How to Control Moisture in a Portland Home

Controlling moisture in your home is essential to your budget and your health. In Portland, this can be a challenge considering all the rain we get. Three-quarters of the year is cold, wet, and overcast, the perfect environment for dampness, lingering condensation, and mildew and mold growth. Too much moisture in your home can lead to wood rot, warped floors, peeling paint, and bad odors, all of which can lead to costly repairs. A moldy home can also cause a number of health issues. For the sake of your health and your pocket book, understanding how to moisture proof your home is essential.

How Does Moisture Enter Your Portland Home?

It first helps to understand how moisture enters your home. You might first think of water from the outside entering your home through cracked foundations, weathered roofs, and leaky or broken pipes. It’s true, these all can lead to insidious water seepage.

Other sources of excess moisture in your home can occur in ways you might think about: long, hot showers; boiling food without lids; hanging wet clothes to dry indoors; and faulty dryer vents can also increase moisture in your home.

The amount of moisture your home holds depends on the temperature of the air. When the temperature decreases, the air holds less moisture. Keeping abreast of moisture levels in your home can help protect yourself and your family financially and physically.

In this article, we show you how to take care of moisture in your Portland home, whether you’ve owned it for years or are just moving in. First, we’ll look at habits in your day-to-day life that can make a difference. Then, we’ll look at remedies to structural issues in your home.

Day-to-Day Habits to Prevent Moisture in Your Portland Home

Summers in Portland are pretty ideal with humidity at its lowest. But in the winter, humidity levels can reach 83% December through February. Here are some ways to help.

Open Windows

Proud of your energy-efficient home? You should be! The reality is, though, that some energy-efficient homes are so air-tight they tend to hold moisture.

Opening windows can go a long way in decreasing the humidity in your home. Of course, the humidity outside must be lower than the humidity inside for this simple trick to work. It may seem counterintuitive to open your windows in the middle of winter, but a slightly ajar window for 30-60 minutes can help decrease inside humidity.

Run Exhaust Fans

This may seem like a no-brainer, but it’s easy to get caught up in getting through the day, forgetting to use exhaust fans in the kitchen and bathrooms. Running fans during and for several minutes after cooking and showering will circulate the air and dry it out. Also, be sure fans and vents pipe hot air and moisture to the outside, not into your attic space.

Run Dehumidifiers

We tend to think of running dehumidifiers during summer months, but as we say above, here in Portland, we see the highest levels of humidity in the winter. One caveat: Be sure to clean your humidifier filter often, and avoid letting the same water sit for long periods of time to prevent mold from growing in the unit.

Structural Remedies to Prevent Moisture in Your Portland Home

While a lot more involved and potentially costly than some of the above-mentioned day-to-day habits, taking extra steps to address the structure of your home is highly recommended to prevent moisture in your Portland home.


The underlayment beneath shingles is required and put there to provide waterproofing protection. Over time, the elements can wear on both shingles and underlayment, causing it to degrade.

If you’re having a home built, be sure your contractor is using the best quality self-adhering materials. On already-existing homes, a good rule of thumb for underlayment and roof replacement is 20-30 years.


It’s a good idea to check the plumbing in your home on a regular basis to be sure water isn’t entering your home via leaks from pinholes in interior pipes, cracks in caulking, or seepage from exterior water outlets, like outside faucets.


Small water leaks like those mentioned just above can cause water to run down a home’s framing behind walls and slowly compromise the integrity of your home’s walls.

Keep an eye out for bubbling, warped, or discolored wall surfaces. This is almost always a sure sign of water invasion. Also, occasionally check the interior of full closets primarily used for storage. Areas like this that are closed up most of the time and don’t get much air or light can be prime breeding grounds for moisture collection, and inevitably, mold and mildew.

Windows and Doors

All it takes is a few windy, rainy days for exterior water to sneak in around windows and doors and start the creation of rot and mold, unless you have the proper flashing installed. A variety of flashings exist, and it’s best to leave this in the hands of a pro. When you hire someone for this project, consult with them beforehand about all the types available and which are best for your home and the climate. Also, consider installing storm windows in your home if you don’t already have them.


People don’t usually tend to think of floors as a place where moisture can collect. But if you own an older home with carpeting, imagine how moisture in the air can settle in and perpetuate high moisture content. Also in some older homes, if carpeting was put down on top of cement without any kind of vapor barrier, any water seepage or dampness will be soaked up into the carpet.

If your budget allows, consider tearing up old carpet and replace it with new (complete with the appropriate vapor protection and sub-flooring, like plywood over insulation). And if you discover wood under the carpet, seriously consider replenishing the original beauty of the wood and using throw rugs, which can be washed and dried on a regular basis.

Basements and Foundations

Basements are welcoming vessels to water. Especially here in Portland. They’re underground, surrounded by perpetually wet earth, and over time, can shift and crack or collect water from leaky pipes. And while you won’t find as many basements in Portland as you do some other parts of the country, they do exist.

If you own a home with a basement for any length of time, you’ve probably encountered moldy overgrowth on a few boxes you have stored away. You may have even experienced a mild to serious flood in your basement.

A few ways to redirect water away from your foundation and, thus, away from your basement are as follows:

  • Do some landscaping around your home’s foundation. Plants soak up water.
  • Excavate to create a downward slope away from the house.
  • Consult a professional about waterproofing.
  • Check your gutters. If they drip too close to your foundation, it’s easy for the water to get inside.
  • Check for pipe, tub, and sink leaks.

Doing what you can to redirect water from your foundation and basement will be a big help in preventing the growth of mole, mildew, and bacteria.

Crawl Spaces

The best way to prevent moisture in a crawl space is to line it with plastic, often called Visqueen, ensuring that all dirt is covered. Also, having a well-ventilated crawl space will keep general moisture down.

Read more about caring for Portland crawl spaces.

A Few Last Word on Preventing Moisture in Your Portland Home

Additional tips to reduce moisture in your Portland home:

  • If you run a humidifier and notice moisture on windows, turn off the humidifier and only run it at intervals.
  • If you see moisture condensing, heat the surface its on. (For example, if it’s on windows, heat up your home for a few minutes.)
  • Leave space between furniture and walls to allow for circulation.

If you’re uncertain about the moisture content in your home:

  • Use a humidity indicator—or hygrometer—to measure the amount of moisture in various areas of your home.
  • Consult a professional contractor to see if your vapor barriers are sufficient.

The good news is that if you take these steps, you’re that much closer to a higher Home Energy Score when the time comes.