Ventilation Requirements for Internal Walls

When you're putting up a new internal wall, it's essential to ensure that any existing ventilation in your property isn't negatively affected. If your project involves creating a new room, you'll also need to guarantee that both the new space and any connected existing rooms are properly ventilated. The precise ventilation levels you'll need to achieve will depend on the room's purpose.

General Ventilation Rules

Generally, your rooms will need two distinct types of ventilation:

1. Purge Ventilation (Quick Air Change)

You achieve this vital rapid air change simply by opening a window. The necessary openable area of the window is determined by how wide it can swing open. Here's what you need to know:

• Windows opening between 15 and 30 degrees: The openable part of your window must provide an area equivalent to at least 1/10th of the room's total floor area.

• Windows opening greater than 30 degrees: You'll need the openable part of your window to provide an area equivalent to at least 1/20th of the room's total floor area.

Keep in mind that any hinged or pivot window that opens less than 15 degrees is not considered suitable for providing purge ventilation.

2. Whole Building Ventilation (Continuous Air Change)

This type of ventilation is also known as trickle ventilation, and you can integrate it into the top of a window frame or use other approved methods. It provides a continuous airflow. The minimum 'equivalent area' (which refers to the overall effectiveness of the opening for ventilation) required will vary depending on the specific room type:

Usually, you'll need to provide both purge ventilation and whole building ventilation. However, if you have different ventilation ideas, alternative approaches might be acceptable, but this requires a specific agreement with your local Building Control Body.

Extract Ventilation

When you create any new kitchen, bathroom (or shower room), utility room, or toilet, you are required to install an effective extract ventilation system. This is essential for controlling condensation and removing unwanted odours.

• Specifics for Toilets: For toilets, you actually have an alternative to a mechanical extract system. You can use 'purge ventilation' – which means an openable window or an external door – provided it meets all the necessary ventilation standards and doesn't raise any security concerns.

• General for All Extract Systems: Remember, any extract ventilation system you choose to install must fully comply with all applicable building requirements.