Reducing condensation

How can changes to building design reduce condensation?

Design changes could involve rethinking of heating systems, upgrading of ventilation systems and methods, improvements in insulation or changes to the layout of accommodation.

1. Temperature levels.

• Install a heating system.
• Improve the heating system.
• Install improved heating controls.
• Install additional radiators or larger sized radiators, or improve radiator positioning.
• Fit double-glazing to reduce heat loss.
• Install wall insulation internally or externally (external insulation reduces cold bridging).
• Fit draught excluders to windows and doors.

2. Ventilation rates.

• Provide mechanical extraction fans in rooms subject to high moisture generation.
• Couple existing or new extraction fans to humidistat controls.
• Install permanent ventilation.
• Fit draught sealing, and door closers to reduce unnecessary ventilation.
• Improve ventilation of (and via) roof and floor voids.

3. Reduce moisture available.

• Change in cooking facilities.
• Install tumble driers with ducted outlet vent.
• Install dehumidifier.
• Install passive stack ventilation system.
• Install ventilation air bricks or vents.
• Install room heaters with flues.

Sometimes you may want to consider a change of layout, in order to improve compartmentalisation of the accommodation. 'Corridors for moisture' - the way moisture moves from an area of higher vapour pressure to one of lower vapour pressure - can often be identified. The route could be horizontal (a lobby perhaps), or vertical (a stairwell) or a combination of both. Additional doors or a new partition or lobby could help reduce the transport of moisture within a home.

It is common for moisture generating activities such as clothes drying on radiators or clothes racks, etc. to be carried out in unsuitable rooms - such as bedrooms - which do not benefit from mechanical ventilation provision. You could solve this by providing dedicated clothes drying equipment - such as a tumble drier with an outlet duct - or hanging clothes to dry in a kitchen or a bathroom which is fitted with a suitable extraction fan. Alternatively, a window sash could be left slightly ajar - probably tolerated in a bathroom or kitchen more than a bedroom. The door to the room used for clothes drying should be kept shut so air moisture can be removed near source.

Building conditions: how changes can reduce condensation

• Re-hang previously removed doors or refit door closers (to improve compartmentalisation).
• Re-hang or adjust badly fitted doors and windows, overhaul catches and locks, etc.
• Repair defective external wall pointing, rendering or defective parts to reduce penetrating dampness.
• Re-seal window frames at reveals to prevent draughts and damp penetration.
• Repair external plumbing, rainwater goods and roofing to reduce penetrating dampness.
• Repair leaking plumbing, baths, tiles and seal abutments to tiling.
• Reduce moisture generation from any of the listed moisture sources.

In order to achieve a mould-free home, strategies to improve or adapt building condition, design, or occupier lifestyle can be implemented. The 3 alternative approaches or various combinations of approach to reduce condensation and achieve a mould-free home are illustrated by the 'condensation diamond'. This diagram summarises the interrelated factors that can produce or remedy condensation mould.

Various fungicides or 'mouldicides' may help to control, inhibit or reduce the scale of mould development, but are unlikely on their own to address the root cause of the mould problem. They represent management of the problem - not a cure.