Let’s face the truth: here in north Georgia, including Atlanta – we’re surrounded by water.
You thought you were surrounded by mountains to the north and rolling hills to the south!
Oh no! You are surrounded by water. And the sooner you realize this truth, the better equipped you can be to manage the high levels of indoor humidity you’re struggling with inside your home.
We live in the SubTropics!
Here’s some trivia that may shock you:
- The average year-around level of humidity in our region is 68%. By the way… that’s wet. Atlanta’s climate is considered “subtropical”.
- The wettest month for us is August, averaging 75% humidity. April is our least humid month, at 61% humidity.
- You and I are most comfortable when humidity stays in the range of 30-50%.
If you’re like me, when I read those statistics, you’re like, “really”? I’m always seeing the relative humidity in the 80% and 90% range! In fact, right now, as I write this article, it’s 3am, on September 21, 2022. My laptop says the humidity is sitting at 78% while it’s 74 degrees outside.
Yesterday at 8am, my phone said it was 93% humidity while I talked with a homeowner.
Putting all else aside, we all can agree on one thing here in Hot’lanta: We suffer from high humidity year-round. We rarely escape it.
Is Your House a Terrarium?
Let me discuss your house for a moment.
If your home was built since 2015 and it’s been maintained properly, it’s likely pretty tight. Remember, the tighter the structure, the more concentrated the pollutants inside the home become. This is called Indoor Air Quality.
So, if you own a tight home, or you are improving the tightness of your home, you must be aware that you need to actively manage higher levels of indoor relative humidity.
Got a Leaky House?
If you’re like the majority of us Atlantans, you live in a house that’s older… and some are much older.
These are considered “leaky” houses! The uncontrolled air infiltration trespasses back and forth between the atmosphere and your living space.
These houses can behave almost bipolar. And on days with milder temperatures, your AC refuses to cycle on, which really drives up the indoor humidity levels. And you feel clammy and sweaty, just lying in bed trying to go to sleep.
I’m telling you, your house is surrounded by water, and it’s a real problem, because your “boat” is taking on water.
Here are a few thoughts to help you deal with high humidity inside your home.
You must recognize that the humidity inside your home comes from two sources:
- INSIDE: Occupants and pets inside the home.
- OUTSIDE: The super-humid atmosphere surrounding your house, as it penetrates the envelope (shell) surrounding your living space. The 2nd Law of Thermodynamics teaches us that wet is always moving toward dry. The moisture in the clay soil under the house and the moisture in the atmosphere is being irresistibly drawn into your conditioned living spaces.
- Buy a dehumidifier. Heck, buy three or four! This is like bailing water in a leaking boat. You never get a rest, because you’re always emptying the bucket(s). By the way, the average portable dehumidifier adds about $40 to your monthly electric bill. Only the desperate would choose this option.
- Install a whole-house dehumidifier on your hvac system(s). This is an ideal way to manage humidity inside your home, because the dehumidifier is “plumbed” into your air duct system. So it actually dries the air throughout the entire zone that is controlled by the air duct system. Expect to spend between $3500 and $4500 to have your hvac tech install a high quality unit. For houses with multiple hvac systems, consider buying and installing a few strategically located weather stations. Monitor the areas of your house for high humidity. Install your first whole-house dehumidifier in the zone with the most stubbornly high humidity. Who knows… you may only need one dehumidifier!
- I really like these because they are most effective. And they do their job on auto-pilot. “Set it and forget it”.
- Some of these units sample the air in your home for 5 minutes, every hour. If that air sample is wetter than the set point on your machine, it activates the blower motor on your hvac air handler, and begins to dehumidify the air, until it reaches one to two percent below your targeted set point.
- If the air sample is equal to or dryer than your set point, the unit waits patiently for another hour, when it samples the air again.
- Quiet. You don’t hear a whole-house dehumidifier. Whereas the noise from a portable unit reminds me of a middle school kid riding a 2-stroke dirt bike. Can you say, “incessant”?
- By all means, do not over-size your central AC system! Today I was called to a little 1400 ft2 house that has a 3 ton package unit cooling it. Why was I called? Because the renter is complaining about mildew. I’m not a licensed hvac guy. But I’ve sat through plenty of training (courtesy of Georgia Power and some EMCs we work with) where I’ve learned that it takes at least 15 to 20 minutes of runtime before your AC begins to remove water from the air inside your home.
- An oversized system will not run long enough to efficiently control the humidity inside your home. The AC comes on, blasts the house with cold air, and shuts off too soon.
- If this is your case, perhaps your hvac tech can slow down the fan speed, so that the unit runs longer.
Motivated to do more?
If you’re motivated to make improvements to your home in ways that help you limit & control the humidity inside the house, consider these ideas:
- If the house is on a vented crawlspace, realize that a huge amount of moisture is entering your home from underneath the floor. As I see it, you have two choices. You don’t do both of these… pick one:
- Encapsulate (seal-up) the crawlspace and install a stand-alone dehumidifier designed for crawlspaces. If you have an hvac system in the crawlspace, this is the ideal improvement, because it captures the duct leakage and you benefit from that previously-lost energy.
- Seal the subfloor, with about 2” coverage of closed-cell spray foam. I always recommend this for clients who don’t want to have to manage a sealed crawlspace. Seniors, landlords, single parents, corporate types who travel all the time, these are the clients who generally prefer to seal the subfloor and leave the vented crawlspace as it is.
- Spend time sealing the envelope of your home.
- Upgrade the windows and doors.
- Address the crawlspace, if you have one.
- Airseal the attic floor.
- Install a shutter seal on your whole house fan shutter, (if you have one).
- Install an Attic Stair Cozy on your pulldown attic stair unit. I personally like the Attic Tent brand.
- Remember, you want the thermal barrier and the air barrier to be the same geometric plane. In other words, allow no air (as little as possible) to be present between your insulation and the floor/walls/ceilings of your house.
- Install exhaust fans in your bathrooms and kitchen.
- Duct them to the atmosphere.
- Confirm that each fan has a working damper!
- Consider replacing the wall switch with a timer, or better yet, replace the switch with a unit that is auto-controlled by the humidity level in the bathroom. Set it at 50% and forget it.
- Is the chimney damper closed? If the fireplace has no damper, buy a “chimney balloon” and use it.
- Definitely consider hiring a Home Performance Company to perform a diagnostic Home Energy Audit where they use a blower door and other tools to measure the tightness of your home, CO levels, etc. for your health and safety. Expect to spend between $500 and $700. Do yourself a big favor, and be home while the audit is being performed. Follow the tech around, and ask lots of questions!
- If you are purchasing a new hvac system, consider the type that has the dehumidifying feature built-in.
- Strongly consider adding a whole-house dehumidifier. These things are true game-changers for your indoor air quality and comfort!
This article hasn’t covered everything you need to know about indoor humidity. But just realizing that your lack of comfort isn’t always related to your thermostat is your starting place. Now you know, that all of us are in hand-to-hand combat with managing the effects of high humidity inside our homes.
We’re all Surrounded by Water!
The folks who are managing humidity best, are the ones who are actively aware that we are surrounded by water. These homeowners are making improvements to their homes that limit how much moisture enters the house from the atmosphere. In other words, they have taken measures to airseal the envelope (shell) of the house. And they use mechanical means (dehumidifier) to manage the humidity inside the house, limiting it to acceptable levels.
Thanks for reading! God Bless You in your quest for a dryer home.
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