As many people are dealing with high outdoor temperatures accompanied by high humidity in the South, comfort issues within the home are popping up left and right. While it is easy to deduce if the HVAC system is maintaining a comfortable temperature by simply checking the thermostat, other factors such as relative humidity also play a role in what is subjectively labeled as ‘comfortable’.
Most people know exactly what high relative humidity feels like – step outside during a hot summer day and the familiar sticky feeling is unmistakable. While Absolute Humidity measures the actual amount of water vapor in the air, Relative Humidity measures the amount of water vapor in the air relative to the air temperature. Higher air temperatures can hold more water vapor than colder temperatures. This means that if two temperatures, 30 degrees and 80 degrees, have the same absolute humidity, the relative humidity will be higher at 30 degrees than 80 degrees. Because of this relationship between temperature and moisture, many of the indoor comfort issues that homeowners have relate to the relative humidity of the home.
Common issues that relate to high indoor relative humidity are high envelope leakage, inadequate ventilation strategies, and oversized HVAC systems. A leaky building envelope allows hot, humid outside air to infiltrate the home; this is exacerbated on upper floors in homes with multiple floors as the stack effect draws in air from the top of the assembly. Bathroom exhaust fans, which are intended to exhaust humidity and odors, often are inadequately ducted and do not exhaust as much air as intended. This can lead to humidity lingering in the bathrooms after showers and raising the relative humidity in the home. Oversized duct systems are one of the most troublesome issues seen regarding high indoor relative humidity due to the cost to replace them. An oversized duct system will often quickly cool the space, which seems nice at first; however, air conditioning is also tasked with dehumidifying the space. These shorter run times, also known as short cycling, can lead to inadequate dehumidification and an increase of relative humidity.
Many homeowners are experiencing these issues this summer; if you are one of them, please call the Building Scientists at E3 and we can conduct a full Home Assessment to help identify your issues and come up with a game plan to return your home to its full comfort
