents: Eliminates ineffective whirlybird-style passive ventilators and delivers active, controllable exhaust, induction, nightflush, and destratification from a single autonomous unit.
• Extends Existing HVAC Life & Resilience: Nightflush pre-cools buildings overnight; exhaust mode removes hot stratified ceiling air to reduce strain on chillers. When grid-tied HVAC fails during brownouts, the SunCooler keeps delivering essential airflow and cooling.
• Off-Grid Heat & Wildfire Resilience: Continues operating on solar + battery during grid stress or extreme events. Dampers can remain sealed during wildfire smoke while still providing critical internal air movement.

SunCoolers providing autonomous ventilation on a high-volume DOT facility.

SunCooler exhaust mode actively ventilating a maintenance shop.

DOT maintenance service centers and equipment shops are large, high-volume facilities where technicians perform heat-generating work such as welding, engine repair, fabrication, and heavy equipment maintenance. These spaces often rely on ineffective passive whirlybird vents, small spinning turbines the size of a basketball, that provide almost no meaningful airflow during calm or hot conditions. When extreme heat hits, evaporative cooling systems lose effectiveness, indoor temperatures soar, and crews face real risks of heat stress, reduced productivity, and forced schedule changes.

Active High-Velocity Ventilation That Replaces Passive Vents

The SunCooler™ directly replaces these passive whirlybirds with a powerful, autonomous rooftop unit that delivers up to 15,000 CFM of high-velocity turbulent airflow. In Exhaust Mode, it rapidly pulls hot, contaminated air out of the shop through the ceiling while creating strong negative pressure that draws fresher air in through doors and wall louvers. The result is continuous, directed air movement across the work floor exactly what technicians need to stay comfortable and productive.

The SunCooler’s high-velocity turbulent air column creates strong convective and evaporative cooling at the occupant level (read more on psychrometric cooling). The SunCooler is more effective at heat mitigation than HVLS fans, simialrly priced, and has numerous air handling modes to optimally control indoor air quality (read more about how the SunCooler outperforms HVSL). Technicians can continue working through heat waves without the facility having to shift work hours to early morning or night shifts.

SunCooler™ exhaust mode replacing passive whirlybird vents in a high-volume maintenance facility.

Keeps Critical DOT Repair Services Flowing

When maintenance shops become too hot, repair turnaround times slow down and critical equipment stays out of service longer. The SunCooler keeps these facilities operational during extreme heat by maintaining strong, reliable airflow without depending on the electrical grid. Because it runs on its own solar array and battery system, it continues working even during brownouts or when grid-tied HVAC and exhaust fans fail.

Nightflush Mode automatically brings in cool nighttime air to pre-charge the building’s thermal mass, so the shop starts the next day significantly cooler. This reduces peak daytime heat load and helps crews begin work in more tolerable conditions.

The system is fully programmable through the intuitive SunConfig interface. Facility managers can schedule Exhaust Mode during peak heat hours, Nightflush overnight, and even Destratification in cooler months to push warm ceiling air down to the work area all without any manual intervention.

Bottom line: The SunCooler transforms under-ventilated maintenance shops from heat liabilities into resilient, productive workspaces keeping DOT repair services running smoothly through the hottest months of the year.

Next: How the SunCooler extends the life of your existing HVAC systems →

Most DOT facilities already have some form of mechanical cooling or ventilation. The SunCooler™ is designed to work with these systems, not against them, by dramatically reducing their workload while providing resilient backup performance when they fail.

Nightflush Pre-Cooling Reduces HVAC Runtime

In Nightflush Mode, the SunCooler automatically reverses at night to pull in the coolest available outdoor air. This flushes out stored daytime heat and pre-cools the building’s thermal mass (concrete floors, walls, and steel structure). The facility starts the next morning significantly cooler, which delays when existing chillers and rooftop units need to turn on and shortens their overall runtime.

Exhaust Mode Lowers the Load on Mechanical Systems

During the day, Exhaust Mode continuously removes the hottest air that has stratified at the ceiling. This hot air would otherwise radiate back down and force HVAC systems to work much harder to maintain comfortable temperatures at the occupant level. By exhausting this heat directly, the SunCooler reduces the cooling load on existing equipment, lowers energy consumption, and decreases wear on compressors and motors.

True Backup Cooling When HVAC Fails

During extreme heat waves, grid brownouts, or equipment failures, traditional HVAC systems often shut down exactly when they are needed most. Because every SunCooler operates completely off-grid with its own solar array and battery backup, it keeps running independently. It continues delivering powerful high-velocity turbulent airflow that provides meaningful psychrometric cooling at the occupant level allowing people to tolerate higher temperatures more safely and comfortably.

Learn more about how high-velocity airflow creates psychrometric cooling and improves heat tolerance.

Next: High-Bay Warehouses & Storage Facilities →

Many DOT districts operate large high-bay warehouses for parts, tools, equipment, and materials storage. These tall, high-volume spaces face the same stratification, poor ventilation, and extreme heat challenges found in commercial distribution centers.

How the SunCooler™ Solves High-Bay Challenges

• Replaces Grid-Powered Exhaust Fans: Drops in as a direct, off-grid replacement with zero wiring or electrical permits required.
• Powerful Destratification: Pushes hot ceiling air down to the floor, delivering up to 30% heating energy savings and more even temperatures throughout the space.
• Nightflush Pre-Cooling: Automatically brings in cool night air to charge the building’s thermal mass, reducing daytime cooling loads and improving conditions for staff.
• High-Velocity Exhaust & Airflow: Effectively ventilates large, often under-ventilated high-bay volumes and breaks up stagnant zones that passive systems miss.
• Fully Autonomous Operation: Scheduled events, environmental sensors, and intelligent battery management (limSOC / maxDOD) keep the system running reliably with minimal oversight.

Read the full High-Bay Warehouses & Distribution Centers page →