Condensation In Your Home
The most prevalent source of unwelcome dampness in buildings is the condensation of water vapour from the air.
The air in buildings might have a high relative humidity level as a result of occupant activities (e.g. cooking, drying clothes, breathing etc.). When this humid air comes into touch with cold surfaces such as windows or chilly walls, it condenses, depositing water. The dew point is the temperature at which water vapour in the air turns to liquid.
Condensation is linked to insufficient heating and ventilation in buildings. It is particularly noticeable when the outside air temperature is low in the winter and the exterior walls and windows are frigid. Typically, the following sequence of events occurs:
- The building is infiltrated with cold air.
- The air is warmed to ensure the passengers’ comfort.
- Warm air absorbs moisture.
- Warm, wet air gets cooled below its Dew Point when it comes into contact with cold surfaces such as walls, windows, and so on.
- Condensation happens as a result of the release of surplus moisture.
Condensation frequently occurs in kitchens and bathrooms (where ambient moisture levels are typically highest), solid external walls, uninsulated solid floors, and cold bridges such as concrete lintels placed in cavity walls.
Intermittent heating and cooling can exacerbate condensation problems by allowing heated damp air to cool, reducing its capacity to hold water. Reduced dew points allow condensation to develop. When the air is reheated, water is reintroduced into it, only to be deposited once the air temperature decreases.
Perhaps the most obvious sign of a condensation problem is running water on windows and walls. If overlooked, this can result in a degradation of the property’s decorative state, stained drapes, and decaying window frames. In poorly ventilated locations, the appearance of mould on the surface of wallpapers and paints. Condensation under suspended floors can significantly increase the likelihood of fungal rot in floor timbers.
A considerably less common type of condensation happens when the Dew Point is achieved within the structure of the building, rather than on the surface of the wall. This is referred to as interstitial condensation and is frequently confused with rising damp or penetrating damp.
Condensation is a serious issue, and where it persists, a specialised surveyor should be consulted to ascertain the source of the problem and to advise or provide solutions. Below, we’ve included just a few of the possible solutions to the problem.
Simply heating the air is unlikely to be a satisfactory solution, both financially and practically. Condensation is almost inevitable unless cold surfaces are avoided and adequate background ventilation is provided. Therefore, any remedial action must include lowering moisture levels, providing adequate ventilation, and removing chilly surfaces.
Improved heating and ventilation, along with targeted action against cold spots, will typically result in a major improvement in conditions, while there may be instances when different approaches are required. A small but consistent background heat source is preferred than intermittent heating, as it will assist in maintaining a greater ambient temperature in the building’s fabric.
Installing adequate extractor fans in a property’s moisture-producing rooms, such as the kitchen, bathroom, and en-suites, will assist in removing the majority of this moisture-laden air from these areas (which are most likely to experience condensation), while incurring minimum operating costs. This is a requirement of the Building Regulations for newly constructed properties, but also applies to existing structures.
There are numerous types of extractor fans available, including those that operate continuously in the background or those equipped with a humidistat that regulates the fan’s operation within specified humidity levels. Additionally, fans with an integrated heat exchanger can be installed, which has the advantage of delivering excellent ventilation while minimising heat loss from the property. It is critical that these sorts of fans are specified and installed professionally by a sufficiently skilled and qualified technician.
Where an open fire or fixed gas fire is present, some “natural” ventilation will occur; it is critical that this is not shut off.
The use of specialised insulation materials attached to the exterior of the building and cavity wall insulation will help to improve the building’s thermal dynamics and may help overcome condensation.
Using a Dehumidifier
A dehumidifier can be used in place of heating and ventilation to control the amount of moisture in the air. This is a device that pulls in air, cools it to eliminate moisture that has accumulated in a reservoir, and then reheats it to a safe temperature before recirculating it.
The primary downside of a dehumidifier is the continual emptying of the collection vessel as it fills. This could be once a day or more, depending on the quantity of wetness. Additionally, there is the issue of ensuring that the dehumidifier is large enough and properly positioned to cover the entire house.
Positive input ventilation systems
Positive input ventilation systems (PIVs) have seen an increase in popularity in recent years. Generally, these machines draw dryer air from roof spaces or lofts and combine it with the air in the dwelling. This is accomplished at a very low rate (less than half of an air change per hour) and has the effect of decreasing the total moisture content and removing wet air from natural leakage.
The advantage of these devices is that they can control excess moisture throughout the entire house from a central position, and because they are ‘fit and forget,’ they require very little maintenance or human input. Only a little diffuser vent on the landing ceiling serves as evidence of the unit. Other devices are also available that can deliver cooler air during the warmer months or include built-in heat exchangers in locations where there is no suitable roof void (in a flat for instance).
Leaflet on Condensation
The PCA has created a brochure to educate households about the causes of and remedies for condensation in the home.
To download a free copy of the leaflet, click here – PCA Condensation leaflet.