SERVING 
Ah, humidity. Now there’s a topic that people really sweat about!
Here in the southeastern United States, we spend a lot of the year worrying about how to reduce the amount of humidity in our homes. But during the winter, those concerns go out the window. Since cooler air holds less moisture, the air isn’t too humid anymore – it’s too dry!
This is why we’re often asked, “What should the humidity be in your house in winter?” When people ask this, they’re usually referring to relative humidity (RH), which is expressed as a percentage and is a useful way to gauge how humid it is in a given environment. Anything over about 60% RH is usually considered too humid, while most people consider anything below 30% RH to be uncomfortably dry.
So, what should the wintertime humidity be in your home? And how can you keep it at that level? Let’s take a look.
Try to keep your humidity at 30% RH or higher
Many people think that their indoor air needs to be over 40% RH, even in winter. In most cases, this isn’t true and honestly isn’t even realistic for most homes.
Unless you live in a super airtight, high performance house that was built in just the past few years, you will probably struggle to keep wintertime humidity at 40% RH or higher. Even if you do live in one of those homes, the air exchange from your ERV might still make it difficult to maintain that RH level. But that’s ok. It really isn’t a problem.
In most homes, most of the time, anything above 30% RH during the winter is great.
Everybody experiences humidity differently, but below 30% RH is the point at which most people start to experience some discomfort. Other people won’t experience dry skin or a scratchy throat until the RH dips below 25% or so. People who are more sensitive might need the RH to be above 35% in order to stay comfortable.
A good way to determine your threshold RH for winter is to buy a hygrometer. Readily available at hardware stores, these little devices monitor your humidity 24/7 and display the RH on a big digital display. By checking your hygrometer regularly, you can get a sense of the humidity levels at which you’re most comfortable.
What if you can’t keep your house humidity above 30% RH in winter?
In many homes, it’s tough to keep the RH high enough to be comfortable. Here’s a step-by-step game plan for increasing indoor humidity:
- Seal air leaks. The air isn’t just dry for no reason. It’s dry because cold winter air is entering your home from the outdoors. The best way to identify your biggest air leaks is to have a home performance pro perform a blower door-guided thermal analysis of your home. This exercise will reveal where the air is getting in, so you can prioritize areas for air sealing.
- Stop removing humidity. Let the steam from your shower hang around. Let your soup simmer with the top off. Hang clothes to dry indoors. After sealing air leaks, the passive humidity generated from these activities may be enough to keep you comfortable. Don’t feel like you have to run your bath or kitchen fans just because they’re there.
- Get a tabletop humidifier. These are often the solution when you just need to increase the moisture in a small space, such as your bedroom while you’re sleeping. After sealing air leaks, you may not even need one, but they’re a good solution if you’re sensitive to sub-40% RH levels.
- Consider a dual fuel system: If you’re planning to replace your gas furnace in the near future, a dual fuel system might help you improve humidity management. Dual fuel systems use a heat pump on most days and a gas furnace for when it’s really cold. Heat pumps tend not to dry out the air as much as gas furnaces, so you may feel more comfortable with this setup.
When should you get a whole-house humidifier?
Only when you’ve tried all of the above strategies and still can’t increase humidity enough to be comfortable.
If you opt for whole-house humidifier installation, get a steam humidifier, not a bypass humidifier. Steam humidifiers boil water on their own and are much more efficient than the bypass models.
Also be sure you only run it when the heat is on. This is especially important when your ducts are outside the building envelope. The reason? Mold.
If you’re constantly pushing hot steam through cold ducts (they get cold quickly when the heat isn’t on), condensation will form inside the ducts. It won’t take long for you to develop a mold problem, which will probably make you more uncomfortable than having dry air!
At PV, we generally discourage customers from buying whole-house humidifiers if they haven’t air sealed their home. We’re big believers in keeping comfortable, heated air inside and dry, uncomfortable air outside during the winter. Air sealing helps you do that without installing expensive new equipment. Some homes still benefit from whole-house humidifiers after air sealing, but many will no longer need one.
So, what should the humidity be in your house in winter?
Whatever is most comfortable to you! 30% RH or higher is a good guideline, but go buy a hygrometer and compare the readings to how you feel.
If you’re struggling to keep your humidity high enough to stay comfortable during the colder months, air sealing your home is a great first step toward solving the problem. Only consider getting a whole-house humidifier if blower door-guided air sealing still hasn’t solved the problem.
If you live in Metro Atlanta and are struggling with uncomfortable, dry indoor air, PV can help! Give us a call at (404) 994-2229 today or fill out the form below.
