Condensation – Black Mould Growth – Aspergillus Niger

Positive Pressure Systems

Garratt’s Damp and Timber has been successfully combating condensation within residential homes for many years. Our wealth of experience has taught us that, as a general rule, the most effective method of preventing condensation is to use a positive pressure ventilation system. These systems can be either wall mounted or loft installed, depending on the layout of the particular property.

Flatmaster positive pressure fans are designed to gently circulate air throughout the whole property. This combats black mould growth and results in fresher, healthier air.

Drimaster positive pressure fans are tucked away in the loft and gently trickle air through a ceiling-mounted vent before circulating air throughout the property.

Condensation in a Nutshell

Condensation will appear on colder surfaces within a property where warm, moist air cools and releases water held as vapour. The damp areas resulting from this process create the perfect environment for the growth of Aspergillus Niger (black mould).

Thanks to the increase in appliances like power showers, washing machines and tumble dryers, it is becoming more common for moist air to become trapped within properties. The increase in selling properties with home improvements like fireplace removal and double glazing has also been proven to play a role.

The Positive Pressure Solution in Brief 

A positive pressure ventilation system will draw fresh, dry external air into the property. The fresh air is then gently circulated throughout the property, creating an airflow in all corners of the house. This constant gentle flow of air will even out the temperature across all walls and surfaces, thereby negating the presence cold spots where condensing can occur. This process also creates a slight internal pressure that will push any moist air out of the property through natural air gaps like subfloor vents, door frames, older window frames and newer window frames with trickle vents. Below, we have illustrated the process based upon a loft-installed unit. The same principle applies to wall-mounted pressure units which draw air in through channels cut through an external wall.

Both the loft-installed and wall-mounted systems can be retro fitted with low-cost heaters, but we have found that customers don’t tend to require this enhancement.  Properties suffering from severe condensation may also benefit from the supplementary fitting of humidistat extractor fans to the main moisture making rooms, primarily the kitchen and bathroom.

Humidistat Extraction Fans

Humidistat fans are a great method of extracting moist air from properties. However, when considering their use, the best starting point is to look at the most common current installation of extractor fans within kitchens and bathrooms.

The typical type of extractor fans installed for many years operates alongside the activation of the room’s light switch. Whilst providing some level of condensation control, this method still often falls short.

A classic example is the process of taking a shower. The light and fan go on and the bathroom fills with high levels of water vapour. Once the shower is over, the light and fan go off. The fan stops operating long before all the water vapour is extracted, meaning that the remaining vapour will migrate throughout the property and condense on cold surfaces. This will result in the exact conditions that you are trying to eradicate.

The best solution for extraction units is to use the more modern humidistat controlled fan. These units are generally easy to install where older style fans are present, as they have the same 6” (150mm) square profile and will vent through the existing wall channel. Humidistat fans do not operate with the light switch, despite using existing wiring. The fan will either constantly trickle at a very low level and boost when humidity rises above a configurable setting, or remain off and boost depending on the model of fan chosen.

Humidistat fans have inbuilt sensors which monitor humidity and will operate only when the humidity threshold is reached. Operation will then continue until the humidity drops below the same threshold. This method of control ensures that extraction only occurs for the duration of time required to control the moisture-laden air and its capacity to cause condensation.

The Benefits

The following benefits can be experienced from our condensation control systems:

  • Improved air quality
  • Dry walls
  • Less housework cleaning black mould from cold surfaces
  • Fresher smelling clothes
  • Less deterioration of internal décor and the associated costs to correct

For further information, please visit our website or call our office to arrange a visit or discussion with one of our fully qualified surveyors.

Call us at 0208 535 7536

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