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Avoiding Condensation Problems

Have you ever noticed water droplets on your window or black mould staining on your walls? (condensation)

Have you ever wondered why the moisture returns around your windows after you have wiped it away? (condensation)

This type of moisture is from the interior air and is commonly referred to as condensation.

What is condensation and how does it form in my home?

Condensation occurs in your home when moist air comes into contact with a surface which is at a lower temperature. Moist air contains water vapour — commonly referred to as humidity. Indoors, we can increase humidity through our activities and lifestyle. If a surface in your home is cold enough, the air in the immediate vicinity of the surface will be cooled sometimes causing the moisture in the air to condense or change into a liquid on the surface.

Condensation forms first on the coldest surfaces of a room; usually on glass surfaces of windows and doors. These surfaces are typically cooled by lower exterior temperatures during the winter months much more so than during the summer.  For example, if it is cold enough outside and/or warm and humid enough inside, condensation may occur on or around your windows resulting in fogging, water or ice on the windows themselves or even a puddle of water on the window frame or sill. Other examples of condensation in your home can include damp spots or mildew / mould on outside walls, in corners and on ceilings.  Areas of your home with poor air circulation, such as behind furniture or in a cupboard or fitted wardrobe, can also be susceptible to condensation.

Condensation caused mould growth to case inside bedroom cupboard.

If a surface in your home is cold enough, the air in the immediate vicinity of the  surface will be cooled causing the moisture in the air to condense or change into a liquid on the surface.

A small amount of condensation appearing on a surface may not necessarily be a problem, depending on the amount of moisture that forms, how long it stays, and whether it accumulates on surfaces that can be damaged by water. Condensation can be short-term during a severe cold spell, or occur in a localized area such as kitchen, bathroom or laundry / utility room. In many instances, condensation moisture simply evaporates back into the air once the surfaces warm up or the moisture source is reduced. An example of this is moisture that condenses on a bathroom window during a shower and quickly disappears shortly after the shower is turned off.  However, as a general rule, steps should be taken to avoid condensation problems wherever possible as moisture can lead to damage, mould and mildew.

Why must I avoid condensation problems?

Condensation can cause serious damage to the interior and structural elements of your home or building. If condensation occurs frequently enough and for prolonged periods of time, materials in contact with the moisture may be damaged. Drywall and wood finishes around windows are two examples of materials in your home that can readily absorb moisture and become damaged if they remain wet for a sustained period of time. If left unchecked, condensation problems can cause:

  • crumbling or soft spots in walls.
  • decay in wood framing or corrosion of steel framing
  • peeling paint
  • damage to the insulation inside the walls, and
  • mould and mildew problems in your home.

    Condensation mould to bathroom due to lack of ventilation. Vent obstructed by net curtain and blind.

Most importantly, taking preventative steps to avoid condensation from occurring in your home will help prevent avoidable and expensive problems in the future and lead to better living conditions for the occupants.

Control of Condensation:

The key factors in controlling condensation are:  Ventilation, Heating and Insulation.

Ventilation – ensure that moisture laden air can exit to the outside
Heating – control fluctuating air temperatures by providing a continuous low level of heating
Insulation – ensure cold surfaces are insulated i.e. by installing cavity wall insulation and loft insulation.

By following a few simple rules, set out below, you could help reduce humidity levels dramatically.

1.  Keep bathroom & kitchen doors closed and open the windows to allow the moisture laden air to vent outside.
2.  Put lids on pans when cooking and use an external vented extractor fan.
3.  Vent tumble driers to the outside.
4.  Dry clothes in one room with the door closed and the window open to allow the moisture evaporating from the damp clothes to vent outside.
5.  Any surface moisture noted should be dried immediately and mould growth removed by cleaning with a damp cloth.

Common signs of condensation are:

Black mould growth or mildew – which typically occurs on cold external walls, in poor ventilated areas such as behind furniture, in UN-ventilated cupboards, wardrobes or corners of rooms and can appear at both floor and ceiling height.

  • Musty damp smell
  • Wet walls and peeling wall paper
  • Water running down windows and walls

Causes of Condensation:

Air in occupied buildings will always contain moisture from activities such as bathing, cooking and washing/drying clothes. Moisture will also enter a building due to the evaporation of water penetrating from the outside caused by building defects.  If this moisture is not vented to the outside, the humidity within the property rises and leads to condensation.

Some common modern day problems which cause condensation damp, especially in older buildings which are being refurbished or modernised are:

  • Installation of double glazed units without the appropriate provision of supplementary ventilation.
  • Installation of showers, Jacuzzis, & saunas with insufficient provision of extractor fans.
  • Tumble driers which are not vented to the outside.
  • The blocking of existing vents designed to vent air to the outside.
  • The sealing of roof voids by the installation of insulation, preventing an adequate through-ventilation via the roof vents in the eaves.
  • The blocking of windows or vents to basement areas.
  • Drying clothes on radiators.
  • Using paraffin or flueless calor gas heaters.

Will dehumidifiers help stop condensation?

De-humidifiers can reduce condensations effectively when rooms are warm and damp, but are of limited benefit when they are cold and humid.  In domestic buildings, simple lifestyle changes that lower himidity and/or keep surface temperatures above “dewpoint” will tend to provide a more practical and less expensive long-term solution.  Similarly, whole-house ventilation systems, which can have a role in controlling condensation, should not automatically be seen as the answer.

If you live in North Wales, Chester or The Wirral and think you may have a condensation problem, call (Wales) 01492 535305, (Chester) 01244 490341 or (Wirral) 0151 959 0086 for honest, friendly and professional advise. Alternatively email us at info@dampaidnorthwales.co.uk or fill in an  enquiry form to enquire or book a survey by one of our specialist damp surveyors to carry out an inspection for dampness due to condensation causing damp walls and black mould growth in your home.