There’s a growing acceptance in the construction industry that breathability is a very important issue. All right thinking men and women now consider that it is vital that we are aware of the issue and that we manage it effectively. Unfortunately, that’s about as good as it gets for the majority of the industry.
The common perception is that breathability refers to the ability of air to move through the structure of a building. WRONG ! Its a whole different issue. I stumbled across a remarkable individual called Neil May when researching this blog post. This guy really has it nailed. Its worth placing the first two paragraphs of his respected paper – Breathability: The Key to Building Performance – so that we can begin to understand what its all about:
Breathability in buildings is not really about air . It is about water: water as a gas and water as a liquid; water inside the building, water outside the building, and water in the walls, floors and roofs themselves (though not about water in pipes!). It is not only about how water moves through structures (water vapour permeability), but also about the ability of materials to absorb and release water as vapour (hygroscopicity) and about the ability of materials to absorb and release water as liquid (capillarity). Water affects everything in building from the health or decay of building fabric, through to the thermal performance of the building and to the health of occupants. Particularly as we try to increase the airtightness, thermal performance and indoor air quality of our buildings, breathability has become a critical issue, affecting all areas both of new build and of renovation.
Our strategy for dealing with water in the air and in the fabric is therefore central to the success or failure of the building as a structure that endures, performs, nurtures and protects – ie the main functions of buildings. If we do not have a strategy, or if we are reliant on unconnected, bolt on solutions to a variety of different problems, then the health of that building will be at risk. Buildings, like people, need to be healthy in themselves, reliant on their own material structures with plenty of excess resource and robustness, rather than dependent on fragile stick on plasters, applied chemicals and mechanical breathing apparatus. Healthy, durable, working buildings can only be brought about by designing with a full understanding of breathability, which is the key to assessing whether or not a building design and construction is successful or not.
OK, still with me ? Unfortunately, this is quite an extensive subject and not possible to cover in a simple blog. For those of you who really want to dig deep I would suggest that Neil May’s paper is an excellent start. This paper is now 11 years old but many of the issues raised are as relevant in today’s construction industry as it was back then.
My main aim in articles such as this is to improve awareness of issues that need to be understood and managed in modern construction build-ups. While the science of breathability may be complex the solutions needed are invariably simple. This is especially the case if one chooses to build with natural materials.