Condensation in buildings has risen from a level of comparative insignificance to become a major domestic problem.  This can be attributed to a change in design of living accommodation and in the lifestyle of the occupants.  A major factor in the last few years has been escalating fuel costs, changes to building design and a growing public awareness of the need to conserve energy resulting in more widespread use of double glazing, better draught exclusion etc.


  • Wet windows/window frames
  • Walls wet to touch
  • Musty smell
  • Black mould forming on walls
  • Mould damage to belongings

We generate much more moisture within our homes than ever before with the advent of tumble dryers, washing machines, dishwashers, showers, internal bathrooms and kitchens, the drying of clothes indoors.  Airborne moisture often has less routes of escape especially within modified properties with the proliferation of double glazing, sealing chimneys cavity wall and loft insulation and central heating, with inadequate ventilation the heavy moisture laden air will remain within the property where it will lead to deterioration of internal décor and musty odours.


Condensation is essentially the product of water which has condensed from warm moist air on contact with a cold surface.  Air holds water in the form of water vapour (moisture).  Warm air is able to hold more moisture than cold air.  Air which contains its maximum moisture content is called saturated.  The amount of moisture in the air is expressed as Relative Humidity, (RH).  Saturated air is said to have 100% RH.  The RH of air with particular moisture content will vary with temperature; so as the air is cooled its relative humidity will increase.

As the room temperature drops the surplus moisture is released as condensation.  The temperature at which this occurs is known as the ‘dew point’.  The higher the moisture content the higher the Dew Point.  To put it simply,  this is like an internal cloud that causes it to rain when the room begins to cool.


Condensation is an issue that mostly presents itself in winter. This is because the external air temperature is lower and as a result the external walls and windows of buildings are colder. 

So how do these factors cause condensation? To start, cold air enters the building, this air is then warmed by the central heating and the warm air takes up moisture.  The warm moisture in the air then comes into contact with the cold surfaces in the building on walls and windows. This causes the air to cool below its Dew Point, creating condensation as the excess moisture is released. 

This process is a little like taking a drinks can out of the fridge, as the cold can comes into contact with the warmer air small drops of moisture appear on the outside of the can.

Intermittent heating and cooling of the property can aggravate condensation problems since it allows warm air to cool, reducing its capacity to hold water.  When the air is reheated water is taken back into the air only to be deposited again when the air temperature drops again, thus creating a continual circuit of wet and dry conditions. It is advisable to keep buildings at a stable temperature in the winter.

FACT: Mould only grows when the relative humidity is 70% and over.


Moisture producing activities (such as bathing, washing, cooking) from human occupancy in buildings can have a significant impact on condensation levels.

FACT: A family of four with associated living will generate approximately 14 litres of water per day!

If properties are sealed ie; double glazed, fully insulated, the blocking of chimneys, etc, as many properties are now, there is nowhere for this moisture to go. This often leads to condensation forming as the humid air comes into contact with cold surfaces.


Improved heating and ventilation along with specific action in relation to cold spots in properties will help, although there are many remedies occupants can use to improve their circumstances.  Each building and occupant is different and sometimes the approach can be personal. As each person has a different lifestyle some will never have a condensation problem whilst others with suffer with it a lot. Often we see clients who have moved into a property that was previously condensation free and wonder what has happened, this is usually due to differences in lifestyle.

The installation of humidistat fans in the moisture making rooms ie: bathrooms and kitchen are often a good choice, these will expel moisture as it is produced, preventing the migration of moisture laden air into cold rooms or areas, so the moisture is taken out at source. 

Particularly cold walls should be insulated by utilising thermally efficient wall linings, however the provision of a vapour barrier on the warm side of the insulation may be necessary to prevent condensation occurring behind the layers of insulation.

Sub floor vents can be installed to improve air flow to the sub floors.

Other devices that may be considered are positive pressure condensation control units.  These take drier air from the roof spaces or lofts and mix this with air in the dwelling. This is done at a very low rate (below half an air change per hour) and has the effect of lowering the total moisture content and removing moisture air from natural leakage.

Our surveyors are able to diagnose the scale and reach of the condensation problem during an inspection. Once identification of condensation has taken place during a survey a suitable solution from the above will be recommended.

It is the time of the year where condensation Is troubling your homes.., If this is something that affects you we c…
1:44 PM Nov 13th|@garrattsdamp
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