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Condensation is the water which results from the conversion of water vapour in the atmosphere.
The air which surrounds us in our homes always contains water vapour, which is usually invisible. A typical example is the steam cloud from a kettle, which rapidly becomes invisible – it has in fact been absorbed into the atmosphere.
The warmer the air, the more water vapour it can hold – but there is a limit to the amount it can hold for a given temperature. When that limit is reached, the air is said to be “saturated”. When saturated air comes into contact with a surface which is at a lower temperature than itself, the air is chilled at the point of contact and sheds its surplus water vapour on that surface – initially in the form of a mist and, if excessive, eventually in the form of droplets of moisture.
An example of this is when a person breathes onto a mirror: condensation occurs because the exhaled air is saturated and its temperature is higher than that of the mirror (which is at room temperature).
Condensation on windows and in conservatories, and the damage it does to paintwork, curtains, wall coverings and window fittings, are problems frequently encountered in all types of building. The increased incidence of condensation in today’s buildings is the direct result of changes in modern living conditions, which have led to warmer and more comfortable rooms.
In many homes, traditional open fires have been replaced by sophisticated heating systems, ill-fitting doors and window frames have been provided with draught excluders, floors have been completely covered by fitted carpets, while ceiling heights have been lowered and the space between loft joists filled with insulating material.
These modern aids to home comfort have created rooms which are warmer but which often have less ventilation and fewer air changes. The result is that the water vapour produced by normal living activities is no longer able to escape up the chimney or through door jambs, window joints and other outlets. In certain circumstances, all these aids to comfort combine to create ideal conditions for the formation of condensation.
The question is how to reduce condensation without sacrificing the benefit of increased comfort. When double glazing is used in conjunction with heating and controlled ventilation, it helps solve this problem – and its effectiveness will be even greater if the elementary precautions referred to in this guide are adopted.
Condensation on the external face (1)
Surface condensation on the outside face of a double glazed unit is a relatively new phenomenon which illustrates that your windows are of good thermal insulation.
The reason for the condensation is because the surface face of the external glass is lower than the external air temperature.
This can be caused when low overnight temperatures are followed by sudden rises and increased moisture in the air. As soon as the temperature rises above the “dew point” of the surrounding air, the condensation will quickly disappear.
We use Low Emissivity glass as standard with the option of using a warm edged spacer bar for further thermal insulation. This means that the warmth in your home is not lost through the windows.
In comparison, single glass and normal double glazed units allow your heat to transfer through the glass to the exterior. This in turn keeps the surface temperature of the external face much higher which prevents condensation forming on the outside pane.
Condensation between the sheets of glass (2 & 3)
Double glazed units are completely sealed during manufacturing. The formation of condensation between the sheets of glass is an indication that the seal has broken and the double glazed unit needs replaced,
We can replace your double glazed unit under the terms or your guarantee. If the double glazed units are not ours or the guarantee has expired we can supply a cost for the replacement. We can also upgrade your double glazed unit with modern technology.
Please contact our sales team for further information.
Condensation on the internal face (4)
When warm air containing a high moisture content comes into contact with cold air or a cold surface, a dew point is reached and the reduced temperature causes some of the moisture to be condensed into water.
The basic causes for condensation on double glazed units are.
Outside temperature
Inadequate heating and ventilation.
Outside temperature
Although the Scottish weather cannot be controlled, the barrier between your home and the elements can be. The specification of your double glazed unit can be a factor for condensation.
The higher the specification of your double glazed units, the more insulated your home is from the outside. That means the cold will not transfer through the glass and the surface temperature of the internal face will be closer to the room temperature.
However, even with the highest specification of double glazed units, condensation can still form. This can be caused by a number of factors as below.
Heating and ventilation
In the UK, condensation in houses is mainly a winter problem particularly where warm moist air is generated in living areas and then penetrates to the colder parts of the building.
The moisture in the air comes from a number of sources within the house. Water vapour is produced in relatively large quantities from normal day to day activities –
Breathing: A 5 person household puts about 17 litres of water into the air every day which is absorbed as water vapour into the atmosphere.
Cooking: Steam clouds can be seen near saucepans and kettles, and then seem to disappear. The clouds have been absorbed into the atmosphere. The cooker itself may be a source of water vapour; eg. An average gas cooker could produce approximately 1 ½ pints of moisture per hour.
Washing up: The vapour clouds given off by the hot water are rapidly absorbed into the atmosphere.
Bathing, laundry, and wet outer clothing: These are often the major sources of water vapour in the home.
Heaters: A flue less gas heater can produce up to 2/3 pint of moisture per hour. Paraffin heaters produce 9 pints of moisture for every 8 pints of fuel burned.
Indoor Plants: A frequently unrecognized but nevertheless significant source of water vapour.
This in turn can cause problems with condensation under the right conditions. The most common places people report condensation problems are in the Bathroom, Bedrooms, unoccupied rooms, Living rooms and kitchens.
Bathroom.
Stop water vapour finding its way into the rest of the house, particularly during and after bathing. After a bath or shower, close the door and open a window for a few minutes. Position a radiator, or heated towel rail, close to the window and consider installing an extractor fan.
Bedrooms.
Check points under “Living Rooms”, particularly with respect to the position of curtains and the provision of vents. ?If possible extend the central heating programme to compensate for the night time drop in external temperature, and the increase in water vapour caused by your breathing. Bedroom windows should be opened during the day to allow at least one complete air change.
Unoccupied rooms
More often than not, people keep unoccupied rooms at a lower temperature than occupied rooms due to heating costs. Moisture can travel throughout the house to these areas and condensate on the cold surfaces.
Living rooms.
Allow the room’s warmth to reach the windows. Position heaters under the windows, and use fittings which hold the curtains at least 15cm to 20cm away from the glass to allow free movement of warm air. Open windows for at least a few minutes each day to permit air changes. Where open fires are not provided, or existing flues are blocked off, see that wall vents are fitted and kept clear. When a gas fire has been installed in an open fire aperture, the back plate should have vent holes below the fire, unless this is provided for in the fire design. ?
Kitchens.
Close internal doors and keep a window open. Alternatively, install extractor fans or cooker hoods, ventilated to the outside air.
Condensation is a ventilation problem and cannot be cured purely by the installation of double glazing. By acting as a heat barrier and providing an inner pane which is considerably warmer than the outer pane, condensation may be reduced.
Modern buildings are designed to eliminate draughts and do not have the natural ventilation that some older houses have with their chimneys and ill-fitting doors and windows. Houses which have been completely sealed by the installation of cavity wall insulation, loft insulation, double glazing, and draught proofing throughout are likely to become moisture traps. In such cases, condensation is a ventilation problem. Provided the rooms are heated normally, the solution will probably be found by providing controlled ventilation. When lack of ventilation is suspected, the householder should consult a heating and ventilation engineer. In the case of the older, “unsealed” buildings, the dominant factor is likely to be the indoor temperature, and additional heat, or the introduction of localised heat near the windows, will probably provide the answer.
It has been said that if two families live as neighbours in a pair of semi-detached houses, and one family has bad condensation and the other does not; if they swapped homes and moved into each others houses, the sufferers would take their condensation problems with them - think about it!