Why Does My House Smell Musty in the Winter?

By Lisa A. Koosis

November 08, 2025

Imagine a cold winter day: Mulled cider is simmering on the stove, and chocolate chip cookies are baking in the oven. You close your eyes, ready to breathe in these classic winter scents, but all you smell is something stale, damp and ... maybe a little moldy? A house can smell musty in winter just from being closed up, but these unpleasant odors can also have other causes — and they can be fixed.

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Here are five reasons a house may feel and smell musty in winter and what you can do to get it wintry fresh again.

5 Reasons a House Smells Musty in Winter

1. Poor Ventilation

The problem: If you’re wondering why there’s a musty smell in your house, the answer could be poor ventilation. During cold winter months, people rarely leave windows or doors open to let in fresh air. Consequently, odors caused by cooking, cleaning and other daily household activities have nowhere to go. Eventually, they may cause your house to smell musty.

How to solve it: Bundle up and open the windows. Letting fresh air move through your house is a quick way to transform it from musty to crisp and clean. You can also improve your home's ventilation by running fans in areas that feel stagnant and musty.

2. High Humidity

The problem: The colder the weather is outside, the lower your home's humidity level should be. If indoor humidity levels exceed 60%, the moisture can trap odors, leaving your home smelling musty and damp.

How to solve it: In winter months, aim for a relative humidity of 25% in your home. To test the humidity, use a hygrometer, which can typically be purchased at Amazon, Walmart or other major retailers for under $10 (CAD 14). To reduce the humidity in your home, run a dehumidifier. If you don’t have a unit, simply open your windows every morning for about half an hour.

3. Mold and Mildew

The problem: If your house smells earthy and cigar-like, you may have mold and mildew. This common cause of wintertime mustiness results from high humidity and dampness. When your house is shut up for the winter months, everyday activities, such as cooking, bathing and dishwashing, can leave moisture in your home. This wetness can foster the growth of mold and mildew, which have a musty smell due to the microbial compounds they release. Dark discolorations on your walls, ceilings and various household objects can also signal a mold and mildew problem.

How to solve it: If you have mold and/or mildew, you inevitably have a moisture problem, so the first step is identifying and fixing the underlying issue. Depending on the problem, this could mean fixing a broken pipe or just running a dehumidifier.

Once the underlying problem is fixed, use vinegar or detergent and water to scrub mold and/or mildew off any hard surfaces, and dry them completely. Mold is nearly impossible to remove from anything porous or absorbent, so throw away any affected materials, such as carpet or ceiling tiles. If the problem is widespread, call in a professional to ensure safe, complete removal.

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4. Dirt Buildup

The problem: Sometimes, when your house smells musty in winter, the problem is as simple as a buildup of dirt, dust and grime. These common household contaminants, which are the result of daily activities, can cause unpleasant odors, particularly in winter months when a house is shuttered against the cold, trapping them inside.

How to solve it: Deep cleaning eliminates odors caused by an accumulation of dirt, dust and grime. For best results, choose products that can break down greasy buildup and focus on commonly overlooked areas, such as baseboards, appliance interiors and under furniture. Rugs can harbor odors, so shampoo or machine wash them per manufacturer instructions, or freshen them with baking soda. Once you’ve completed a deep clean, maintain it by dusting, vacuuming and wiping down countertops and other surfaces regularly.

5. Damp Clothing and Footwear

The problem: Whether you’ve been shoveling snow or the kids were out building a snowman, winter means wet clothes and footwear. If these soggy items aren’t dried properly, they can contribute to a damp smell in your house.

How to solve it: To dry wet clothes properly, spread them out on a drying rack in a well-ventilated area. Crack open a nearby window to increase ventilation and let out moisture. Be sure not to layer them, and turn the items over periodically. You can also make use of sunny days by hanging soggy coats and sweatshirts outside to dry.

Before putting items away, make sure they’re completely dry. If the smell persists, launder musty items with vinegar or baking soda to remove stubborn odors.

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