Relative Humidity - A Primer
Understanding the Impact of Relative Humidity to Your Home
The last thing a homeowner wants is a damp living space. But the in-home factors leading to high relative humidity (RH) give you just that. Uncontrolled RH (not the hot air that comes from a family member) & a lack of fresh air are the two biggest causes of unhealthy & damaging conditions to multi-family homes. Constantly tightening building standards have had an unintended result over the years - deteriorating ability to manage RH & maintain healthy indoor air.
In a series of posts, we'll answer some basic questions about RH, describe positive aspects of controlling it correctly; outline factors that make RH excessive in the home; and give tips on the steps you can take to control it.
Q: What is relative humidity (RH)?
Relative humidity is defined as the amount of moisture a fixed volume of air can ‘hold’ at a given temperature.
Q: Why does temperature matter where RH is concerned?
Warmer air ‘holds’ a greater volume of water than cooler air, therefore temperature control plays an important part in managing RH. When warm air cools it ‘drops’ the excess volume of water it can no longer hold in the form of condensation, creating a damp feeling. On your building surfaces, opportunity for mold and mildew growth, trapping of allergens, & appearance of allergy or asthma symptoms can present themselves.
Factoid: Interior RH approaching 50% results in risk of condensation.
Interior RH at 60% or greater can trigger mold and mildew growth without visible moisture being present. Excessive interior RH dramatically increases air pressure within an individual home unit. Homes relying on baseboard or radiant electric heat often inadequately circulate air within the unit, leading to cold spots that can trigger significant condensation when adjacent cooling air loses its ability to hold moisture. Wet surfaces are the result.
Q: What is an ideal RH level for my Strata home?
RH levels lower than 30% cause most people some skin or respiratory discomfort and levels above 50% are the beginning of other problems. A median RH level of 40% serves most homeowners well.
Q: Is weather channel humidity the same as RH?
No. Weather reports refer to absolute humidity or the actual amount of moisture in outside air regardless of temperature. Relative Humidity & Absolute Humidity are terms that cannot be used interchangeably – an important fact to remember when addressing sourcing & using fresh air.
Even though the onset of RH issues is relatively invisible to the naked eye, it's important to address the issues at that point in time. Finding and addressing RH Issues is part of the many building assessment services we offer. Give us a call for a no cost conversation, and bring your questions.
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