The Right Conditions for Mold Growth

We all know that mold inside our home or business can be a potential health hazard. We also know that proper remediation techniques can be the difference between healthy air quality and a recurring mold infestation. We know that mold can occur anywhere in our homes and businesses, but certain areas are especially susceptible to mold damage. But, what conditions does mold need to grow?

Mold needs a material that it can grow on, such as sheet rock or wood. Mold digests cellulose materials, even those that may be on the surface of other items such as masonry block or brick. Mold does not grow on masonry itself.

The most obvious condition within a property that molds needs to grow is wet material from water damage. Water damage always needs to be addressed immediately. Mold can grow as quickly as just a few days. Water damage sometimes is not discovered until it has been there for weeks or sometimes even months. Small plumbing leaks can cause significant mold problems. A constant supply of new water and moisture allows mold to grow day after day. Sometimes property owners will not discover underlying water until they see dark mold discoloration in the building materials. There does not have to be actual water standing on the floors or wet walls to have mold growth. Just elevated humidity can grow mold.

Bathrooms are the moldiest place in the home, typically. Bathrooms have a near constant flow of water and high humidity. These combined factors are a recipe for mold growth. Most common factors in bathroom mold growth are leaks in your plumbing, improper ventilation, or rotted subfloors. A leak behind a bathtub, sink or toilet may go unnoticed, growing silently between the drywall. Some things you may notice if you have a leak are the sound of water, odd smells, or even your water bill going up. If you suspect you have a water leak, but don’t notice any signs, one way to check without ripping out your bathroom is to mark the indicator on your meter and use no water for an hour. If the indicator moves over the hour with no consumption, you may have a problem.

Basements are very prone to mold growth. This is because basements often require very little cooling. Basements have concrete floors which stay cool and most basement walls are underground or partially underground which also keeps the walls cool. When the AC is not in use there is no condensation going on at the AC coil. Condensation at the AC coil is the only way humidity is removed in most homes during the summer. A cool area with elevated humidity creates a cave like environment. Humidity levels within a home should be less than 55%. If an area smells musty it may have an elevated mold spore count. If the humidity stays elevated long enough you will start to see surface growth on many surfaces such as walls, ceilings, furniture and other contents. Humidity is often overlooked and in some homes the humidity is high enough to grow mold causing allergens, but not elevated enough to rot materials.

Crawl spaces are unique places where mold is often found. Crawl spaces are prone to both water intrusion and elevated humidity. Most property owners never go into their crawl space and ignore it until there is a problem.  Most crawl spaces received very little to no direct sunlight. Sunlight will kill most mold and bacteria this is why we do not see mold growth on the sunny side of the home but you do see it on the shady side.  Most crawl spaces depend on moisture barriers, foundation vents and cross ventilation for moisture control. Often the humidity outside is elevated and many crawl spaces are being cross ventilated with damp air, therefore there is no drying effect during the summer months or during rainy  periods. The soil can breathe many gallons of water daily into a crawlspace. Therefor, moisture barriers are critical and controlling crawl space moisture.  If your crawl space needs moisture control it is best to have someone look at all the unique variables of your crawl space and design a system that will keep your crawl space dry. Some crawl spaces need french drains, sump pumps, the humidifiers, booster vans and encapsulated system while other crawl spaces need only a minimal addition of plastic moisture.

Attic areas are the least likely areas in a home to grow mold. However, when an attic is not designed properly mold may appear. Most attics need ventilation from the lower edges of the roof that will slowly move up and then be released at the ridge of the roof. Attics are typically very hot and dry places. The most likely areas for water or moisture intrusions are at the chimneys, valleys, leaks in the roofing, and plumbing boots. Leaks in your roofing is probably the most common source of mold in attics. Mold will start to grow and rot the wood at the location of the leaks. Many times the leak is small and goes unnoticed inside the home. This allows the mold to grow unchecked. Checking over your attic periodically helps detection before mold growth gets out of hand.

Preventing conditions that mold will need to grow is the best thing property owners can do. The easiest thing to do is to always allow the heating and air-conditioning system to be left on between 72 and 74, remember the heating and air units not only control the temperature within a home, but also keep the humidity low.

Next know the condition of your home:

  • Do I have a dry crawl space?
  • Do my gutters exit water away from the foundation of my home?
  • How old is my roof?
  • Is my chimney flashing correctly installed?
  • How old are my plumbing boots?
  • Do I need to update my Windows?
  • Do my windows create condensation?
  • Do my windows leak?

If these terms do not make sense it may be worth paying someone to come out and inspect these items and explain to you what condition your home is in. If you do not have mold but have the conditions you may prevent mold growth and save money on future mold remediation efforts.If elevated humidity or water concerns go unaddressed mold will eventually grow. If you have any suspicion of mold the sooner you respond the better. Even if there isn’t a problem, you may gain peace of mind. Be careful of the contractor or inspection firm you pick. Try to research and ask for referrals. Honesty is a good starting point, but also having the knowledge to correctly diagnose and inspect mold is critical.

John has over 23 years of Indoor Air Quality experience. Some of the certifications he holds are: C.I.E Certified Indoor Environmentalist #00666 C.M.R Certified Mold Remediator #04124 Construction Engineering Technology Degree NADCA (National Air Duct Cleaning Association) Certifications: A.S.C.S Air System Cleaning Specialist # 9011357 C.V.I Certified Ventilation System Inspector # C203080526 V.S.M.R Ventilation System Mold Remediator # V303060706 Active Member of IAQA #1070 EPA Radon Certified
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