How Your Home Can Fight Humidity with a Summer & Winter Setting on Your Furnace

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How Your Home Can Fight Humidity with a Summer & Winter Setting on Your Furnace


Humidity is important for keeping comfortable inside your home. On average, relative humidity levels between 20% and 50% are considered comfortable and safe your home’s structure. There are several ways to help combat humidity inside your home, and one of these may be located somewhere along your furnace’s ducts – the switch for summer and winter.

Cold Climates & the Summer/Winter Setting

Most of the homes that have summer/winter switches somewhere along the ductwork are located in cold weather climates. The switch itself is typically a single lever that you pull one direction for summer and the other direction for winter. Homes with humidifiers typically have this switch, and it can play a very important role in protecting the structure of your home.

The Difference between Settings

In some homes, the summer/winter switch only has two positions – open or closed. These positions should be indicated near the switch. In some homes, and on many newer HVAC systems with humidifiers built right in, you can choose from a variety of settings. Many have four, eight, or even as many as 10 different humidity settings that allow you to decide how much moist air enters your home’s ductwork. In these cases, you may notice the letters “W” and “S” located near specific settings indicating which the manufacturer believes is the best setting during peak

heating and cooling seasons.

Why the Summer/Winter Switch is Important

In the wintertime, the switch (which is actually a valve of sorts) should be left open, allowing air that passes through the humidifier to also pass through the ducts. This helps to put moisture into the air during the cold winter months as needed. During the summer months, you would need to close the valve. Leaving it open would effectively send moist air through your air conditioner, making it work harder to cool the air inside your home and rendering it quite inefficient.

For example, if it is 15 degrees outside with a relative humidity of 60%, the relative humidity inside your home will be much, much lower – usually only about 10% of the humidity outdoors.

As the cold outdoor air makes its way inside your home, your furnace heats it, which causes it to expand in volume, but does not add more moisture without the humidifier. In this scenario, without the humidifier, it is likely that the indoor relative humidity would only be about 6% – far too low for comfort, and low enough that it may cause wooden elements in your home to split and crack. In the summer

If your home has a summer/winter switch or valve, it is important to make use of it each season. Not only will it help to keep your home more comfortable, but failing to move the switch as recommended could lead to a lack of important moisture during the winter, too much moisture during the summer, and higher energy bills caused by reductions in your air conditioner’s cooling capacity.

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