Understanding Relative Humidity

The important point of order for understanding humidity is the “relative humidity.” It’s a confusing concept that’s hard to understand, and the formulas used to create the number you see on the news can be very difficult to determine.

The good news for you is that you don’t need to know all the ins and outs. You just need to know the absolute basics.

Water in the Air 

Relative humidity is a measurement that describes how much water is in the air relative to how much water the air can hold maximum. That means an area at 60% humidity is holding 60% of the water it could hold at most.

Warmer air can hold more water than cooler air. That means the summertime air can hold more water than air during the winter. Although the relative humidity may not change much, it’s common for higher humidity to be more uncomfortable in warmer climates because there’s more water in the air.

If you live in a coastal climate, you’ll typically have higher relative humidity in the area. That’s because the air around you absorbs the water from the ocean.

Warm Air Cooling

Because warmer air can hold more water than cooler air, that can actually lead to problems when the two collide. It’s a very complicated process to determine the actual relative humidity when two types of air collide, but what’s important to remember is that it can very quickly turn into condensation.

Essentially, when warm air cools drastically, the relative humidity shoots up. Relative humidity above 100% turns into condensation because the air is so saturated with moisture that it has to leech out somehow.

That means if you’re in a situation where warmer air is cooling down quickly, such as a crawl space with open vents letting in cool external air, you’re almost invariably going to end up handling condensation. It’s important to pay attention to this facet of the process.

The Right Relative Humidity Year-Round

Before you look for the ideal crawl space humidity level, you should think about the right humidity in your house as a whole. Typically, humans do best in humidity levels ranging from 30-60%, with most people feeling most comfortable around 50-60%.

So what should humidity be in the crawl space? That’s a difficult question to answer. However, 60% humidity in the crawl space should probably be the top end of your ideal crawl space humidity level. Most people aim for around 55% to avoid any unforeseen problems.

Of course, this may change around the year as the external relative humidity changes with the temperature. Depending on your space, you may need to look into purchasing a dehumidifier for maximum comfort.

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