Mold in Cold Temperatures: 9 Common Winter Mold Questions

by | Feb 19, 2020 | Mold | 0 comments

Mold is commonly thought of as a seasonal problem, and many homeowners think mold issues disappear when the weather is cold. But while temperature does affect the way mold grows, it’s a year-round problem.

Mold growing on indoor surfaces can damage your home and negatively impact your health. It’s important to be aware of how and where mold can grow in your home, even during the winter months.

Keep reading to learn the answers to the top 9 most-asked winter mold questions.

1. Can mold grow in cold temperatures?

The short answer is yes. Mold requires three things to grow: enough moisture, an adequate food source, and the right temperature. But contrary to what many people think, mold doesn’t only grow in warm environments.

Different types of molds thrive under different conditions, and some molds are more likely to grow in the winter months than others. Each type of mold has minimum and maximum temperature ranges for growth, with many varieties of fungi thriving in environments between 60 and 80 degrees Fahrenheit. Unfortunately, the right temperature conditions for mold growth are also ideal for our comfort, and we tend to heat or cool our homes to stay within those parameters.

2. What types of mold can grow in the winter?

The most common types of winter mold include: Alternaria, Cladosporium, and Penicillium.

Alternaria is a genus of fungi whose species are all common plant pathogens. It thrives in cold temperatures, particularly when moisture is present. It typically appears gray or black and, when it grows indoors, it tends to be found in humid environments such as in bathtubs, on shower curtains and bath mats, or on basement walls.

The Cladosporium genus includes some of the most common indoor and outdoor mold species. It’s able to survive in temperatures as low as 4 degrees Celsius (39.2° Fahrenheit). Species within this genus appear differently, but the most common ones to find indoors are generally brown to blackish-brown or greenish-gray in color.

Penicillium species survive in temperatures ranging from 7 to 35 degrees Celsius (44.6° to 95° Fahrenheit), so these molds are commonly found in all seasons. Like other common indoor molds, it thrives in moist conditions and is generally found on damp building materials, carpets, mattresses, and upholstered furniture.

3. Does mold die in the winter?

Cold weather will not kill mold. Mold spores are opportunistic in the sense that they wait for the right conditions and then begin to spread.

Extreme temperatures do not kill mold, but they can deactivate them. Even when temperatures drop below freezing, mold spores don’t die; they simply become dormant and will begin to multiply and grow again as soon as the temperature rises.

That’s why controlling the temperature alone will not solve your mold problems. The key to removing mold from your home and keeping it from popping back up is to control humidity levels and prevent the buildup of moisture.

4. Why does mold grow on windows in winter?

The fall and winter months bring precipitation and dew, and surfaces in our homes that collect moisture, like window panes, are ideal places for mold to expand and grow.

rain on window

Moisture collects on and around windows in the winter due to condensation, which happens when warm air hits a cold surface. When the temperature drops during the winter, the warm air in your home comes into contact with the cool glass of your window panes, depositing water vapor and leading to moisture buildup around your windows. That’s why moisture, and sometimes mold, tends to collect around windows during the colder months.

5. Do mold allergies go away in winter?

Mold allergies are common and can cause a variety of unpleasant symptoms, including sneezing and runny nose, coughing, itchy eyes, nose, throat, or skin, and watery eyes. Mold can also trigger asthma attacks in asthma sufferers who are allergic to mold. Many people notice their allergy symptoms decrease when the temperature drops.

Unfortunately, people with mold allergies often actually experience more symptoms during the winter when they’re more likely to be indoors for long periods of time. Mold allergies can be worsened by indoor heat, which can send mold spores that have collected in your ducts and other places into the air.

6. How do you prevent mold from growing in the winter?

Here’s what you can do in your home to prevent mold from growing and spreading during the winter months; these strategies will also help prevent and improve mold allergies:

  1. Try to keep humidity below 50% throughout your home at all times.
  2. Inspect pipes and fix plumbing leaks as soon as possible to prevent water from collecting.
  3. Use mold-killing cleaners in bathrooms and areas of your kitchen where moisture collects.
  4. Avoid having carpets or rugs near windows, sinks, or other places that tend to become wet.
  5. Inspect your air ducts and change the filters on your furnace regularly.
  6. Always use a ventilation fan during showers or baths.
  7. Clean your gutters regularly to prevent moisture from building up on collected debris.
  8. Get rid of old recycled material, newspapers, and any upholstery or fabric that has been exposed to moisture.

7. What are the health consequences of being exposed to mold?

Indoor molds can pose a risk to human health when spores land on wet or damp surfaces and begin growing. Molds produce a variety of allergens and irritants that can cause a range of unpleasant and even dangerous symptoms when spores are inhaled or touched. These symptoms can occur immediately after exposure, or they can be delayed in some cases.

The most common health risks and symptoms of mold exposure include:

  • Nose irritation and sneezing
  • Eye irritation
  • Skin rashes
  • Throat irritation
  • Breathing issues
  • Asthma attacks

8. Where does mold typically grow?

Molds are fungal growths, which are a perfectly natural part of the environment. Species of mold can be found almost anywhere moisture and oxygen are present, thriving in outdoor environments like in soil or on plants and dead or decaying matter.

Molds are also frequently present in wet or damp indoor areas. The most common places to find indoor mold include:

  • Around leaks in windows, roofs, or pipes
  • Where flooding or moisture-accumulation has occurred
  • In dust
  • In paints, wallpaper, or drywall
  • On carpets, fabrics, or upholstery
  • In insulation material
  • On paper products
  • In or around indoor plant pots

In some cases, mold may be easy to see and identify. However, it’s important to be aware of hidden mold that may not be visible due to its location. If you don’t see any visible signs of mold, you may still be able to identify a problem if you smell an earthy or musty odor, if your home has recently sustained water damage, or if you’re experiencing health problems.

9. Is it possible to get rid of winter mold by yourself?

It’s impossible to get rid of all mold spores in an indoor environment. Some spores will always remain in the air or contained in household dust. But mold that has landed on a surface and begun to grow should be addressed as quickly as possible.

According to the CDC, whether or not a homeowner or building owner should handle mold cleanup without the help of a professional depends on: 1) the size of the moldy area (less than 10 square feet), 2) the extent of any water damage to the area and whether any contaminated water may have been present, 3) if you’re planning to hire contractors to work in your home, 4) if you suspect your HVAC system has been contaminated with mold, and 5) if you have any health concerns.

If you choose to try to get rid of winter mold yourself, it’s important to strictly and carefully follow official mold cleanup guidelines and take every precaution to protect your safety and the safety of others.

mold on wall

Mold needs the right temperature, humidity conditions, and a food source to grow. Room-temperature conditions and organic material such as paper, cardboard, wood, and ceiling tiles are nearly impossible to remove from your home. That’s why the best way to prevent the spread of mold is to control moisture. Using dehumidifiers and a meter to test humidity levels will help stop moisture from building up and prevent mold around windows.

RELATED: Everything You Need to Know About Household Mold

Year Round Mold Remediation To Protect Your Home and Family

Although mold is an important component of maintaining a strong outdoor ecosystem, indoor mold can cause damage to your home and your health. Whether you’ve smelled an odd, earthy scent in your home, noticed symptoms of mold allergy, or are having trouble breathing, a professional mold inspection will provide the answers you need.

At JSE Labs, we’re dedicated to providing accurate, professional mold testing. We offer in-home inspections and testing conducted by our skilled environmental consultants. We also provide specialized in-lab testing, which allows you to collect your own sample and submit it to us.

Contact us today or give us a call at (503) 659-8338​ to check your home for mold.

Jennifer Malgren

Jennifer Malgren

Jennifer is the Laboratory Manager of JSE Labs, and holds a BS in Environmental Studies & Science from Portland State University. She is an avid learner and enjoys exploring new topics related to natural processes and the environment. She has experience analyzing hazardous materials, including asbestos and lead, and is committed to promoting safe and sustainable practices in the workplace and beyond. When not in the laboratory, Jennifer can be found exploring the Pacific Northwest with her Catahoula Leopard Dog, Oliver, or volunteering locally.

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