The U.S. Environmental Protection Agency (EPA) warns against letting indoor relative humidity (RH) go above 60%. It recommends 30% to 50% RH as the optimal range. That can be difficult to achieve even when running your cooling system. Let’s explore some steps you can take to achieve your ideal RH.

Avoid Open Windows and Doors When RH Is High

Without any cooling or dehumidification, the RH outside dictates the RH in your home. RH is the measure of water vapor in the air within the context of temperature. At higher temperatures, the air can hold more moisture. That’s why the air is naturally more humid in summer. Airing out your home on comfortable summer days is a great option, but pay attention to the RH. If the outdoor RH is above 60%, you’re better off relying on your air conditioning and ventilation systems.

Reseal Your Home

It’s wise to schedule a home energy audit every few years. During this appointment, your auditor will assess the building envelope of your house. When it comes to RH, the important aspects of a building envelope are natural ventilation and insulation. Older houses often have too much natural ventilation. This includes cracks in walls and the foundation and gaps between windows and doors. In this scenario, it can be very difficult to maintain ideal RH, as moist summer air will continue to flow into the home. Insufficient and/or worn insulation lends itself to high humidity for similar reasons. Resealing the house and replacing old insulation can make a big difference in relative humidity.

Install a Whole-House Fan

A whole-house fan is a great option for newer homes that have a tight building envelope. It can actually reduce your reliance on your AC and help maintain optimal RH when running it. You can run the fan in spring and early summer and not have to run your AC. Once it starts to get hotter and more humid, you can switch over to the AC or heat pump instead. You generally won’t want to run both at the same time because doing this would waste energy.

Schedule a Spring HVAC Tune-Up

Schedule seasonal HVAC maintenance in spring before you’ll need to run your cooling system. There are a number of great reasons to do so. When it comes to humidity, a top concern is the evaporator coil. Over time, it builds up grime that makes it less efficient. A byproduct of that inefficiency is failure to remove moisture from the air. A home can feel cool but still a bit muggy. This will help you avoid that problem. During maintenance, your technician will also clean the condenser coil and ensure that you don’t have refrigerant microleaks. Those issues can cause higher humidity as well.

Swap Out Your HVAC Filter as Needed

Central cooling systems have one or more supply vents that require an air filter. That filter is there to keep the system clean and help improve indoor air quality. It can also restrict airflow. If it does that too much, the system will work harder and struggle to remove moisture from the air.

Filters have a minimum efficiency reporting value (MERV) rating. Find the MERV rating that your HVAC system supports. It will usually be between MERV 8 and 13. Use the highest MERV rating your system allows. During summer, check the filter every couple of weeks. Swap it out when dust begins to cake up.

If you have a mini-split, you may have a washable filter instead. If so, wash the filter every other week, and replace it once a year. Springtime is a perfect time to swap filters.

Install a Whole-House Dehumidifier

A dehumidification system is by far the best way to maintain RH in summer. Portable dehumidifiers are an option, and a relatively inexpensive one at that. The drawback is that they only provide benefits in your immediate space. A whole-house dehumidifier provides your optimal RH throughout the entire home. They automatically drain as well, which makes them much more convenient. If you have central AC, your technician can integrate it into your system. This has the added benefit of making your AC much more efficient and subject to less wear and tear.

Invest in a Smart Thermostat

If you choose a whole-house dehumidifier, also opt for a smart thermostat with humidity control. A smart thermostat will make it much easier to coordinate the dehumidifier and AC to achieve your optimal temperature and RH. It will also save you money. The U.S. Department of Energy (DOE) estimates that a smart thermostat can reduce your cooling bill by as much as 10%.

Keep Room Dehumidifiers Clean and Emptied

If you do use portable dehumidifiers, be sure to keep them clean and emptied. Room dehumidifiers can easily collect 5 gallons of water a day. If they fill up to capacity, that will trip the wet switch, and the unit will stop working until emptied.

Use Your Ceiling Fans

Air movement is a natural way to remove humidity from the air. Ceiling fans make you feel cooler and more comfortable. Another benefit is that they distribute the cooling more evenly throughout a home. This helps you avoid the warmer and more humid air rising to the top of your rooms. Note that, if RH is above 50% and you’re not running your AC or whole-house fan, turn the ceiling fans off. In that scenario, the fans can actually increase RH.

Run Your Exhaust Fans

Kitchens and bathrooms are significant sources of moisture that can affect your entire home. Run exhausts in bathrooms while bathing and showering. Keep the exhaust running until all the moisture is gone. In the kitchen, turn the fans on as soon as you start to cook. Keep them running for 10 minutes after you have finished.

Run Water-Using Appliances at Night

Avoid doing laundry and running the dishwasher during the day. These appliances add a great deal of moisture to the air. This will be much less noticeable if you run them at night. You can even run the dishwasher when you go to bed.

Take Care With Houseplants

You may have heard of humidity-absorbing plants. Whether these have a significant effect on indoor RH is a matter of some debate. Many experts agree that even humidity-absorbing plants end up increasing RH overall due to watering. Having houseplants is alright. Just avoid having too many, and be careful not to overwater them. That can cause high RH in addition to mold.

Indoor Air Quality Experts in San Antonio

If you need professional assistance achieving and maintaining your optimal RH, [company name] is here to provide it. Our indoor air quality team also specializes in ductwork, including cleaning and resealing, insulation, thermostats and air purifiers. We have HVAC technicians who install and service electric and gas furnaces, central air conditioners, heat pumps and ductless mini-splits. We also specialize in generators and tank and tankless water heaters.

Contact us at [company name] today to schedule an appointment or get answers to any questions you may have.

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