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Last edited 31 Jan 2021
Fire insulation in buildings
Fire occurs as a result of a series of very rapid chemical reactions between a fuel and oxygen that releases heat and light. For combustion to occur, oxygen, heat and a fuel source must all be present; this is the ‘fire triangle’. Flames are the visible manifestation of combustion.
Fire insulation (or more usually fire-rated or fire-resistant insulation) is a term that covers insulation materials which have insulative properties but are also non-combustible or have limited combustibility. As passive fire protection elements, they do not need to be activated to provide fire resistance and hence can help prevent the spread of flame between spaces and components within and between buildings.
A typical example is stone wool insulation which can be non-combustible. Other types of insulation that may provide fire resistance include mineral wool, fibreglass and cellulose-based wool insulation. Sheep’s wool is regarded as a sustainable insulation solution but must first be treated to make it more fire resistant. Some of these products are available in blankets (supplied in rolls) and/or rigid slabs.
- Floors and ceilings;
- On structural steel;
- Cavity barriers and firestopping;
- HVAC applications.
 Regulations and standards
Part B of the Building Regulations sets out the fire performance requirements of buildings. For a fire-rated insulation to be used in a building it must pass certain British Standard (BS) tests: products are classified according to how they perform in the tests, enabling specifiers and contractors to choose the best fire-rated insulation for a given application. The tests are:
- BS 476-1: Fire tests on building materials and structures, and
- BS EN 13501-1:2018: Fire classification of construction products and building elements (Classification using test data from reaction to fire tests). This has become the construction industry’s main ‘go to’ standard for fire insulation. It provides the reaction to fire classification procedure for all construction products, including products incorporated within building elements with the exception of power, control and communication cables which are covered by EN 13501-6. Products are considered in relation to their end-use application.
- Combustibility (divided into seven classifications from A1 (non-combustible), A2 (limited combustibility) right through to F (easily flammable);
- Smoke emission during combustion (s1 (highest), s2 or s3 (lowest)), and
- The level of production of flaming droplets/particles during combustion (d0 (highest), d1 or d2 (lowest)).
The 2017 Grenfell Tower Fire is thought to have been exacerbated by ACM cladding which incorporated a Celotex RS5000 PIR insulation. As a result, In December 2018 changes to approved document 7 came into force banning combustible materials in the cladding for buildings over 18m in height.
For more infomation see: Grenfell Tower fire.
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