When a commercial building closes for the holidays, the HVAC system may continue running for days or weeks without employees or customers inside. But an empty building still responds to outdoor temperature, humidity, sunlight, and moisture. The question is not simply whether to leave the HVAC system on or turn it off.
Normal occupied settings may use more energy than necessary, while shutting the system down completely can create other concerns depending on the season, building, equipment, and length of the closure.
At Restore-It, we understand how HVAC performance and indoor conditions can affect commercial spaces. Before you lock the doors, it is worth considering how your HVAC settings can affect energy use, humidity, equipment operation, and the building itself.
In this guide, we will explain what can happen to your HVAC system during an extended holiday closure, what factors to consider when adjusting its operation, and what to check before leaving and when you return.
What Changes When a Commercial Building Sits Empty?
When occupancy drops, heating and cooling demand usually changes. Employees, customers, lighting, equipment, and doors opening throughout the day all affect indoor conditions. When those activities stop, the building may need less heating or cooling.
The building still responds to outdoor temperature, humidity, sunlight, and existing moisture sources.
That means HVAC needs may change, not disappear. The goal during a closure is generally not to maintain normal occupied conditions, but to keep the building within conditions appropriate for the season, equipment, and building requirements.
Should You Turn Off the HVAC in an Empty Commercial Building?
There is no single HVAC setting that fits every commercial building. A temperature setback or occupancy schedule can reduce heating and cooling demand during unoccupied periods. The U.S. Department of Energy identifies holiday scheduling and temperature setbacks as opportunities to reduce commercial building energy use.
|
HVAC approach |
Potential benefit |
What to consider |
|
Normal occupied settings |
Maintains typical conditions |
May use more energy than necessary |
|
Temperature setback |
Reduces heating or cooling demand |
Must account for weather and building requirements |
|
Occupancy schedule |
Automates reduced operation |
Requires properly configured controls |
|
Complete shutdown |
Eliminates HVAC operation |
Can create temperature or moisture concerns |
|
Minimum operation |
Maintains basic environmental control |
Depends on the building and system |
Before choosing an approach, consider the season, expected weather, building type, equipment, and closure length.
In cold weather, shutting the system down can allow indoor temperatures to fall enough to create freeze-related concerns. In warm or humid weather, losing cooling and dehumidification can allow indoor humidity to rise. Environmental Protection Agency (EPA) recommends maintaining indoor relative humidity below 60%, ideally between 30% and 50% when possible. High humidity and condensation can contribute to moisture and mold problems.
An energy-saving setting should still account for the building and its contents.
Can an Empty Commercial Building Develop HVAC or Moisture Problems?
Yes. An empty building can still experience moisture and HVAC problems, and some may go unnoticed until the building reopens.
Humidity Can Become a Problem
HVAC systems can help remove moisture from indoor air, but if humidity is not adequately controlled, condensation can develop on cold surfaces. EPA recommends maintaining indoor relative humidity below 60%, with 30% to 50% considered ideal when possible.
For a commercial building sitting empty, humidity can be harder to notice because there are no employees or customers reporting sticky air, musty odors, or uneven cooling. Those signs may not become apparent until the building reopens.
If you want to learn more about how humidity affects commercial buildings in South Arkansas, read Restore-It's guide below!
Poor Airflow Can Affect Certain Areas
A system can be operating while certain rooms or zones receive inadequate airflow. Checking only one thermostat may not reveal what is happening throughout a larger building.
Small HVAC Problems Can Go Unnoticed
Look for signs such as:
- Water or condensation around HVAC equipment
- Unusual equipment noises
- Poor airflow
- Noticeable temperature differences
- Short cycling
- A system that does not reach the expected temperature
- Musty odors or other signs of moisture
These signs do not identify the cause by themselves, but they warrant investigation.
Arkansas Weather Can Change Conditions Quickly
Arkansas weather can bring significant changes in temperature and humidity. A setting that is appropriate when a building closes may not provide the same protection later in the closure. Your plan should account for the season and expected weather rather than assuming conditions will remain the same.
What Should You Check Before Leaving Your Commercial Building for the Holidays?
Before closing the doors, make sure the HVAC system is operating normally and that your unoccupied settings match the building's needs.
Check Your HVAC Schedule and Thermostat Settings
Confirm that temperature setbacks, occupancy schedules, alarms, and building automation controls are programmed correctly.
Inspect Around HVAC Equipment
Look for water, condensation, visible damage, blocked access, unusual sounds, and maintenance issues. Check filters when they are part of your routine maintenance program.
Check Airflow and Temperature Differences
If one area already feels significantly warmer or cooler than another, do not assume the problem will disappear while the building is empty.
Consider What Happens if the Weather Changes
Review whether your settings provide appropriate protection for the expected conditions during the closure.
If you notice an HVAC issue before your holiday closure, it is better to address it while the building is still operating normally.
What Should You Do Before Reopening the Building?
Your HVAC plan does not end when the business reopens. Walk through the building before employees or customers return.
Check Indoor Temperature and Humidity
Check temperature and humidity in different areas, especially spaces with limited airflow. Look for condensation, water stains, damp materials, musty odors, and signs of roof, plumbing, or HVAC leaks.
EPA recommends addressing moisture sources promptly and keeping HVAC condensate pans and drains clean and unobstructed.
Check HVAC Operation
Make sure the system starts and runs as expected, air is reaching the areas that need it, and routine maintenance items are in order.
Walk Through Unoccupied Areas
Check storage rooms, mechanical spaces, closets, and other areas that received less attention.
Address Problems Before Employees or Customers Return
If you find excess moisture, visible water, unusual odors, or HVAC performance problems, address them before normal occupancy resumes.
For buildings that have been shut down or operated at reduced capacity for a prolonged period, Centers for Disease Control and Prevention (CDC) guidance recommends checking for hazards such as mold and moisture before reopening. For HVAC systems that were inactive during a prolonged shutdown, CDC guidance also describes a 48- to 72-hour flush-out period after moisture and mold concerns have been assessed or addressed. This guidance is specific to prolonged shutdowns, not every holiday closure.
When Should You Have a Commercial HVAC System Inspected?
Consider professional inspection when the system is not maintaining expected temperatures, airflow is inconsistent, moisture or condensation persists, unusual odors or equipment sounds appear, water is present around equipment, or performance changes after reopening.
An inspection can help determine whether the concern involves airflow, controls, maintenance, moisture, or another HVAC issue. Cleaning may be appropriate for some systems, but it is not a substitute for diagnosing mechanical or control problems.
What Should You Do With the HVAC System in Your Building?
An empty commercial building still needs an HVAC plan. Leaving the system at normal occupied settings may waste energy, while shutting it down completely may create other concerns depending on the building and season.
Before closing, review your settings, check the system, and consider the weather and length of the closure. Before reopening, walk through the building, check temperature and humidity, look for moisture, and make sure the HVAC system is operating as expected.
If you are considering HVAC cleaning before or after an extended closure, knowing what to expect from the service can help you plan.
Topics:
