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Controlling Indoor Humidity

Here in Middle Tennessee, our summers are known for their extreme humidity, making breathing harder and making us feel sticky and sweaty. Humidity refers to the amount of water vapor in the air, and in Middle Tennessee, we live in an area where water sources are plentiful (lakes, streams, rivers, and rainfall) and the land is contoured like a basin (low areas surrounded by hills) making it easy for damp air to stagnate.  

When it comes to humidity inside, symptoms such as itching, sneezing, and coughing, are often due to allergic reactions to the organisms that thrive in humidity.  Humidity promotes bacteria, fungus, and mold growth, and attracts bugs, especially dust mites.  All are significant indoor allergens and can set off allergic sensitivity, trigger rhinitis, eye or skin irritation, wheezing, asthma and other respiratory conditions.  High humidity can cause a house to rot, promotes paint peeling, and can damage both the interior and exterior of your house.  It also attracts pests (even snakes!) who are always looking for water.

The ideal indoor humidity is 35-50%.  Mold thrives in humidities of 65% and above.  Although lower humidity will result in lower mold and dust mite growth, drying out too much causes other problems, such as skin irritation, difficulty breathing and static electricity.  Low indoor humidity is a bigger issue in winter months, and high indoor humidity can be a big issue during the summer.  A hygrometer can tell you the exact relative humidity, and some Smart Thermostats today may even have a hygrometer built-in. 

Tips for Lowering Indoor Humidity

Because lowering indoor humidity is essential to your whole household, we've compiled some important tips for you here:

Air Conditioning. Air conditioning makes you feel comfortable by helping to control the humidity. But if your air conditioner is over-sized, it may not be running long enough to decrease the humidity (see our blog post about this here). As air conditioners pull out moisture from the air, the condensate must have a place to go, so make sure your air conditioner's drain is not plugged up (see our blog post about this here).

Ventilation and Exhaust Fans. Vent the areas that create moisture, like the shower, bathroom, kitchen, and laundry room. Make sure you turn on the vent fans, and turn them off when the moisture has dissipated. Running them too long in the summer wastes air conditioning, which itself serves as a dehumidifier. If you do not have exhaust fans, consider installing some.

Room Fans. If air is not circulating in your home, humidity levels will rise. Use ceiling fans or room fans when possible. This will also help your air conditioner to be more efficient.

Home Décor. Carpet can trap moisture and is one of the favorite homes of humidity-loving dust mites. Steam cleaning carpets is best done in winter months when humidities are naturally lower. Some house plants can extract water from the air, thus helping to lower indoor humidity levels: Boston Fern, Peace Lilly, Reed Palm, English Ivy, Tillandsia (air plants), and small cacti plants are some examples.

Proper Construction. If you don't build properly, moisture can condense inside walls and cause rot, or on the inside of the house causing fogging of windows. Gutters and downspouts should be extended to carry rainwater away from the foundation, and the grade should be sloped away from the foundation to shed water away from the house. A buried exterior drainage system can be installed to take care of water near the base of the house, or near a concrete slab. House wrap, such as Tyvek and Typar, allows moisture to pass through but not air (making the house more energy efficient). Some house wraps and siding don't allow for the house to dry out, and once the insulation is wet, it loses its thermal qualities. Some areas such as crawl spaces or basements require sealing the ground with a moisture barrier.

Dehumidifiers. This is an appliance that extracts the water from the air in your home, and stores it in a tank (which must be emptied) or drains into a sink or house drain. Some are self-regulating in that they come on or off based on the humidity level. Although portable dehumidifiers are the most common, there are also ducted (to an outside wall) and stationary units available. Be sure to place the dehumidifier in an open area, that it is appropriately sized for the room, and that you check and clean the filters often. Installing a dehumidifier may be the best solution for a musty basement.