ALL ABOUT MOULD -PART 2

                                                                   How Mould Grows

Critical Requirements: There are four critical requirements for Mould growth –Mould spores, food, proper temperatures and considerable moisture. Removal of any one of these items will prohibit Mould growth.

1.       Mould Spores.  Ranging in size from 3 to 40 microns (human hair is 100-150 microns), Mould spores are everywhere. There is no reasonable, reliable and cost-effective means of eliminating them from environments that humans inhabit. So, trying to control Mould growth through the elimination of Mould spores is not feasible.

2.       Mould Food.  Almost any substance that contains carbon atoms (organic substance) will provide sufficient nutrients to support Mould growth. Even the oil from your skin that is left when you touch an otherwise unsuitable surface, like stainless steel, or the soap residue left from a good cleaning will provide sufficient nutrients to feed some Moulds. The most common materials found in homes like wood, paper and organic fibers are among the most preferred of Mould nutrients. Thus, eliminating Mould food from the environment is a virtually impossible task.

3.       Appropriate Temperatures.  Most Moulds grow very well at the same temperatures that humans prefer 77-86° F (25-30°C). In addition, temperatures close to freezing are not cold enough to prevent Mould growth nor are desert-like temperatures. Therefore, it is not feasible to control Mould growth in our home environment through the control of temperature.

4.       Considerable Moisture.  Barring Xerophilic Moulds, most other Moulds require the presence of considerable moisture for growth. Various species of Mould have different moisture requirements. The vast majority of Mould species require water levels equivalent to moisture content corresponding to a relative humidity of at least 70 percent. In fact, the great majority of serious, large Mould outbreaks inside buildings occur where porous, cellulose-type materials have literally been kept wet by liquid water or sustained condensation.

Human beings prefer humidity below the critical relative humidity for Mould growth. Thus, of the four basic requirements for Mould growth, moisture is the only Mould growth requirement to control in environments that humans inhabit.

Common household Moulds have a characteristic "musty" or "earthy" smell, and growing colonies of Mould can also be visually observed in many cases. Most people are familiar with Mouldy bread or Mould growth on cheese or other food products that have been kept too long, so the "green fuzzy" characteristic of most Mould growth is familiar. And those who have lived in Florida have heard the expression "green shoe syndrome" which refers to the fact that Mould is particularly fond of leather products left unused for periods of time in dark humid places. In Assam, India, shoes turn green if not used once every 4-5 days!

Although most active Mould colonies appear greenish to black (typical of Mould growing on bathroom tile grout) in color, the characteristics of Mould colonies growing behind vinyl wall covering in buildings takes on   very different characteristics. These Mould outbreaks typically result in pinkish to yellowish staining of the wall covering. They are quite important because they indicate serious, detrimental moisture accumulations within the gypsum wallboard behind the wall covering that cannot be removed by your air conditioning or dehumidification systems. Where these problems appear, they usually require the assistance of a professional (ibid).

Practices That facilitate Mould Growth

The following practices aid in the growth of Moulds inside homes located in hot, humid climates, e.g., Florida. Mould growth on the outside of homes is not covered here.

Air Conditioner Operation: Setting the fan mode switch of your air conditioner thermostat in the ON position. When set to the ON position the blower fan runs continuously and the moisture which has condensed on your air conditioner's (AC) evaporator coil during cooling is re-evaporated and blown back into your home before it can drain off the coil and out of your home. This causes the relative humidity in your home to be significantly greater than if the AC thermostat fan mode switch is set to another position. Even in the "auto" position, some ACs run the blower for 1-3 minutes after the compressor shuts off.

AC Sizing: Oversizing of ACs is common. The more an AC is oversized, the poorer its humidity removal performance, especially at higher thermostat settings. This is because, during each air conditioning on cycle, the moisture removal does not reach full capacity for about the first three minutes of operation. The more the system is oversized, the shorter the on-cycle during which moisture is removed. Thus, if a home is properly sized with a 2-ton AC and a 4-ton system is installed, the 2-ton machine would do a much better job removing moisture even though the 4-ton machine had twice the nameplate humidity removal capability.

Space Pressurization: It is important that homes in hot, humid climates be pressurized slightly with respect to outdoors. The reason is simple. If homes are depressurized with respect to the outdoors, then hot, humid outdoor air will be pulled through the very small air pathways that exist in all building envelopes (walls, ceilings, floors, etc.). To get from the outside of the home to the inside, this air often follows circuitous pathways, e.g., the air may enter the wall system high on the exterior where an outdoor light fixture is mounted and exit the wall system low on the indoors where an electrical outlet is located. If the home has an AC, the gypsum wallboard will be relatively cold — often colder than the dew point temperature of the humid outdoor air that must flow along that gypsum wallboard to that indoor electrical outlet. In Florida, it is not uncommon for summertime outdoor air dew point temperatures to be greater than 80° F! When this occurs, the colder gypsum wallboard condenses the moisture out of the air that is flowing along its rear surface on its way to the electrical outlet that is serving as its pathway into the air conditioned home. As illustrated in the figure below, this can result in moisture accumulation within the wallboard, which, in turn, can result in significant Mould growth.

Shut Interior Doors: Interior doors are kept shut when the AC is on. This results in space pressurization problems in the home (ibid).

Comparison of Wall Systems Moisture Contents

                       

The diagrams in Fig. 9, based on detailed computer simulations that model the combined impacts of heat, moisture and air transport illustrate the importance of this air flow phenomena. The wall on the left bounds a space that is pressurized with respect to the outdoors and the one on the right bounds a space that is depressurized. The 2 Pa (Pascal) pressure gradient is very, very small — there are 101,325 Pa in one atmosphere. Clearly, it is the direction of the pressure gradient rather than its magnitude that is critically important here. You very much want your home slightly overpressurized in hot, humid climates so that dry, cool indoor air is pushed out of the home through the walls (figure on left) rather than have hot, humid outdoor air sucked into the home through the walls (figure on right). Fortunately, it is relatively easy to pressurize a home — all that is necessary is that slightly more air be brought into the home than is exhausted. This normally requires a positive mechanical ventilation system (ibid).

Other items that cause depressurization in homes:

·         Exhaust fans (bathroom, kitchen, attic, crawlspace, etc.)

·         Clothes dryers

·         Supply duct leaks

Sundry items that foster Mould in homes

You can't Mould-proof your home, but you can make it Mould-resistant. Look out for:

·         Leaking Pipes. The worst leaks are those that go undetected because they are hidden out of view, like inside a wall. By the time you discover them, Mould has usually started to grow already.

·         Leaks in the Roof. A roof that leaks into the attic might not be discovered until it's already led to Mould growth. Check the attic regularly for leaks.

·         Wet Clothes. Clothes left in a pile waiting to be washed for more than a day and clothes left wet for over a day after being washed may also foster Mould.

·         Drying your clothes. Drying your clothes in a dryer instead of outside on the line releases a large amount of moisture into your home if the drier is not vented outside the house. Clothes drying inside on indoor clothes lines or racks will also create a buildup of moisture inside unless the room is well ventilated.

·         Damp Basement. Basements often contain higher amounts of moisture or humidity than other rooms because they are usually not well ventilated. Basements are also often colder meaning more condensation occurs which leads to dampness and humidity. Also any water from leaks in your home will often end up running down to the basement since it is lower than all the other rooms. Not only is Mould more likely to grow in basements but because they are usually neglected Mould growth may not be discovered until it is well set in.

·         Flooding. This is a dangerous after effect of a calamity. Your house will be very wet for a long time during a flood, taking days or even weeks to dry out. Since Mould only needs a suitable surface to be wet for 24 hours before it can grow this means there is a huge risk of Mould growth.

Some dangerous toxic Moulds require more extreme conditions than common Moulds do, such as Stachybotrys Chartarum, which requires material to be very wet for several days to grow. Your home is at great risk of being infested with dangerous toxic Moulds (ibid).

·         Water at the house's foundation. Water building up in the yard and ground around the base of your house can cause frequent water problems for the foundation of your home. If the ground around your home slopes towards the house rainwater will end up building up at the foundation. If this causes constant problems you might even need to do some landscaping to modify the slope of the ground so water drains away from the house. Alternatively ditches and drains can be dug to channel water away from the home.

·         Lack of Sensors. Install a digital temperature and relative humidity (RH) sensor and observe your indoor relative humidity. During the hot summer, with the AC on, the RH should not exceed 55 percent during the day on a regular basis. If it does, you probably have problems either with leaks in your duct system or with your air conditioner unit itself – it could be too large, improperly charged or have insufficient air flow across the coil. Consult a qualified AC expert.

The highest relative humidity in your home is likely to occur during mild weather when your AC is not needed during the day. In tropical climate, the outdoor relative humidity reaches very near 100 percent on most nights, regardless of daytime temperatures. If your home is open to the outdoors during these periods, the materials in your home will adsorb moisture from this very humid air, regardless of the temperature (ibid).

If this moisture is not removed during the following day, the moisture of the materials in your home can stay at or above 75 percent for extended periods and Mould is likely to grow on these surfaces. If you have RH levels exceeding 70-75percent for extended periods, and find it difficult to control Mould growth on surfaces in your home in spring, fall and winter, you may need to invest in some type of dehumidification system. Consult a qualified mechanical system expert.

·         Whole-House Ventilation Fans — Opened Windows: Ventilation fans induct moisture when it is humid outdoors, especially if you have noticed Mould growth in your home or you are having trouble controlling the relative humidity in your home. In addition, windows open for long periods when it is humid outside (e.g., during nights and evenings) will create unnecessary bother if you are experiencing Mould growth problems in your home.

·         Vinyl Wall Covering: Impermeable interior surfaces like vinyl wall coverings can result in severe

Mould problems in hot humid climates. Moisture coming from outdoors can accumulate within

the gypsum wallboard behind the vinyl wall covering. This normally occurs as a result of house depressurization where outdoor air is being sucked into the home through the very minute air pathways that exist in all normal wall systems.

As stated, outbreaks of Mould often occur beneath the wall covering on the surface of the gypsum wallboard, normally characterized by pinkish to yellowish "splotches" on the vinyl wall covering. The moisture accumulation also can be severe enough to cause the gypsum wallboard to badly deteriorate and become "mushy." If you have noticed these symptoms, a building science professional should be called in. Positive pressurization of your home is one method of minimizing the potential occurrence of this problem.

·         Return Air Pathways: It is important that there be sufficient air flow pathways for the supply air that is delivered to each room of a home to return to the AC’s air handler unit (the box with the blower fan). Otherwise, the part of the home containing the main return to the air handler unit will be "starved" for air, resulting in depressurization of this space with respect to the outdoors. If this occurs, outdoor air will be drawn through the small pathways that exist in the exterior building envelope. In hot, humid climates, these air flows can result in the accumulation of moisture within the gypsum wallboard, especially if it has vinyl wall covering. This, in turn, can result in the rapid and abundant growth of Moulds —the cellulose (paper) on gypsum wallboard makes an excellent, preferred Mould food.

If room doors are kept open, there will be sufficient return air pathways. However, if rooms doors are closed, the rule-of-thumb is that there should be about 50 square inches of "free" air transfer area for each 100 cubic feet per minute (cfm) of supply air to the room. The term "free" means a simple, clear hole in the wall between the room and the remainder of the home. If, for appearance and privacy reasons, this hole is to be covered by grilles on each side of the wall, then the overall return air pathway area needs to be increased by about 40 percent to account for the air flow resistance of the grilles, or about 70 square inches per 100 cfm of supply air flow.

·         Bathrooms: In most bathrooms, tiles in and around showers and tubs are regularly wet. As a result, most bathrooms grow Mould and require regular cleaning. A weak solution of water and common household bleach can be used to regularly clean these areas and keep them free of Mould. Silent exhaust fans are also recommended to remove excess moisture when somebody is bathing or showering.

·         Exterior Water Management: Redirect water away from the home's exterior — redirect sprinklers so that they don't spray on the walls. Landscape with hills that direct water flow away from the home to forestall Mould.

·         Water Damage: Water damage from major water intrusion in homes should be dried within 24 hours if at all possible. For severe flooding and severe water damage for more than 48 hours, a trained restoration professional should be consulted regarding cleanup procedures.

·         Small Leaks: Even small water leaks will cause Mould problems. Rainwater leaks from improperly flashed windows, wall and roof penetrations and plumbing leaks should be promptly repaired. Periodically inspect under sinks and vanities for signs of water leakage. Use your nose and smell for "musty" or "earthy" odors – they usually indicate the presence of Mould. Fix all water leaks promptly.                                                           

·         Moisture Condensation: Single-pane, metal-frame windows generally condense water on the inside in winter. It is good practice to remove this condensation before it can run off and be absorbed by porous materials like wood casing or gypsum wallboard. Condensation can also occur on other surfaces in homes. If condensation is noticed on interior surfaces in summer, it may indicate a number of problems, including inability to control indoor humidity, AC supply registers aimed directly at interior surfaces, duct leakage problems and pressure imbalances or all of the above. Contact a professional to help diagnose the cause.

·         Closets: Fungi like the dark and closets are rarely supplied with conditioned air as a standard part of AC systems. As a result it is not all that uncommon to have Mould or mildew occur in closets, especially on leather. Leave the closet doors open to provide more conditioned air circulation inside.

·         The Kitchen. One reason why is because there's lots of moisture in the kitchen, e.g., water from running taps, steam from boiling water, fridges and dishwashers, etc. Another reason is there's always plenty of food in the kitchen for Mould to start to grow on.

·         Lack of Ventilation and Stagnant Air. Poor circulation throughout the home sustains dampness or potential moisture, especially in attics, basements, crawlspaces and laundry rooms. Overly “tight” homes designed for energy efficiency can have Mould problems due poor circulation.

Prepare for Melting Snow

Water is always eager to make its way into our living spaces. One crack is enough to cause a serious problem in any indoor environment. As temperatures increase after a snowy winter, homeowners should be aware of vulnerable areas such as rooftops, windows, and other possible ports of entry.

Basements are typically the area of a structure most at risk for water damage because they are located below grade and surrounded by soil. Soil releases water it has absorbed during rain or when snow melts, and the water can end up in the basement through leaks or cracks. Water can even migrate through solid concrete walls via capillary action, which is a phenomenon whereby liquid spontaneously rises in a narrow space, such as a thin tube, or via porous materials. Wet basements can cause problems that include peeling paint, toxic Mould contamination, building rot, foundation collapse, and termite damage. Even interior air quality can be affected if naturally occurring gasses released by the soil are being transmitted into the basement.

Potential Signs of Mould

If you have Mould growing in your house, it will be a gracious visitor and indicate its presence. Some common signs to watch out for are:

Ø  Smelling a Mould Odor

§  When you have Mould growing hidden away in your house, often a Mouldy smell might be the only clue that it's there. Don't ignore Mould odors if you can't see any Mould. You should thoroughly inspect your home before any Mould problems get worse.

Ø  Seeing Signs of Mould Growth

§  Visible Mould growth might seem like an obvious sign of Mould. However many people don't notice small amounts of Mould growth or they think it's just soot or dirt. Sometimes people simply ignore visible Mould in their house. If you can see Mould growth, even if it's only small, you should take action immediately to remove the Mould. Small Mould patches can spread and the fact that there is any Mould shows that the conditions in your home are right for Mould to grow. If you don't take care of Mould it will soon become a bigger problem. Visible Mould growth could also be a sign that there is a much larger Mould colony growing hidden away from view.

Ø  Signs of Water Problems

§  If you have had any long term moisture problems in your house it's usually inevitable they will lead to Mould beginning to grow. So if you know you've had some water problems in your home then it's a pretty good sign you could have Mould. Some signs that you have a moisture problem include water stains or discoloration on walls, floors or ceilings in your house. Seeing these could be a clue that there is Mould growing within or behind the material.

§  Another sign of a moisture problem is surface abnormalities like peeling, bubbling or cracking of the paint or wallpaper. If your walls are bowed, bulging or warped it probably means moisture has got into them. Yet another clue is the surface of walls or other materials feeling damp.

Ø  Water Leaks

§  The above signs of water problems in homes are usually created by leaks. If you already know that you have had a water leak (such as leaking pipes or a leaking ceiling) then just that knowledge by itself, even if you don't see signs of water damage, is a good sign that you might have Mould growing in your house around the area where the leak was.                                   

§  Mould growth from leaks can often be hidden. If the leak was behind a wall or other surface then any Mould will probably be hidden behind the surface too. Even if the leak was not behind a surface there could still be Mould hidden out of view behind a wall or other surface from water which seeped through.    

§  On the exterior of the house there are areas that appear to be “wet” or do not dry out for days after rainy weather. There could be some water in the walls or cavities that are holding water indicating a leak and nowhere for the water to escape.    

Ø  Past Flooding

§  If your house has been flooded in the past then it's likely that Mould would've started to grow. Any Mould would probably be growing in places where flood water remained the longest such as in the basement. Floods can often create Mould growing out of view behind walls or under floors.

Ø  Condensation

§  If you see a lot of condensation in your home then it's a sign that you have a high amount of moisture and hence a sign that you could have a Mould problem. Condensation will occur on surfaces such as glass windows or metal pipes. Mould could be growing where the condensation builds up and collects. Rusting indoor pipes are a sign that you could have a lot of condensation in your house.

§  Besides the fact that condensation creates a buildup of moisture for Mould to grow on, condensation can also be a sign that you have a humidity problem in your home. A high humidity level can feed Mould, another sign that you might have a potential Mould problem.

Ø  Paint

§  When there is a lot of moisture, paint may start to come off surfaces. Paint, or wallpaper, may be peeling, cracked, bulging or bubbling, if moisture is building up behind it.

Ø  Rust

§  Rust in the home is a sign of a moisture problem. You might see rust on nails or metal pipes, meaning you have high humidity, condensation, a water leak, or some other water problem.

Ø  Warping

§  When moisture gets into wood, drywall and other materials it can cause bowing. If you see warped walls, or other surfaces, you probably have a moisture problem.

Ø  Deterioration

§  Water problems can deteriorate materials in your home. Seeing building materials which have deteriorated from moisture can be another sign of Mould.

§  Blocked Gutters

§  When it rains, you may see water building up on the ground near your house. This is usually caused by blocked gutters, or ground sloping towards your house.

§  It can be a sign of indoor moisture problems, because the water can seep into the walls or the foundation. Blocked gutters can also cause water to run down into the roof, or down the walls.

Ø  Allergy Symptoms, Headaches or Memory Problems

§  Sneezing, runny nose, red eyes - if you just can’t seem to kick the allergy symptoms no matter what the season the problem could be inside your home not outdoors. When Mould is growing in your apartment it can cause severe allergic reactions when it’s inhaled or touched. If you’re allergic to Mould serious health concerns like asthma attacks can occur. If you’re allergy symptoms are worse at home than they are outdoors or at other locations then it’s quite possible you have a Mould problem.

§  The biggest cause for concern when it comes to Mould is mycotoxins. These are produced by toxic strains of Mould and can cause serious health problems. Symptoms include dizziness, headaches, short attention span, memory loss and trouble concentrating. This essay will look at toxins in detail later. For the moment, the pecking order is Stachybrotys, Aspergillus,

Acremonium and Alternaria.

§  Lots of House Plants - House plants require consistent watering, which increases moisture levels inside. Bonzai lovers, beware!

Some Moulds that Affect Humans

Acremonium and Alternaria: Both these species, though not considered the most dangerous types of Mould, do give off toxins that cause ill health effects or allergies in people. Acremonium is often found growing very close to the Stachybrotys Mould – the most dangerous type of Mould found so far.

Aspergillus: Studies show this specie of Mould is the second most dangerous Mould type next to Stachybotrys.

Mould spreads quickly. Do remember that Mould spreads – quickly. The best time to take care of a Mould problem is immediately after finding it. The longer remediation is put off, the more will Mould grow – as will the job of removing Mould. If you wait too long it can be impossible to remove all the Mould. Moreover, even if there is just a slight trace of one toxic Mould type, and a large amount of a not so dangerous Mould – each gives off spores and both reproduce at a fast pace. It won’t be long before the area is overrun with toxic Mould looking for a new area to permeate.

Who is Most At Risk?

Certain individuals are more at risk for developing complications when exposed to dangerous household Mould. If you fall into one of these groups you need to be aware of your risk:

Ø  People with allergies:

·         Although this seems obvious, it’s important to consider how they are exposed to Mould. People with allergies to dust will realize that Mould may trigger an attack. However, what if you aren’t allergic to dust, are you safe around Mould? Surprisingly, no. Many people are allergic to Mould that is ingested instead of inhaled. This means that for a person without a dust allergy they can have a serious reaction if they eat something containing Mould. Foods such as mushrooms, dried fruits and soy sauce can cause this reaction.

Ø  People with compromised immune systems:

·         Our immune systems work to ward off illness and allergies. If a person has been through chemotherapy, is living with HIV or has an inherited autoimmune disease, they are more likely to react to being exposed to Mould. Mould is a very strong allergen and for someone without their immune system to protect them, they can quickly develop complications.

Ø  People with lung disease:

·         Just as a person with a compromised immune system may be more prone to complications caused by Mould, the same is true of those with an underlying lung problem. Mould, when breathed in, can become lodged within the lungs. For someone with a lung condition, this can lead to a worsening of their symptoms or in some cases infection.