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Well-being: preventing condensation in your home

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Secondary Glazing in Practice

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energy efficiency

Condensation within buildings is a perennial issue. It is generally considered a nuisance, but in fact, black mould caused by untreated condensation can have a detrimental effect on an occupant’s health. If untreated the consequences of condensation can be a contributing factor in chronic ill health, with children and the elderly being particularly susceptible. Condensation is caused by the precipitation of water molecules held within warm moist air. This occurs when warm moist air comes into contact with a cold surface. When this surface is non porous, such as a pane of glass, the precipitation collects into water droplets which run down its surface. However, when the cold surface is formed of a porous or semi porous material such as paintwork and wood, some of the moisture is absorbed by the material. When this dampening process is persistent black mould ‘Stachybotrys Chartarum’ will start to grow. Left untreated it will start to undermine the surface on which it has formed. It is a ‘toxic mould’ which produces mycotoxins which have been directly linked to “… increased prevalence of respiratory symptoms, allergies and asthma as well as perturbation of the immunological system”. (WHO guidelines for indoor air quality: dampness and mould) 21 pints of condensation in 24 hours The average home generates 21 pints of condensation every 24 hours Everyday living activities such as washing and cooking produce 9.5 litres of moisture, whilst just breathing creates 15,000mls. This moisture evaporates into the warm air of a typical, centrally heated house which is held in the form of vapour. Thus, when this moisture rich warm air hits a colder surface, it instantly cools and turns back into water/condensation Only three generations ago an internal bathroom allowing occupants to have daily showers was unheard of and sheets were washed once a week! Our twenty first century pursuit of cleanliness has resulted in an exponential increase the amount of water vapour generated in a typical home. Our homes are now centrally heated and warm the air within can hold large amounts of water without us even noticing the build-up. The traditional outlets for allowing access water to escape were features such as open chimneys and even poorly fitted windows and doors. Now our super water laden warm interiors are in danger of being hermetically sealed; chimneys are often blocked or even removed whilst double glazed windows and energy efficient doors are plugging the remaining escape routes. It appears that in our quest to produce ever more energy efficient houses, house builders and occupiers can over seal them, preventing potentially damaging water vapour escaping into the outside atmosphere. If a building suffers from condensation, a few simple precautions taken to reduce the build-up of moisture can be all that is needed to address the problem.
  1. Open a window after using the shower or bath and leave it open for at least ten minutes with the door closed to vent any excess moisture
  2. Try to dry washing, were possible, outside. If it has to be dried inside, keep the washing in a closed room with an open window
  3. When cooking, use an extractor fan and shut the kitchen door. Use saucepan lids and if necessary, open a window or door to help excess steam escape
  4. Try to keep the ambient temperature constant, as rapid cooling and heating of the interior of a building could result in warm air holding excess water vapour which when cooled produces condensation
If condensation is still a problem, then it is recommended that a specialist damp company is consulted to ensure that the building’s fabric is sufficiently vented to allow for normal everyday activities. A comfortable, well-regulated internal environment requires a balance between the building’s ability to breath, with the occupants desire to stay warm and comfortable (and with hopefully manageable heating bills). Double and secondary glazing will help in preventing condensation on the room side glass pane with U-values of up to 1.35. A fully independent well sealed frame ensures minimum air leakage and traps an insulating layer of air, which cuts down heat loss by 40-50%. This can be increased to 60% if low-E glass is used. Sealed units can also be fitted to provide triple glazing. Single pane windows will always be liable to condensation as they provide very minimal thermal insulation and present a very cold surface in winter months. The combined approach of installing thermally efficient windows, ensuring good ventilation together with introducing the four lifestyle changes above is the best antidote to the scourge of condensation. According to WHO “The most important means for avoiding adverse health effects is the prevention (or minimization) of persistent dampness and microbial growth on interior surfaces and in building structures.