Is Lüften the secret to the UK’s damp & mould issues?

Although no one wants to let out the precious warm air they have spent money creating, keeping our homes tightly shut during winter may be doing more harm than good. Evidence suggests we should be looking towards our mainland Europe cousins in a bid to keep on top of mould and damp.

Lüften is the German practice of airing a home (luft means air). Every day, people will open their windows as wide as possible for a short period of time, commonly between 3 and 10 minutes, first thing in the morning, whatever the temperature – even if there is snow outside.

Opening windows wide creates Stoßlüften – shock-ventilation that allows humid air (the type that creates damp and mould) to leave a property and dry, fresh air to enter. So important is Lüften in Germany and many Scandinavian countries that it is frequently mandated in rental agreements, which forces tenants to air their homes.

Lüften certainly feels counterintuitive in the depths of winter, with the UK population preferring to keep everything shut in a bid to stay warm. In doing so, however, we create condensation and encourage the growth of mould and damp.

For example, take a look at your windows first thing on a chilly morning or after bathing. Chances are the glass is running with condensation and the rubber seals are wet. There may even be black mould speckles on sealant and in recesses.

These are common signs of poor ventilation, with the issue exacerbated by modern lifestyles. Trapped humid air – from baths, showers, cooking, wet washing and that expelled when we breathe – turns to condensation when it meets cold surfaces like glass, tiles and rendered walls.

A good dose of lüften every day, together with keeping trickle vents open, using extractor fans and dehumidifiers, creating a constant ambient temperature between 18°C and 21°C, and keeping lids on pans when boiling water, will reduce the amount of condensation created. Promptly wiping away any that does form helps prevent mould and damp. In addition, tenants shouldn’t push furniture against a wall so it touches, as this traps moist air and encourages mould – a gap will help air circulate.

Lüften, however, isn’t the cure for every damp and mould issue. The most serious problems arise from structural defects that allow water ingress or trap moisture. The root causes of penetrating and rising damp can’t be treated by a tenant. Instead, speedy intervention by the landlord is required if the following are evidenced:

Condensation in lofts: issues include gaps in sealant and around pipework, spray foam insulation that traps moisture against timber supports, badly-fitting loft hatches and insulation that blocks air vents.

Failing damp course: if there are tide marks, peeling paint/wallpaper, white salt deposits/efflorescence, mould, musty smells and rotten skirting boards, water could be seeping into the fabric of the building from the ground up due a failing damp course.

Brickwork & roof issues: penetrating damp works its way from the outside in. Cracked brickwork, missing mortar, blocked gutters and air bricks, leaky down pipes, damaged roof tiles and faulty flashing are a recipe for water ingress. This may show up inside as peeling wallpaper, bubbling paintwork, flaky plaster, decaying timber and water marks  - especially on external walls – as well as a musty odour. Problems can sometimes be pinpointed from the outside by localised wet patches and excessive moss growth.

Ventilation: while a tenant should be educated to open windows and doors periodically, landlords must ensure it is possible to do so safely. A landlord should also ensure all extractor fans are sufficient and in good working order, that any heating is working and consider supplying a dehumidifier.

If you are in any doubt who is responsible for providing ventilation, reducing condensation, and treating damp and mould, please contact our lettings team.