Most people associate high humidity levels with summer, but did you know that your home can have high humidity levels in the winter as well depending on your home and climate?
So, how do you reduce the indoor humidity in your home during the winter? In most climates, humidity levels tend to be low during the winter. High humidity levels inside a home during the winter are unusual, therefore, and usually a sign of major issues like water leaks, condensation problems and poor ventilation. Solving those issues, in addition to adding a powerful dehumidifier, should solve most humidity problems.
We’ll take a look at each one of those possible problems and how to fix them. We’ll discuss the following solutions that will help lower humidity during the winter months:
- Keep relative humidity (RH) in the 30% to 60% range.
- Check for condensation on windows, and replace windows when necessary.
- Upgrade single-glaze windows to at least double-glazed windows.
- Check and fix leaks around the roof, eaves, plumbing fixtures, and sump pumps, especially after recent snow or rain.
- Reseal windows and doors.
- Check that gutter downspouts extend at least several feet away from the home.
- Check for moist foundation walls and apply waterproof paint like DRYLOK.
- Reduce the number of houseplants in your home.
- Take shorter, colder showers.
- After your shower, wipe down the mirror and shower, and run the exhaust fan at least 30 minutes longer than usual.
- Test exhaust fans to make sure they are venting properly (including those in the laundry and kitchen).
- Open windows in new construction homes more frequently during dry weather days, so the trapped moisture can escape.
- Consider whole house ventilation system in extreme cases.
- Buy at least one dehumidifier for each level of your home.
- Clear trees near windows to allow more sunlight.
- Make sure your land doesn’t slope directly towards basement windows or doors, and install drainage pipes if necessary.
Humidity Differences During Summer and Winter
Hot air contains more moisture than cold air, which is why the air feels different to us during the summer and winter months. We describe the air as dry, static, or itchy during the winter, while we describe the air as sticky, wet, or muggy during the summer. For most of us in the United States, the moisture contained in the air is about 3 to 15 times higher during a typical summer day than it is during a winter day.
This measure of water vapor inside air is known as relative humidity (RH), and when air is at 100% RH, it’s considered to be fully saturated, or said to contain all the water that it can possibly hold given the current surrounding conditions. This is when the gas condenses into liquid water, or reaches its dew point.
The “summer vs. winter” comparison isn’t a blanket statement and will depend on the climate around your home at any given time. For example, in some coastal climates with seasonality (like the Pacific West), the humidity can actually be higher during the winter than in the summer oftentimes, thanks to the proximity to water.
Not only that, but the humidity levels can fluctuate on a daily basis, regardless of the season. And so can the temperature.
The dew point usually is just slightly lower than the temperature, meaning that a sudden drop in temperature of only about 10 °F to 20 °F in day-to-day weather can introduce moisture into your home, even in the winter. This can cause condensation on windows, help mold thrive, and put strain on your HVAC system.
The Ideal Relative Humidity (RH) Setting to Aim For
Ideally, you want the RH inside your home to consistently stay between 30% and 60%. If you can get it between 30% and 50%, even better, since some mold and bacteria still tend to thrive above the 50% mark.
This is a range that’s shown to be best for comfort. 30% RH is the minimum – anything below that will cause health problems like respiratory infections, dry skin, dry eyes, nosebleeds, and dehydration, for example. Damage to wood furniture and surfaces is also common below this threshold. Although, you may find that constantly trying to keep humidity near 30% is hard to do anyway.
You’ll find that your home’s RH levels tend to follow the outside temperature. It’s much easier to keep humidity levels low when the air outside is cold and is less able to hold on to water vapor anyway, while you may struggle to keep RH below 70% during a hot and humid summer day. This is why experts recommend a range rather than a set RH level.
If the air inside your home is constantly at the dew point temperature, then condensation is inevitable. Fog or frost on windows, walls, or other surfaces in a home are sure signs that the home has a humidity problem.
Compare the thermostat setting inside your home to the temperature outside. In theory, a higher temperature inside your home during a cold winter should shield your home from condensation since the warm air in your home can hold more moisture rather than allowing it to condense. If there is still condensation on the windows even when the thermostat is set to high, then you’ll already know the RH inside the home is high.
Pay attention to each level of your home. Warm air naturally rises to the top levels of your home, and each home is naturally designed to allow this heated air to escape through the chimneys, wall cracks and ceilings. It isn’t unusual to see more condensation on a few top windows in a home, but it can be alarming if almost all the windows in a home are like this. New-construction homes that are tightly sealed amd homes that are weatherized are more likely to have a condensation problem.
Tips to Reduce Humidity In Winter Months/Winter Moisture Problems
Now that you know a bit about relative humidity and how condensation can affect a home, let’s take a look at some common solutions to these problems.
Take Care of Leaks, First and Foremost
Before even considering dehumidification, always check for leaks first.
It seems like this tip is a given, but it’s always good to take a second look. Leaks can happen in the least obvious places inside a home. Go beyond just checking the roof, check the eaves to make sure water hasn’t found its way into the attic on the sides. This is especially important if there was frozen ice on the roof that has recently melted.
Look at all the plumbing fixtures, checking under the sinks and bath tubs. Are there any moist foundation walls or floors in the basement? Is the rain allowed to slope away from your home, and are the gutter downspouts extended out? Is the sump pump covered or open? If your basement windows are in the ground, are they covered by window well covers like these?
Limit Humidity Created Indoors
A home is to be lived in, and an average family can easily produce about 1 to 2 gallons of moisture just by…well, being themselves.
If you have an immediate need to reduce humidity levels, remember that cooking, taking showers, and even the natural transpiration by houseplants (especially those with large, broad leaves) all produce water vapor.
So consider reducing a few houseplants, and always run exhaust fans after shower and kitchen use. And make sure to test all exhaust fans (including those in the laundry room) to make sure they’re venting to the outside properly.
Let Your Home “Breathe”
New construction homes are now being built more air-tight than ever, so air (and the moisture inside) is now more likely to be trapped than to escape out naturally.
So while your home may be great at preventing heat from escaping during the winter months, it’s also retaining water vapor and just cycling it over and over again. There is little that can be done with a new home when it comes to ventilation. The most affordable solution is to install or upgrade the exhaust fans.
A few other solutions like a whole-house ventilation system are possible, although for most homeowners, these options are either unnecessary or too expensive.
“Glaze Up” Your Windows and Add Insulation
The solution to reducing humidity levels in a home can be summed up in one phrase – never let your home’s inside get below the dew point.
The more susceptible the building surfaces in a home are to the outside cold air, the more likely condensation is to occur. It’s when a hot surface is suddenly cooled to the dew point that condensation occurs.
One perfect example of this are single-glazed windows. Because they’re poorly insulated, their temperature tends to be low enough to hover below the dew point. Thus, the gas water vapor condenses to liquid.
If condensation on windows is a problem, then the solution will be double-, triple- or quadruple-glazed windows.
Consider other ways to keep your building surfaces from getting cold. Apply insulation to walls, attic and crawlspaces.
Dehumidifiers are a great solution to reducing humidity and I always recommend them.
But if you decide to purchase one, you need to know that it will run mostly during the late spring to early fall. The fact is that dehumidifiers aren’t really intended to be used during cold winters since the coils inside them can easily freeze up. That is if you purchase the traditional refrigerant/compressor dehumidifier.
There are dehumidifiers on the market that can run year-round and aren’t affected by cold climates, as long as the temperature inside the home is kept above freezing. This quiet unit from Amazon should be able to dehumidify one level of the average home.
When first operating a dehumidifier, keep in mind is that relative humidity (RH) levels won’t start dropping immediately. The dehumidifier will need to extract the excess moisture from the walls, wood floors, and wood furniture first before it can dehumidify the overall air in the room. Depending on how severe the humidity is, this may take from a few hours to even a few weeks.
Why can’t my dehumidifier keep the humidity levels down?
If the dehumidifier is on constantly but the RH levels won’t move, it probably means that the dehumidifier doesn’t have the capacity at the given ambient temperature. Sadly, the square footage recommendations for compressor dehumidifiers are marketed at 80 °F or 86 °F. If you keep your themostat lower than that, chances are that it’s too small for the space. This is one of the reasons why I recommend desiccant dehumidifiers instead of compressor dehumidifiers.
Another reason is that the coils might have frozen over and only the fan is working.
What is a comfortable relative humidity (RH) level to maintain in my home?
The Environmental Protection Agency (EPA) recommends levels between 30% and 50%. You’ll find that in the summer, the percentage that’s achievable tends to be higher, while in the winter, you may need to keep the RH levels closer to the 30% mark to avoid condensation in your home. It’s also good to test each occupant in your home as the RH levels change. Some people are more sensitive to low humidity levels than others.