Mold In The Home



It can grow inside walls, below carpets, inside kitchen and bathroom cupboards and behind the tile in the shower. What can we do about it? How do we even know it's there? Should I be worried about the health implications?  What damage can it do to my home? These and other questions we will answer in this posting about Mold In The Home.

What is mold?

Mold growth in attic due to improper attic ventilation and poor duct insulation.

Mold growth in attic due to improper attic ventilation and poor duct insulation.

Mold is a type of fungi. Fungi, or fungus, belong to a taxonomic classification of their own. Molds are the most typical form of fungus found on earth, comprising approximately 25% of the earth’s biomass. The main role of fungi in the ecosystem is to break down dead materials such as fallen leaves, trees, insects and animal carcasses. The enzyme that assists fungi in breaking down dead materials also helps mold to damage the components and building materials of our houses. Mold is essentially a type of fungus that grows in our homes. It can be seen around shower walls, windows, sinks, on wet insulation and inside walls that have become wet for extended periods of time. 

Mold grows by producing microscopic spores. Mold spores are everywhere. They cannot be eliminated from the environment. Mold spores can be found floating through the air and on settled dust; however, they will not grow if moisture is not present. Discovering mold in our home raises three major concerns: 

1) The potential health effects of exposure to mold and their byproducts,

2) The effects of fungal contamination on the structural integrity of a building,

3) The negative aesthetic effects of visible mold and its smell.

Although the issue of whether exposure to indoor fungi causes adverse health effects is controversial, there is no doubt that a seriously mold-contaminated building can suffer structural damage, and that a foul-smelling, fungus-filled building is aesthetically unpleasing.

Should I be concerned?

Mold is not usually a problem indoors unless it lands on a wet or damp area and begins growing.  As mold grows, it digests whatever it grows on. Mold growth can damage buildings and furnishings, it can rot wood, damage drywall, and eventually cause structural damage to buildings. Mold can cause cosmetic damage and stain furnishings. The potential human health effects of mold are also a concern. It is important, therefore, to prevent mold from growing indoors.
People who have concerns about structural damage or the aesthetic effects of indoor mold growth should seek the services of a certified mold inspector.  People who have concerns about health effects of mold exposure should seek the advice of a healthcare professional.

What are the negative health effects of mold?

The inhalation of mold and mold spores can cause adverse health effects in some people. Mold produces allergens and irritants, and in some instances, mold can produce potentially toxic substances called mycotoxins. Contrary to common belief, though, there is no conclusive evidence that proves that mold in a building directly causes human illnesses. However, individuals with respiratory conditions (such as allergies and asthma), and people with weakened immune systems (people with HIV/AIDS, chemotherapy patients, and organ transplant recipients, etc) may be more susceptible to the negative health effects of mold. 

What are the symptoms of Mold Exposure?

Allergies and hay fever-like symptoms along with headaches, sneezing, a stuffy or runny nose, irritated eyes, and skin rash, are the most common type of reaction associated with prolonged exposure to mold. All of these symptoms may be caused by other exposures or conditions unrelated to mold growth; therefore, it is important not to assume that mold is the cause of these symptoms. The effects of mold exposure can be acute or chronic. If a person experiences these symptoms only when occupying a particular building, then that person may possibly be experiencing symptoms of mold exposure. For more detailed information on mold and its health effects, consult a healthcare professional.

What does mold need to grow?

Mold needs three things to grow. Moisture, Food, and Temperature.

  • Temperature is the easiest ingredient to come by: anywhere between 4-37 °C will do. So, pretty much everywhere and always in Vancouver. 
  • Food is also in abundant supply in a home: wood, insulation, drywall, paper, etc. Virtually any organic substance can be a place where mold can grow. Mold can also be found on an inorganic substance like glass or concrete because it will grow on the dirt and dust found there.
  • Moisture. Here’s where we have to pay attention. Controlling moisture and humidity in your home will control mold growth in your home. This means maintaining a low relative humidity (RH) inside the house, sealing drafts and air leaks, and preventing water from penetrating the building enclosure.

What is relative humidity?

The science behind relative humidity (RH) is that warm air has a greater moisture-holding capacity than cold air. So, when you heat up cold air, the humidity level (RH) drops (and vice versa). An example of this is that a glass of ice water gets covered with condensation when it is left in the sun in the summer. The air next to the glass cools. Cool air can not hold as much moisture, so the extra moisture condenses out of the cooling air and is deposited on the glass.  Another example is when cool air comes into your home (via either infiltration or ventilation) and mixes with the inside air- it is warmed, thereby lowering the RH. This is why we sometimes get chapped lips in the winter- Warming the cold air makes it really dry.

What is a good humidity level to maintain inside the house?

That depends on the time of year. In the winter months, it is better to keep the house dryer than in the summer months. In the winter, RH should be kept between 30% and 40%. In the summer- between 40-50% is good. The reason we want to keep the RH lower in the winter than in the summer is that it helps prevent condensation buildup on windows and other surfaces. The highest RH in a room is always next to the coldest surface so it is important to keep the average RH of a room lower in the winter because condensation could form on the cold walls and windows if the average RH is too high. The condensation forming on the cold walls and windows could raise the moisture content in the building materials which may result in mold growth.    

At 64% relative humidity, mold could be growing in this storage locker area.

At 64% relative humidity, mold could be growing in this storage locker area.

What’s the difference between relative humidity and moisture content?

Relative humidity is the amount of water vapour in the air and moisture content is the amount of absorbed water in a material. For example, the moisture content (MC) of hardwood flooring is supposed to be around 6-8%. Fiber saturation (the maximum amount of water it can hold) of wood is around 28%.  Mold can start to grow on wood with a MC above 19%. Mold can start to grow on drywall when the MC is above 0.6%, on brick above 0.8%, wallpaper above 10.5%, and concrete above 5%.

How does mold grow inside walls?

There are many ways that mold can grow inside a wall. Examples are:

  • warm air continually escaping through air leaks in a building enclosure condenses as it cools on its way out,
  • water from outside leaking into a wall or roof, etc,
  • plumbing leaks.

How do we ensure that condensation is not forming in the walls?

Essential what we are trying to do in this instance is to prevent warm, moist air from contacting cool surfaces. If we have a leak in the air barrier of the wall and warm air is escaping through it to the outside, it is possible that that air will condense inside the wall. This is a perfect breeding ground for mold.

To correct this situation:

  • If moldy insulation and other building materials are present, replace them and ensure the wall cavity is properly insulated,
  • Ensure continuity of the air barrier and vapour barrier and that the vapour barrier is properly located on the warm-in-winter side of the wall,
  • Ensure that the relative humidity inside the home is maintained at levels that are not conducive to vapour related problems should a leak in the air barrier occur. This can be accomplished through dehumidification or proper use of ventilation and heating.

How do we prevent water from leaking into a wall?

Regular home maintenance is a good place to start. The old adage ‘A stitch in time saves nine’ holds true in this instance. All too often regular home maintenance goes unattended for far too long and the damage can become severe. Often replacing a bit of caulking, or repairing a damaged piece of flashing, or a damaged piece of siding, or maintaining proper connections of the downspout can go a long way to preventing water from getting into the walls.

What about plumbing leaks?

The same can be said here as in the above section. Repair problems as they occur and the damage can be kept to a minimum.

What do you look for when performing a mold inspection?

When I’m inspecting a home for mold I bring a variety of inspection tools that help me identify the presence of mold. Among these tools include:

  • Moisture meter,
  • Psychrometer (temperature and humidity meter),
  • Infrared camera,
  • Infrared thermometer,
  • Air sampling pump with air sample cassettes,
  • Bio Tape slides,
  • Swabs.

Depending on the scale of the inspection being performed, the air pump and Bio Tape and swabs may or may not be used. If I am performing an IAC2 type inspection they will be used; but, sometimes that isn’t necessary or is cost prohibitive. By the principle of, ‘If it looks like a duck and quacks like a duck; it’s a duck.”, we may not need to take it to that extent.

Often all a client wants is to have certain areas of their home inspected to identify problem areas so they can know if they need to be concerned and/or proceed with repairs. In this case, I would examine potential problem areas (such as shower walls, basement floors and walls, kitchen and bathroom sink areas, exterior walls and windows, etc) with the infrared camera and moisture meter, etc, and take humidity readings in various locations around the suspect area. These measurements and my 30 years experience is often enough information to know if an area needs repairs and I can offer recommendations as to how to proceed.

If we need to take it to the next level, we can take air samples and Bio Tape samples and swabs and send them to a lab to know exactly what we are dealing with. We can even open walls and send samples of drywall, insulation, and carpet to the lab for testing.

What is an IAC2 Mold Inspection?

An IAC2 Mold Inspection is a certified mold inspection which includes a non-invasive, visual examination of the readily accessible, visible, and installed systems and components listed in the IAC2 Mold Inspection Standards of Practice, as well as at least one sampling for mold growth, according to the IAC2 Mold Sampling Procedures. The inspector shall report moisture intrusion, water damage, musty odours, apparent mold growth, and/or conditions conducive to mold growth.

Some conditions conducive to mold growth include:
•    defects in systems or components that may allow water or moisture penetration;
•    evidence of flooding;
•    water damage;
•    water stains;
•    standing water or puddles;
•    indoor surfaces that are too cold;
•    carpeting that was wet;
•    houseplants (watering them can generate large amounts of moisture);
•    over-watering of potted plants;
•    indoor humidity that is too high;
•    the use of a humidifier;
•    steam radiators;
•    line-drying the laundry indoors;
•    firewood stored indoors;
•    condensation problems;
•    condensing moisture on air-conditioning ducts and windowpanes;
•    negative grading;
•    water inside a perimeter-drainage channel;
•    irrigation sprinkler systems that are not spraying efficiently;
•    downspouts not discharging far enough away from the building;
•    clogged or inoperative gutter system;
•    leaking gutters;
•    improperly installed flashing;
•    the deteriorated condition of the roof covering;
•    roof leaks;
•    missing vapour barrier;
•    plumbing system leaks, or defects in appliances, such as a leaking dishwasher;
•    loosely secured toilets with leaking wax rings or seals;
•    the overflow of water from tubs, sinks or toilets;
•    water inside a sump pump bucket;
•    dripping water valves;
•    improper or inadequate discharge of exhaust from the clothes dryer, bath vent
     or kitchen fan;
•    improper venting of combustion appliances;
•    a dirty air filter or a clogged condensate drainage in the HVAC system;
•    failure to vent clothes dryer exhaust outdoors (including electric dryers);
•    non-insulated ductwork inside a non-conditioned space;
•    inadequately ventilated spaces, such as an attic space with its vents blocked by  
•    crawlspaces with exposed dirt floors;
•    moisture movement through basement walls and slab;
•    water or moisture intrusion at carpeting in the corner of a below-grade basement;
•    a fire-suppression sprinkler head that is dripping water; and
•    any building system or component that may contribute to a moisture problem.

High moisture meter readings on shower wall creates a good breading ground for mold inside the wall.

High moisture meter readings on shower wall creates a good breading ground for mold inside the wall.

Hidden Problems

In most cases, finding indoor mold growth may not be easy. Mold does not need light to grow; it can grow in dark areas and on hidden surfaces, such as the backside of drywall, wallpaper and paneling, on the top-side of ceiling tiles, and on the underside of carpets and pads. Possible locations of hidden mold also include damp areas behind walls and in crawlspaces, inside pipe and utility chases, on the back side of insulation in attics and joist spaces, and on roof materials above ceiling tiles. 

Investigating for hidden mold can be difficult.  It requires a professional with experience in inspecting for water and moisture problems.  A certified home inspector is best qualified to perform a thorough mold inspection.  Certified home inspectors are trained to locate and identify moisture intrusion, condensation, and humidity problems.  Certified home inspectors are trained in building science, which is required to investigate moisture intrusion and conditions conducive to mold growth.

8 Questions that can be answered by a visual examination and mold sampling of a building:

  1. Is there water intrusion in the building?
  2. Are there any components in the building that are water-damaged?
  3. Are there musty, moldy odours in the building?
  4. Is there any visible, apparent mold?
  5. Is that which is visible actually mold?
  6. Are there indications of hidden mold growth?
  7. Are there conditions conducive to mold growth?
  8. What should be done if mold growth is discovered?

To address these concerns and questions appropriately, a visual examination must be performed to a standard, mold samples must be taken, laboratory analysis must be included, and accurate reporting must be documented.  Proper collection, handling, and documentation of mold samples are all required for a conclusive, credible report.  All inspection procedures should be followed carefully and precisely.

Do you provide a written report with your inspection?

Usually, but not always. 

Sometimes a client just needs someone with experience and good testing equipment to examine their home to determine if there are areas inside the home that are suspect for mold and to suggest ways to proceed with dealing with these areas. For these clients, a written report may not be necessary. They can walk around with me on the inspection and they will know first hand what the problems are and how to proceed. The added expense of lab testing and written reports may not be necessary. We provide this service.

Some clients want to know exactly what the situation is inside their home with regards to a potential mold problem. They want to know details on the quality of the air inside their home and they want confirmation that the staining on their walls (for example) is, in fact, mold. For these clients, air samples and Bio Tape slides and swabs will need to be collected and sent to a lab for analysis and the inspection findings and lab results will be documented in a detailed, written report. We also provide this service.

Mold and decay needs to be removed and the damage repaired.

Mold and decay needs to be removed and the damage repaired.

Once the Inspection is done, then what do I do?

That depends on what is found. Usually what is required is to have the damaged areas cut out and removed and rebuilt or repaired to their original state. A good, licensed building contractor can do that and it’s happening all over the city all the time. 

If the problem is extensive, a full-on remediation plan may be required. This can include a containment plan, determining the level of personal protective equipment (PPE) needed, the method of cleanup, the use of biocides, bio-aerosol sampling, etc. We won’t go into detail of that here but you can email me if you need to know more. 

Then what?

Now that you have learned a few things about mold, you need to know how to prevent it from growing in your home. The most important thing to remember for mold growth prevention is moisture control. Water intrusion into the home should be controlled. If water leaks into the home through a roof leak or the basement gets wet during a flood, etc, the cause of the leak should be corrected immediately and the area should be dried out. 

Routine maintenance includes:

  • Keep your home and its contents dry. When they get wet, dry them within 24-48 hours,
  • Keep the building clean and dry,
  • Fix leaky plumbing and any leaks in the building's enclosure as soon as possible,
  • Watch for condensation and wet spots. Fix the sources of moisture problems as soon as possible,
  • Prevent moisture due to condensation by increasing the surface temperature or reducing the moisture level in the air (humidity). To increase the surface temperature, insulate or increase air circulation. To reduce the moisture level in the air, repair leaks and increase ventilation (if outside air is cold and dry), or dehumidify (if outdoor air is warm and humid),
  • Keep heating, ventilation and air conditioning (HVAC) drip pans clean, flowing properly, and unobstructed,
  • Vent moisture-generating appliances, such as dryers, to the outside,
  • Maintain indoor humidity below 60% relative humidity (ideally between 30% and 50%),
  • Perform regular building and HVAC inspections and scheduled maintenance,
  • Don't let foundations stay wet. Provide drainage, and slope the ground away from the foundation,
  • If you are not experienced with home and building repairs, you may want to consult a professional when making necessary repairs, or for assistance related to mold-prevention changes to your home or building.

Apogee Inspections is a full-service inspection company. We have almost 30 years experience in construction and the home inspection industry. We’ve seen it all and we know what to look for. We have the technical knowledge and experience to perform a wide variety of inspection services. If you think you might have a mold problem in your home, please feel free to give is a call to discuss it. Phone consultations are free. If you want to book an inspection, click here