Building Biology | Mould
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You can’t always see or even smell it, however it affects almost 1 in 3 Australian homes and can have devastating consequences on the lives of those who can’t make antibodies against it. I’m talking about MOULD which many are referring to as the next asbestos. So given that fungi are nature’s greatest decomposers and have been around well before us, why is mould such a problem now? Energy efficient homes are like plastic bags (air and water tight) with compromised passive ventilation. Consequently there has been a considerable increase in the number of complaints to the Building Commission about condensation issues. In addition we have gone from using natural building materials like hard wood timbers that naturally contain resins that are resistent to fungal attack to predigested particle board that has become the perfect fast food for mould. The two factors come together to create a toxic time bomb. Read Body+Soul article ‘Mould – is it making you sick?’  Download PDF

The cause of mould is moisture

Micro-organisms require food and moisture to thrive. As they are everywhere on this planet from the Arctic to the Antartica, and most building materials and furnishings in our homes are the perfect fast food for mould, the key to addressing mould problems is to identify the source of the moisture. Once moisture sits on a surface for more than 48 hours, the microbes on the surface will attempt to take over the space by producing endotoxins, mycotoxins and microbial volatile organic compounds which can dramatically impact the indoor air quality and affect the health of the occupants.

  • condensation issues: will be seen as water droplets on a surface. This can arise from the use of humidifiers, drying wet clothes inside a room with poor passive ventilation, unflued gas appliances, steam created from kitchen (cooking), laundry (washing, dryer) or bathroom activities (showering, bathing), too many occupants in a bedroom (we exhale water vapour), lack of insulation in the house and single paned windows (creates condensation on the walls and/or windows)
  • plumbing, gutter or roof issues allowing moisture to penetrate inside the building
  • building on a flood plain or aquifer
  • insufficient drainage around the home
  • building into a hill, on or at the bottom of a hill
  • garden beds butting up against the house;
  • sprinklers spraying on the home
  • living in humid areas (consistently above 70% relative humidity)
  • absent or insufficient water proof barriers in the wet areas of the home
  • insufficient subfloor ventilation
  • damage to the damp proof course
  • metal framed homes creates thermal bridges (condensation occurs)
  • concrete slab has not yet cured and is consequently releasing tonnes of moisture into the indoor air mass
  • water damaged timber was used to build a home (or was left out in the rain during construction)
  • building materials and furnishings in the home such as vinyl, metals, ceramics or sealed timbers/concrete have poor hygroscopicity (ie do not breathe). This creates a greater difference in surface temperatures

24% of the population cannot create antibodies to mould; so every time these people are in a water-damaged building, they feel unwell

Health effects

Black Mould or rather a single species of fungi is unlikely to be responsible for the vast array of health effects seen in a water damaged building. It is now thought that it is the chemical stew of microbes (bacteria and fungi) as well as their by-products (fragments, spores, endotoxins, mycotoxins…) that is likely to be responsible for the health effects. Around a quarter of the population have a genotype (haplotype) that does not enable them to produce antibodies to fungi; so everytime they walk into a mouldy building, it sets up an inflammatory response in their body that doesn’t switch off. In contrast the rest of the population produce antibodies to these microbes which enables them to recognise and clear them from the body. This inflammation affects key neuropeptides in the brain – vasoactive intestinal polypeptide, melanocyte stimulating hormone and in some cases antidiuretic hormone which can cause much of the symptoms associated with Chronic Fatigue Syndrome (see below). This is why some people in a water damaged home can get very sick, whilst their partners can be completely well. For a detailed discussion on the adverse health effects arising from exposure to mould, refer to

  • Fatigue that is not alleviated by sleep which completely affects their circadian rhythm (microsleeps during the day, unable to sleep at night…)
  • Lung problems such as recurrent colds and flu that are difficult to get rid of, cough, sinusitus, hayfever, pneumonia.
  • Chronic fatigue syndrome: headache, sleep disturbances, brain fog (loss of words, poor short term memory, forgetful), fibromyalgia (unusual body aches and pains) and inability to thermoregulate (hot and cold)
  • About 30% of  patients will experience excessive urination and thirst (not related to diabetes) and easy to get shocked when touching appliances. This is due to changes in osmolality due to issues with Antidiuretic hormone.
  • Many patients go on to develop chemical sensitivity and electromagnetic hypersensitivity which are almost identical in their presentation
  • Symptoms improve when they are away from the water damaged (mouldy) area

Treating mould illness

There are very few health practitioners who have a good understanding of the devastating effects of mould illness especially in those people who are often misdiagnosed with Chronic Fatigue Syndrome. I have a list of health practitioners who specialise in environmental illnesses here.

It’s All In The Eyes!

Visual contrast sensitivity (VCS) testing measures your ability to distinguish between finer and finer increments of light versus dark lines (contrast) which differs to the visual acuity testing conducted in a routine eye exam. Night driving is an example of an activity that requires good contrast sensitivity. VCS testing has been used extensively by the military for aviators as it appears to be a better indicator of visual performance under day and night conditions than visual acuity. Loss of contrast sensitivity may indicate eye disease (glaucoma, cataracts, diabetic retinopathy and macular degeneration) or neurodegenerative and inflammatory diseases affecting the optic nerve such as multiple sclerosis, Alzheimers disease and biotoxin (mould) illness. Consequently VCS testing has been used by the US EPA, NIOSH and the Centre for Disease Control. What I find so useful about this test is its accuracy in identifying mould illnesses (in conjunction with other inflammatory biomarkers) and its ability to monitor the progress of the mould affected patient. I routinely request all of my clients to do the test, pre and post remediation. Of course, whilst a diagnosis for mould illness cannot be established from this test alone, it is a simple tool that can easily be implemented to gauge changes in the client’s health. The VCS test takes about 10 minutes and is free though they ask for a donation.

Testing the home for mould

In some of the worst homes affected by mould, I could not see any visible mould or smell dampness. Mould testing is a complicated procedure that involves moisture mapping to determine the extent of the water-damaged materials, air, dust and/or surface sampling (which are then sent to the lab to be cultured and analysed), use of borescopes and thermal imaging cameras to identify hidden mould and temperature differences, a good understanding of psychrometrics and the hygroscopicity of building materials and so forth. If the area of visible mould exceeds one square metre, or if you are experiencing the above symptoms and your health practitioner is unable to identify the cause of your complaint, consider hiring a building biologist or accredited mould remediator to investigate.

Certificate in Mould Testing

The Australian College of Environmental Studies provides a Certificate in Mould Testing. which includes nationally accredited units from the Advanced Diploma of Building Biology (10194NAT).

Cleaning mould

Reference: Nicole Bijlsma’s book Healthy Home Healthy Family. (3rd edition)

There is a lot of hype on social media about how to kill mould that is completely unfounded, so I want to set the record straight in relation to the use of bleach, ozone and essential oils and their impact on mould. Bleach is ineffective in killing fungi (however, it is effective against bacteria), because it is highly alkaline and may provide the microbes in a water-damaged building with a food source. Furthermore, it only ‘bleaches’ the mould until such time that the melanin compounds in the hyphae (the branching filamentous cells of the fungus) recover and, voila, within weeks the mould becomes visible again. Similarly, ozone should NEVER be used in a water-damaged building because it is an eye, nose and lung irritant; it is ineffective at killing mould spores; it reacts with numerous volatile organic compounds in a water-damaged building to create more toxic chemicals; it may degrade the colours of surfaces such as paintings; and lastly, it is very reactive with synthetic materials such as plastics, nylon and the rubber backing on carpets and curtains. For these reasons, the US Environmental Protection Agency has issued warnings against using ozone inside a building. Whilst several studies have confirmed that tea tree and clove essential oils are remarkably effective antifungal agents, they should be used sparingly (or not at all) in mould remediation jobs because the amount required can be toxic to children and to chemically sensitive individuals. Furthermore, killing mould is irrelevant when most spores are already ‘dead’ (can’t germinate) but may still cause harm when they are inhaled.

The best way to deal with mould is to physically remove it. This can be achieved by conducting a HEPA sandwich which involves vacuuming the affected non-porous surface using a vacuum cleaner fitted with a HEPA filter, then wiping with a damp microfibre cloth, and vacuuming again. The microfibre cloth should be soaked in ½ litre of water to which a generous squirt of dishwashing liquid has been added. This procedure will remove the biofilm that microbes in a water-damaged building feed on. The cloths should then be rinsed thoroughly before reusing. At the end of the job, the cloths should be discarded along with the HEPA filter and disposable vacuum cleaner bag.

  • For non-porous surfaces such as plastic, metal, concrete, hard timbers, sealed timbers, laminate, glass, ceramic and porcelain, and semi-porous items made from plywood, masonry, unsealed timber, oriented strandboard and brick, a HEPA sandwich is recommended. If mould has infiltrated and stained the material, bleach or hydrogen peroxide (less toxic option) may need to be used to ‘bleach’ the stains once the microbes have been removed. If the stains are extensive (e.g. on timber joists, bearers or floors), a mould remediator can use abrasive methods such as wire brushing, sanding or media blasting.
  • Porous and semi-porous materials such as soft furnishings, wicker furniture, unsealed timber, paintings, rugs, tapestries, mattresses, leather and paper (books) should be discarded if they do not dry out within 48 hours or assessed by a mould remediator to determine if they are salvageable. For porous surfaces like plasterboard, ceiling tiles, insulation, soft timbers, particle board and medium density fibreboard, an alcoholic solution (70% alcohol to 30% water) is effective providing they were not wet for more than 48 hours. Semi-porous items such as upholstery and carpeting may need to be cleaned using hot water extraction (steam cleaning), however much of the heat is dissipated on contact, and considerable temperature and pressure is required to enable the steam to penetrate multilayered items which may damage the item. If the mould remediator insists on using ozone for porous items like furnishings, this should always be conducted off site by a specialist laundering company.