Insect droppings full of partially digested mold spores

Insect droppings full of partially digested mold spores (Photo by Mold Manager)

Efflorescence, commonly mistaken for mold

Efflorescence, commonly mistaken for mold (Photo by Mold Manager)

Ice build up in poorly vented attic

Ice build up in poorly vented attic (Photo by Mold Manager)

Water leak in wall cavity behind insulation

Water leak in wall cavity behind insulation (Photo by Mold Manager)

Rusted tack strip, an indicator of moisture and mold

Rusted tack strip, an indicator of moisture and mold (Photo by Mold Manager)

What is Mold and Mildew?

Mould and mildew (or mold and mildew) are general terms that are commonly applied to a group of micro-organisms that belong to the kingdom of fungi. These are tiny decay organisms that will exist wherever liquid moisture and nutrition combine in a 4-30°C. temperature range. Although individual spores are usually too small to be seen by the unaided eye, they become visible when colonies produce large numbers of spores. Their main growth structures are miniature pipe lines called hyphae or mycelium. Moulds are fungi that produce and disperse vast numbers of spores directly from the hyphae so that they can find other suitable locations for growth by random distribution. Inhalation or contact with these spores or the volatile products produced by actively growing fungi can trigger symptoms in sensitive individuals. Mould colonies often support mite populations which are also highly allergenic.

Where is Mold Likely to be Found Indoors
Common Canadian Indoor Mold Sources

Mold in Basements - The vast majority of mold issues tend to be found in below grade  in occupied spaces. This is particularly true of basement offices or apartments, classrooms in schools and basements in houses. Some unhealthy conditions like floods are obvious but the majority of sub-grade space is prone to subtle condensation. The majority of individuals seriously affected by mold have tended to occupy basement offices or bedrooms or been heavily exposed to air borne influences from such spaces.

Basements tend to be at risk to mold growth for two primary reasons. Water runs down hill and eventually collects in the basement either from inside where leaks can occur or outside where foundation deficiencies and sump failures or plumbing ruptures translate into basement flooding.

However, the major concern in Canadian basements is mold growth from condensation. Often with limited air movement and ventilation, surface temperatures of the floor and walls can drop below dew point particularly in humid summer weather. Temperatures as low as 5°C are common in corners where stored items often protect the floor from the proper distribution of heat. Dew point temperatures can be as high as 16°C during humid summer weather making conditions perfect for condensation and mold growth. Basements also tend to be cleaned less frequently than other areas in a house. Any problems which exist are thus compounded rather than reduced. Often the floor around a sump pit has very high levels of mold growth simply because the humidity and condensation tend to be higher in that region. Many homeowners choose to reduce energy consumption in the summer and turn off their furnace fans and air exchangers. These measures are often counter-productive and foster copious mold growth in tightly sealed homes. Sometimes mold growth is visible on cardboard boxes, leather coats or even the surface of furniture but more often it is not “visible”. Air sampling and cultured tests are needed to adequately reveal this type of contamination. In severe cases, the baseboards and walls develop visible  mold growth and support vibrant mite populations which are highly allergenic. In a round about way, spiders are often an indicator of mold since they need humid conditions and feed on the insects that are supported by mold. As a general rule, the more spiders = more mold.

Finished basements with sub-floors can hide water infiltration. mold Manager (RIFDS Inc.) has found a number of basement apartments with significant water issues under the subfloor and severe health reactions in the occupants. In most cases, these issues were not apparent to the occupant. mold Manager (RIFDS Inc.) does not recommend that basements below grade be used as living space unless they are checked frequently for moisture issues, unless there are no musty odours, unless the humidity and temperatures are monitored, and controlled to avoid reaching dew point and unless they are regularly cleaned. Even then no guarantees can be offered that this type of space will be suitable.

Moist dirt floors in any building and pipe chases in commercial buildings can produce mold volatiles, mold spores and support populations of insects and mites. Ductwork can distribute musty odours from the crawl space throughout the whole house.

Mold in Bathrooms - Plumbing leaks are obvious issues in bathrooms but can go unnoticed for long periods of time. Even minor staining and leaks on any ceilings below a bathroom should be taken seriously and corrected immediately. The grout in tiled showers can leak if not sealed properly. Water behind the tiles can produce mold on any wood or regular drywall. Products like cement board lower the risks of mold growth. One piece showers or continuous walls are far superior to tile but can leak around any openings for the plumbing or experience pipe leaks or condensation on the pipes. Teenagers tend to be hard on walls and floors by having long showers and not closing the shower curtain adequately. Condensation is also an issue in poorly vented bathrooms with with visible mold developing on the ceiling and upper walls.

Mold in Attics - Roof leaks from improperly installed flashing, damaged shingles or ice dams can produce damage and rot both in the attic and along any pathway the water takes. Condensation in attics occurs when too much moisture escapes from a house and too little ventilation is available to eliminate it. Bathroom or kitchen  fans should not be ducted to the attic. Marijuana grow-ops often duct excess moisture to an attic producing condensation that runs into the wall cavities. When this this situation occurs, the best option is often to tear the house down.  Many home inspectors target even light mold growth from attic condensation as a reason not to buy a home. In reality the risks of exposure to “attic mold” inside a home tend to be lower than the risks of exposure to “outdoor mold” when a window is open and a breeze is blowing. However, perceptions often guide decisions and this can be an issue at time of sale. Light mold growth can be removed by dry ice blasting. More serious mold growth and structural rot may need a partial or complete roof replacement. Attics should be regularly checked for leaks and the development of staining on the trusses or sheathing. If you're buying a new house, always check the attic before finally signing on the proverbial dotted line.

Windows - Windows can introduce water to a home via leaks but a more commonly encountered issue is condensation. If household humidity is too high during the winter months, condensation will occur and support mold growth. Initially the growth is a cosmetic issue but if not corrected large quantities of mold can develop on the window or the run off can get behind drywall and baseboards or under carpet and hardwood flooring and do a lot of damage. Our climate changes constantly and we have to allow our indoor conditions to vary in response to what is happening outdoors if we want to control window condensation. An increase in ventilation rates, either mechanically with something like an air exchanger or manually by slightly opening a window can make a world of difference. Most mold from window condensation is unsightly and small quantities are not usually dangerous.  Prolonged conditions and prolific mold growth can be much more serious. In severe cases, mold can sometimes be seen growing across the window panes. Small children in close proximity to persistently wet windows tend to be at greatest risk.

Fan coil units and large HVAC systems - Mold growth seldom occurs in heating systems but can occur in air conditioned systems particularly those that have insulation lining the ducts or the main fan units. Mold growth is most likely to occur  during hot humid weather when moist air condenses on the cool surfaces and the unit is temporarily off for an evening or weekend. The mold can develop during humid summer weather and be released when the heating season begins. In summer, musty odours are usually the issue, but in fall and winter spore dispersal is more likely to occur.

Mold in Houses: New home issues - Surprisingly the Mold Manager visits more new homes than old homes. New homes often have issues left over from construction and builder deficiencies.  Issues in new home are often covered by warranty so are more likely to be addressed with experts by the home owner or builder.  Older homes are often not sealed well and are well ventilated and come with lower expectations with respect to mold issues. Building in winter and during wet weather can create issues that weren't as prevalent in the past as they are today. The Mold Manager is often called in to new homes to deal with builder-buyer disputes and provide assessments and advice to all parties involved.