Ventilation must be improved regularly by exchange of stale air with fresh. The propensity to save fuel and increase security prevents many from opening windows.

Improvements in heating and insulation have influenced building design and natural ventilation via gaps in floor boards, porous materials in construction and around windows and doors and construction of walls, presence of open fires and chimneys has been replaced with waterproof materials, draft sealants, vapour barrier forming décor, fitted carpets and no chimneys.

There are many routes and means of ventilation. Passive ventilation works with air bricks, trickle vents, gaps in floor boards and around window and door openings. Active means includes mechanical extractor fans, air exchange units including heat recovery, positive pressure units. Depending on the structure and layout several types of active and passive ventilation may be required to achieve effective performance.

One of the negative points about ventilation is heat loss. Heat recovery systems can save up to 95 per cent of the heat normally lost in mechanical exchange or extraction.

The one size fits all is not necessarily the one stop solution. A serious condensation problem will require evaluation of RH and potential WA prior to specification of type of unit and system. Post installation may then require monitoring for effectiveness with potential adjustments thereafter.

The proliferation of vapour forming appliances and personal hygiene has increased the volume of water used by domestic householders. Thus making ventilation air exchange even more critical.

Thus the specialist surveyor must now be able to take into account the commonest form of dampness within a structure i.e. condensation but in doing so he must be aware of how it is formed its cure and its effects.


Ventilation and the ISSE

The ISSE have for many years been advising clients on condensation control. Condensation is not a new phenomenon but in many ways it is exacerbated by modern living in houses which were built and designed for an earlier generation.

The use of modern tightly sealed and fitted windows and doors has shifted the problem to walls – especially those wall areas contained within built in wardrobes.

Unsightly mould growth discolours decorations and eventually the presence of increasing amounts of fungal mould spores within a living area can cause or make worse asthma and other respiratory conditions.

Advice on control of condensation should always focus on reducing vapour in the air by advising clients not to dry clothes on radiators, ensure windows are kept open for at least one hour after using the bathroom or kitchen – internal doors should also be closed to limit the water vapour travelling from an area such as bathroom to bedroom. However this advice is rarely acted upon enough to reduce the problem significantly.

The ample supply of hot water we now have from central heating systems, which our parents did not enjoy, has also contributed to a significant uplift in water vapour in the air. Increased burglary risk and most couples both working means day time ventilation with the window open is not an option.

Blocked up chimneys have also eliminated at least one safe means of air exchange.