Why Does My House Smell Musty?

How fresh is your home? If you enter your property and catch a whiff of damp, rather than the sweet-scented interior you crave, finding and eliminating the cause of the odor is a priority.

Unfortunately, sometimes identifying why your home smells musty can be a challenge. To help, we’ve listed some common causes of a musty smell, as well as described some effective solutions to get rid of that unpleasant odor once and for all.

If you want answers to the questions, “Why does my house smell musty?”, and, perhaps more importantly, “How can I rid my house of a musty smell?”, read on.


Why Does My House Smell Musty?

You may not want to hear this, but the distinctive musty smell in a property is due to mold spores. When you inhale that unpleasant reek, you’re actually breathing in a whole bunch of spores!

There are always some mold spores present in the air. In normal conditions, these don’t present a problem. If the conditions are right for spores to multiply, they will do so. When you can detect the musty odor, you know you’re dealing with a high volume of spores.

Mold thrives where there is excessive moisture. Almost all musty smells eventually lead back to unacceptably high levels of damp.


Slow Leaks

A slow leak may be due to a cracked pipe, a leaking seal, or water penetrating a roof, wall, or floor due to structural damage. Any moisture that enters the fabric of a building and is left to linger provides an ideal environment for mold to thrive.


Failure to Properly Dry a Property Following Water Damage

As well as floods caused by severe weather, a burst pipe, leaking washing machine, or overflowing bath can all be causes of flooding. Even if the initial cause of the flooding is fixed, if the drying process is incomplete then the remaining moisture will provide the conditions needed for mold to grow.



If you have high humidity in your home, coupled with a lack of airflow, it’s likely you’re going to encounter problems with condensation. Condensation is water vapor that’s encountered a cooler surface (typically the walls or windows of your home). Losing heat, the water vapor condenses into water droplets, creating condensation.

Condensation is common in kitchens and bathrooms, where steam is likely to be produced intermittently. It can also occur in other rooms in the home, particularly during the cooler months when windows are less likely to be open.


Poorly Performing HVAC

When was the last time you changed the air filter in your HVAC system? Or had the ducts cleaned? If you’ve neglected your HVAC, or have got a system that isn’t performing sufficiently well to keep your home ventilated, it’s likely that the humidity in your home is higher than it should be. This contributes to condensation, which in turn increases the chances of mold growth.

In addition, over time your HVAC ducts collect grime, dirt, and mold spores. If they’re not cleaned regularly, you can get a build-up of spores, leading to moldy, musty air being recirculated in your home.


Dirty or Old Carpets

Particularly if you’ve taken on a furnished tenancy, the carpets in your lounge or bedrooms could be decades old. Surface cleaning will be insufficient to remove all the grime, dirt, and spores that drift down to the base of the carpet over the years.

Carpets made from natural materials will also tend to absorb moisture from the atmosphere, particularly if humidity levels are high. This can lead to a musty smell in carpeted rooms, even if the carpets have been regularly vacuumed.


Poor Airflow

This may be due to the house being unoccupied for a period of time (so windows haven’t been opened regularly), or be down to poorly performing HVAC that isn’t providing sufficient air exchange. Whatever the reason might be, the result is a build-up of damp, stale air that’s likely to harbor high levels of mold spores.


How Can I Rid my House of a Musty Smell?

A musty smell will naturally diminish when the volume of mold spores in the air is reduced to a low level. Provided the levels of mold spores are kept low, the smell shouldn’t return. Getting rid of the musty smell is a two-part process. In the first instance, the mold spores need to be removed as far as possible. Secondly, preventative steps should be taken to prevent the problem from reoccurring.


Remove Patches of Obvious Mold

If there are patches of mold on walls, ceilings, or floors, these need to be removed. Larger or denser patches of mold should be removed by professionals, as they have the right equipment and protective clothing to do the job properly. Smaller patches can be carefully removed, using a suitable mold removal product.

Remember that some mold spores are toxic, so exercise care when removing the mold – if in doubt, use a professional.


Fix Any Leaks

Identifying and repairing slow leaks and/or structural problems that are allowing rain or dampness to enter your property is essential. If you can’t identify the location of a slow leak, it may be necessary to call in a plumber, who will use a moisture meter and/or infrared camera to identify the likely location of the leak.


Deep Clean/Replace Old Carpets

If a deep clean doesn’t solve the problem, it may be necessary to replace older carpets. Whilst the carpets are being replaced, it’s a good opportunity to check whether there are any signs of damp on the underlying floor surface. Structural work may be needed to ensure fresh carpets are laid on an intact sub-strait.


Seal Walls and Floors

Something as simple as applying a fresh coat of paint could be all that’s needed to seal walls, creating a smooth, mold-resistant surface. Similarly, sealing floors ensures that any damp that’s coming up from the foundations, or that’s already in the sub-strait, doesn’t penetrate any further into the home.

Many contemporary sealants and paints include an agent designed to discourage the growth of mold. Applying these products can help to deter spore growth, contributing to a fresher, better-smelling property.


Control Condensation and Humidity

If condensation is contributing to the mold build-up that’s causing the musty smell, it’s important to improve airflow and take steps to reduce humidity in the home. There are a number of measures that homeowners can take, such as:

  • Ensure windows are opened regularly to allow adequate ventilation.
  • Install an extractor fan in the kitchen, to remove some of the excess humidity generated during cooking.
  • Consider purchasing a dehumidifier.
  • Make sure laundry is dried in a drier, not hung on radiators to dry.


Get Your HVAC Thoroughly Cleaned, Inspected, and Replaced if Necessary

Your HVAC system plays a key role in keeping your home free of unpleasant musty smells. Not only is a fully functional HVAC installation vital to keep musty odors at bay, if the system isn’t cleaned regularly, but it can also become a cause of unwelcome odors.

If musty odors are detected, we recommend calling in a professional team to give your ducts a deep clean. In addition, the air filter should be replaced (if it hasn’t been changed recently), to ensure your interior air isn’t passing through a filter that’s full of dirt, allergens, and mold spores.

Musty smells can develop if your HVAC isn’t working correctly. Over the years, particularly if the system isn’t regularly maintained, its performance can gradually decline. A thorough service, including replacement of any defective parts and ensuring that coolant levels are correct, can help to bring your HVAC back up to standard.

Many people find that simply having their HVAC system overhauled can significantly improve the interior air quality of their home.


HVAC Replacement

If an HVAC system is old or isn’t appropriate for the property, it may be time to think about a replacement. Modern systems are capable of keeping temperature and humidity within optimal levels, minimizing the chances of mold growth that will cause unwanted musty smells.

Not only will you enjoy the added benefits that a fresh HVAC system can bring (such as reduced energy bills, better temperature control and more even cooling or heating), you may also notice a considerable difference in the quality of your air. With a new HVAC system, the air often smells sweeter and cleaner, as the system efficiently removes unwanted particulate matter, preventing buildup.


One-Stop HVAC Solution

Are you concerned about your interior air quality? Help is at hand! Highly experienced and professional, the team at Kaiser Air Conditioning Indoor Air Quality Services is dedicated to keeping your home at the right temperature and smelling fresh.

Serving Ventura County, get in touch with Kaiser Air Conditioning Indoor Air Quality Services for a complete solution to all your HVAC requirements.