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We were asked to visit a property by a letting agent in Durham who we regularly carry out work for, they had received a call from their tenant regarding damp and mould problems, the property is situated in Shildon, Co Durham. The landlord himself couldn’t visit the property due to work commitments and the fact he lives hundreds of miles away Kent. During the initial telephone call with the letting agents I had my suspicions the property may be suffering from condensation problems, so before I set off I made sure I was armed with all my surveying kit including hygrometer & infra red thermometer.

I always enjoy my little jaunts through the old mining villages of Durham, they seem to be places where little has changed over the years and you get a real feel of community spirit amongst the locals, when I’m in such a place I always keep an eye out for a local butchers as they tend to be top notch, the quality of the food they sell is fantastic and quite often is from a farm down the road, I often find myself coming home with a plate pie or two for my tea.

However, I digress, the house in question was an end terraced house, once I entered the house I was hit by the musty smell and could feel the humidity as soon as I entered the living room, before I was shown the areas of concern I asked the tenant a few questions relating to the property, it appeared the landlord had carried out various refurbishment works earlier in the year, they mainly consisted of new upvc windows & doors, new insulated roof and wall and loft insulation fitted under the Green Deal.

Below are a few pictures from inside the property, note the black mould covering the walls, this is one of the more serious cases of black mould I’ve seen in a while.

I set about carrying out the survey, one of the first readings I took was Relative Humidity (RH%), this tells me how much moisture is present in the air by measuring the percentage of water vapour, the second reading I took was air temperature, the reasons for these measurements is to determine ‘Dew Point’. Dew Point is the temperature that water vapour reverts back to its liquid form and condenses on surfaces, you’ll often find surveyors saying things like ” Oh….the relative humidity is really high that’s what causing condensation”.

In reality high relative humidity readings alone means nothing, you can have a relative humidity reading of say 87% and no signs of condensation, yet another house down the street could have the same relative humidity (87%) and be suffering from condensation, the reason for this is the difference in temperature, warm air can hold much more water than cold air, that’s why you always have to take temperature readings as well as relative humidity.

A good example of this…..when you get in your car first thing on a cold winters morning your windows steam up, this is simply water vapour produced from you breathing which condenses on the cold surface of your windscreen, once you turn the heaters on this warms up the surface of your windscreen, the windscreens temperature rises above ‘dew point’ (the temperature which water vapour turns back to its liquid state) and no longer steams up, you could drive another hundred miles and as long as the windscreen temperature is above due point no steaming will occur.

So back to the house in question, the average RH% was 82% and the air temperature was on average 14°C this equates to a dew point of 11°C, so any surface below this temperature will be subject to condensation forming, I took surface readings of all walls & ceilings suffering from black mould and they all returned temperature readings below due point, the bathroom and kitchen are back to back and housed in a single storey extension to the rear of the property, the walls were colder than other walls due to a combination of being single skinned (one brick wide) and external walls, the ceilings were cold because of the rooms having a flat roof construction above them with no insulation.

The solution to rid the property of black mould is to increase ventilation in the property as it does not have any forms of ventilation at present, the problem of ventilation has not been helped by the fact that the property had been super well insulated due to the recent upgrades, double glazing, new insulated main roof and loft & wall insulation, which effectively seals the property up like a tupper-ware box and the moisture laden air has no where to escape and simply condenses on cold surfaces below due point, the humid environment creates the perfect conditions for black mould to grow, black mould spores are present everywhere just waiting for the right conditions to thrive.

We have specified a PIV (Positive Input Ventilation) system to be installed, this will ventilate the property sufficiently to reduce the levels of moisture in the air and in doing so will create an environment where condensation cannot exist, another added bonus of using this system is it will rid the property of musty smells and  increased air quality making you breathe more easily.

If you suspect any damp related problems please give us a call on 0191 4159471 and we will carry out a survey to determine exactly what’s happening to your property, wrong diagnosis can result in costly, unnecessary works being carried out.