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Fighting Mould & Condensation In The Home


Understanding Mould

  • Mould can be harmful or helpful — depending on where it grows.
  • Mould needs moisture to grow.
  • Mould does not grow on dry materials.
  • Mould growing inside a home can affect the occupants.

Moulds are microscopic fungi, a group of organisms which also includes mushrooms and yeasts. Fungi are highly adapted to grow and reproduce rapidly, producing spores and mycelia in the process.

You encounter mould every day. Foods spoil because of mould. Leaves decay and pieces of wood lying on the ground rot due to mould. That fuzzy black growth on wet window sills is mold. Paper or fabrics stored in a damp place get a musty smell that is due to the action of molds.

Moulds can be useful to people. The drug penicillin is obtained from a specific type of mould. Some foods and beverages are made by the actions of moulds. The good kinds of moulds are selected and grown in a controlled fashion.

Moulds are undesirable when they grow where we don’t want them, such as in homes. Over 270 species of mold have been identified as living in Uk homes. Moulds that grow inside may be different from the ones found outdoors.

What makes moulds grow?

Moulds will grow if we provide them with moisture and nutrients. If we keep things dry, moulds do not grow.

High moisture levels can be the result of water coming in from the outside, through the floor, walls or roof; or from plumbing leaks; or moisture produced by the people living in the home, through daily activities like bathing, washing clothes or cooking. Water enters the building when there is a weakness or failure in the structure. Moisture accumulates within the home when there is not enough ventilation to expel that moisture.

Different kinds of moulds grow on different materials. Certain kinds of moulds like an extremely wet environment. Other kinds of moulds may be growing even if no water can be seen. Dampness inside the material can be enough to allow them to grow.

Why are moulds a concern?

Damage to materials is one concern. Materials get stained or discoloured, and over time they are ruined. Mouldy paper and cardboard disintegrate over time. Fabrics are damaged. Continued mould growth can be indicative of moisture conditions favourable for growth of fungi that cause wood rot and structural damage.

When moulds are growing inside the home, there may be health concerns. Moulds release chemicals and spores.

Health experts indicate that, depending on the type of mould present in a home, the amount and degree of exposure, and the health condition of the occupant, the health effects of mold can range from being insignificant to causing allergic reactions and illness.

Pregnant women, infants, the elderly and those with health problems, such as respiratory disease or a weakened immune system, are more at risk when exposed to mould. Consult your family Doctor if you believe there is someone who may be at risk.

Is there a mould problem?

Moulds are always found in the air outside and in all buildings. They come into the home in many ways — through open windows or doors, on clothing, pets, food or furniture. The problem starts when mould grows inside the home.

Some mould growing, for example on the window sill but not elsewhere, is not a cause of concern. You can clean the mould yourself. The presence of mould is a sign that there is too much moisture in your home — a situation which must be corrected.

Inspect the home to find the extent of the mould.


How can you tell if it is mould?


Discoloration is a sign of mold. However, all discoloration is not due to mould. Carpeting near Skirting boards, for example, can be stained by outdoor pollution entering the home. Stains or soot may also be caused by the smoke from burning candles or cigarettes.

Mould may be any colour: black, white, red, orange, yellow, blue or violet. Dab a drop of household bleach onto a suspected spot. If the stain loses its colour or disappears, it may be mould. If there is no change, it probably isn’t mold.


Sometimes moulds are hidden and cannot be seen. A musty or earthy smell often indicates the presence of moulds. But a smell may not be present for all moulds. Even when you don’t notice a smell, wet spots, dampness or evidence of a water leak are indications of moisture problems and mould may follow.

How much mould is growing?

One way to know is to estimate the area of the mould.

Mould is considered to cover a “small area” if the patch is no larger than a square meter. There should be no more than three patches, each patch smaller than a square meter. Clean up small areas yourself using a detergent solution, household rubber gloves and a dust mask for protection

Small mouldy areas in homes may become larger over time, if ignored, so it’s important to clean up and remove even small patches of mould.

The mould area is considered “moderate” if there are more than three patches, each patch smaller than a square meter, or there is one or more isolated patches larger than a square meter but smaller than 3 square metres (size of a 4 x 8 foot sheet of plywood). Assessment by a professional is recommended. You can clean up moderate amounts of mold but you must follow the proper procedures and use the proper protective equipment.

A mould area is considered “extensive” if a single patch of mould is larger in area than a sheet of plywood. Being exposed to this much mould is not a good idea. Do not attempt to clean up large areas of mould yourself. You need professional help to determine why the mould is there in the first place and how to clean it up.

When should you seek professional help?

You may need professional help when:

  • There is a lot of mould
  • The home is very damp and moist
  • Mould comes back after repeated cleaning
  • A family member suffers from asthma or respiratory problems or other health problems that appear to be aggravated inside the home

How To Avoid Condensation And Mould In Your Home


During the winter months, many properties suffer from damp and mould growth due to condensation.

Causes and signs of condensation

Air can hold moisture – the warmer the air, the more moisture it can hold. If moist air is cooled by contact with cold surfaces, such as walls, windows or mirrors, the moisture condenses into water droplets (condensation).

Mould often occurs because of condensation. It appears as pinpoint black spots, usually on the side surfaces of external walls, in corners and in poorly ventilated spaces, such as behind cupboards and wardrobes.

Principles of condensation control

The control of condensation requires a combination of sufficient heating, ventilation and insulation.

Sufficient heating + insulation + adequate ventilation = less condensation



By introducing low level heating, the temperature of internal surfaces will rise. This will reduce cooling of any moisture-laden air and, consequently, the amount of condensation.

Ideally, low level background heating should be continuous, as any short bursts of heat may not result in a suitable rise in surface temperatures.


Thermal insulation, such as loft or cavity wall insulation, draught proofing and double glazing, will help to reduce the amount of heat lost from a property. This will not only help keep internal room temperatures higher, but will also help keep fuel bills down.


Adequate ventilation is essential to allow moisture-laden air to escape from the home before condensation occurs. Mechanical extract ventilation systems in the kitchen and bathroom, can prove very effective in reducing condensation, especially when fitted with an effective humidistat control.

Extreme cases

  • a dehumidifier, which extracts moisture from the air, can be bought or hired.
  • wipe down surfaces affected by condensation regularly, to prevent mould growth.
  • mould can be removed by washing the surface with a disinfectant or a fungicidal wash. This must be used in accordance with the manufacturers’ instructions.

Mould-inhibiting paints and sprays can also help to reduce the effects of condensation.

How to reduce condensation

  • pull wardrobes and furniture away from walls, and keep tops of wardrobes clear, to allow air to circulate.
  • close doors and open windows when cooking.
  • keep lids on saucepans when cooking.
  • keep bathroom doors closed when bathing, and open windows slightly afterwards.
  • do not dry clothes on radiators, unless ventilation is increased.
  • only use Liquid Petroleum Gas or paraffin heaters in ventilated rooms, as these fuels produce water vapour during combustion.

Other causes of damp

Check the following;

  • all accessible plumbing for leaks
  • guttering and down pipes for cracks and blockages (for example, leaves)
  • overflows and waste pipes under sinks for leaks
  • possible roof leaks
  • damaged outside walls or eroded pointing
  • high garden or path levels overlapping the damp proof course

07/01/2013 Posted by | Building Concepts, Heat Recovery, Heating, mould, mould growth, MVHR, Ventilation | | Leave a comment


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