Essential Ventilation

Whenever you add new rooms to your home, you must ensure they have proper ventilation. This is crucial for maintaining a healthy environment. The specific type and size of the room will determine the exact amount of ventilation you need.

If you're installing a new internal wall, be careful not to negatively affect the airflow in existing rooms. It's important that when you create a new space, any rooms already there continue to receive adequate ventilation.

What You Need for General Ventilation

Typically, your rooms will need two primary forms of ventilation to meet building standards:

• Purge Ventilation: This type involves quickly clearing the air by opening a window. Here's what you need to know about the required clear opening area:

  • If your window opens at an angle between 15 and 30 degrees, the clear opening area must be at least 1/10th of the room's floor area.

  • If your window opens at an angle greater than 30 degrees, the clear opening area must be at least 1/20th of the room's floor area.

  Please note: Windows that are hinged or pivot and open less than 15 degrees are not suitable for providing purge ventilation.

• Whole Building (Trickle) Ventilation: This provides continuous, low-level airflow throughout the building. You can often find this integrated into the top of your window frame, or it can be achieved through other methods. The required "equivalent area" for this type of ventilation varies depending on the room:

  
  

  Room Category	Minimum Equivalent Area
  Habitable room or kitchen (multi-storey home)	8,000 mm²
  Habitable room or kitchen (single-storey home)	10,000 mm²
  Bathroom (with or without a toilet)	4,000 mm²

You'll usually need both purge and whole building ventilation for your rooms. However, if you discuss it with your Building Control Body and they provide their agreement, you might be able to use different ventilation solutions.

Required Extract Ventilation

You must install an extract ventilation system in any new kitchen, bathroom (including shower rooms), utility room, or toilet. This system helps to reduce moisture and remove unwanted odours effectively.

For toilets specifically, you have an alternative: you can use 'purge ventilation' instead. This means having a window or a door that opens directly to an external wall.