Homeowners Special Report

written by Peter Falk

 

Experts guide to beating condensation. Peter Fall a fellow of the Royal Institute of Chartered Surveyors (FRICS), with over 30 years experience. His practice specialises in property and construction. He lectures in the construction and maintenance of buildings.

 

Dedicated to his profession, Peter has served in a range of capacities including Chairman, President and Secretary General of Royal Institute of Chartered Surveyors forums and now shares his expertise throughout Europe.

 

His years as Chairman of the Commission on Building Pathology especially equip Peter to comment on the perils of unchecked damp and condensation in our home.

 

We have long recognised the connection between cold damp homes and ill health. The Romans built their houses with under floor heating systems as well as a type of damp proof course.You might say that they needed to do that in the British climate but the same examples of construction can be sen in the ruins of Pompeii.

 

When the Romans left, it took almost 1500 years before we British addressed the heating of our homes by more than an just an open fire and longer still before we flirted with the first damp proof courses. It is only in the last 70 years that damp proof courses were made compulsory in all new homes. But even now we have not eliminated other causes of dampness.

 

Construction techniques employed in housing have developed at a very rapid rate to accommodate our desire for an every improving standard of living. The need to provide a home that is open, light and warm has changed the way we heat our homes. The cost of fuel to provide this heat, together with our appreciation of the effect of burning fossil fuels upon the world at large, has meant that we are constantly striving to reduce the amount of fuel we consume, despite raising the level of warmth we demand in our homes.

 

One effect of these changes is we have cut off most of the incipient ventilation routes that were inherent with older construction and produced a largely air tight box to prevent the loss of heat by leaks and draughts.

 

All of this would not be a problem but for the fact that our modern lifestyles produce considerable quantities of moisture in the course of our normal living. Simply sitting watching the television means every hour we each give off 0.06 litres of moisture as vapour. This is chicken feed when compared to one litre for every bath and three litres when cooking a family meal.

 

This moisture must go somewhere. In the past it was absorbed into the atmosphere within the home before leaking out through the gaps around windows or doors or simply up the chimney but now these routes have been eliminated and the moisture is trapped. The atmosphere in our homes always

 

This moisture must go somewhere. In the past it was absorbed into the atmosphere within the home before leaking out through the gaps around windows or doors or simply up the chimney but now these routes have been eliminated and the moisture is trapped. The atmosphere in our homes always has some moisture present, in the form of vapour. The level of moisture affects the overall comfort and discomfort levels in the home.The total amount the air can absorb depends upon its temperature. As the air warms up so it can absorb more moisture in the form of vapour. When the air-cools it must release some of the moisture.When the warm moist air comes into contact with a cool surface, such as a window, the vapour reverts to water as it condenses on the cool surface.

 

The effect of condensation on a window is easily seen but unfortunately condensation isn’t restricted to windows. The vapour will condense out onto any surface that is sufficiently cool. This can be the wall, floor, ceiling, and even the bathroom fittings.

 

Water running down the window is easily seen and as the surfaces are none porous the water pools and can be dried up at regular intervals. It is simply an inconvenience.Water that condenses on a porous surface is a different matter. Plaster or timber will soak up the moisture and hold it until the adjacent atmosphere changes and can re absorb the moisture back into the atmosphere. To do this however the adjacent atmosphere needs to be both dry and warm. Unfortunately in modern houses that suffer from condensation, that does not often happen. The atmosphere continues to have high levels of water vapour as it absorbs yet more moisture from living activities. Instead the condensation continues to occur as new vapour soaks into the already damp plaster or wood surfaces, increasing the dampness problem.

 

The first sign the household sees of a problem is a damp patch on the plaster. Frequently this is at the corner of a room where two outside walls meet. This patch is often at low level and can be mistaken as rising damp caused by a failure of the damp proof course.

 

Sometimes the dampness is found when the floor coverings are lifted and the underside of the coverings is seen to be wet.

 

A less than wary occupier may miss these early signs or even ignore them as an irrelevance that will go away as mysteriously as it came. Unfortunately it will not go away. It will get worse.

 

The next warning sign is the development of small yellow brown spots that turn into a black dust that smudges when you rub it.These spots of condensation mould start to join up and give off a foisty smell so readily associated with damp. If this condensation occurs on or adjacent to clothes or carpets the mould can turn blue and white depending upon the material.

 

Whilst it is possible to wipe away the mould, that can only be a short-term remedy. As long as the conditions are present for condensation to occur, so the mould will re grow. The only permanent remedy is to eliminate the causes and they are the high level of moisture vapour in the atmosphere and the cold surfaces.

 

We could start by cutting down the moisture producers, but that means less people living in the house or less cooking or washing. Not a supportable suggestion.

 

Next we could open the windows and vent the humid atmosphere out of the building.This is a good solution for most of the year but in the colder months, when the condensation problem is at its worst, the open window releases warm air that cost money to heat up and replaces it with cold air that needs to be heated. In other words it is the same as when we had draughts.

 

It is possible to install an extractor fan that is operated by a humidistat.This fan removes the warm moist air from the room before passing the air over a heat exchanger to salvage the heat for reuse before exhausting the cooled air into the external atmosphere. Quite a complex piece of equipment that is only cost effective on a block of flats or a commercial buildings.

 

A simple and cost effective solution is the install a dehumidifier. This will remove the moisture, before recirculating the air and heat within the house. To avoid a multitude of dehumidifiers, the single unit will need to be centrally positioned near to the kitchen or bathroom, to quickly act on the high humidity air before it spreads around the house.

 

Each of these however does not help the second cause, the cold surface.To do this we must insulate the surface so that the warmth in the atmosphere is absorbed and retained to a level where condensation does not occur. On cavity walls we can introduce cavity insulation. We can apply thermal insulation to either the external or internal surfaces of the wall. We can double glaze our windows and replace the doors with a fully insulated uPVC door and frame. All measures both provide a warm internal surface as well as reduce the heat loss from the house.

 

The complete answer is a combination of the two. Lower the moisture levels in the atmosphere and increase the temperature of the internal surfaces.

 

 

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