The ATTMA have started to release statistics from Lodgement onto the website that give an insight into how the construction industry is managing air tightness testing requirements. Most importantly, the failure rates when low design air permeability targets are attempted, which are as high as 41% when aiming for less than 2.00 m3.h.m2@50Pa. Over 110000 air tests have been recorded since Lodgement went live on 1st September 2015, with over 500 lodgements being made every single day! Lodgement data from across the UK now gives us an insight into the industry as a whole.
The ATTMA are becoming increasingly concerned with air tightness testing not marrying up with the ventilation strategy. There are two main causes for concern, System 1 ventilation (intermittent extractors with trickle ventilators) and System 4 – Mechanical Ventilation with Heat Recovery.
System 1 ventilation provides a small amount of air through trickle ventilators, usually installed into the windows, and individual extractors, typically installed into kitchens and bathrooms. System 1 ventilation does not typically provide enough airflow when very low air tightness tests are achieved. The result can be damp, mould and stagnant air that is proven to be harmful for health.
It is the opposite that happens with system 4 ventilation types. System 4 relies on a heat exchanger in order to recycle warm air from the building and move the heat from that air into fresh air to create warm, fresh (often filtered) air. In order for this to work efficiently, the building needs to be relatively air tight, ideally less than 3.00 m3.h.m2@50pa. A staggering 87% of air tests lodged as of May 2016 showed that the best practice target of less than 3.00 m3.h.m2@50Pa was achieved!
The live statistics page can be viewed at: Lodgement Statistics. These are updated monthly.