Why Your Second Floor Is So Humid (and 5 Ways to Reduce It)


If you live in a two-story house, you’ve probably noticed that warm air tends to go to the upper floor.

But are you also noticing that with this heat also comes humidity? So why exactly could your second floor be so humid? Many factors can contribute to the humidity level in a home, such as poor insulation, a faulty air conditioning system, a leaky attic, the climate and summer season, and even whether you use exhaust fans when you shower or cook in your home.

For example, in Florida, the average humidity inside the homes is much higher than that in Colorado.

You may not know the ideal humidity level changes from season to season and room to room. A bedroom approximately requires 50% relative humidity year-round. This helps to reduce allergens and dust mites. 

Also, while the ideal relative humidity levels are below 60% in summer, they drop much lower in the winter.

But those are just a few reasons why you’re seeing high humidity levels on the upper floor. There are a lot more.


How Can You Tell if the Humidity Level in Your Room is High?

Having a comfortable humidity level in your home is critical. Here are a few common signs that may mean it’s too high.

  • If you have difficulty breathing, this means your home has a high level of humidity that can cause chest tightness and wheezing. This can often lead to people having asthma. If you have a high level of humidity, it can cause respiratory problems. The humid air has less oxygen and more water, which causes breathing issues. 
  • You need to look out for wet stains or crumbly plasterboard on the ceiling. You will see moisture as dark spots, which can be difficult to spot under some lighting conditions.  
  • Check your home for the smell of mold or mildew. Pests like termites, dust mites, and cockroaches thrive in this type of humidity. Their presence can lead to health issues.
  • Check for the condensation on the cooler surfaces like a mirror, windows, pipes, and also your basement. When you find it, check the surrounding environment to ensure that the moisture does not spread to the wall or adjacent surfaces.

Some of these signs may not indicate humidity, it is safe to get your home checked if you are experiencing any of these things. 


Reducing Humidity Inside the House

There are many ways to reduce the humidity in your home. 


  • Dehumidifiers

Dehumidifiers are installed in areas that tend to be damp, like bathrooms, basements, and even some kitchens. They work at their best when a room or an area has been sealed off, including all doors and windows.

They extract moisture from the air but make sure that they are away from walls or other objects to allow sufficient air to flow. If you live in a cold climate, you may need to buy a desiccant dehumidifier.


  • Ventilation

Make sure that the areas where moisture is present are properly ventilated, like kitchens and bathrooms. Turn the ventilation fans on and keep them on when the room has moisture. Get extra fans if you think there’s a problem with moisture. Replace exhaust fans and make sure they have a CFM rating powerful enough for the area of the space.


  • Air Conditioning Systems

A lot of two-story houses have a separate AC unit that delivers cool, crisp air to the second floor, or that’s the way it’s supposed to be.

That’s because conditioners are designed to remove moisture from your home’s air.

But if you’re noticing humidity instead of that dry, crisp air, it could be because of leaky ductwork or poor insulation somewhere in your home. This in turn overworks your unit – not only does it become humid, but the air conditioning is staying on constantly without being able to bring the temperature down.

If this is happening, it’s time to check if you have a clogged condensate line in the furnace. It’s very much possible that a leak could be coming from a furnace in the attic, which may explain why it’s more humid on the upper floor.


  • Insulation

Insulation is used to stop heat and keep excess particles from entering your home. If the walls of your home are properly insulated, they will prevent warm and cool air from escaping or entering through gaps. 

Some ideas to help you achieve that are:

  • Reseal around your windows to avoid moisture and condensation. And if your windows are at least 10 to 20 years old, it may be time to replace them.
  • Check the attic for leaks. It’s very possible that the reason your second floor is humid and the first floor isn’t is because there’s a leak in the roof or attic.
  • Check other areas above that may leak and insulate them. For example, the area around the chimney and vents may have some loose roof shingles around them.
  • Make sure you have a proper vapor barrier in the basement or crawl space, but be careful to not install it where water may pool and cause mold. It’s always best to start off with exterior options when it comes to waterproofing, but it can get expensive to do this.


  • Change Your Lifestyle

Making small lifestyle changes can reduce humidity. For example, you could make sure you turn on the exhaust fans in the kitchen and bathrooms before you start cooking and showering, and keep them running another half hour after you finish.

Although, there are many ways you can reduce humidity, here are some quick tips for improving humidity levels inside your home:

  • Take cold showers instead of hot showers because hot showers cause humid air. 
  • Always turn on your exhaust fans while showering or while working in the kitchen. Keep them on a little longer even after you are done working or showering. 
  • Try installing fewer carpets in your home as they retain moisture. Instead install tiles, woods, or something else that is easy to wipe moisture off of. 
  • Although having plants inside your home is lively and beautiful you might want to reduce the number of plants you have inside your home. Plants undergo transpiration, which is just a fancy way of saying they produce water. So swap out those tropical plants for some succulents, or get rid of them entirely.
  • Instead of using wallpapers or vinyl coverings, paint your walls. Mold loves the combination of humidity with organic nutrients to feed off of like wallpaper adhesive. You get what this might turn into? So avoid it before it becomes an issue.
  • Whenever buying an AC unit for your home, make sure it is the right size. Getting a smaller or larger size AC unit contributes to humidity in your house. Also, remember to change your filters frequently so that the unit can operate at its peak airflow and draw out as much water from the air as possible. 


Reducing Humidity Outside Your Home

Many things can be done outside of your home to reduce humidity inside your home:

  • Make sure that all drainage gutters or easements are sloping away from your house. This way, the water will stay away from your house and does not flood your basement
  • Many people have clothes they can’t put in the dryer. Although in winters, they use indoor drying racks, it is preferred to use outdoor drying racks or clothing lines in summers.
  • Get your roof checked regularly for cracks, molds, etc. Be sure to monitor all your vents leading to the outdoors, such as your dryer vent because, over time, they can break down and might need to be repaired or replaced. 
  • Hire a professional to check the foundation of your house. If your foundation walls are moist to the touch, it’s possible that there is no proper barrier.