Schools see more seasonal swings than most buildings: long summer vacancies, winter start-ups after breaks and rooms that change occupancy by the hour. Each season has its own risk. This guide lists them and what to do.
Risks and checks by season
| Season | Risk | What to do |
|---|---|---|
| Summer break | Mold and musty odors in unoccupied, humid rooms | Keep dehumidification running where needed and monitor humidity |
| Late summer start-up | Dust and stale air in systems that sat idle | Flush and start systems before occupancy, check filters and dampers |
| Autumn | Simultaneous heating and cooling in mild weather | Check controls and economizers |
| Winter | Frozen coils, boiler problems, cold classrooms | Test freeze protection and heating before the cold, keep classroom airflow balanced |
| After winter break | Cold start-up and condensation | Warm up buildings before return and check for leaks |
| Spring | High pollen and rapid temperature swings | Check filters, outdoor air and controls |
The summer vacancy problem
Turning the air conditioning off for the summer is tempting. In humid climates, though, a building without dehumidification can grow mold on porous materials. If budgets require setback, keep humidity under control with a minimum run schedule and a humidity sensor, and check rooms for odor and moisture before school opens.
Start-up checklist before reopening
- Walk the building and look for leaks and damp materials.
- Change filters and inspect coils and drain pans.
- Run systems with outdoor air for a period before staff arrive.
- Verify exhaust fans and outdoor air dampers.
- Measure airflow in a sample of rooms and compare with design.
- Record findings and fix before students return.
See a calendar for school HVAC maintenance and seasonal airflow adjustments.
Common mistakes
- Switching everything off over the break. Humidity can ruin more than the savings.
- Restarting without a check. A stuck damper on opening day affects every room on it.
- Ignoring shoulder seasons. They waste the most energy.
Questions school facility teams ask about seasonal HVAC
How warm should we keep an empty building in summer?
The key is humidity, not temperature. Hold relative humidity in a safe range with a minimum schedule, and follow your own guidance.
What about winter break?
Keep enough heat to prevent freezing pipes and coils, and bring spaces to temperature before return.
Who checks the system?
Your maintenance team for routine checks, and a balancer for measured airflow and outdoor air. See how balancing affects classroom comfort.
Example: reopening after a hot, humid summer
Picture a school that set its cooling back for the summer. In August, a walk finds a musty smell in two classrooms and condensation on a supply diffuser. Humidity loggers show the rooms stayed damp for weeks. The fix starts with finding and drying the cause, then running the air handlers with dehumidification before staff return, and checking the diffuser and ceiling for growth. The lesson is to monitor humidity during vacancy and to inspect before reopening, because the signs are easy to catch early and costly to treat late.
Related reading: Seasonal Air Quality Checks for Commercial Buildings, How to Handle Seasonal HVAC Challenges: Summer and Winter Tips and How Healthcare Facilities Can Prepare for Seasonal HVAC Demands.
To check your school’s systems before the season changes, call Ghazi Hussain at (908) 323-9780.
