Defect 1 – Condensation

In the first of our new ten article series, we kick things off with one of the most common defects around – found in almost every home in the country to a varying degree – condensation.

Condensation itself is extremely common. You see it all the time; on your windscreen, on the insides of your windows on a cool day, beading on the surface of your cool glass of something refreshing. Technically speaking, it occurs when vapour is cooled to its saturation limit, resulting in transformation from a gaseous to a liquid form.

Winter is the worst time for this, with cool walls and freezing external temperatures in stark contrast to a warm, moist internal environment. In such circumstances, the process usually follows these steps:

  • Cold air enters the building
  • The air is warmed for the comfort of the occupants
  • The warm air takes up moisture
  • The warm, moist air comes into contact with cold surfaces, walls, windows, etc. and is cooled below its Dew Point
  • Condensation occurs as the excess moisture is released

The problem comes when condensation forms on elements of the internal structure,  with the moisture acting to speed deterioration and directly cause myriad issues – from fungal decay in floor timbers, to black-spot mould on walls and ceilings.

Modern homes are built to be extremely air tight, in accordance with Part L of the Building Regulations. The very worst air tightness results permissible are now 10 m3/( – which, suffice to say, is extremely tight. They are also typically built with strong trickle and purge ventilation systems, which help to moderate the internal humidity and avoid condensation issues.

Older properties are not so lucky, however, and buildings with solid, un-insulated walls are particularly susceptible to issues.

A level of condensation in such buildings is almost inevitable, but it is possible to manage this and avoid the defects that stem from it.

As is the advice of the Property Care Association, serious condensation should be assessed by a specialist surveyor. Lighter issues can be helped by a variety of tactics though, which should seek to address both the moisture content in the air and the presence of cold surfaces.

  • Try to maintain a modest increase in background heat, as opposed to intermittent heating, as this will increase the ambient temperature of the building’s fabric.
  • Consider ‘purge’ ventilation in areas which produce the most airborne moisture – like bathrooms and the kitchen. This might take the form of a small mechanical extractor fan, which these days can be bought with a humidistat that will activate the fan based on real-time humidity readings.
  • You might consider external, internal or cavity wall insulation to help improve the thermal dynamics of the building. Schemes like the Government’s Energy Companies Obligation exist to improve the insulation of the UK’s housing stock, with a particular focus on older properties. Insulation under the scheme is free and there are numerous providers all around the country.
  • Consider investing in a dehumidifier. This is a device that draws in the warm air, cools it down to encourage condensation and captures the water in a reservoir.
  • If the problem persists, consider a positive pressure condensation control unit. It won’t be a cheap solution, in fact it would set you back several hundred pounds, but they can be extremely effective. A mechanical installation placed in your dry, well ventilated loft space will mix that air with the moist air of your home, changing the house’s air content around once every two hours or so. The moist air is therefore removed by natural leakage, reducing the potential for condensation build up.

Surveyors come across condensation issues almost every week. If you’re concerned about a mould formation, damp patch or any other symptom of dampness – don’t hesitate to speak to your local professional. They can guide you through the sensible steps to take and give advice tailored to your particular issue.

Watch out for article 2 in next month’s edition, when we’ll cover ‘Water Ingress’ – where it can get in and what to do about it when it does.

*Back to March 2016 Newsletter*

©     SJ