10 Ways Indoor Air Quality Declines as Homes Age

So you’ve found a charming house built in the 1970s or 1980s, and you’re about to put down your offer? Congratulations! Of course, with its handcrafted details, distinct architecture, and generous rooms, that house is bound to have a long list of pros. But in aging homes, the air quality may not be on that list.

As houses age, they may give in to time and become vulnerable to various contaminants and pollutants. Many of these could directly impact the indoor air quality. In this article, we’ll explore the different ways in which IAQs decline in older homes.

What is the Link Between a Home’s Age and Its IAQ?

Old homes have their charm. There’s no denying that. And the longer you’ve lived in a house, the more it feels like home. But if you don’t care for your aging home properly, it may become extremely susceptible to indoor air quality issues.

As it stands, indoor air is usually 2 to 5 times worse than outdoor air, according to the EPA.

In poorly maintained older homes, this difference can be larger. But why is that? What happens as a home ages that makes its indoor air quality decline? Here’s why aging homes’ air quality may get worse:

Deteriorating materials that contain asbestos
Crumbling lead-based paint
Foundation cracks that allow radon to seep in
Aging HVAC systems and ductwork
Ventilation issues in old homes
Decades of dust and debris buildup in walls and vents
Outdated building materials off-gassing VOCs

10 Ways in Which the IAQ Declines as Homes Age (and What You Can Do)

If you want to keep an aging home’s air quality high, you must first know the main ways in which the IAQ can decline with time. Then, it becomes easier to know what to look for and what steps to take to prevent the buildup of indoor pollutants in older homes.

Here are the top 10 ways in which a home’s indoor air quality becomes poorer with age.

1. Radon Seeping in Through Cracks in the Foundation

Radon is a radioactive gas that’s naturally formed in the soil beneath your home when uranium breaks down. If your foundation develops cracks over time, this gas can seep into your home easily. And you’ll never know it’s there, because it’s colorless, odorless, and absolutely impossible to detect manually.

But why is radon in the air a bad thing? The American Lung Association has the answer:

In the US, radon is the second leading cause of lung cancer.
Among non-smokers, it’s the number one cause of this cancer.

That’s not all. Every state in the country has shown elevated levels of this dangerous gas. In some states, around 1 in 3 homes have unsafe radon levels.

The EPA particularly flags states in the Rocky Mountain and Great Plains region, like:

Montana
Colorado
South Dakota
North Dakota
Wyoming
Utah

What you can do:

If you live in any of the high-risk states or if your neighbors’ homes have tested positive for radon, consider indoor air quality testing. It’s the only way to know if this gas is circulating in your home.

Get in touch with InHaus Lab if you live in Aspen, Denver, Minneapolis, or nearby areas, and schedule your IAQ test today.

2. Aging Materials Off-Gassing VOCs

VOCs or volatile organic compounds are harmful chemicals that evaporate at room temperature and contaminate the air inside your home. They’re used to make many common building materials and household products, like:

Fragrances
Paints
Cleaning products
Pressed wood furniture
Fabrics

Older homes may have higher levels of VOCs. This is because the materials listed above may break down over time, releasing more chemicals in the air and causing VOC buildup.

These VOCs can cause:

Eye, nose, and throat irritation
Headaches and dizziness
Nausea
Liver and kidney damage
Central nervous system damage
Memory and concentration problems
Increased risk of cancer with long-term exposure

What you can do:

Make sure your home is well-ventilated. Replace old materials with low-VOC or no-VOC alternatives. And test the VOC levels at regular intervals.

3. Lead Paint Crumbling With Time

In modern homes, lead-based paint is usually not a hazard because, in 1978, the federal government banned the use of such paint. But if your home was built before this turning point, it may well be a hotspot for such dangerous paints.

According to the EPA, the likelihood of homes containing lead-based paints depends greatly on when they were built. See for yourself:

If Your Home Was Built:	Then, the Likelihood of Containing Lead-Based Paint
Before 1940	87%
Between 1940 and 1959	69%
Between 1960 and 1977	24%

Still, such toxic paint can be found in millions of homes under layers of safer, newer paint. As the new paint chips off, the lead-based paint may once again be exposed to the indoor atmosphere.

These paints are harmful because, with time, they peel off and crumble into fine dust particles that mix with the air in your home. You may then inhale this dust, and over the long term, it could cause lead poisoning, which is a serious and irreversible condition.

What you can do:

Keep painted surfaces in good condition to prevent chipping and peeling, and use a HEPA vacuum to clean up any paint chips and dust. Also, seal deteriorating painted surfaces with fresh paint right away.

4. Carbon Monoxide Leaks from Old Furnaces

Carbon monoxide is a colorless, odorless gas that’s formed when aging furnaces and fuel-burning appliances can no longer burn fuel completely. This incomplete combustion creates carbon monoxide as a byproduct.

This gas then directly leaks into the air and circulates inside your house. In old homes with ventilation issues, carbon monoxide can easily build up. And it’s dangerous because it can cause:

Headaches and dizziness
Nausea and vomiting
Confusion and disorientation
Shortness of breath
Loss of consciousness
Brain damage with prolonged exposure

What you can do:

Install carbon monoxide detectors on every floor of your home and get your fuel-burning appliances inspected and serviced regularly.

5. HVAC Systems Failing to Function Efficiently

Your HVAC system is responsible for circulating, filtering, and conditioning the air throughout your home. When it works perfectly, it keeps pollutants, allergens, and moisture in check. This keeps the IAQ normal.

However, as your home ages, so does your HVAC system. In older homes, HVAC systems may be decades past their prime if they haven’t been maintained well. Filters become clogged, coils collect dust and breed bacteria, and the system is no longer efficient enough to ventilate your home properly.

This is very bad news because, instead of cleaning your air, aging HVAC systems can spread contaminants or let them build up indoors.

And this is harmful because it can:

Circulate dust, mold spores, and allergens throughout your home
Allow humidity levels to rise
Spread bacteria and other airborne pathogens
Worsen symptoms for people with asthma and allergies
Reduce the oxygen levels in poorly ventilated spaces

What you can do:

Have your HVAC system professionally inspected every year, replace the filters regularly, and consider upgrading to a modern system if yours is over 15 years old.

6. Mold Infestations from Moisture Buildup

Aging homes’ air quality can also be affected by mold growth. With time, the infrastructure in your house weakens. Pipes develop steady leaks, roofs and windows no longer seal tight, and water may intrude into your basement.

All these factors give mold the perfect conditions it needs to grow.

Mold thrives in damp, poorly ventilated spaces. And older homes have plenty of such areas. Once it takes root, mold spreads quickly behind the walls, under the floors, and even through the ductwork.

Often, people buy older homes and realise much later that they have a case of stubborn mold. This post on Reddit is about one such case, and it has insights and inputs from other people with similar experiences.

Mold growth can be an issue because it:

Triggers allergic reactions
Worsens asthma and other respiratory conditions
Causes chronic cough and wheezing
Irritates the eyes, throat, and nose
Can lead to serious lung infections

What you can do:

Fix water leaks promptly, keep your home well-ventilated, and above all, maintain humidity levels between 30% and 50%. Use a dehumidifier if any room or basement gets too damp.

And if you notice anything that looks suspiciously like mold, call a professional mold testing company like InHaus Lab right away.

InHaus Lab's air quality testing services include mold testing, which helps you figure out exactly where any hidden mold is in your home. You can then focus on remediation.

7. Asbestos Breaking Down Over Time

Asbestos was once widely used in construction and building materials like floor tiles, ceiling sheets, and even insulation panels. Then, in the 1980s, it was largely phased out. Still, it was only recently that the last permitted form of asbestos was permanently banned, as reported by the EPA.

There’s a very good reason for all this alarm against asbestos. Asbestos is a known carcinogen.

And it’s no ordinary cancer-causing agent, either. Exposure to this group of minerals has been linked to:

Lung cancer
Ovarian cancer
Mesothelioma
Laryngeal cancer

In older homes, materials that use asbestos may still be present. As they age, they break down and release microscopic fibers into the air. You breathe this contaminated indoor air, and that could lead to chronic or serious health issues.

What you can do:

If your home was built before 1980, do not disturb any materials that are suspected to contain asbestos. In case something needs to be removed or renovated, seek professional help.

8. Allergens from Pest Infestations

Aging homes may also be prone to pest infestations. That’s simply because they have more entry points, like gaps in foundations, cracks in the walls, and weakening seals around windows and doors.

Over time, pollen, dust, and pests may all find their way in more easily. And together, they lead to increased levels of indoor pollutants in older homes. Allergens like pollen and dust directly affect the respiratory tract. Pests, meanwhile, may leave behind droppings or shed skin indoors, which all break down into fine particles that mix into your indoor air and trigger allergies.

What you can do:

Seal any gaps or cracks in your home’s foundation, walls, and windows. Keep your home clean and dry. And if you suspect an infestation, call pest control right away.

Indoor air quality testing is also crucial for such homes. It can help you assess the levels of allergens inside your house, so you can decide what to do next to improve your IAQ.

9. Weatherproofing Wearing Down

The weatherproofing in your home is your first line of defence against the outdoor environment. It includes the insulation, caulking, and the seals around your doors and windows.

When your home is old, it succumbs to usual wear and tear, and all of these materials crack, shrink, or deteriorate. This creates gaps that ultimately compromise an aging home’s air quality.

Pollutants that can enter your home due to compromised weatherproofing are:

Pollen and outdoor allergens
Vehicle exhaust
Traffic pollution
Pesticides from the surrounding soil
Mold spores from outdoor vegetation
Radon and soil gases
Dust and particulate matter

What you can do:

Inspect your home’s seals, caulking, and weatherstripping annually. Replace anything that shows signs of cracking or wear and tear.

10. Accumulation of Dust and Debris

Over the years, dust and debris build up in places you cannot easily see or reach. Think inside wall cavities, behind baseboards, inside ductwork, and beneath loose flooring. Decades of such accumulation can be a terrible thing because it creates a reservoir of pollutants and contaminants.

These particles break free and circulate in the air. Depending on the materials used in building your home, such particles may be more than just dust. They may include mold spores, pest allergens, asbestos fibres, and lead.

What you can do:

Have your ductwork professionally cleaned every few years, vacuum regularly using a HEPA-filter vacuum, and pay attention to hidden areas behind appliances, under flooring, and inside wall vents.

Stay Ahead With Indoor Air Quality Testing

Time will do its thing. So, as homes age, they become susceptible to many of the issues we’ve covered above. But as a homeowner, you’re not totally powerless. There is one thing you can do to stay ahead of the inevitable issues that will crop up over the long term.

Get your IAQ tested regularly — preferably, every 2 to 3 years.

This way, you’ll know right away if your old home has ventilation issues or if there’s a radon leak. You’ll know the level of VOC buildup over time, and what indoor pollutants are hitting dangerously high levels.

InHaus Lab’s air quality testing services can tell you all this and more.

We check for allergens, VOCs, particulate matter, radon, and carbon monoxide. With our calibrated sampling, precise lab testing, and science-backed methods, you can see exactly how your home’s age is affecting its IAQ. Once you know that, you can take remedial action right away.

Aging Home Air Quality FAQs

1. What indoor air pollutants usually affect homes built before 1980?

Homes built before 1980 may contain asbestos and lead paint, which break down over time and affect the air quality. They may also be vulnerable to radon leaks and mold infestations.

2. If I live in an older home, how can I benefit from air quality testing services?

Testing can help identify hidden pollutants like radon and mold early. This means you can take targeted action before such pollutants cause serious health problems.

3. What are the most cost-effective ways to improve the IAQ in aging homes?

You can seal the air leaks, improve ventilation, and use HEPA air purifiers to make some immediate improvements to your IAQ. Also, fix any leaks and moisture issues, and replace old HVAC filters regularly. These simple steps can make a big difference.

4. Are all aging homes prone to air quality issues?

Not necessarily. In well-maintained aging homes, the air quality can be good. The risk depends on the level of ventilation and moisture control. The type of building materials used can also impact IAQ.

5. Should I get the IAQ tested before buying an old home?

Absolutely! When you get the indoor air quality tested before you buy an aging home, you may find hidden issues like mold infestations, radon leaks, or high VOC levels. This gives you negotiating power and also helps you see what you need to fix.

6. What qualifies as an ‘older home’ in 2026?

Generally, homes built in or before the 1980s are considered ‘older’ homes because they typically use outdated materials. However, some experts may include all homes built before 2000 in this category, particularly for IAQ concerns.

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