Condensation in a building usually occurs when warm air comes into contact with a cold surface. At a given temperature, air is capable of containing an amount of water as invisible vapour and the warmer the air, the more water vapour it contains.

When the air is cooled below its saturation point (dew point) it causes the excess water vapour to change into liquid water. The condensed water appears as water droplets or water film on non-absorbent services such as windows and doors. This form of condensation is described as 'surface condensation'.

Test:

Take a cold bottle of milk, from the fridge, into a warm room - See what happens!

Conditions for Condensation:

Condensation in properties is mainly a winter problem where warm moist air is generated in living areas and then penetrates into colder parts of the building.

Causes of Condensation:

Water vapour is produced in relatively large quantities from a large number of activities.

We all produce water vapour, when we breathe - almost two pints per day, also when we take a shower, bath, boil a kettle, cook the dinner or dry the washing. When doing so there are large quantities of water vapour released into the air.

Typical examples of moisture caused by a number of domestic situations include:-

In occupied premises condensation is largely related to modern living standards, economic pressure and changes in building design.

The effect of moisture generation is further aggravated by the way houses are ventilated. It is theoretically possible to avoid condensation by adequate ventilation. Up to the late 1960's there was natural ventilation in many homes because of poorly fitted windows and doors and open fireplaces.

In older properties the walls are often colder or have 'cold spots' caused by different building materials. Stone walled houses or solid brick walls are particularly prone.

Present attitudes have eliminated natural ventilation by the use of double glazing, draught excluders, fitted carpets (preventing air movement up through suspended floors) and the removal of open fireplaces, and with the introduction of central heating.

In addition many houses remain unoccupied and un heated throughout the greater part of the day allowing the fabric of the building to cool down, then the moisture producing activities are then concentrated in a short period of time. This sudden increase in warm air produces condensation as the air comes into contact with the relatively cold structure which is still warming up.

What are the effects of Condensation?

The effects of condensation can be seen as streaming windows, resulting in
pools of water on window sills which can eventually cause rotting at the bottom of timber frames. Black mould will form on cold spots typically in corners, behind furniture, behind curtains and in cupboards where there is little or no air movement. Clothes and furnishings can become mildewed, and leather is particularly vulnerable.

Questions and Answers:

Q - I did not have condensation before my new windows were
installed. There must be something wrong with them?

A - This is a common assumption but is incorrect. DOUBLE
GLAZING CANNOT CAUSE CONDENSATION. By acting as a
heat barrier and providing an inner pane which is
considerably warmer than the outer pane, the likelihood of
condensation forming is reduced. Windows cannot and will
not produce any water. The water is produced by normal
living conditions.

Q - How do I know if I have condensation?

A - Condensation will take many forms, the most common being
steaming windows and puddles of water on the window sills.
In extreme cases, dark spots of mould will appear around the
windows, wall coverings and mastic seals throughout the
house. If dark mould spots are found treat the affected areas
immediately.

Phoenix Tip:

To treat the affected area use household bleach (three parts water one part bleach) or Milton fluid. Both will kill the mould spores and prevent them spreading.

Q - Can doubled Glazing help?

A - Sealed unit replacement windows will act as a insulator,
reducing heat loss which under normal circumstances would
be conducted from the inside of the room to the outside.
However sealed units act as a an insulator and not a source
of heat, therefore rooms should be adequately heated. The
likelihood of condensation forming on a warm surface is
therefore reduced.

Q - How do I reduce condensation?

A - All modern houses and properties which have had improved
insulation and replacement windows are likely to trap
moisture build-up. This can be identified and dealt with by
providing natural ventilation to change the air on a regular
basis and by maintaining an even temperature. An effective
way of controlling condensation is by leaving air bricks un-
blocked and by leaving trickle vents open, in addition to
opening a window or by controlling the causes of moisture.

Phoenix Tip:

Follow these three steps, to help reduce condensation in your home: -

1) Produce less moisture:

• Cover pans and do not leave kettles boiling.
• Keep doors closed when cooking and bathing.
• Dry washing outdoors on a line or put in the bathroom with the door closed and the window open or fan on.
• Do not dry clothes on radiators.
• Ensure tumble dryers are vented, to the outside air.

2) Ventilate to remove moisture:

A home can be ventilated without making draughts;

• Keep a small window ajar when someone is in the room, or at home.
• Ventilate kitchens and bathrooms.
• Ensure extractor fans are working correctly, and have one installed.
• Ventilate cupboards and wardrobes and avoid overloading them, as this will prevent the circulation of air.
• Where possible, position wardrobes and furniture against internal walls.
• If your windows have been recently renewed, open the trickle ventilators provided.

3) Insulate, draught proof and heat the home:

• Insulation and draught proofing will help keep your home warm and will help reduce your fuel bills.
• In cold weather, keep low background heating on all day, even when there is no one at home.
• Do not block permanent ventilators and / or close trickle vents.

Remember:

IF YOU ARE IN ANY DOUBT CONTACT YOUR REPAIR AND MAINTENANCE SERVICE PROVIDER FOR ADVICE