Musty Smells in Older Homes — What They Usually Mean

(And How to Fix the Cause, Not Just Cover It Up)

If you live in South Louisiana and your home has that musty “old house” smell, you’re not alone.

Most homeowners try:

• candles

• air fresheners

• plug-ins

• extra cleaning

…and the smell still comes back.

That’s because musty odor is almost never just “a smell.”It’s usually a sign of moisture + trapped air + organic material somewhere in the house.

Let’s break it down in plain language.

What Does “Musty” Usually Mean?

That musty smell is typically caused by:

✅ humidity that stays too high✅ dust and organic material (wood, drywall paper, insulation)✅ stagnant air / poor ventilation✅ a hidden moisture source

When moisture lingers, it feeds:

• mildew

• mold spores

• bacteria growth

• damp wood smell

Even if you don’t see mold, the smell can still be present.

The #1 Rule: Musty Smell Usually Means Moisture Is Staying Somewhere

In South Louisiana, a house can smell musty from:

• a crawl space

• an attic issue

• a bathroom ventilation issue

• a small roof/wall leak

• an AC system not removing humidity

• old flooring or subfloor moisture

• damp closets with low airflow

Where Musty Smells Usually Come From (Most Common Causes)

1. Crawl Space / Raised Home Moisture

If your house is raised, the air under the home can affect everything above it.

Common causes:

• wet soil under the house

• poor drainage outside

• open vents letting humid air in

• plumbing leaks

• no vapor barrier

• standing water after heavy rains

If that air is damp and musty, it can move upward into the home through:

• gaps in the floor

• plumbing penetrations

• unsealed subfloor areas

• old flooring seams

✅ Signs it’s the crawl space:

• smell strongest near floors

• worse after rain

• worse in summer

• smell is “earthy” or “mildew-like”

2. Bathroom Humidity That Never Fully Leaves

Bathrooms are musty factories when moisture isn’t removed correctly.

Common reasons:

• the fan vents into the attic (or nowhere)

• fan duct is disconnected/crushed

• fan is too weak

• shower moisture stays trapped in walls or grout

✅ Signs it’s bathroom-related:

• smell hits you when you open the bathroom door

• towels smell fast

• caulk darkens quickly

• mildew shows up repeatedly

3. AC Is Cooling, But Not Dehumidifying

This is a huge one in Louisiana.

Your AC should remove humidity, but it may not if:

• it’s oversized and short-cycles

• airflow is wrong

• ductwork leaks in attic/crawl space

• return air placement is poor

So your home is cool… but smells damp anyway.

✅ Signs it’s HVAC/humidity related:

• musty smell throughout the home

• home feels sticky even at 70–72°

• smell is worse in summer

• closets smell musty

4. Attic Mold / Damp Insulation / Poor Venting

Sometimes musty smell comes from above.

If your attic has:

• roof leaks

• poor ventilation

• bathroom fans dumping moisture into attic

• old insulation holding moisture

• major air leaks from the house into attic

…it can create a musty odor that drifts down through ceiling penetrations.

✅ Signs it’s attic-related:

• smell is strongest in certain rooms

• smell worsens on hot afternoons

• smell comes and goes with temperature swings

5. Hidden Water Intrusion (Small Leaks = Big Smells)

A tiny leak over time can create the smell before it shows obvious damage.

Common leak areas:

• around windows

• roof flashing

• siding joints

• old caulk seams

• showers/tubs

• under sinks

• behind toilets

• around exterior doors

✅ Signs it’s a hidden leak:

• smell is strongest in one spot

• paint bubbles nearby

• trim feels soft

• discoloration appears eventually

6. Closets, Back Bedrooms, and “Dead Air Zones”

Musty smell can come from places with low airflow.

These areas trap humid air:

• closets (especially on exterior walls)

• guest rooms rarely used

• laundry rooms

• rooms with closed vents

✅ Signs:

• smell is strongest when opening closet/door

• clothing smells musty quickly

• corners feel “stale”

Sometimes the fix is as simple as:

• airflow improvements

• sealing exterior wall leaks

• humidity control

What NOT to Do (Common “Fixes” That Fail)

❌ Air fresheners

They mask the smell, but moisture continues.

❌ Ozone machines (without addressing moisture)

Temporary improvement, but the smell returns.

❌ Painting over it

Paint doesn’t remove moisture or mold.

❌ Deep cleaning only

Cleaning helps, but it doesn’t stop humidity sources.

How to Find the Source (Easy Homeowner Steps)

✅ Step 1: Identify WHERE it’s strongest

• one room?

• near floors?

• near ceilings?

• only closets?

• only after rain?

✅ Step 2: Identify WHEN it’s strongest

• summer afternoons?

• mornings?

• after storms?

• after showers?

• when AC runs less?

✅ Step 3: Use a cheap humidity meter

If your indoor humidity stays above:

• 60% consistently, you’ve found a major clue.

What Actually Fixes Musty Smells in Louisiana Homes

Real fixes depend on the source, but common solutions include:

✅ Fixing water intrusion (roof/windows/siding)✅ Correct crawl space moisture control✅ Properly venting bathroom fans to the exterior✅ Improving attic ventilation + stopping fan vents into attic✅ HVAC airflow corrections (so it dehumidifies properly)✅ A dedicated whole-home dehumidifier (in some homes, huge improvement)✅ Air sealing gaps between home and crawl space/attic

Why This Matters Before a Remodel

If you remodel without solving the musty problem, you can end up with:

• mold behind new walls

• warped wood and trim movement

• flooring issues

• recurring odor even after “new” finishes

A good remodel should feel:✅ cleaner✅ tighter✅ healthier✅ fresher

Not “new but still musty.”

Quick Reality Check

A musty smell is usually a warning light, not a personality trait of the home.

Older homes in South Louisiana can be incredible — but they need the right moisture strategy.

Need Help Identifying the Source?

At Cajun Conservation, we work on older homes across South Louisiana and we’re big on doing things the right way—so the finished remodel holds up in this climate.

Question for you:Is the musty smell strongest near the floors, near the ceiling, or inside closets?