We like to keep things simple and explain residential ventilation in a non-jargon way that you can actually make sense of. Today, we’re talking building regs and extract rates. If you’re an installer, wholesaler, or even just a homeowner trying to understand how to properly ventilate a house, then keep reading…

Firstly, welcome to Part F…

What Is Part F and Why Does It Matter?

Part F is essentially the rulebook for how to properly ventilate. It sets out the standards for how much stale air we should be removing from rooms like kitchens and bathrooms where moisture, smells, and pollutants tend to build up. The aim is to mitigate the risk of things like damp, mould and poor air quality from taking hold in our homes.

If you’re putting in a ventilation system – or advising someone who is – knowing what Part F says about extract rates is key. It helps make sure that whatever fan or system you install actually does the job it’s meant to do.

The Basics Of Extract Ventilation

When we talk about extract ventilation, we’re talking about how much air needs to be pulled out of a room (not how much fresh air is brought in, we’ll save that for another day).

There are two main ways to do this: intermittent extraction and continuous extraction. Part F sets the minimum standards for both of these methods.

Intermittent Extraction

These are your standard bathroom or kitchen fans that kick in when you switch on the light or when the room gets steamy. They run for a short time, then switch off again.

As stated in Part F, these are the minimum extract rates you need when using Intermittent:

• Kitchen (if situated by hob): 30 l/s
• Kitchen (elsewhere): 60 l/s
• Bathroom: 15 l/s
• Utility Room: 30 l/s
• WC: 6 l/s

It’s a simple approach that works well in many homes, especially where budgets or retrofit constraints are tight. However, because these fans only run when switched on, they can leave moisture and pollutants lingering between uses, which is where continuous systems come in.

Continuous Extraction

As homes have become more airtight and energy-efficient, continuous extract systems have grown in popularity.

These systems run at a low level 24/7, steadily extracting stale air from rooms like bathrooms and kitchens. They then boost to a higher level when needed, for example during a shower or when cooking.

Typical boost rates would be:

• Kitchen: 13 l/s
• Bathroom: 8 l/s
• Utility Room: 8 l/s
• WC: 6 l/s

If you’re an installer or wholesaler, it’s crucial to know these numbers when selecting fans or designing a system. For homeowners, it’s about understanding that the fan or system you choose can have a big impact on your home’s health and comfort.

 

Whichever route you choose to go, testing is now mandatory. Every mechanical extract fan in a new home must be tested after installation to prove it’s hitting the right airflow levels.

When it comes to ventilation, extract rates are often treated as a technical detail in reality, they are at the core of a healthy, functional home. They’re the numbers that tell us whether air is actually being removed at the speed it needs to be to prevent issues like damp, mould, and lingering pollutants.

Understanding these rates means you’re delivering performance that makes a measurable difference to the people living in that space.