Approved Document O – It’s not me, it’s you

27.04.2023 2 min read

There’s something I’ve been needing to say for a while now.  It might be controversial but hopefully not enough to get me cancelled.

So here goes…

The noise criteria in Approved Document O are bobbins.

There, I said it.

The numbers chosen are effective values from BS 8233 with a relaxation of 10 dB (I understand that originally the authors weren’t going to allow any relaxation).  However, when coupled with the relatively large openings required to mitigate overheating, I’ve been finding it unfeasible to mitigate overheating naturally and without additional mechanical ventilation/cooling even in relatively quiet areas.  Approved Document O (ADO) won’t even let us allow for blinds or curtains in bedrooms to help reduce overheating. Who doesn’t have blinds or curtains in their bedroom for goodness sake?

Consequently, the criteria are adding cost and energy usage to new homes.  In my opinion, the authors were at best foolhardy and at worst reckless.

Now for the avoidance of doubt, I’m not actually saying that the noise limits selected are wrong.  They’re not that dissimilar to the values proposed in the Acoustics, Ventilation, and Overheating Residential Design Guide produced by the Association of Noise Consultants.  However, what should have happened prior to these criteria being introduced as a Building Regulation is for the feasibility of how they could be achieved in practice should have been tested and demonstrated by the authors.  To date, I’ve seen no evidence that this happened but instead, ADO was published and it was left to the industry to work things out on the authors’ behalf.

The fact that the Institute of Acoustics and ANC had to produce an interpretation of what ADO meant is just another demonstration that it’s as clear as mud.

For me, the best way forward would be for the authors to publish case studies (preferably of actual projects or alternatively hypothetical schemes) to demonstrate how their criteria can be met using naturally ventilated solutions in moderately noisy environments.  If they can’t, there should be some acknowledgement that achieving the criteria will, in most cases, require additional mechanical ventilation/cooling.

Currently, I’m conflicted between my passion for achieving good acoustic conditions inside residential properties and the potentially unsustainable energy requirements that the ADO criteria dictate.

Key Contacts

Nigel Burton Director - Noise & Vibration