Why Does My Old House Smell Funny? [5 Causes]

Last Updated on February 5, 2024

Old houses have that unique charm and character. But they also have that weird, musty, dusty old house smell. When we were looking for our first home we toured a lot of old houses. And some smelled, well, a bit funky. It left me wondering – what WAS that smell? After some research, I found the 5 main causes of old house smell. And towards the end of this post, I’ll give you 8 effective ways to remove it…..

Why do old houses smell? Here's 5 causes and reasons for that Old House Smell

5 Causes of Old House Smell

Maybe you just bought an old house. Or inherited an old house from a relative. And it has that, well, less than desirable dingy, stagnant smell.

And you’re wondering – where is it coming from? Old houses smells may be attributed to one (or a combination) of these 5 causes:

Mold and Mildew
Tobacco Smoke
Pets and Critters
Dirty HVAC Systems
No Ventilation

It’s essential that you understand the source of your old house smell so that you can pick the right cleaning solution to be rid of it!!

1. Mold & Mildew

Mold and mildew are the most common causes of an old house smell (and one of the most common hazards of an old house). It creates that readily identifiable musty, mildewy smell.

What is Mold & Mildew?

Mold is naturally occurring and actually expected to be in our homes. But only at low concentrations. It’s when there is uncontrolled growth that is becomes an issue. Mold loves to grow in areas of water (or moisture) inside your home combined with high humidity.

But, how does water get into home in the first place? Unfortunately, water gets our homes incredibly easily through several ways:

Leaky interior plumbing
Roof leaks
Clogged gutters
Heavy rainstorms

Where is Mold & Mildew in Your Home?

Unfortunately, Mold can be found almost anywhere, from the obviously visual area of showers, tubs, windows and siding. But mold also hides behind walls, inside HVAC ducts, or in attics or basements.

And if you have an old home, you have increased risk of mold and mildew. Older homes tend to experience more issues since they are more likely to have cracked foundations and leaky pipes into which water and moisture can seep, providing the perfect environment for mold to grow.

Note: While most molds are benign, some types of mold can exacerbate allergies and asthma, or cause more serious infections with people with compromised immune systems.

Want to learn more? Check out the USEPA’s Brief Guide to Mold and Moisture in Your Home.

2. Tobacco Smoke

Cigarette and cigar smoke releases nicotine and other chemicals that leave a sticky residue almost everywhere – walls, floors, ceiling tiles, and carpets. And can leave a yellowish-brown stain on ceilings, walls, and floors, in ventilation systems, and even on appliances.

While porous surfaces are the most vulnerable to soaking up the scent, tobacco smoke particles can attach themselves to almost any surface.

And if not thoroughly removed, the smell can linger for years. And impact the home’s selling price. According to Realtor.com, houses owned by smokers are valued 30% less than smoke-free homes.

3. Pets & Pests

Pets. We love them. We have a 80-pound doggie that’s like my 4^th child.

We love our dog Dulce, but she sheds like there is no tomorrow! One of the reasons we love our robotic vacuum #sato #doghair #vacuum #easycleaning — Dulce – our dog. All 80 pounds of love and fur!

But they have accidents.

And if those urine and feces accidents aren’t thoroughly cleaned up off the floor (hardwood or carpet), it can leave a odorous scent that will stink up the house for a long time.

Pets aren’t the only animals that leave their scents behind in old houses. Under the right conditions, pests can easily invade, get comfy and transform your home into THEIR home.

Over time, all houses experience wear and tear, right? Cracks form in building components like plaster, wood, caulk, etc… Siding peels and warps. And all this wear and tear create gaps and small holes.

Gaps that pests exploit.

Little critters like squirrels, chipmunks, rats, mice etc… (more than I’d like to think about).

These pests sneak into small openings created by the wear and tear in an old house and make themselves right at home. They leave extra food to rot. Pests, uh, poop and pee. They might even die and leave their carcass in the house! [Been there, cleaned that….]

Yuck.

Not the best smell to come home to….

woman holding nose with 5 reasons why old houses smell

4. Old HVAC Systems

The age of heating, venting and air conditioning (HVAC) systems in old houses could easily be decades old. [When we looked at houses 10 years ago we found a furnace that will so old it was still encased in asbestos. It was huge and scary and looked like something that would come alive in a horror movie].

If old HVAC systems are not properly maintained, they could be a significant source for that old house smell.

How?

Over the years, grime, dust and mold accumulate in an old house’s heating and cooling system. Perhaps the previous owners never changed the filter. Or they never gave the vents or registers a good cleaning. Or maybe there’s an accumulation of water somewhere in the HVAC system that caused mold or mildew.

How does that affect your house? As fresh air blows through the HVAC’s ducts and vents, it combines with the dust, dirt and mold spores. And spews it all (including that funky smell) out to circulate throughout the house….

Note: A dirty HVAC system can do more damage than just cause an old house smell. It can also cause potential health effects, such as aggravate allergy and asthma symptoms. Plus, dirty HVAC systems tend to be less energy-efficient, which translates to higher heating and cooling expenses. UGH!!!

5. No Ventilation

Sufficient airflow is imperative for a fresh-smelling house. And when a house is closed up for too long, there is no airflow and the air smells stagnant. What exactly is stagnant air? It’s the smell of the accumulation of pollutants (like tobacco smoke) and mold in the air.

Why would a house have poor ventilation and stagnant air? Maybe the old house was abandoned and uninhabited for many years. Or the previous owner was a little old lady who closed everything up like Fort Knox.

Either way, boarded up and locked tight, that lack of airflow created that old house smell.

Next Step?

So now that you know the main causes of old house smells, what’s the next step?

Eradicate that stagnant stench from your old house with these 8 Effective Ways to Remove Old House Smells….