Hot Environmental Topics

A comprehensive resource for homeowners and real estate professionals.

Introduction

Mold—it's the unwelcome houseguest that no homeowner or realtor wants to encounter. Beyond being unsightly, mold can compromise structural integrity, decrease property values, and pose serious health risks. Whether you're a homeowner wanting to protect your living space or a realtor helping clients maintain valuable properties, understanding mold prevention is essential.

In this guide, we'll explore practical, effective strategies to keep homes mold-free, identify early warning signs, and address small problems before they become costly nightmares.

Understanding Mold: Know Your Enemy

Mold is a type of fungus that reproduces by releasing spores into the air. These microscopic particles are virtually everywhere, both indoors and outdoors. When spores land on damp surfaces with organic material (like wood, drywall, or fabric), they can quickly develop into mold colonies under the right conditions.

What mold needs to grow:

• Moisture or high humidity (above 60%)
• Food source (almost any organic material)
• Oxygen
• Warm temperatures (typically 77-86°F, though some molds can grow in cooler environments)
• Time (as little as 24-48 hours under ideal conditions)

Common Household Mold Hot Spots

Bathrooms

• Shower stalls and curtains
• Under and around toilets
• Sink cabinets
• Grout between tiles
• Ceiling (especially if ventilation is poor)

Kitchen

• Under the sink
• Behind the refrigerator
• Microwave and other appliances
• Garbage disposal areas

Basement & Crawl Spaces

• Around foundation cracks
• Near sump pumps
• Around windows
• On exposed dirt

Other Problematic Areas

• Window sills and frames
• Air conditioning units and ductwork
• Attic spaces (especially around roof leaks)
• Laundry areas
• Under carpeting in damp areas

10 Essential Mold Prevention Strategies

1. Control Indoor Humidity

Maintain indoor humidity between 30% and 50%. Use dehumidifiers in naturally damp spaces like basements, and monitor levels with a hygrometer (humidity meter).

2. Ensure Proper Ventilation

• Install and use exhaust fans in bathrooms, kitchens, and laundry rooms
• Ensure dryer vents direct air outside, not into attics or crawl spaces
• Consider energy-efficient ventilation systems for whole-house humidity control

3. Address Water Issues Promptly

• Fix leaky roofs, windows, and pipes within 24-48 hours
• Inspect water-using appliances regularly (water heaters, washing machines, dishwashers)
• Clean and repair roof gutters to prevent water seepage

4. Improve Air Circulation

• Don't push furniture completely against the walls
• Open doors between rooms
• Use ceiling fans to increase air movement
• Open windows when weather permits (unless outdoor humidity is high)

5. Basement and Foundation Care

• Apply waterproof sealants to basement walls and floors
• Ensure proper grading around foundations to direct water away
• Consider installing a sump pump if basement flooding is an issue

6. Smart Bathroom Habits

• Squeegee shower walls after use
• Hang towels to dry completely
• Leave the shower doors/curtains open to allow drying
• Clean bathroom surfaces regularly with mold-inhibiting products

7. Strategic Landscaping

• Don't place mulch directly against home foundations
• Trim vegetation to allow airflow near exterior walls
• Ensure sprinklers don't spray directly onto the house

8. Mold-Resistant Building Materials

When renovating or building, consider:

• Mold-resistant drywall or Sheetrock
• Mold-inhibiting paints
• Paperless drywall for bathrooms
• Cement board in shower and bath areas

9. Regular Home Inspections

• Check hidden areas quarterly (behind appliances, under sinks)
• Inspect attics during rainy seasons
• Look for water stains, discoloration, or musty odors

10. HVAC Maintenance

• Change air filters regularly (every 1-3 months)
• Have ducts professionally cleaned if mold is suspected
• Consider UV lights for HVAC systems to kill airborne spores

Early Warning Signs of Mold Problems

Be alert for these indicators that mold might be developing:

• Musty, earthy odors
• Visible water stains or discoloration
• Peeling or bubbling paint/wallpaper
• Warping of wood
• Increased allergy symptoms indoors
• Excessive condensation on windows or pipes

Health Impacts: Why Mold Prevention Matters

Mold exposure can cause various health issues, especially for sensitive individuals:

• Nasal congestion, coughing, and wheezing
• Eye irritation
• Throat irritation
• Skin rashes
• Headaches
• More severe reactions in those with asthma or compromised immune systems

For Realtors: Protecting Your Clients and Listings

During Property Evaluations

• Know how to spot potential mold issues during walkthroughs
• Recognize "cover-up" signs like fresh paint in unusual areas
• Include mold inspections in standard home inspection recommendations

When Listing Properties

• Advise sellers on addressing mold issues before listing
• Document mold remediation efforts
• Understand disclosure requirements in your state
• Consider pre-listing inspections to identify problems early

Protecting Vacant Properties

• Set thermostats appropriately (usually above 55°F)
• Consider periodic dehumidification
• Ensure regular property checks
• Maintain minimal water use in plumbing systems

DIY Mold Cleaning Solutions

Important Safety Notes:

• Never mix bleach with ammonia or other household cleaners
• Always wear gloves and a mask when cleaning mold
• Ensure adequate ventilation

When to Call Professionals

Consider professional help when:

• Mold is inside HVAC systems
• There's mold growth after flooding with contaminated water
• You suspect hidden mold in walls or ceilings
• Residents experience health symptoms potentially related to mold
• Different smells that you are unfamiliar with, especially in attics, crawl spaces and basements

Seasonal Mold Prevention Calendar

Spring

• Check for winter water damage
• Clean gutters after spring blossoms
• Inspect the roof after winter weather
• Test the sump pump before spring rains

Summer

• Monitor air conditioning systems
• Check for condensation issues
• Inspect outdoor sprinkler spray patterns
• Clean and dry pool equipment properly

Fall

• Clear gutters of autumn leaves
• Check window seals before winter
• Inspect attic ventilation
• Examine the basement for summer condensation issues

Winter

• Monitor indoor humidity during the heating season
• Check for ice dams on roofs
• Ensure proper ventilation when using humidifiers
• Inspect pipes in cold areas for condensation

Conclusion

Preventing mold is far easier and more cost-effective than addressing an established problem. By implementing these strategies, homeowners can protect their health and property value, while realtors can better serve clients by identifying potential issues early.

Remember, the key to successful mold prevention lies in controlling moisture, ensuring proper ventilation, and staying vigilant through regular inspections. Taking these proactive steps today can save thousands in remediation costs tomorrow.

Let us agree that we spend most of our lives indoors, and air quality can affect human health. You know you go outside to get fresh air but also want clean air indoors. Most buildings we assess for air quality have few measures in place to help improve indoor air quality.  Think about it, what do you do to improve indoor air quality?

Many people unwittingly do things indoors that are detrimental to air quality. What are those?

I will provide a wide range of measures you can implement to improve indoor air quality. Many people adopt only a few of these measures, which is perfectly fine. Small steps can lead to significant improvements. I believe that 10 minutes of exercise today is better than doing no exercise at all. While an hour of exercise is ideal, it's not always practical.

There are countless Peloton bikes, Bowflex systems, and treadmills that end up gathering dust or being used to dry clothes, despite being purchased with the best intentions for exercise. Therefore, even if you decide to implement just one of the options I suggest, you are still making progress toward better indoor air quality.

12 Steps of Better Indoor Air Quality 

1. Indoor Plants

Indoor plants help filter air and remove indoor air contaminants. Plants can remove carbon dioxide, which is a by-product of human occupancy of a room. Houseplants can remove formaldehyde, benzene, and a host of other compounds found indoors. They also add moisture to indoor air, as viruses thrive in low humidity environments you want a relative humidity above 50 year-round in living spaces. I keep plants on the porch and patio in season, and during the colder months, I move indoors.  Regardless, always have plants indoors, invariably some plants die over the winter, so the plants are an ongoing project.

I was at a wedding where I was asked about what I do for a living and when they found out I was an environmental consultant, I was asked about indoor air quality and plants. They read an article dismissing improved air quality and plants, possibly a Reddit thread.   To be transparent, some critics say if a plant removed 90% of contaminants, 10% of contamination remains. Fact, but I will take ANY air quality improvement.  I refer to a research study evaluating multiple studies on plants and indoor air quality. The study concluded that indoor plants help reduce indoor contaminants, which just so happens to agree with me.  Effects of indoor plants on air quality: a systematic review | Health & Environmental Research Online (HERO) | US EPA

2. Unscented Cleaning

We are conditioned to believe that scents signify cleanliness.  Think lemon, pine, citrus, but if you read the labels there are no natural ingredients in these cleaners, all chemicals with names that are hard to pronounce. Let me tell you a harsh fact, scent does not improve cleaning ability, it is all in your head.  Sure, if you cut a lemon in half, you can clean surfaces with it because the acid properties of the lemon make a good cleaning impact, but be real, you do not do that.  All the scents added to cleaners add chemicals to your indoor air, it's true. There is a scent in women’s perfume that is also used in toilet cleaners. You should lean towards neutral cleaners, meaning scentless.

3. Shake out your doormats and remove shoes after entering a home.

Some cultures recognize that your feet touch the ground that is loaded with all sorts of things you do not want to know about.  Outside your home is a bathroom to animals and a lush green lawn will likely contain pesticides and herbicides.  Mats trap these unwanted ingredients, shaking out mats helps ensure you do not have carryover in your home.   Sounds simple and it is, effective. Taking off shoes also helps, but good luck with that with kids.

4. Use the kitchen exhaust fan

Every kitchen should have an exhaust fan that vents outside. This is most important if you have a gas stove. Gas stoves burn natural gas, which generates nitrogen dioxide (NO2) which is harmful to human health. EPA regulates  (NO2) levels outside but not indoors, FYI. The pilot light for gas appliances can also emit benzene, which is a known carcinogen. If you have a gas appliance you have this exposure but running the exhaust fan while cooking helps extract these harmful (as well as others I am not going to explain) outside the home. 

Try not to burn toast. The US Environmental Protection Agency (EPA) says that acrylamide, a chemical found in burnt toast, is "likely to be carcinogenic to humans". Even if you do not care about acrylamide (you likely never heard the word before), when you burn toast or anything you are cooking, there is smoke but not combustion.  The smoke has a small particulate 10 micrometers in diameter (10 micrometers is five times smaller than the width of a human hair), which is a small particulate that is hard for your body to filter and can be pulled deeper into your lungs.  Let’s agree your toaster is typically not next to an exhaust fan so you are filling the room or the area with small particulates that humans are filtering with their lungs, bad stuff.  Again, run the exhaust fan to try and capture these small particulates, even if you do not burn toast if you are cooking you are generating airborne small particulates.   The same goes for burning candles and I know this will hit home for many people you do not want to hear this, but do not burn candles.    If you happen to be a person who has a small room air filer, operate it in the kitchen.

5. Prevent Mold

Mold is a biological contaminant and a well-known air pollutant. That musty smell people associate with mold, is a sign of active mold growth. Mold consumes organic matter and as with any biological process, a waste by-product occurs.  Musty means an assortment of chemical compounds in the air including mycotoxins, microbial volatile organic compounds and components of the organic matter being consumed by the mold. Mold = moisture, remove moisture and you remove the driver of mold growth. Simple solutions include operating a dehumidifier in basements to extract excess moisture. In my humble opinion, every basement and crawlspace should have an operating dehumidifier.   Install and operate an exhaust fan in bathrooms where you bathe. If you have a fan already, do three things,

• use it.
• when in use hold a paper towel to the fan, if the fan suction cannot hold the towel in place, the fans suck in the wrong way. 
• Lastly make sure the exhaust is sent outside, not to the attic.

There are amazing Panasonic exhaust fans that are whisper quiet and have controls to operate when motion or humidity are detected, taking human error out of the equation.  Use humidistat-controlled exhaust fans in attics to control moisture.

6. Clean your Ducts

Although EPA says you should not clean your ducts, because it stirs up all the crap in the ducts, if you removed a duct and looked inside, you would be disgusted by how dirty it is.  Duct cleaning is not going to remove 100% of this material, but it will remove a lot, and more will come loose a week or so after you get the ducts cleaned, from movement and vibration in the house, so you should check your HVAC air filter a week or so after cleaning.  Post cleaning you install a new filter which will typically get dirty a week or two after cleaning.  Duct cleaning every 5 to 10 years is great, spend no more than $500 for a typical home, and do not apply any fungicides or other compounds in the ducts, they do nothing.

If you have no ducts, i.e., electric or radiator heat, do nothing; these are some of the healthiest heat sources. If you have central air with ducts, well you may need cleaning.

7. HVAC Systems are the Lungs of your home.

I naively thought that after COVID-19, people would take a greater interest in improving air quality, and your HVAC is the lungs of any building. But spending money on HVAC is not sexy. That said you can make small tweaks to forced hot air systems to improve air quality. Cleaning the ducts is one aspect.  You can also upgrade your filters on the system. I use MERV 16, which is like hospital-grade air, but anything with a MERV above 10 is great. The higher the Merv the smaller particulate the filter can capture. Think of an N-95 Mask on your HVAC system.  If you have heat in winter you have dry air, viruses thrive in low-humidity environments. Adding and operating a whole house humidifier in season (winter) will make your indoor environment more comfortable.

I am on the fence about UV light in HVAC, there are arguments that although UV has a sanitizing effect on air, the air must spend time being exposed to the UV light to be effective. That said I added it to mine as the cost was minimal and I did it in conjunction with a whole house humidifier, so the company was already at my house.

8. Chemical Storage

You have gallons upon gallons of chemicals in your home and yes chemicals in containers off gas. Ever open a pail of paint and find it dried out?   The container did not hold an airtight seal. You should strive to keep chemicals outside your living space, like a garage or shed. Yes, I know paints do not like extreme cold and may go bad, but how often do you touch up paint?   A countermeasure is to take a photo of the paint container or lid that will have all the paint information which you can take to the paint store and purchase a new container, and, yes paint can be purchased in 5-gallon, 1-gallon, and quart containers if your touch up job is small. Dispose of remnant paint at a household hazardous waste day.

9. Know when indoor air quality is poor.

How are you supposed to know when indoor air is bad? Anytime you have people over, holidays in particular, CO2 levels are screaming high from people breathing. Keep a window open slightly when you entertain and maintain a low draw on your kitchen exhaust fan to help pull air out and fresh air in. There are actual CO2 monitors you can install in a home to tell you when levels are elevated.  There are also air quality meters you can purchase. I am on the fence about residential air monitors as the sensors have a finite life and are not widely known so the cost is high and the quality questionable.   When Consumer Reports starts testing air quality meters I might change my opinion.

In the winter keep a window open to introduce fresh air for a short period of time every day.  Hey, it is cheap. You know higher-end HVAC systems know that dilution is the solution to indoor air pollution, so they pull a volume of fresh air from the outside and condition it before sending it through the house. Yes, pulling hot or cold air and making it cold and warming air takes energy, but that’s part of healthy air. Fresh air goes a long way to improving indoor air quality.

10. Test building materials before renovation in homes built before 1978.

My home is from the 1930s, I have a few outdated green building products in my home. By outdated I mean asbestos and lead paint, both past green building products, but now we know they are a health hazard.  Lead paint was banned by the Consumer Product Safety Commission in 1978, asbestos was phased out around that time as well. When you decide to remove a wall to make a great room, that wall may have lead paint and asbestos in the plaster, which will become airborne during and after demolition. That sexy popcorn ceiling likely has asbestos. You should test older building materials to ensure you are not exposing workers or your family to these hazards.

11. Home improvements and furniture in warmer weather

Do you like the new car smell, how about the new carpet scent? Both are bad for you. Buying furniture with fire retardants or installing new carpet in winter when you cannot open your windows and air out the chemicals allows chemical build-up in your home. New items need to time to off gas, which can be accomplished by placing items in the sun or if not possible opens windows and allow the compounds to dissipate.  Windows are open in warmer months, you get the idea.  New things also off-gas formaldehyde and the EPA is targeting this harmful compound. Executive Summary of the Risk Evaluation for Formaldehyde

12. Replace fluorescent light bulbs

Fluorescent tube bulbs and squiggly compact fluorescent bulbs contain small amounts of mercury. If these bulbs are broken the mercury is released into the air they become a contaminant.