Condensation, Mould and Air Movement
in your home

Independent Surveyors can help solve problems

We are qualified independent surveyors who can provide help and advice with regard to building surveys, structural surveys, independent valuations, property surveys, full structural reports, engineers reports, specific defects report, home buyers reports or any other property matters . As you can see from this article we use lots of sketches and photos in our reports as the feedback we have from you the client is that the sketches and photos really help them understand the reports. We, of course, like to meet you at the property during the survey and we are more than happy to talk to you about the reports.

For further advice with regard to condensation, mould and air movement in your home or any other property matter, please free phone 0800 298 5424 for a friendly chat with one of our surveyors.

Condensation, where it comes from and what causes it?

Unfortunately we are now frequently seeing problems with condensation in properties and regularly see condensation more and more – why? Condensation can be in the form of mould on the walls and this black mould on the walls can be interpreted in many different ways by both the people living in the property or the people about to buy the property or the tradesmen that come to look at the property. Often people fear it relates to a roof leak or a pipe leak or something similar. However in our experience black mould is very usually condensation.

One theory on condensation that is not heard that often

We have over the years heard time and time again that the problems relate to the user of the property and how they use it. Whilst we have dealt with cases where this is very much correct and with a little knowledge people get to better understand how their houses and properties work, we feel with our ever increasing requirements to warm a house and producing more and more situations where the houses and flats are simply not designed to cope with the way that we are using them. What is interesting with the ever increasing requirements to be more energy efficient is the way that houses are being built is changing although outwardly it doesn't look like it; this we feel has an impact on the mould and how frequently it will occur in properties.

The way we design and build houses is constantly changing

It should be remembered that whilst our houses from a hundred or two hundred years ago still look fairly similar to houses of today, i.e. they have walls and they have a roof, they have windows and they sometimes have a chimney, the materials and the way that we are building the houses has varied considerably. There have been changes in design from everything from the architects and designers that originally designed the houses to the way users modify them with the ever popular DIY alterations and amendments, to the way the Building Regulations is forcing developers to look at the way they build.

Leaky houses versus airtight houses

This is a term that has been used more and more referring to old houses that they are leaky houses and leak heat; a modern house being airtight. However with these terms we also need to remember that an older house tends to work very differently with the materials breathing whereas the more modern house tends to work with watertight and airtight solutions.

Airtight houses – do they cause condensation problems?

We recently went to a conference where the Architect proudly explained how he had designed airtight houses that were like ‘Tupperware' boxes as they were so tightly sealed. We are not sure whether this will give us the required or desired effect for an environment that we want to all live in. Whilst it may be a lot warmer, and older houses to some extent are draughty (you can always put a jumper on), we believe there will be a lot of problems to come with this type of design.

We are aware that the above paragraph is very much out of step with modern thinking with a push for ever more energy efficient houses however we have spent time in the past with architects. We understand that they produce a drawing, manage the construction and then move onto their next new project. However as building surveyors we get to see the results of the design and we are aware that architects, although many of them are very clever, don't get to understand the problems that their designs have caused due to the way that people live within properties and this is often the unknown or uncertain factor.

In a pre-war property, airflow both in the house and into the house would have been via many ways. The windows, for example, were sliding sash windows, and didn't fit that well which gave air movement and real fires were used which also gave real air movement in a property.

We shouldn't forget that it was common to have a suspended timber floor like we have shown in the adjoining sketch. Underneath the suspended timber floor you had air movement from the airbricks that were outside the property. This air movement often included air movement up between the floor boards as we didn't have wall to wall carpet, we simply had a carpet for the middle of the floor and the air movement was considerable underneath the property.

Although we haven't experienced it, we are told that in a suspended timber floor sometimes you can still feel draughts coming up through the floor boards. We are not saying that these environments were ideal, as it certainly wouldn't be as warm as today with a draughty house, but it did give a movement of air around a property which in turn reduces the chances of condensation.

The arrival of central heating

With the arrival of central heating, back boilers and electric storage heaters, this meant that there wasn't as much air movement as you don't need air as you do with a real fire to activate this type of heating. There was air circulation often caused by the non airtight windows and doors which allowed movement around the property. There was also movement by the different materials that the heat came into contact with such as the single glazed windows which then cooled the air and the ceilings which also allowed the warm air to go up through them.

The 1970's and Energy Efficiency arrives

The heading says that in the 1970's Energy Efficiency arrives; this is not strictly true as most people would say that Energy Efficiency arrived because of the oil crisis and the need to save money. This was the first time people looked at how the buildings worked from an Energy Efficiency point of view.

This resulted in basic improvements such as insulations to lofts and insulations to cavities and the starting of the multi-million or is it multi-billion pound double glazing industry. This then changed how air moved within a house. No longer did you have such big differences between the wall temperatures and the window temperatures and the ceiling temperatures which means that air starts to sit in the same place within a house and there is no way when it gets over-moist for it to escape.

Condensation and humidity in a house

There are all sorts of terms used in relation to condensation. One of the main ones to understand is humidity. This is what needs to be generated amongst other things to cause condensation. Humidity refers to an over moist atmosphere, this occurs when activity takes place which creates humidity. This can, for example be:

Cooking
Showers
Baths, particularly long baths
Washing
Washing machines
Drying washing on radiators on a rainy day

The air movement in a house also has to be considered, a lack of air movement results in humidity moving with the flow of warm air rising and cold air sinking and the moisture being drawn to the colder rooms, often to colder spots in colder rooms such as the corners or within cupboards. This results in a blackening of these areas, which is why air movement is so important in a property.

Heat loss in a poorly insulated house

If you look at a typical older property there is considerable heat loss. Everybody is forever trying to improve the heat loss in a house (see the adjacent sketch). Approximately:

25% goes through the roof

35% goes through the walls

25% goes through the windows

15% goes through the floors

Heat loss in a house

The sketch shows how heat travels through materials.

How does air move in a modern airtight house/flat?

The best example or the worst example that we see of this is in a modern high-spec flat or apartment which is part of perhaps a scheme of twenty plus apartments. Here, the flat or apartment is surrounded by well insulated other flats and apartments so if you are on the second floor for example, you may only have one external wall, the other walls are internal, either onto adjoining flats or apartments or corridors. We have surveyed properties where people who live in this type of environment say that they hardly ever need to put their heating on, which is an incredible thing to say in our climate!

Ventilation/Extraction

A way of helping to reduce condensation is to have large humidity controlled extract fans within the kitchens and bathrooms which are moisture generating areas. Beware that extract fans are vented to outside air rather than into the roof as per the photo below!

What do the ovals or circles in our building surveys mean?

We utilise a system of ovals and circles within our structural surveys and building surveys to highlight problem areas so that you are not left wondering what the problem is.