• JeanetteWilliamsBBS

Underlying reasons and solutions for common mould issues:

If you find you have mould and are not quite sure why have a look at the following common problems to see if you can make some changes.

Mould presenting on windows and window frames is due to the poor insulative properties of single glazed glass, screens, metal window frames that are not thermally broken and cool air being trapped behind blinds, shutters and /or curtains. Dust trapped in frames and on glass then becomes food for mould

· Opening widows and blinds, shutters and /or curtains can reduce the risk of condensation forming.

· Regularly vacuuming and damp dusting window frames and cleaning windows will reduce the risk for mould growth.


When mould presents on the bottom of furniture, at skirtings, under beds and inside the bottom of wardrobes it is often due to cool and humid air penetrating from the subfloor.


Elevated levels of indoor absolute humidity can be improved by addressing ventilation, this includes:

· Mechanical subfloor ducted ventilation that creates negative air in the subfloor to prevent contaminated air from entering the living space.

· Installing an energy recovery / heat recovery ventilation system that helps to reduce humidity and condensation whilst improving fresh air exchange.

· Ensuring kitchen, bathrooms and laundry are fitted with exhaust fans that vent to the outdoors and not the ceiling cavity.

· Opening doors and window as much as possible.


When mould presents on the walls and doors of wardrobes / cupboards that are not above a subfloor it is often due to one or more of the following:


· The location of the wardrobe / cupboard next to a bathroom or laundry with water damage.

o Solution is to rectify the water ingress and replace / structurally dry water damaged building materials.

o Solution is to rectify the water ingress and replace / structurally dry water damaged building materials.


· The location of the wardrobe on a southern wall that lacks insulation.

o Solution is to either insulate the walls or install storage dehumidifiers to reduce the risk of condensation (Dampp Chasers from Mitey Fresh).


· Overcrowding of wardrobes resulting in poor ventilation and dust accumulation.

o Solution is to declutter and do an annual wardrobe spring clean. Installing wardrobe dehumidifiers can also help (Dampp Chasers from Mitey Fresh).

o Install shelving that allows for air flow – keeping in mind that exposed surfaces should be dusted to reduce the accumulation of dust.


· Poor ventilation in the bedroom due to keeping windows shut overnight or only having sliding glass doors that cannot be left open for security reasons.

o Solution is to maintain good ventilation by opening windows during the day and nights. Install security locks so that windows and sliding doors can be left partially open.


· Putting sweaty shoes or damp clothes in wardrobe.

o Solution is to ensure all clothes are dry before putting in wardrobes.

o Shoes recently worn should be left in an open area to dry / breath


· Mirrored doors or metal framed doors that have cold surfaces and therefore reach dew point resulting in condensation:

o Solution is to replace metallic and mirrored doors with timber frames that tend to have warmer surface temperature than metal.


· Dust collecting on the inside of slatted doors and metal runners:

o Solution is to dust regularly to prevent the accumulation of dust on exposed surfaces.


A damp subfloor with limited ventilation and rising damp, particularly in older buildings can lead to raised levels of humidity indoors. The following would need to be addressed:

· Rectify the damp proof course.

· Remove damp building materials.

· Structural drying.

· Removing the top 200mm of soil if there is evidence of efflorescence or mould.

· Installing ducted subfloor ventilation that will create negative pressure in the subfloor to reduce the risk for future mould growth.


Elevated levels of indoor relative humidity, low surface temperatures, condensation, cool indoor temperatures and high dew point temperatures create increased risk for mould and can be improved by:

· Even heating of living spaces in the cooler months as cool air cannot take as much moisture as warm air. When the air is cool relative humidity will increase, reaching levels of 70% or more whilst warmer rooms will have a lower relative humidity. Since relative humidity above 70% mould can support mould growth, cooler rooms can become mould contaminated.


· Surfaces such as single glazed windows, metallic window frames and metallic / mirrored wardrobe doors have poor insulative properties and therefore often have cool surface temperatures, which increases the risk of condensation. Heating an area will also increase these surface temperatures and reduce the risk of condensation forming. Condensation increases the risk for mould contamination.


· Storage and wardrobe areas on the cooler south side or above a dirt subfloor are at higher risk of condensation forming on lower walls and inside doors, often resulting in mould at skirtings and lower corners. Wardrobe / storage dehumidifiers (heaters) can reduce the risk for condensation and mould.


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