Basements are a great feature of a home, and quite practical. A finished basement typically is considered space one could live in – it has insulation, drywall and is centrally heated. Its rooms can be used for any purpose like home offices, playrooms, home theaters, in-law suites, laundry rooms, among others. An unfinished basement, on the other hand, doesn’t have these features, so it’s prone to dust, dirt, and is often rarely used by homeowners.
One might think that unfinished basements can contribute to poor indoor quality a lot more than finished basements would, but not necessarily so. Both types of basements are plagued by various negatives and both can give a home that unpleasant basement smell.
In this post, we’ll take a look at what exactly causes those nasty basement odors and then we’ll discuss what exactly you need to do to clean it all out and improve the air quality of your basement.
What’s Inside the Air in Your Basement
I’m sure you’re more interested in the solution rather than the cause of that unpleasant smell in your basement, so I won’t spend too much time on this subject.
However, it’s important to at least have some basic knowledge of basement air pollution before even trying to make any improvements, so here’s a brief overview of what commonly pollutes indoor air.
Volatile Organic Compounds (VOCs)
VOCs are typically found in the manufacturing process of various items. The problem with VOCs is that they off-gas. In other words, these gaseous chemicals continue to detach from a product and continue to circulate in the air for months, sometimes even years.
There are hundreds of VOCs commonly found, but you’d usually find them in composite wood products like laminate flooring, furniture, or kitchen cabinets. They’re also found as ingredients in household cleaners and aerosol products like hairspray, for example. Most products that have to do with painting or varnishing contain VOCs, from the latex paint on your walls to the polyurethane finish on the balusters in the hallway.
VOCs can cause respiratory discomfort, asthma, and allergic reactions. Some have even been named Group 1 carcinogens, meaning that they will cause cancer at certain levels of exposure.
Microbial Volatile Organic Compounds (mVOCs)
These are mVOCs that are produced by nature itself, rather than a factory. mVOCs include things like mold spores, bacteria, and viruses. As far as basements are concerned, mold is the largest contributor to poor indoor air quality, so the rest of the post will focus on the mold. It thrives in moisture and settled organic material, which makes the basement perfect for its growth.
Mold comes in all shapes and sizes, there is no single species that can infect a home. For that reason, its effects on health may vary. Most people will experience allergic reactions like coughing, wheezing, runny nose, irritating throat, while in other instances some people might have mild shortness of breath. There are, however, some molds that can be even more dangerous. Those who already have allergies or weak immune systems will react more severely to mold.
Carbon monoxide is a colorless and odorless gas that can become lethal quickly. Because it’s hard to detect, it’s known as the silent killer. Carbon monoxide forms under two conditions in your home. There is either a lack of oxygen in the air, so carbon monoxide forms instead of carbon dioxide. Or, faulty appliances that give off heat don’t vent properly and allow carbon monoxide to build up inside the home instead of outside.
Radon is a radioactive element that enters the home from the soil. Basements are especially susceptible to radon, although homes built on a slab can also have high radon readings. The problem with radon is that it decays once it enters a home. During this decaying process, it breaks down from its gas form into heavy metal solids like polonium and lead.
Most people are familiar with lead poisoning in older buildings. However, if your home has high radon levels, your basement will by default have lead in it. Another problem is that radon enters into the body and then decays into polonium a few days later. Unfortunately, at that point, polonium has already lodged itself in the lungs and settled as a solid. This ultimately can cause lung cancer and lead to death.
Particulate matter is a general term that’s used to describe broadly the particles that are suspended in the air. As you can imagine, particulate matter can contain many things, like gases, dust mites, dirt, smoke, atmospheric air pollutants, etc.
Most particulate matter is caught, thanks to filtration systems. It’s the particles that are less than 10 microns in size that are of highest concern when it comes to indoor air quality. Fine particles, which are less than 2.5 microns in size are an even bigger concern.
That’s because the body is unable to naturally filter out small particles, so those substances can easily enter the lungs or bloodstream.
Asbestos isn’t discussed as much as it used to be when it comes to indoor air quality, but it has to be mentioned when talking about basements. If your home was built before 1975, you very well might have asbestos-containing building materials lurking in your basement.
The EPA recommends to leave it alone and not agitate the area. But realistically, as your home ages and you live and clean in your home, you’re bound to run into an issue with asbestos sooner or later. It’s best to call an asbestos inspector and play it safe.
(For more details on what’s exactly polluting your indoor air, read this post.)
How to Improve the Air in Your Basement
Now that you know a bit about what’s in your indoor air, the real question is, how do you improve it?
It all depends on where you are in the process. Some of you may be building a brand new home and want to make sure you do things right before the foundation is even poured to save yourself thousands of dollars you may have to dish out in the future. On the other hand, some of you may have an old basement that was flooded over a year ago and you just can’t seem to get the bad odor and moisture out.
Either way, there’s a solution for everyone. Depending on where you are in the process, some tips will apply to your situation more than others.
Remember to always follow the building codes of your jurisdiction and to call in an expert in serious situations.
Control the Moisture in the Air
The major culprit in basements is moisture, plain and simple. Moisture can find its way into basements through several different means. Some examples include:
- A downsloping lot allows rainwater to run towards the house, instead of away.
- No vapor barrier on the foundation walls.
- Vapor molecules are cycled through the home’s ventilation system into the basement after you take a bath.
- Cracks in the foundation allow water vapor to wick up from moist soil into your home.
- Condensation caused by leaky pipes.
If you’re still in the early stages of building your home, then you’re lucky enough to make sure things are done right from the very start. A lot of these can be done on existing homes, but will obviously be more than an afternoon project.
So let’s look into some possibilities you have.
Get a Good Dehumidifier
A dehumidifier solves the majority of the moisture problem, so it’s one of the first things you should be thinking about. The problem is that not all dehumidifiers are created equally. If you buy the wrong one, you may find it to be annoying to keep up with and it probably won’t work in a year or two.
So what’s the right dehumidifier for your basement?
It will obviously depend on your budget. The most powerful dehumidifiers are also the most expensive ones. A large basement in a humid climate will need a powerful dehumidifier like an Aprilaire whole-home dehumidifier, for example.
On the other side of the spectrum, you don’t want a dehumidifier that just isn’t the right fit. When it comes to basements, some things you may consider when choosing the right dehumidifier are:
- Match the moisture removal capacity to the size and conditions of your basement.
- Smaller portable dehumidifiers take out about 50 to 70 pints of water per day, which usually isn’t enough for many basements. Even if the dehumidifier is being advertised as covering thousands of square feet, what really matters is how much water it’s able to remove per day in your situation. If you live in a humid climate, that may not be very much.
- That’s because this rate of water removal estimate is based on a temperature in a room that’s at 80℉ and has 60% relative humidity. This standard is known as the AHAM standard. The problem is that in many climates, basements tend to be cool, damp places. The cooler a space is and the higher the base relative humidity is, the harder it is for a dehumidifier to pull water from the air. So, that portable 70- to 90-pint per day dehumidifier you just bought may not even be able to draw out half of its advertised capacity once you put it in a cool, damp basement. It will have to run constantly and its motor will be stressed, sooner or later.
- However, if you live in a less humid climate or have a small basement, a smaller dehumidifier that takes out 70 pints of water per day (like this one from Homelabs) might be the right fit for your home.
- Choose a whole-home dehumidifier instead of a portable one.
- It’s wise to invest in a whole-home dehumidifier to improve the air in your entire home rather than just a single space.
- If you have a large basement, or a large home overall, or live in a humid climate, a whole-home dehumidifier is the better option. Portable dehumidifiers might be less expensive at first, but you’ll quickly learn their disadvantages if you have a large home.
- Portable dehumidifiers can be a drain on your energy bill when they’re being pushed at maximum capacity and beyond. If used improperly, they can have a short lifespan. Rather than buy a portable dehumidifier every year or two that’s clearly not the right size for your home, why not invest in one that has a warranty and will last for years?
- Divert the collected water to the outside automatically.
- Another thing to consider is how the water will be removed from the dehumidifier. Are you willing to go to the basement every 1 to 2 days to empty out the container, or do you want a system that will simply divert the water to the outside of your home?
- Most dehumidifiers will allow you to attach a simple hose so that the water can be diverted towards the outside. You may also choose to attach ducts to the dehumidifier to achieve this.
- Look for energy efficiency.
- Expect for a dehumidifier to be on almost constantly. As you can probably tell, a small difference in energy efficiency can add up to hundreds of dollars on your energy bill every year. An energy-star rated dehumidifier uses up to 30% less energy compared to those that don’t have the rating.
- Look for a built-in defrost function.
- Many dehumidifiers stop working because the coils inside freeze. Make sure your dehumidifier has a defrost built in, or else it will break down when its coils freeze.
Divert Water Away from Your House
Don’t think that just caulking your home from the outside will keep the moisture out. The wrong kinds of sealants can do very little to keep water out of a home. Caulking alone won’t help if your home doesn’t have flashing. If you just caulk the window, water will just go behind the exterior wall and come inside from the back of it. You can buy the best, most expensive window that there is, but if it isn’t flashed properly, moisture will still have a chance to come into the house.
Make sure all doors, windows, ledges, and any other place where water might enter the home is properly flashed. Flashing isn’t just for windows. It’s for any exterior surface where water might sit and come inside (like brick ledges that stick out from Hardiplank, for example). Aluminum sheeting is fairly inexpensive, so this can be a quick fix if you’re handy.
Look for any possible water leaks. Install a water sensor and monitor to warn you early of possible water damage before it becomes too late and too costly.
Another thing is to think about is what happens to your home when it rains.
It just might be that rain isn’t drained properly and is coming into your basement. The EPA recommends that every house needs at least a 5% downslope around its immediate 10-foot perimeter, and then a 2% slope after that. Install drainage systems and redirect your downspouts several feet away from the house through the ground. Inside the basement, a peripheral drainage system with an automated sump pump might also be a solution for a basement that’s constantly damp.
The house itself must be built to push water away, too. Most of us take this as a given. Sure, we all know that a roof must slope, have gutters and downspouts. But you’d be surprised what you can find when you take a closer look. Does your home have kick-out flashing and rain diverters where they’re absolutely needed?
A simple, yet often overlooked solution is to cover your basement window wells to keep the water and debris out.
Look at the foundation walls and assess their current condition. At its worst, the moisture could be severely eating away at your home, with the brick or stone outside of your basement being eaten away by the moisture that’s moving up. This moisture carries salts with it, so if you notice the concrete bricks turning an odd white, it should be a major concern.
Salt deposits in basement brought in by moisture.
If your home is still being built, you have greater control over the process of keeping moisture out. Sit down with your builder and ask them what they’re doing to keep the water out for the long term. Some suggestions to bring up with your builder are:
- Is there a layer of gravel under the foundation and around the home?
- What kind of vapor barrier is the builder using in the basements?
- Are they using wood or steel building materials?
- How are they sealing or waterproofing the outside of the basement? (You may wish to ask for a coat with Drylok liquid rubber foundation sealant to deter future mold.)
- Will they be installing a sump pump in your home?
- Will rainwater slope away from the house? If not, will there be drainage systems in place?
There are obviously a lot more possibilities available that can help you keep moisture out of your home. To go into more depth, I encourage you to read up on the EPA’s guidelines. The EPA has a great resource that shows diagrams of how a basement needs to be built properly to keep moisture out (skip ahead to page 35, Figure 2-3).
Don’t Give Mold a Chance
Stop the Food Source for Mold
Mold feeds on organic matter found around your home, which typically are the building materials like drywall.
If your house is still being built or you’re about to finish an unfinished basement, avoid organic building materials in the basement that mold can feed off of.
Stay away from building products that have paper film. Go with metal foil insulation. Instead of wood studs, choose metal studs. Instead of ordinary drywall, choose mold-resistant drywall. Some drywall can even take out harmful VOCs from the air. It’s a bit more costly, but it’s a worthwhile investment over the long term. It will improve the air in your home and avoid mold issues later on when it’s time to sell your home.
When it comes to basements, don’t forget to also choose your flooring wisely. Dehumidifiers will have a hard time getting water out of the air if your entire basement has carpet. Laminate flooring will not only warp if there’s moisture, but the organic wood in it is ideal nutrition for mold. Vinyl flooring is full of unhealthy chemicals, so choose an eco-friendly option if this is your flooring of choice. For most homes, ceramic tile is the best option and will be easy to clean up in case the basement floods.
Clean and Remove Any Existing Mold
If your home is already infested by mold, you must immediately start to remove it. The solution can be as simple as cross-ventilating the home by opening the windows to push the spores outside. Consider cleaning the area with simple cleaners like borax or washing soda. Vinegar is very potent when it comes to killing mold. After cleaning, use a bleach and water cleaning mixture to disinfect the area overall. Tea tree oil is effective at removing mold as well.
If you have a more serious mold issue, remember that disinfectants and filters have their limitations. Disinfectants work for only 48 hours, so you may have to clean the area a few times before you notice that the mold is gone. Filters only trap mold, so the mold could still be in your home giving off toxins.
When cleaning, remember to keep the relative humidity low. If it’s between 30% to 40%, the mold will have a harder time growing back again. Once the area is disinfected, mold will still be present. Killing mold alone won’t be enough. Scrub the surfaces with a scrubbing brush, take anything you can outside to air out the spores, or cross-ventilate the space to get as much of the mold out as possible.
EPA’s guide to mold is a good read if you’d like more information about mold. In case you’re wondering if you could take care of the mold on your own, the EPA recommends to take care of the mold by yourself if the affected area is up to 10 square feet. For any area larger than that, consider hiring a professional or taking more drastic measures than just cleaning the area with basic water and detergent.
When cleaning up, use an N95 respiratory mask with activated carbon to keep yourself safe. Avoid face masks and go with properly fitted respirators so that the small particles that come up from the cleaning won’t go through. A regular face mask only blocks large particles and will probably filter out most mold spores since those are 1 micron and above in size usually. However, a regular face mask may not block out small dust particles, gases, and other substances that come up as you clean up the space. Remember to wear gloves – do not touch moldy with bare hands.
How do you know if you’ve properly cleaned up the space? Once you see no visible mold, come back a few days later and keep checking the space for a certain period of time. If the mold doesn’t come back, then you’ve probably cleaned up the space from the mold. If the mold does come back, you must clean it up again. Remember to keep the area dry and keep the relative humidity (RH) low to keep the mold from recurring.
If the mold is causing serious health issues, is taking up a large area, or is rapidly spreading, then it’s wise to hire a professional instead of trying to handle it yourself.
If you’ve successfully removed the mold, remember to be diligent so that it doesn’t come back. Keep the humidity under control with a dehumidifier (aim to stay below 40% relative humidity if possible), cross-ventilate the area constantly, be on the lookout for any new leaks in the foundation, and keep organic food sources out as much as possible.
Employ HEPA filters in appliances whenever possible. Stay away from filters labeled “HEPA-type” or “HEPA-like” – look for labels like “True HEPA,” unless you specifically know that those filters will be able to filter out mold spores, which tend to be 1 micron in size and above.
Test for Radon
Most people don’t think their home has radon or aren’t concerned with it, but there are increasing findings that show radon to be more common than most people think it is. For example, Minnesota’s Department of Health has found recently that 40% of homes in the state have dangerous radon levels, yet only 1% are being tested for radon every year.
The EPA recommends testing your home for radon every year, but unfortunately, most homeowners don’t heed this advice. If you have a basement, radon should be especially important. Radon tends to be found in the soil where there is radioactive rock in the soil. Areas where coal, volcanic rock and limestone exist, for example, can contain radon. When in the ground, it’s referred to as uranium, which then decays into radon once it’s inside the home. However, don’t let the geography fool you. Poorly constructed homes can make a home vulnerable, no matter what the uranium level in the soil is!
The EPA states that acceptable levels of radon in homes should be below 4 picocuries per Liter (4 pCi/L). However, since radon is so dangerous, it’s obviously best to keep the level in your home as close to zero as possible.
Radon varies in your home, it won’t be the same. Not only that, it can vary on a daily basis. This video explains how radon levels can vary in a basement and why the standard radon testing kits that you’d mail out to a lab aren’t enough:
(The detector used in the video is the Corentium portable radon detector and is made by Airthings. )
If you find radon in your home, the solution will depend on how severe the readings are.
The less expensive option is to just seal all cracks, openings and sump pumps where radon might seep in and to constantly ventilate the space. Sometimes installing more return ducts or new fans helps to pressurize the basement and push the stagnant air out, while bringing fresh air in. Just keep in mind that introducing more air into the house can also lead to more moisture and condensation, so combine this tactic with proper dehumidifying.
However, since radon is so dangerous, it’s always a good idea to get a professional opinion. It’s possible that your home needs a better solution than just sealing off the cracks in the foundation. If this is the case, a professional will likely recommend a radon mitigation plan.
This typically involves drilling into the floor to install PVC pipes that suck the radon out of the soil and divert it away. That way, the radon is pushed outside instead of entering the home. The professional may refer to this as sub-slab suction. Don’t attempt this yourself unless you have enough expertise. These PVC pipes must be placed strategically and unobtrusively in a home. That way, if there is a radon leak, the radon won’t dissipate into fragile living areas of the home.
Prevent Carbon Monoxide
High levels of carbon monoxide can be lethal. For that reason, most homes have a carbon monoxide detector. Imagine the alarm going off in the middle of the night, while you’re sleeping on the upper floor of the house. If the level is high enough, you may only have minutes before the carbon monoxide level becomes lethal.
Carbon monoxide detectors save lives, plain and simple.
Detectors with a digital readout will be most informative. Regular carbon monoxide detectors can go off even at low levels at prolonged exposures. Unless your detector has a digital readout, you won’t know what the exact carbon monoxide level is when the alarm goes off.
It’s good practice to regularly reset and test your carbon monoxide detectors to make sure they’re functioning. It’s also recommended to replace their batteries twice a year. Never let your carbon monoxide detector get to a point when the battery is already dead. Each floor in a home should have at least one detector. They should be installed near every occupied bedroom, in case the detector goes off at night and its alarm is weakened.
Carbon monoxide detectors should be installed wherever there’s a chance for incomplete combustion – that’s why they’re commonly seen in garages and kitchens. But if your home is quite large, don’t forget to also install a detector near fireplaces, furnaces, and laundry dryers.
It’s also recommended to have certain appliances checked annually. If they’re not venting properly or are faulty, it’s possible that carbon monoxide could be accumulating on the inside of the home.
Declutter and Throw Away Old Items
If you treat your basement like a shed or storage unit, then it needs a thorough cleaning if you want to improve the air quality of your overall home.
First, throw away everything that you don’t need, especially old things. Not only is this necessary to get the dust out of your home, but it’s also necessary to eliminate off-gassing that’s still going on.
Have you painted something in your home in the past and have a rack full of old paint buckets, varnishes, thinners, or aerosol sprays? Throw those out – they’re probably still off-gassing VOCs and getting into your ventilation system. Next time you paint, choose an eco-friendly paint without any VOCs and buy just enough to get the project done. Don’t let old paints accumulate. They’re drying out anyway and won’t be as good as new.
Cleaning supplies also commonly have VOCs, so throw out the dangerous ones and switch them out for natural cleaning supplies. If you have old couches in your basement, they might be off-gassing VOCs too if their fabrics have a fire-retardant finish. Remember, old furniture items made of composite wood likely have formaldehyde in it. Keep anything made of PVC to a minimum in your basement to avoid plasticizers like phthalates from accumulating on surfaces elsewhere in the basement.
Simplify your basement. The more things you have in it, the greater the surface area for dust to accumulate is. Not only that, but stacking up things high in your basement can block air ducts and weaken ventilation, which can lead you down the path to moisture, mold, and a higher energy bill.
If your basement still has unpleasant odors after a thorough cleaning, consider introducing bamboo charcoal air-purifying bags. They’re a natural way to trap odor-causing particles. Just keep in mind that bamboo charcoal needs to be set outside once a month to clear out the pores in the charcoal. If you absolutely want a light fragrance to freshen the space, choose a natural neutralizer instead of a harsh air freshener that just masks the odors.
When it comes to storing your shoes, clothes, and bedding, keep it all tucked away neatly and minimize the amount of dust that can collect. Consider these convenient storage bags. They stack up to free up space and allow for proper ventilation while keeping things away from the ground and away from moisture. They also contain bamboo charcoal to fend off odors. And if that isn’t enough and you still need to save more space, vacuum storage bags can essentially compress those bulky comforters and pillows up to 80% of their volume.
As far as clothing is concerned, stay away from mothballs whenever possible. Mothballs contain napthalene, which can cause nausea, dizziness and kidney damage (among many other effects) even if inhaled. Hangers made of cedar are a safer, more natural way to keep mothballs away.
Filter the Fine Particles Out
Fine particles are defined as particulate matter that’s 2.5 microns or smaller. A basement can be a difficult area to keep ventilated, so it’s certainly not a place in your home where fine particles should be.
A lot of that is out of our control because of outdoor air pollution, but some of it is possible to control. For example, laser printers are notorious for releasing fine particles. If you have a basement home office, keep the printer under an opened window, or upstairs and print wirelessly. If you have a kitchen in the basement, either turn on the exhaust fan when cooking or cook upstairs in the main kitchen.
When looking for the right air filter, the MERV rating system is a good gauge. The average air filter in a home is only rated a MERV 4 or 5. It can only catch half of the particles that are 6 microns wide. To be able to catch smaller particles, an air filter with a higher MERV rating is needed.
Even though the highest-rated MERV filters are generally the best, they can block airflow and be a strain on your energy bill if your HVAC system isn’t built for them. Unless your home has occupants with fragile health, you may not necessarily need the highest rated air filter. You may wish to consider a MERV-11 air filter for your home.
No matter which air filter you choose, remember to regularly change them out. If you have extremely poor air quality, you may even have to change out your air filters monthly until the air improves.
Don’t just rely on your air conditioning to filter out the air. Combine it with a true HEPA filter for your appliances like your basement air purifiers and vacuum cleaners. HEPA filters trap 99.97% of airborne particles.
Monitor and Maintain Your Indoor Air Quality
Hopefully, the information above has served as a checklist to you. Once you have taken care of some of the more alarming issues, all you need to do is to monitor and maintain the air in your home.
In the past, air quality monitors were hard to read and expensive. Luckily, the new generation of air quality monitors is more affordable and simplified enough for all homeowners to understand. Most home air quality monitors are able to give you a general sense of what’s in your air. My favorite is the Foobot, but there are obviously many others that may be just as good for your home.
Foobot Indoor Air Quality Monitor
- Has connectivity to your smartphone or tablet, with an attractive and easy-to-read display.
- Color-coded to simplify your air quality.
- Has historic readings to help you improve and monitor indoor air quality over time.
- Reads several important VOCs and gives the reading as TVOC, or Total Volatile Organic Compounds.
- Offers several other readings like fine particulate matter.
- Carbon dioxide reading is built in, but data are received indirectly through the other measurements.
- Also interprets outdoor air pollution.
- IFTTT smart home connections are possible with some dehumidifiers and air purifiers.
- Works with NEST thermostats and Amazon Alexa.
If you’d like a simpler, budget-friendly air quality monitor, but don’t need to store historical data over time, then this multifunctional monitor might be a better fit for your home. If you don’t have smart integration with dehumidifiers or air purifiers, but want a comparable function, then you may like the Awair Glow. It switches those devices on or off as long as it’s plugged into the same outlet.
Hopefully you have found information in this post to make your basement and its air a more enjoyable space. Although keeping moisture out is the primary factor, indoor air quality has many factors that can contribute to it. Even after your basement air has been cleaned of pollutants, it’s wise to have an air quality monitor in place to keep track of it.
And as always, if you have additional tips or natural cleaning ideas to contribute, feel free to share in the comments.