Top Issues with Negative Building Pressurization in Commercial Buildings
Negative air pressure can be a major concern in commercial buildings and lead to a range of issues. Negative building pressure (as opposed to its opposite, positive pressure) happens when the volume of air being exhausted from the building exceeds the volume of fresh air being supplied through the HVAC system. This creates a situation where unconditioned outside air infiltrates the building through unintended pathways, such as cracks, gaps, or improperly sealed doors and windows. All of this can significantly affect the indoor environment and occupants’ health and comfort. Negative building pressure can also contribute to higher HVAC energy costs.
Watch the short video below to see how negative building pressurization can cause damage to your facility.
What Causes Negative Pressure in Commercial Buildings?
Building pressurization plays a crucial role in maintaining a healthy indoor environment. However, several common issues can arise, compromising the desired pressurization levels. Understanding these issues is essential for effective troubleshooting and resolution. Some of the common issues with building pressurization include:
Malfunctioning HVAC Systems
One issue leading to negative pressurization is the presence of an old heating, ventilation, and air conditioning unit that struggles to keep the building cool. It may be tempting to close the outside air damper in an attempt to ease the workload on the system. While this may provide temporary relief in cooling the building, it ultimately cuts off the outdoor air supply and results in negative pressure. This causes the building to pull in unconditioned warm air through gaps and cracks in the building envelope, bypassing the air filters and cooling coils in the HVAC units. A possible consequence is high relative humidity within the building and condensation on cooler surfaces, such as HVAC diffusers.
Improper Ventilation Design
Flaws in the building design can cause negative pressure. This could include inadequate ventilation systems or the addition of building exhaust without consideration for additional outside air makeup supply. These design deficiencies can result in an imbalance of airflow and contribute to negative pressure. For example, kitchens with big exhaust hoods are often accompanied by a makeup air unit that is supposed to balance the amount of air. However, if the makeup air is not properly conditioned or if occupants find it uncomfortable, they may find ways to turn off the makeup air, disrupting the balance and causing negative pressure.
Blocked Airflow
In certain building designs, particularly hotels, outside air supply is introduced in the corridors to balance bathroom exhaust in the guest rooms. The makeup air from the corridor creates a balance in air pressure by flowing beneath doors into the guestrooms. But if thresholds or door sweeps block this airflow, the makeup air from the corridors is restricted while the exhaust fans in the bathrooms continue to operate. This creates a negative pressure situation and can lead to mold growth on the walls.
Improper Maintenance
Improper maintenance can also contribute to negative pressure in commercial buildings. Neglecting regular cleaning and servicing of HVAC systems can lead to issues such as clogged filters, malfunctioning dampers, blocked outside air intakes, or sensors falling out of calibration. These maintenance issues can hinder the proper flow of air and disrupt the balance between air supply and exhaust, causing negative pressure problems.
These factors contribute to a building with far-reaching issues. For example, a healthcare facility experiencing mold and condensation called GHP to find the root cause was improper pressurization.
These common issues with building pressurization highlight the importance of addressing and resolving them promptly. Failure to do so can result in a range of problems.
Top 3 Risks of Negative Building Pressurization
Moisture and Mold
Negative building pressurization can create moisture and mold problems. Excess moisture enters the building through the unintended pathways caused by negative pressurization and increases relative humidity inside the building. A possible result is condensation and mold growth, especially when a vapor barrier such as wallpaper is present. This not only poses a health risk to occupants but can damage building materials and compromise the structural integrity of those building materials. Mold growth can lead to odors, discoloration, and deterioration of surfaces, requiring costly remediation and repairs.
Poor Indoor Air Quality
Negative building pressurization can result in the infiltration of outside air containing pollutants, allergens, and contaminants. These can include dust, pollen, exhaust fumes, and even harmful gases. Poor indoor air quality is potentially harmful to the health of building occupants. It can lead to respiratory issues, allergies, and asthma attacks. In addition, there is a risk of heightened carbon monoxide levels since imbalanced pressurization can impact the proper functionality of exhaust systems.
Temperature and Comfort Issues
Negative building pressurization can cause increased relative humidity and uneven temperature distribution within the building. This can result in certain areas feeling colder or hotter than others, leading to discomfort for building occupants.
How Do You Prevent Negative Pressure in Commercial Buildings?
It’s vital to address the problems associated with negative building pressure. Here are some effective strategies for limiting negative pressure in a commercial building:
Inspect and Maintain HVAC Systems: Regular inspection and maintenance of HVAC systems is crucial for ensuring proper airflow and preventing negative pressure. This includes cleaning or replacing air filters, checking and adjusting dampers, and ensuring that all components are functioning correctly. Keeping HVAC systems in optimal condition maintains the balance between outside air supply and exhaust air, reducing the risk of negative pressure.
Building Automation System: Implementing a building automation system can help proactively monitor and control building pressurization. This system can regulate the operation of HVAC systems, adjust damper settings, and monitor air quality to ensure that the desired pressurization levels are maintained. By automating these processes, it becomes easier to identify and address any issues that may arise, preventing negative pressure situations.
Proper Ventilation Design: It is essential to ensure that the building design includes adequate ventilation systems and properly placed air intake and exhaust points. Regularly monitoring performance relative to design is also critical, as systems and space use may change over time. By addressing any design deficiencies and ensuring a balance of airflow, you can minimize negative pressure.
Do You Have a Negative Pressure Issue in your Building?
Download our guide for our top 10 regular maintenance tips to evaluate your building pressurization.
