• I AM HOME Building Biology

Mould in Your Home: how bad is it and what you can do about it.

With all the media coverage and the national inquiry into the biotoxin illness last year, you are most likely well aware that mould inside our homes is a bit of a big thing at the moment. Every second home I inspect has some sort of water/moisture damage and mould as a result. Mould is a type of fungi (like mushrooms) and they are everywhere. They are the nature’s greatest decomposers and, honestly, we need them to survive. But we do not need them in our homes, or at east in the high concentration levels and types that can be harmful to our health.

Some Facts About Moulds

Moulds feed on dead organic matter because they cannot make their own food. They grow on biodegradable building materials like timber, paper products like cardboard, books, plasterboard, clothes, furnishings, insulation, wallpaper, glues and dust. They do not grow on inorganic materials like masonry, concrete, rocks, stone, glass, plastic or ceramic tiles EXCEPT when and where there is sufficient dust, dirt, grease or oil present on the surface. In addition, concrete and masonry usually act as reservoirs of excess moisture. So, if there is dust on the surface of the concrete, you might get mould as it will feed off the dust (which has all of the organic matter in it like human skin cells, insect parts, animal dander etc).

You don’t have to see it or smell it for it to be an issue, however, if there is a damp/musty odour inside the home, it is an indication that mould, bacteria and other microbes are actively growing and need to be addressed (US EPA 2001).

Only 25% of mould spores are viable (live and able to germinate), the other 75% are dead but can still pose a health risk (US EPA 2001). That is why killing mould is futile or irrelevant because 3/4 of it is already dead.

As most conventional building materials and furnishings are the ideal ‘fast food’ for fungi, the key to addressing mould is to find and eliminate the source of moisture. Within 48 hours of moisture being present, the spores, which are already sitting on surfaces, will begin to grow, break of hyphae and produce mycotoxins. An it's not just mould, mould spores, hyphal fragments and mycotoxins, but also the bacteria and bacterial endotoxins and other cell wall components, protozoa, increase presence of rodents, insects and dust mites, and increased deterioration of building materials with consequent offgassing of toxic fumes such as formaldehyde (WHO 2009; IOM 2004). All of these can produce toxins and other chemicals which become a 'microbial stew' that you breathe in and which can lead to adverse health effects.

Mould and Health Effects

Illness resulting from exposure to water-damaged building can be caused by infection, toxicity, allergy, and inflammatory responses triggered by exposure to one or more of the agents present in water-damaged buildings and are often mediated by oxidative stress. Types of disorders that can be seen resulting from water-damaged environments, mold, mycotoxins and bacteria include infections and mycoses, chronic and fungal rhinosinusitis, IgE-mediated sensitivity and asthma, other hypersensitivity reactions, pulmonary inflammatory disease, immune suppression and modulation, autoimmune disorders, mitochondrial toxicity, carcinogenicity, renal toxicity, neurotoxicity, and even DNA mutations (Thrasher, Kilburn & Immers 2006). Exposure to the 'microbial stew' in a water-damaged building can lead to chronic inflammation in the body, especially if you fall into the 24% of population with a variation of the Human leukocyte antigen (HLA) gene that cannot mount an effective immune response (detoxify) to biotoxins in their systems.

Most commonly, however, many mechanisms are interacting in an individual at any given time, making it imperative to address the illness with a comprehensive, multifaceted approach. Although respiratory symptoms are common from exposure to water-damaged indoor environments, it is important to note that a person can have multiple symptoms which are often debilitating, including fatigue, neurocognitive symptoms, myalgia, arthralgia, headache, insomnia, dizziness, anxiety, depression, irritability, gastrointestinal problems, tremors, balance disturbance, palpitations, vasculitis, angioedema, and autonomic nervous system dysfunction (Curtis & Lieberman 2004; Rea et al. 2004). The development of chemical sensitivity is also commonly seen after exposure and can have a severe impact on a person’s life (Rea et al. 2004).

Some of the most distressing symptoms encountered by people following exposure to water-damaged indoor environments and toxigenic molds include neurocognitive disturbances. A disturbing study, conducted in Poland, measured IQ scores in children exposed to indoor mould for greater than two years, showed statistically significant IQ deficits in children exposed to indoor mould (Jedrychowski, Maugeri, Perera et al. 2011).

You can read more about adverse health effects of mould in this article.

Why is mould such a big problem now?

In new homes, it is most often the build up of water vapour due to inadequate ventilation and inability of water vapour to move through the building envelope because many of them are built with impermeable vapour wraps, no vapour cavities inadequate roof space and/ or subfloor ventilation. On top of that, the building code does not require the steam from the home to be exhausted directly to the outside, and the bathroom can have either a window or an exhaust fan vented to the roof cavity, which usually is not strong enough anyway. Built-in laundries, poor workmanship and inadequate waterproofing in wet areas as well as transition form sheet based to liquid waterproof membranes in the 80s have all contributed their fair share of moisture and mould problems in our homes. On top of that, we use cheap ‘was wood' products and glues in our homes, which are ideal food for fungi. Moulds cannot digest cellulose, so these pre-digested MDF and plywood products are so easy for them to chew on. In contrast, hard timbers, which are rarely used in construction nowadays, contain resins that are naturally resistant to mould growth.

In older homes, most of the time it is lack of maintenance, inadequate subfloor ventilation and new additions with concrete slab and flat rooves that frequently become an issue.

What are the different causes of mould in a building?

MOULD problem in a building is always a MOISTURE problem.

You always have to look for moisture inside the home. And it can be liquid moisture (water pooling or flowing) and/or moisture in the building materials and/or moisture in the air (high relative and specific humidity).

Moisture can be present in liquid form like from overflowing gutters, drainage related issues, a flood, heavy rain, burst pipe under the kitchen sink.

Moisture in your home can also be in building materials resulting from one flood or from a long-term drip of a broken pipe under the house, leaky air conditioning, rising damp, and so on.

Moisture can also be in the air - high humidity, which can result from a combination of factors including inadequate ventilation resulting from not opening windows; not using exhaust fans vented to the outdoors when cooking, bathing or drying clothes; operating unflued gas heaters, indoor pools, spas, drying clothes indoors or in a conventional clothes dryer. If not vented adequately outdoors (mechanically and by opening windows), this moisture in the air sustained over a period of time can be absorbed by porous and some semi-porous materials and will condense on the cold surfaces or even inside the walls and create perfect conditions for mould growth.

Porous materials, like particle board, soft leather and sometimes carpet that have not been dried out within 48 hours of the water damage event, will be contaminated with mould spores and will need to be discarded (US EPA 2001).

What else increases the risk of mould?

Dust, clutter, carpet, poor housekeeping, building orientation (south facing rooms that lack sunlight, cheap building materials, energy efficient buildings, poor building design, relative humidity.

What to do if you have mould in your home?

Can you clean it up yourself? Sometimes, yes. It depends on how severe the water damage and contamination is, how long it has been left unaddressed and how sensitive you are to mould.

If a professional has already found and stopped a moisture problem or any ongoing water intrusion issues, removed water-damaged porous building materials and you only have to do the cleaning of a small amount (less than 1 square meter) of surface mould, then you can probably do it yourself by following the steps outlined in the infographic below.

It is always advisable to consult a mould inspector and/or mould remediator to help determine whether something can be a DIY remediation or needs to be handled by a professional.

Wearing personal protective equipment (gloves, full, face mask and a Tyvek suit) is vital during the mould cleaning because mould spores and fragments will be dispersed in the air and might produce toxic compounds which can be inhaled or absorbed through the skin and can be enough to trigger some of the adverse health symptoms described above.

Also, if you are sensitive, immuno-compromised or are one of the 24% of population that fall into the group which cannot effectively detox biotoxins from their bodies, then it goes without saying that you cannot do the cleaning yourself under any circumstances.

What can be cleaned and how?

Possessions can be broadly categorised into one of three types: non-porous, semi-porous and porous. Water-damaged contents and building materials can be categorised by the Condition (1,2 or 3) as per "Standard and Reference Guide for Professional Remediation ANSI/IICRC R520 - 2015".

The following table provides a general guide on what to do with a variety of water-damaged contents depending on their porosity and condition. For a more detailed description, refer to the IICRC R520 guide or a professional remediator that holds IICRC certification.

What can you do to prevent mould in your home?

1. Let the sun inside your home.

Open shutters, blinds and curtains every day. Take your doonas, pillows, rugs and soft furnishings outside and beat the dust (and mould spores) out of them regularly.

2. Improve ventilation and airflow.

Open windows on warm, dry days and turn your ceiling or stand alone fans on. Open doors between rooms and wardrobes to circulate air inside enclosed spaces.

3. Check and fix leaks immediately.

Remember, you have 48 hours to dry your porous and semi-porous materials. Regularly check gutters and downpipes, the condition of your roof, window seals, shower and bathroom seals, braided water hoses that connect appliances, and make sure nothing is blocking those subfloor vents and that water is not pooling next to the building foundations!

4. Keep humidity levels between 45% and 55% in your home. This can be achieved by ensuring that the exhaust fans in the kitchen, bathroom and laundry are ducted to the outside and using them (leave them on for at least 15 minutes after you have finished showering, bathing, cooking); opening windows; hanging wet towels and bath mats outside to enable them to dry after use; ensuring the exhaust air from the clothes dryer is vented to the outside and by using a dehumidifier. For more tips and the dehumidifier brand I recommend, read the Moisture in your home and what you can do to prevent mould growth blog.

5. Reduce clutter and dust load. The best way to reduce dust in a home is to stop wearing shoes indoors, avoid carpets and drapes as well as unflued gas heaters, minimise clutter and clean with damp microfibre cloths and a HEPA vacuum.

Use damp microfibre cloth followed by a dry, clean tea towel and an allergy friendly vacuum cleaner fitted with a HEPA filter. Without a quality HEPA filter, up to 80% of contaminants will recirculate back into the indoor air. Here you will find a list of of vacuum cleaners recommended by building biologists. 
If you’ve got a budget, go for one of Miele C3 models with an Active HEPA filter. If you have an unlimited budget, go for the Sauber Intelligence or Excellence Models.


If you think you need a moisture and mould assessment, don't hesitate to contact me. You can find more information on my Moisture and Mould Assessment page.

Turn your house into a healthy home!


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