Ventilation Requirements for Your New Habitable Space

When you're transforming your garage into a new living area, it's crucial to ensure proper air circulation. Good ventilation isn't just about comfort; it maintains healthy air quality and prevents dampness or mould. The exact ventilation you'll need will depend on your room's purpose and dimensions.

Also, if your project involves creating new rooms or altering existing ones with internal walls, you must make sure that the ventilation in other parts of your home isn't compromised.

Understanding the Types of Ventilation You'll Need

For most projects, you'll generally need to incorporate two main types of ventilation: purge ventilation and whole building ventilation. Let's look at each.

1. Purge Ventilation

Purge ventilation is designed for rapid air changes, like when you want to quickly clear a stuffy room or remove strong odours. You achieve this by simply opening a window. However, the minimum size of that opening depends on how far the window can open:

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

• Should your window open wider, exceeding 30 degrees, then the required open area is at least 1/20th of the room's floor area.

• Be aware that hinged or pivot windows opening less than 15 degrees do not qualify for purge ventilation.

2. Whole Building Ventilation (Trickle Ventilation)

Whole building ventilation, often called trickle ventilation, provides a continuous, low-level airflow to maintain general air quality throughout your home. This is usually integrated into window frames as small 'trickle vents' or provided through other constant ventilation systems. The minimum 'equivalent area' required for these vents depends on what type of room it is:

3. Extract Ventilation

You'll also need to install mechanical extract ventilation in any new kitchen, bathroom (including shower rooms), utility room, or toilet. This system is essential for rapidly removing unpleasant odours and significantly cutting down on condensation.

• However, for toilets specifically, you might be able to use an opening window or an external door for ventilation (this counts as purge ventilation), as long as it meets the necessary size requirements and doesn't create a security risk.

• Remember, any extract ventilation system you put in must meet all relevant building regulations.

If you have a different idea for ventilation, or an alternative system in mind, it might be approved if you first discuss and agree upon it with your local building control body.