In case of fire: Exterior Insulation Finishing Systems in Ontario
Some types of buildings, especially public buildings such as hospitals, schools or corporate offices, require more fire proofing than normal within the building envelope. Exterior Insulating Finishing Systems do not offer additional fire proofing, however extensive testing has proven that EIFS does not detract whatsoever from the fire proofing of a preexisting wall that already meets necessary fire codes. In short, the fire resistance that is required by local building codes must be met by the supporting wall, and applying EIFS will not reduce the abilities of any fire proofing that is already in place.
However, the combustible properties of expanded polystyrene foam (EPS), the foam insulation most commonly used in EIFS, remain. The EPS used in EIFS is what primarily provides fire with a fuel source. The base coat may or may not be considered a secondary fuel source as base coats can be either combustible or non-combustible, for example: Portland cement-based adhesives are less combustible than thin, non-cementitious base coats.
EIFS factors that affect the rate at which fire spreads
The risk of fire spreading through the EIFS when it originates from the interior of a building is small, mostly because of the many layers of drywall and drywall substrates it must first burn through before it reaches the insulating foam. The main dangers fire proposes for EIFS walls comes from the exterior – fires on the outside of the building or emanating from windows, doorways and other openings, where the EPS is only separated from the flames by the finish and base coat.
The ease of fire spreading from one floor to another is one of the large safety issues facing taller buildings with EIFS. Installing the EIFS in a manner so that it ends at each floor and begins on the next, by incorporate an expansion joint between floors, can prevent the fire from spreading from floor to floor through the EIFS.
Incorporating noncombustible materials within the EIFS foam at each floor line is a possibility, although difficult, and can be something to be discussed with builders and designers.
Modifying EIFS and installation methods that mitigate fire concerns
Using thinner foam may provide less fuel for potential fires, but will lessen the overall insulating properties of the EIFS.
There are many other ways to further modify the EIFS to enhance its fire-resistance.
Sealing or edge back wrap
Windows and doors are locations where the fire poses a significant danger because of the possibility it may touch and spread through the foam insulation when fire breaches these openings in the building and makes it through to the exterior. While the reinforcing fiberglass mesh – especially that of a higher grade – can withstand the heat, sealing the EIFS by employing back wrap on the edges can prevent the fire from reaching the combustible core of the material too quickly. If EIFS is used as a large overhang, soffit or ceiling where a window might be in close proximity, the need for this back wrap is significantly amplified because the overhanging can collapse if the foam melts.
Expanded polystyrene foam insulation has a relatively low melting point, and once the fire reaches the core of the EIFS, the EPS will liquify and can travel with ease. Applying back wrap to prevent the fire from reaching the foam, which can either result in the liquid foam further surging beyond the other EIFS layers causing the fire to spread or falling off of the substrate completely, will prevent the foam from liquifying.
It is also recommended to keep EIFS away from notable external sources of heat, such as lights and exhausts, due to this lower melting point.
Choice of substrate
A gypsum-based sheathing is more fire resistant than wood sheathings, but materials like concrete offer much more fire-resistance as a non-combustible substrate.
Installing EIFS indoors
EIFS lamina is generally much too thin to offer the adequate fire protection that is required on inside walls by most building codes. Therefore, it is not recommended for inside installation.
Interesting to note: Combustible materials provide fire with fuel to burn. Non-combustible materials do not. According to ING Canada, Canadian insurers classify EIFS as both combustible and non-combustible for commercial building rating purposes. Oddly enough, non-combustible forms of insulation are commonly used in Europe, where they are less needed because EIFS is typically installed on solid masonry walls and must meet must stricter fire codes.
Even though the foam plastic insulation and coatings used in EIFS can be classified as combustible, EIFS can still be used on buildings that require specific fire prevention codes to be followed and can be modified to further protect against fire-related problems.