I live in Tennessee, so humidity, especially when warmer weather starts to come around is a HUGE issue. Most people only consider the humidity outside. Those that do consider it indoors usually only worry about it in the wintertime when having the heat on is drying out their skin, sinuses (with dryness-related nasal nosebleeds as a behavior driver), eyes, etc.—in other words, the lack of moisture is what concerns them and makes them uncomfortable. I’m here to tell you, though, that excess and trapped moisture and improper ventilation indoors can be a budding health hazard.
Why?
Because, excess moisture is the #1 cause of indoor mold growth—more problematic than leaks even. This is mostly because 1) our hermetically sealed, energy-efficient homes are constructed with materials that trap air and moisture, and 2) a catastrophic leak or a significant water intrusion issue is more difficult to ignore. Consider this, a pipe bursts and you have a waterfall in your kitchen. You are probably going to immediately call a plumber to stop the leak, fix the pipe, and then repair the damage. On the other hand, if your cooktop fan is pumping all of the steam from your boiling pots directly into your soffit and creating significant mold growth in your attic, you may not even be aware of the issue, so that you can address it. (Note: Even small, slow leaks can produce massive amounts of water, especially if they aren’t promptly addressed.) Thus, knowing some simple tips for controlling that moisture can mean a big difference in the overall health of your home. This is especially pertinent for those people who suffer from allergies, asthma, and chronic illness. The presence of even a very small amount of mold in the home can lead to acute health issues, like chronic sinusitis, trouble breathing, vertigo, fatigue, upper respiratory issues, and much more for this population of people.
To help you identify some pesky sources of indoor moisture, here are 10 tips (some are not what you’d expect) to control indoor moisture and make your home healthier and less prone to mold growth:
1.) Dehumidify your basement. 
It doesn’t matter if your basement is finished or unfinished, you need to actively control the humidity levels down there. Cool air becomes more easily saturated with moisture than warm air, which is why basements tend to harbor mold—they are closet to the ground and usually have more than one exterior wall. There is also the stack effect to consider in the basement, or the effect of convection air circulation, when as the warm air inside your home rises and escapes through openings to the outside, any cold exterior air is sucked inside. In the wintertime, basements and crawlspaces are the principal cold air entrance points. Active dehumidification in your basement helps eliminate the cold, clammy feeling that can sometimes occur. Make sure all windows are closed and run a dehumidifier down there around the clock, or at least very frequently. You may even want to invest in some ceiling or box fans to make sure the air is properly circulating. Many people don’t go down into their basements every day or open them up to the rest of the house. This tends to be more of a problem for unfinished basements. Whatever the case, if you can keep the air moving and have a dehumidifier going to suck away the moisture, you can significantly decrease the chances of mold growth and better the air quality. If you don’t want to have to empty the dehumidifier yourself everyday, you can even find one that drains, or that you can attach a hose to it and run it outside to drain. Nowadays, the options are great.
We rigged our dehumidifier to drain outside.
2.) Check for leaks frequently and address them immediately.
Never ignore the obvious. Wherever you have pipes, you could potentially have a leak. Open your kitchen, bathroom, laundry room, etc., cabinets a few times a month and look for and feel for moisture and leaks. Also, move your washing machine and refrigerator once a month to check the water lines and connections for leaks. Finding these early and addressing them immediately can save you money and potential sickness from the fallout of not knowing about or addressing them until a mold issue exists.
3.) Monitor exterior water-flow and keep gutters clean and properly functioning. When your gutters and downspouts are not working properly, are clogged, and/or overflow, water can build up near your home’s foundation and seep inside. This can also occur if you haven’t properly routed water-flow patterns and areas of pooling and congregation around your home. A particular place of concern for water intrusion in these situations are basements. I like to tell people to walk around the exterior of their home during a good rain. Take an umbrella and walk the entire perimeter of your house.
We routed water to run off of our patio and down into drain in our yard.
Watch for gutters overflowing, water streaming from the roof in a dumping pattern, or areas where water seems to be pooling near or around your home. If water is not running and routed away from the foundation, you could have a problem on your hands. This can be easily fixed by having your gutters cleaned, unclogging your downspouts, adding angles or rounded pieces to flat areas or roofing, grading and angling landscaping away from your home, and adding drainage systems on your patio or in your yard to route the water away from your home. Some of these fixes are even relatively easy DIY projects. The point is to observe how water behaves outside of and around your home and fix things accordingly.
4.) Place a pan beneath your water heater and attach an overflow alarm to it.
A pump and just a water heater pan are not enough, because the pump can become clogged and the pan can leak or overflow. 7.8 million water heaters are replaced in the US annually, due to leaks, overflows and age-related issues. If you install a battery-operated floor water alarm to the pan of your water heater, it will alert you immediately if and when there is a water overflow. Since most of us are not checking our water heaters daily, or even up in our attics or down in our basements that frequently, where the water heater is usually located, this simple device can potentially save you thousands in water damage and subsequent mold remediation costs.
5.) Seal and dehumidify your crawlspace. 
There is so much I could say about crawlspaces and mold—they are notorious breeders and sources of largescale mold and air-quality issues in homes. Another topic for another day, I guess. I will reign myself in and keep my suggestions here related only to moisture control. If your home sits on a crawlspace, if you do nothing else, make sure that crawlspace is properly sealed from the outside (the stack effect again) and is kept dry with dehumidification. If the crawlspace is accessible to the home, make sure any returns are sealed so as not to suck moldy, musty air into your home or to entrain it into the entire HVAC system. If the floor of the crawlspace is dirt, cover it with plastic to create a vapor barrier. It is my opinion, after speaking with numerous Building Biologists and Indoor Air Care Specialists, that a crawlspace should be isolated from the indoors of a home and dehumidified rather than ventilated to the indoors or outdoors. Because this space sometimes runs the length of a home, it communicates with the indoor air and needs to be kept as dry as possible, so that it does not harbor molds and bacteria. In a crawlspace, you want to both keep outdoor allergens and pests out, while not allowing moisture, dust, mold, dirt and bacteria in to circulate in your home.
6.) Keep a finished basement warm. This seems like a weird one, right? Keeping a finished basement at 60 degrees F will help to prevent moisture build-up that can also lead to mold. Simply not allowing the temperature to dip below 60 keeps relative humidity low. The heat will rise from the basement to the rest of the home and will also prevent any congregation of moisture to the lowest and coldest places inside.
7.) Add a breeze to your bathroom. I advise EVERYONE to do this. Whether you own your home, or are renting, you can bring additional fans into your bathrooms to help dry and circulate the air. This is separate from bathroom ventilation and exhaust fans than I have discussed before. (HERE is a link to that post.) While proper ventilation in the bathroom is crucial to the health of your home—and ventilation that does NOT vent into your attic or roof, but to the outside—addition air flow can also speed water evaporation on ceilings and walls after your shower. Leaving the door to the bathroom open with the fans blowing post-shower is the best way to fully dry out the space as quickly as possible. You will even find this to be a hack with your bathroom cleaning. You will not be scrubbing mold and mildew from grout as often, because the moisture is not sitting there to create the issue. Tower oscillating fans are perfect for this, because they don’t take up much space and can look modern and stylish.
8.) Heat and/or ventilate your walk-in closet. Many of us do not consider our closets as much as we should. Closets, especially those with two outside walls can get moldy, because the air stays cooler than the air in the rest of the house. Don’t forget, you also have a HUGE amount of organic material in there for mold to grow on! There are safe ways to heat and ventilate your closet. Talk with an HVAC expert about installing a supply and return or about creating more air circulation through the space. Also, try to not pack things too closely together on the racks, floor, or shelves. This will help the air to move through your things and will prevent smelly, musty odors from congregating in your clothing. I also advise people to use tile, wood, or some other hard surface flooring in closets.
It is not as plush on your feet but will also prevent moisture from staying in the area. Finally, if your closet is located inside of your bathroom, keep the door closed while you are showering or bathing. When finished, open the door and run a fan inside your closet, in addition to one in the bathroom, to speed evaporation.
9.) Actively measure and check your indoor humidity. 
You don’t have to have an expensive whole-house dehumidification system to know your indoor humidity levels. A hygrometer costs from $5 up and can be used wirelessly in many areas of your home to check and monitor humidity. You can place sensors in your basement, attic, and other areas of the home. 
Then, you can check daily whether the relative humidity is rising above 50 percent. If it is, you need to take steps to improve and encourage dehumidification. Mold can start to grow, even when there is not standing water when humidity levels indoors get to be 60%. Knowing your relative humidity levels helps you to proactively take the steps necessary to prevent mold growth.
10.) Isolate your attic from the rest of your home. Even a well-ventilated attic is at risk for mold growth if moisture gets in. Seal it off from the rest of your home by making sure bathroom, kitchen, and dryer exhaust fans do not vent into the attic, applying sealing hardware or attachments to attic doors, and pull-down stairs, and by sealing up gaps around recessed lights. (If there are gaps around your recessed ceiling lights, the warmer air rises through the gaps.) 
This is to protect your attic from harboring the excess moisture from the conditioned air in the rest of your home. I also advise people to have professionals HEPA vacuum away any and all fiberglass insulation in the attic. It is toxic, absorbs water and grows mold easily, and can become a nesting place for pests. Instead of fiberglass, opt for bagged insulation that is contained and has a vapor/moisture barrier. This will keep both you and your home much healthier.
There you have it. The list is by no means exhaustive but should get you thinking and working towards a healthier indoor environment.
What would you like for me to write about next? I want your input!
