Don’t over spec Part F

New requirements for Part F came into force in June. Over a month on and there’s still confusion about what you have to do to comply.

Paul Dowling, our Technical Manager, explains what you need to do to stay on the right side of regulation as well as dispelling some common misconceptions surrounding Part F.

The first thing I’m going to do is point you to our guide to Part F, which is here: It explains what Part F is and how you comply in detail. I’d urge you to read it because it will save you a stack of time and potentially cost.

What I’m going to try and do here, is strip things back to the very basics:

1 – What is Part F?

Part F sets out the requirement for ventilation in buildings, including new and existing homes, focussing on air quality and the replacement of old stale air with fresh air.

2 – What does EA stand for?

EA in ventilation stands for Equivalent Area. This is a measure of how much air passes through a vent as a measurement of airflow performance, i.e. how effective it is in replacing stale air with fresh air – it’s the measure that you need to comply with.

3 – What does Part F mean for replacement windows?

It’s easiest to present this in the table below which highlights the new requirements since June 15th this year if the windows that you’re replacing, don’t already have trickle vents:

If they do have trickle vents whatever you’re putting back must deliver the same EA as what was there originally. You can work this out by checking the vents for their EA rating. If you can’t you need to treat the windows as if they didn’t have trickle vents.

4 – Who is responsible for Part F compliance?

You are! As a manufacturer we don’t know where the windows we make are going to be fitted. You need to make sure that what you’re ordering complies with the regulations for that particular room, in that particular property.

5 – Do all windows need to have trickle vents?

No, they don’t – and this is where we’re seeing over specification. The regulation sets the requirement for the room – not the window. So, in practical terms, if you’re replacing windows in a bedroom or living room, you need to achieve background ventilation of 8,000EA in total – not per window.

If the room has more than one window depending on their sizes you might choose to only put trickle vents in one of the two windows. This is a really important point, it’s about the room not the window.

We’ve seen customers specify 8000EA trickle vents on each window in multi window rooms. That’s definite overkill and could make properties freezing in winter, so if you want to avoid customer complaints, you need to remember – in every case, it’s about the room not the window. This is one of the most common points of confusion Part F can cause.

6 – Could I just bore out a hole and fit an air brick?

Yes, absolutely but you would still be responsible for making sure that the EA for the room was sufficient, plus run the risk of more cost with remedial work.

7 – What about new build?

You can relax. The architect or developer should tell you exactly what you need to supply in the specification but other than drawing a small distinction between multi and single storey buildings, it’s more or less the same (see our guide for full details)

8 – Do I need to put trickle vents in front doors?

No. Even where a front door opens directly into a habitable room, the logic is that it would have a window in it, so you wouldn’t need to provide ventilation through your door frame. Just to be clear, the same goes for bi-fold and inline sliding doors!

9 – What if it’s not practical to fit trickle vents?

This is the really important point. You’re required by Part F to do what is ‘technically feasible’. If you can’t meet the requirements you can’t – but you’ll need to be able to argue your case on inspection.

10 – What if the customer refuses to have trickle vents installed?

People have mentioned waivers or indemnity policies where customers refuse trickle vents. Don’t go there, they offer you no protection, this is a regulatory requirement, it’s not up to the consumer to decide what they do and don’t comply with.

There’s a lot more I could say (and which we do say, in our guide to Part F and Part L). If there is a single take away point remembering that the ventilation requirement is for the room, not the window, is the most important, because it stops over-specification. 

It also gives you design flexibility and the option of using trickle vents more discretely in some windows rather than others, which may make things more palatable for your customers! I hope that dispels some confusion surround Part F.

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