Changes to BS5250 call for a holistic approach to building design
In this article, our Technical Director Iain Fairnington, looks at the changes to the recently updated
code of practice BS5250 and what it means for all involved in
building design and construction.
The recent changes to BS5250 call for a new approach from designers and contractors on managing moisture in building design and construction. What is represented by these changes is the need for a holistic approach, emphasised by the renaming of the withdrawn standard “Code of Practice for Control of Condensation in Buildings” to the new “Management of Moisture in Buildings - Code of Practice.”
Regulation 7 of the Building Regulations of Approved Document B: November 2018 stipulates; “building work shall be carried out so that materials which become part of an external wall, or specified attachment, of a relevant building are of European Classification A2-s1, d0 or Class A1, classified in accordance with BS EN 13501-1:2007+A1:2009 entitled “Fire classification of construction products and building elements.”
An article on the BSI website explains the rationale for the changes as follows:
“This revision of BS5250 comes at a time when buildings are under increasing stress from moisture for two complementary reasons:
- The effects of climate change will impact directly on buildings because of increased penetration of driving rain, more frequent, deeper and longer lasting flooding and increased atmospheric humidity that slows drying rates.
- Energy conservation measures to combat climate change include reduction in ventilation, which increases internal humidity, and increased levels of thermal insulation, which makes the outer layers of the fabric colder. Energy saving retrofit of traditional buildings, which have been in equilibrium with the ambient climate for many years, can lead to significant moisture problems in the structure.”
So, what are the fundamental changes, and how do they impact designers and contractors?
From condensation control to managing moisture
The new standard recognises the impact of moisture from both an internal perspective (condensation) and external (driving rain and increased atmospheric humidity).
This change recognises a clear need to manage the balance of Heat, Air and Moisture movement throughout the building’s life cycle from design, construction, completion and use. Some companies already stress the importance of these factors under the principles of HAMM (Heat Air Moisture Movement), which emphasises the management of heat, air and moisture.