We have certainly experienced a wet winter and spring. When it’s wet outside, most of us look for tell-tale signs of a moisture problem like water infiltration or flooding. But did you know that this excess moisture may be affecting your building and the air you breathe in less obvious way?
The amount of water vapor in the air (also known as humidity) can have a dramatic effect on how your building “breathes” and how your HVAC operates.
How your building breathes
Let’s look first at this idea of your building “breathing”. Walls might seem solid, but did you know that air and water vapor are moving through your building’s wall systems right now? We call this process “breathing”.
Temperature and percentage of humidity are the two factors that affect where air and water vapor will go. That means that rising temperatures and increased moisture in the spring affect how your building breathes.
The general rule is that air (and water vapor) will try to move wherever there is less pressure. In the winter time, you have cold, damp weather outside and warm dry conditions inside. In this case, water vapor will try to get outside the building where air pressure is lower.
In the summer time, this situation is reversed. You have hot, humid weather outside and cooler air inside. This means the pressure outside the building is much higher than inside, which encourages water vapor to travel inside the building.
Spring time is a unique time when the pressure balance is constantly changing. You have lots of excess moisture (humidity) sitting outside and rising temperatures outside. When you have lots of excess moisture (like the precipitation we’ve had this year), you’re going to see that water vapor start trying to move inside in the form of water vapor. So even though you might not notice water infiltration or a leak, your building is probably taking on water that you cannot see.
One surprising problem we’ve created in trying to make energy efficient buildings is building structures too “tight”. For example, in hospitals you do not want a lot of air traveling through your building walls because you don’t want outdoor particles getting into your indoor air. However, when you build walls so “efficiently” that they cannot breathe, you also make it impossible for water vapor to escape. This causes water vapor to condense or get trapped in the space inside walls when there is a large temperature/humidity differential.
This is what happened in a recently-completed healthcare facility. The building was less than a year old, but mold had started to grow inside the walls because they weren’t able to breathe and release excess moisture. Contractors had to tear down the walls, remediate the mold and re finish the rooms. Not the kind of problem you’d expect to have in a brand-new building!
How does your building compensate for wet conditions outside?
How do we prevent all this moisture movement from causing problems? Your best friend is an efficient HVAC system, which should be able to moderate both the temperature and humidity of the air inside your building and moderate some of the natural vapor movement at play.
You are probably familiar with the idea that your air conditioning will cool outdoor air. But did you know that your HVAC is also responsible for removing excess moisture from air that comes through the intake? This is a big job for your HVAC system and can put a strain on your HVAC system, especially if you’re just firing up for the season.
So, what’s the takeaway here? First, make sure your HVAC is kept in good working order so that it can condition and moderate your indoor air. And second, don’t be surprised if your building smells musty. It would be a sign that your building is not breathing properly. If you suspect a problem, there is no need to panic. Have someone come out and check your HVAC system to ensure it’s working properly. If you continue to suspect a problem, you can always ask and IAQ expert to conduct an assessment of your building or a mold assessment to identify the cause of any musty odors.