Mould and Mildew: the facts

It may come as a surprise, but with
the steamy summer upon us, it’s important to keep mould and mildew
considerations in mind when it comes to your home.

David Ewerse, maintenance and
janitorial coordinator for Roper’s Enterprises Ltd, is a mould expert who’s
seen it all. From homes that were uninhabited for years, to apartments with the
air conditioning accidentally left off for a mere few weeks, there’s always a
chance mould and mildew may strike, given the right opportunity.

“Mould and mildew have similar
characteristics, but they are different types of fungi which are found
everywhere inside and outside,” says Ewerse.

“Mould & mildew can grow on
almost any substance when moisture and the required warm temperature are
present. Mould is often black, green, red, or blue in colour, while mildew is
usually gray or white.”

When mould and mildew reproduce,
they make spores that can be carried by air currents. When these spores land on
a moist surface that is suitable for surviving, they begin to grow. It’s
startling to learn that mold and mildew are normally found indoors at levels
that do not affect most healthy individuals.

The right conditions

“Mould and mildew growth in an
indoor environment is typically related to water or moisture,” says Ewerse.

“For significant mold and mildew
growth which is not being shown on my assessment of the apartment, there must
be a source of water, which can be invisible humidity.”

Invisible humidity, he explains,
can be caused from hot air build-up, especially when the air-conditioning unit
is not frequently used or outdoor natural cool air is not flowing inside.

“Both our indoor and outdoor
environment has mould and mildew spores present. There is no such thing as a
mould- and mildew-free environment in the earth’s biosphere,” he says.

“Moisture will always be the
decaying process caused by the mould and mildew. Mould and mildew growth begins
between 24 hours and 10 days from the provision of the growing conditions, but
cannot be measured to know the age of the mould.”

Pierre Beaudet of Cayman Climate
controls says that changes in local construction methods impact mould and

“The main dehumidifier in your home
is your AC unit,” he says.

“For it to work, it has to run for
a long period of time. In the past, in Cayman most houses were built from
concrete and not well insulated, meaning the AC systems would run and run.”

However, because of the high levels
of insulation people are putting in their homes these days in an effort to be
more energy efficient, homes stay cooler longer.

That means that the AC units are
not running for very long periods of time any more.

Despite this, Beaduet says some
homebuilders in Cayman are still using the same size air conditioning units
they were using in the past, which is a mistake.

“You need to reduce the capacity of
the AC unit so it runs longer. That will allow it to remove humidity as well as
cool your house.”

A smaller, modern AC unit, running
longer, shouldn’t use any more electricity than a larger counterpart only
running sporadically throughout the day.

It’s all about the moisture

The ability of air to hold moisture
directly relates to its temperature. The warmer air is, the more moisture it is
capable of holding When enough latent heat is removed from water vapour, it
condenses into water.

Beaudet notes that humans, as well
as houses, are more comfortable in dryer conditions. In addition, when the air
is dryer, it doesn’t feel as hot.

In some cases, well insulated homes
may well be more humid than the air outside.

“The most expensive aspect of
running the AC is changing water vapour to water,” says Beaudet.

“You need to calibrate the AC
system to turn the vapour into water so it can be collected and drained more
efficiently,” he adds.

“In some places, a perfect setting
is 45 to 55 per cent humidity, and you will see system running 2 hours and
stopping one hour.”

He notes that some simple
decisions, like making sure that ventilation ducts have smooth surfaces so they
are less likely to collect moisture, and installing the correct type of air
conditioning system upfront instead of having to resort to costly auxiliary
dehumidification systems to combat mould and mildew, can make a huge difference.


Move air by using the air
conditioning will prevent mould and mildew from growing, since it has the same
effect as lowering the humidity inside the apartment.

Keep the indoor temperature at
approximately 74 degrees Fahrenheit (23.3 Celsius) or basically lower than the
outside temperature, as mould and mildew need a higher temperature to grow and
do not like cool conditions.

If not using the air-conditioning
unit on a cool night, allow the cool air from outside to flow into the apartment
by opening windows.

Do not use the air-conditioning
unit with windows open, as this will over- work your AC, and allow hot air to
enter, and not allow the thermostat to cut out the AC unit.

Do not allow any build up of dust,
as this is a food source for mould and mildew if present, so prevent this by
having a proper cleaning schedule.

Keep the AC on auto, set the temp
to 74 degrees and the AC will always come on if the humidity and temperature
inside gets warmer than 74 degrees.

During the cooler months, the AC
unit, when set in auto and at the correct temperature, will most times not come
on and increase your electricity consumption. When the warmer months are here,
the AC unit will obviously come on more frequently and your electricity consumption
will increase.

Every location in
Grand Cayman may vary with natural air flow, so residents must make choices
about using AC if there is no cool air from outside to reduce the humidity and
prevent mould and mildew.