Let your Home Breath

Ventilation is the unsung hero in maintaining a comfortable and healthy indoor environment within a building. It serves the crucial function of exchanging or replacing air to control temperature, replenish oxygen, and remove undesired elements such as moisture, odours, smoke, heat, dust, airborne bacteria, and carbon dioxide. The role of ventilation in managing moisture levels is especially significant as it helps in averting issues related to condensation, damp, and mould.

The Science of Ventilation: Vapour Pressure Differential

In regions with cold and wet climates, like the UK during winter, the vapour pressure indoors is usually higher than that outdoors, even when it’s raining. This differential in vapour pressure underscores the necessity of exchanging internal air with external air to manage moisture levels effectively within a building.

Regulatory Framework: Building Regulations Part F

The importance of ventilation is recognized in the UK Building Regulations Part F 2010, which stipulates the requirements for ventilation in buildings. Although a revision was made in 2020, it has not been adopted yet. Here is the link to the online PDF file of Building Regulations Part F 2010 for a deeper understanding.

Types of Ventilation

Continuous Ventilation

Continuous ventilation operates constantly to maintain a steady level of air quality. However, it can be untargeted, expensive to install, and costly due to the replacement of warm air expelled. Moreover, there’s a risk of condensation within the system.

Heat Recovery and Positive Input Ventilation (PIV)

Heat Recovery and PIV systems are often untargeted and risk short-circuiting warm air with relatively low relative humidity through gaps around windows and doors. Their focus tends to divert from the primary objective of removing vapour.

Purge Ventilation

Purge ventilation is occasional and is used to rapidly replace air in a space, useful for removing pollutants or excess moisture after specific activities.

Targeted Ventilation Solutions

Targeted ventilation strategies focus on removing moisture at the source, which is more effective and economical. Examples include:

  1. Fast Bathroom Extractor Fans:
    • Capable of blowing an A4 paper to at least 45° when held up to the outside vent.
    • Should have a 30-minute overrun to continue operation after showers, ensuring all moisture is expelled.
    • Keeping the bathroom door closed prevents vapour from diffusing into other parts of the property.
  2. Fast Kitchen Extractor Fan:
    • Should be used whenever cooking, or alternatively, keep tops on pots and pans to reduce moisture release.
    • Capable of blowing an A4 paper to nearly 90° when held up to the outside vent.
    • Continuous operation is advisable if the environment is humid.
  3. Outdoor Drying or Dehumidifiers:
    • Dry clothes outside or use a dryer with a closed door and open window, or employ a dehumidifier to control moisture.


Targeted ventilation strategies like fast extractor fans in bathrooms and kitchens, coupled with outdoor drying or dehumidifiers, provide an effective and economical solution to managing moisture and preventing related issues within buildings. These measures prioritise the removal of vapour over other considerations like cooling, ensuring a healthy and comfortable indoor environment with minimal expenses.

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