Condensation is usually most intense in the period from November through to April, known to surveyors as ‘condensation season’, a time when it is invariably cooler outside a house than within.
The source of condensation in the home is invariably warm water vapour generated by everyday activities including baths, showers, cooking, ironing and laundry drying indoors. The obvious answer is to stop the creation of the condensation at source wherever possible. However, this is not always very easy or practical to do and once condensation is present, it will then depend on the design of the building, its air circulation, ventilation and insulation, as to how you might deal with it. If moisture is trapped within the fabric of the structure and unable to disperse, usually due to poor or non-existent ventilation, it then condenses on cold surfaces. It is often worse in dead air pockets, such as corners, outside of the main air circulation patterns.
Generally, rooms are slightly more humid at ground level and when ventilation is inefficient, this is where damp collects and produces mould spores which can be injurious to health. Mould will also be found in those areas where vapour condenses on cold surfaces such as dead air pockets, cold water pipework runs, plastered corners, double-glazed window reveals, water cisterns and suchlike.
Condensation is often mistaken for damp within the walls of a house but it’s not the same thing at all. Also, some of the worst condensation damage can be found in the roof void, sometimes visible as white spore mould on timbers. Heat obviously rises and the warm water-laden vapour is taken up with it to condense on the underside of impermeable surfaces such as roofing felt and then run down it in rivulets. Increased insulation levels are often responsible for trapping moisture within a building, so it is essential that any roof insulation upgrades are allied to the provision of adequate ventilation and air flow.
Oddly enough, older houses are often able to deal better with condensation by dispelling water by evaporation through the basic building fabric and through natural ventilation (also know as draughts!) around doorways, windows, eaves, fireplaces, etc. This is as long as the building has not been sealed though. If an old period house is covered with a harsh cement-based render, this can effectively lock damp inside the walls. Handmade bricks, most traditional hardwoods and lime-based materials – intrinsic to period buildings – need to be allowed to breathe and covering them with a waterproof shell is wrong. Water vapour creates pressure and will attempt to move through a wall to drier conditions outside. However it is not just visible surfaces that are affected. Significant problems can be created within cavities, or inside a chimney stack (especially as soot deposits attract damp like a sponge) usually due to inadequate ventilation. Sometimes, where chemical damp injection work has been carried out, insufficient amounts of damp-affected wall plaster were removed beforehand and the dormant salts left behind absorb condensation, showing up later as areas of damp above the newly injected course. This may seem negligible during the summer months only appearing saturated during winter and the condensation season.
If you have any concerns about condensation affecting your property then please get in touch with Snow Walker. We are professional building surveyors with years of experience and will happily provide remedial advice for dealing with condensation problems in your home.