HUMIDITY PROBLEMS IN COMMERCIAL BUILDINGS | Rasmussen Mechanical
Maintaining acceptable humidity levels in the Midwest can be much more challenging than in other, dryer, parts of the country. Controlling humidity comes down to being able to limit the amount of moisture that gets into the building. Moisture load data is a key tool used when deciding which HVAC system is appropriate for a building. This data is taken from a study done by ASHRAE which examined peak moisture conditions globally. The goal is to use this data to install a system that keeps relative humidity between 40% and 60%. Anything over 60% and mold can begin to grow more readily. Let’s take a closer look at mold and then we will discuss how to prevent it from causing problems in your building.
Understanding Mold
Mold can thrive in damp environments that also contain organic material (material that used to be alive). This includes wood studs, drywall paper backing, paneling and a number of other sources. When these areas have a relative humidity above 60% or higher the chances for mold growth increases. As mold consumes these organic materials, it begins shooting mold spores into the air. These spores are what we often associate with a “damp or musty” smell in a space. Not only is this bad for building materials, but it is also the cause of respiratory problems and allergies for tenants. Preventing mold can go a long way in improving indoor air quality and also protecting building materials.
Important Note: Another common place mold can wreak havoc on are evaporator coils. Ensure your system is getting the maintenance it needs to prevent mold growth and treat it if it is occurring.
What Are the most common causes of humidity problems in a commercial building?
A study done by Don Gatley, which examined 79 different moisture issues in commercial buildings over a 25-year period, found that all except 4 were caused by building suction or excess humidity in ventilation and make-up air. These are also some of the most common humidity problems we see when addressing humidity issues with customers.
How To Solve Excess Humidity In Ventilation And Make-Up Air
One of the more popular ways for buildings to deal with high humidity issues is ventilation dehumidification. This is because for most buildings, ventilation and make-up air carry the biggest humidity load. By installing a ventilation dehumidification unit, you can drop the humidity level before the air enters the building. This helps ensure that relative humidity doesn’t spike above 60% even during peak humidity season.
When installing one of these units you should also add a return air connection for humidity control during unoccupied hours. By installing a return air connection, you can reduce exterior ventilation during unoccupied hours and still maintain a low relative humidity in your building. This prevents the dehumidifier from running when it is not needed and saves you money on energy costs.
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How To Solve Building Suction Issues
One common cause of severe moisture problems according to an article written by ASHRAE, is humid outdoor air being pulled through the exterior walls by suction created accidentally. This suction is usually created by unsealed return air or exhaust ducts, or by packaged air-conditioning units installed in the walls without tight seals. This hot air which is sucked into to walls then comes into contact with cool surfaces and condensation occurs.
In order to prevent this, it is important to ensure that leaks are sealed. You also want to ensure that excess exhaust doesn’t leave the building creating a negative pressure. While a positive pressure is ideal to prevent suction, it is important to note that even though a room has a positive pressure, it doesn’t mean that outdoor air can’t be pulled in behind walls. How is this possible? Poorly sealed exhaust fans or wall mounted AC units can create a negative pressure behind the walls while the room itself maintains a positive pressure.
Watch Out For Water Seepage
Sometimes odors and dampness that gets associated with an HVAC system actually has another cause, water seepage. Water seeping into buildings through joints in the concrete foundation can often lead to fungal growth if not dealt with correctly. As moisture seeps in it often comes in contact with organic building materials that allows mold to begin growing. While improving air flow rates in rooms affected by exterior water intrusion will aid in drying out the space, these issues need to have their root cause (poor exterior drainage) dealt with first.
Humidity Problems Got You Down?
Reach out to the experts at Rasmussen Mechanical Services and ensure your facility is safe. Call us at 1–800–237–3141, email sales@rasmech.com , chat with a support agent , or online.
