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MOULD GROWTH WITHIN BUILDINGS

Not all indoor moulds present a risk to human health, but a large concentration of any mould or fungi is likely to be accompanied by others, including toxic ones.

The majority of buildings contain mould spores, but some buildings are mouldier than others. Indoor moulds can be remarkably tolerant of dry conditions but none can live without some minimal moisture source for a prolonged period of time. Excessively mouldy buildings generally have a source of moisture leading to unusually excessive mould growth. The source of the moisture may be a moist sub-floor environment, a dripping pipe, a leaking roof or some other fairly obvious cause. In many cases the mould can be readily seen growing on walls or other materials in contact with the moisture source. Sometimes the moisture can occur inside walls and not be visually apparent. A common but not so obvious cause of moisture in colder winter months is condensation inside south facing walls. Severely mouldy buildings may have a musty smell, but this is not necessarily always obvious. Sometimes the only sign of a problem is persistent ill health of the buildings occupants, such as headaches, nausea, respiratory symptoms, etc. It is now common knowledge that mouldy buildings can present a serious health risk to occupants. In fact, some infant deaths have been convincingly linked to indoor moulds and Stephen Koelewyn's own research, carried out since 1993 while inspecting buildings links mould and other non wood decay fungi growth to Asthma and other respiratory problems in buildings occupants were certain species of mould are present.. Any building with an apparent mould problem should be thoroughly investigated by and expert who has a particular interest in the health of buildings.

In recent years, through my use of thermal imaging on a daily basis whist carrying out inspections, I have gained a better understanding of condensation within buildings, humidity accumulation and vapour transfers, condensation is easier to detect than vapours and areas of high pressure zones and low pressure zones within the micro environment of a buildings interior, these factors combined have a significant influence on potential mould growth and the material deterioration of some building components.

Certain materials have more favourable growth conditions for various species of mould and/or fungi than others, materials high in cellulose will promote certain species while materials that originate from animals will readily promote the growth of other species, leather shoes and the woollen jumper are often the first fabrics to show signs of mould growth.

Mould spores are forever present in the the air and on surfaces around the human habitat, however these spores need favourable conditions to germinate and reproduce successfully, it is minimising these favourable conditions that we as experts hope to teach property owners and property occupants. By doing so we can help in improving the living conditions of others.

Humans commonly live in a moist environment, our bodies make up is primarily fluids, the food we eat and what we drink commonly has a moisture content, we shower daily and we wash our hands regularly. We wash our clothes and wash the floors, we boil our water and cook our meals.

To understand the accumulated moisture around the common home we first need to understand the basics of humidity. Warm air expands and therefore can absorb a large quantity of moisture while cold air condenses and therefore extracts the moisture that has been absorbed when the air was warm - this phenomena is known as condensation, it is the basis of this theory that we have a condenser unit in our fridge and in our air conditioning unit.

As humans we generally like to be warm in winter and cool off in summer, we like our habitat to be a mild, comfortable temperature and hence we warm the building interior in winter and we cool during summer. When we warm our habitat in winter we are effectively creating a warm box with cold surrounds, the interior is warmer than the exterior and it is these thermal differentials that cause condensation which effectively is moisture contained in warm air is squeezed out of the air rapidly while the air cools.

So what does this all mean and what does it have to do with mould growth, in particular during the colder months we tend to close the windows and doors of our dwelling to achieve minimal draft and maximum heating effectiveness from our heating appliances.

An adult human will normally loose 2.5 litres of fluid a day and will consume 2.5 litres of fluid a day. Losses are generally, Faeces 6% - Water Vapour (lungs) 13% - Diffusions & Sweat 19% - Urine 62%.  So 32% of 2.5 litres of fluid are extracted per human into the atmosphere in a day, for this example we will say we have 1 litre of fluid per human per 24 hour period, should this human exert additional energy through sexual activity then the fluid extracted to the atmosphere is said to increase by half a litre per human.

So we have established that each human contributes say 1 litre of moisture to the interior of the warm dwelling, this litre is readily absorbed by the warm air, curtains, mattress, carpet, towels clothing etc'. In addition to this moisture we have a hot shower, the steam from the shower contributes another few litres per human occupant, we have a morning coffee, the kettle steam adds another 100ml, we cook an egg, wash the dishes with warm water and then we use the biggest offender of all - the clothes drier - a clothes drier can contribute some 3 litres of moisture into the air and surrounding linings on a single cycle. Once we multiply all this moisture from all the various contributors and multiply it by say four for a nucleus family - we might reach 10 litres of moisture daily - hard to believe - let me pour a ten litre bucket of water over your suitcase and see how you feel. This incredible amount of moisture that is absorbed into all surfaces and substances around the home is the initial source for condensation on those cold winter nights, it is this moisture that provides growing conditions for mould spores. What I have not highlighted here is that if the dwelling is left sealed without adequate ventilation day after day then these moisture levels multiply dramatically. I have lifted carpet in a house that is saturated with moisture simply due to moisture from occupant activity.

In addition to human related moisture we have poor sub-floor conditions, leaking window sills, leaking pipes etc' - just to make things worse.

So what can we do - we do not wish to stop breathing just yet that will happen in due course. We need to adapt our living habits to accommodate these natural phenomena.

Most people awake on a cold winters morning, dash in to have a hot shower, put the kettle on for some coffee, make some hot breakfast and get ready for work. The last thing you want to do on a winters morning is to open the external doors and windows - you need the cupboard open to choose your clothing for the day, you put a wet towel on the rack have breakfast close the door behind you and race off to work, all that moisture is waiting where you left it for when you come home - providing ideal conditions for mould growth.

You need to leave windows open, in particular during the winter months, to allow for adequate cross flow ventilation, in addition you need to leave cupboards open while ventilating the interior of the dwelling, the clothes drier needs to be ducted to the exterior and extraction fans in bathrooms need to be used at all times and left to run for at least ten minutes after completing the shower. A rangehood that is ducted to the exterior should be used when cooking. The air conditioning unit can be activated periodically for cooling during winter months simply as a dehumidifier. Where possible vents should be fitted to ceilings as moist humid air naturally rises and will leave the room naturally where these types of vents are located. Rotary extraction fans fitted to the roof line increase ventilation significantly and improvements to sub-floor environment may also provide significant improvements in habitat moisture content.

When mould growth becomes apparent on surfaces the surfaces should be cleaned with either superheated steam or bleach, the majority of mould preventative products are basically bleach with deodorisers or colouring to disguise the odour of bleach but it is the cheap bottle of bleach from the bottom supermarket shelf that will be most effective in killing off mould. Bleach will only kill the living mould organisms (hyphae) that come in contact with the bleach, the mould spores (seeds) are generally not effected so it takes multiple treatments to eventually reduce the mould growth significantly.

A dry well ventilated house will not have noticeable mould or fungi growth, even if it is facing south and has no sunlight. This I can confirm from my personal experience of inspected buildings since 1992 and building since 1977.

Ground floor units are more frequently found to have more severe mould growth than upper level units due to security issues.

Bedrooms of young couples often have a large mouldy ceiling with growth concentrated above the double bed and to walls around the mattress.

Large families living in small units or houses will always have a mould problem due to numbers of humans - rarely can a building with so many humans living in close proximity to each other be properly ventilated and often a dehumidifier needs to be used.

In addition to all our moisture problems we have an additional critical influence on mould growth that should not be disregarded. The naked flame of wood or bare flame gas heaters and gas stoves burns off Nitrogen Dioxide, Nitric Oxide and Carbon Monoxide. The Nitrogen Dioxide from the naked flame of gas appliances is an ideal fertiliser for mould and where a gas stove and/or heater is used without being properly flued then the mould growth will be significant and mould will spread rapidly - even by using bleach weekly it would be difficult to minimise the mould growth significantly.

I have provided this web page as a manner to share some of my knowledge and hopefully help some people, unfortunately this page prompts people to call me for further free information , many people are demanding when seeking further free information and have little regard for the fact that I may be carrying out other work when they call & are reluctant to understand that I do not always have the opportunity to talk for extended periods on the phone. Secondly I do not have the privilege to travel around Sydney assessing the condition of properties and providing appropriate advice free of charge.


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Last modified: 1 January, 2017

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