Condensation and its control

What is condensation? 

Condensation is the change of water from its gaseous form (water vapour) into liquid form. Arguably, it is the most common type of damp-related occurrence we see in buildings; nearly all of us at some point in our lives have awoken to find water droplets running down our windows.

This liquid forming on your windows is called Condensation. The reason this happens is all down to the temperature inside and outside the property, as well as the amount of moisture in the air on the inside of the property. This varies between all properties and depends on the activities of each household (e.g., cooking, breathing, hot showers, & drying clothes all increase the moisture within the air).

When this water-laden air encounters a surface colder than itself, the warm air is unable to retain the same amount of water, releasing physical water onto the cold surface. The point at which water in the air changes from vapour to liquid is called the Dew Point or Point of Saturation.

Running water on windows or walls will perhaps be the first indication of a condensation problem within a household. If ignored, this can lead to the deterioration of the décor features within, causing wallpaper to bubble and peel, curtains to stain, and a general musty smell in the property. Ultimately, black spot mould will begin to grow in poorly ventilated areas, aggravating health problems such as asthma.

How Is Condensation Caused?

Condensation occurs when warm air full of moisture encounters a cold surface. Most commonly, this tends to be around windows or external walls. It is often associated with poor ventilation and becomes more apparent in winter when external walls and windows are coldest.

Warm air absorbs moisture through daily living standards. On average, an individual’s daily routine of cooking, showers, drying clothes, and breathing generates approximately 1 pint of water per day, 7 pints per week. Rising air currents carry this moisture-laden air upwards until it meets a cold surface. Prior to the widespread use of double glazing, cavity wall insulation, or prefab roofing designs, this humid, stale air would find an escape route through the loft or warped timber window frames. Today, however, there is no natural escape route in modern homes for this stale, humid air, causing condensation and poor indoor air quality.

Understanding the physical properties of air gives us a better view of how condensation occurs. A given volume of air at 20°C (68°F) can hold twice the amount of water vapour than at 10°C (50°F). The saturation pressure of water vapour increases with temperature. The actual partial pressure of water vapour is proportional to the amount of moisture in the air. So, when the temperature rises, you can put more moisture into the air until the vapour pressure hits the saturation pressure. At that point, the relative humidity is 100%. If you then take this saturated humid air and cool it, the saturation pressure drops, and suddenly the air has more moisture in it than it can retain in vapour form, so it condenses against a cold surface. This is why a can of coke sweats; it cools the air next to it, and moisture from the air condenses on the outside of the can.

Treatments For Condensation

Treating condensation begins by establishing the main cause, whether it’s poor living conditions, unsuitable extractor fans, or general poor ventilation. Simply heating the air is unlikely to be a satisfactory solution, not only on grounds of cost but also practicality. Unless cold surfaces are eliminated, condensation is almost inevitable. Any remedial action must involve both lowering moisture levels and eliminating cold surfaces.

Improvements to heating and ventilation, coupled with specific action in relation to cold spots, will usually result in a significant improvement in conditions, although there may be circumstances in which alternative methods are required. A modest but constant background heat is preferable to intermittent heating since this helps maintain higher ambient temperatures in the building’s fabric.

Old extractor fans were commonly wired up to activate with the light switch. This works well if the lights are left on after a shower or bath, although most people tend to turn the lights off after exiting the bathroom, leaving any humid air free to travel around the property. The installation of an extractor fan incorporating a humidistat in the kitchen and bathroom will remove moisture-laden air from the two areas most responsible for condensation with minimal costs. These types of extractor fans are normally set to operate when relative humidity reaches 50%, helping to reduce condensation.

A Positive Input Ventilation (PIV) is a low-energy home ventilation system and is an effective way to control indoor air quality. A PIV is usually loft-mounted and is ultra-quiet. They work by pushing harmful air out and replacing it with fresh filtered air from the loft space into the unit’s filters. The air temperature increases before passing down via ducting and air vents into the main household, constantly circulating fresh air and preventing any condensation buildup.

Installation of Internal Wall Insulation (IWI) on external walls will eliminate cold spots, reducing the risk of condensation and mould growth.

Condensation Investigation Survey

A survey will examine the affected and surrounding areas to determine the cause of the condensation and mould problems. It will assess the suitability of ventilation around the property, such as kitchens and bathrooms. Various equipment is used, and readings are recorded for a full and comprehensive survey report that outlines the observations and recommendations.

If you would like a survey carried out, please contact us to arrange an appointment.