Permanent Fire Load of the Building Envelope

Sammanfattning: Fire load, the total thermal energy released by the combustion of a material, is an essential part of determining a building’s fire performance and the associated fire protection strategies. Elements in a structure are typically categorized into two types of fire loads: permanent and temporary. Permanent fire loads represent the combustible materials in the building envelope. With the advent of energy efficiency, polymer-based materials with unique burning behaviors have been utilized more in the building envelope. These, and other materials that experience delamination, charring, melting, etc., can affect the way permanent fire loads are quantified. National guidelines prescribe the use of the heat of combustion (HoC), which is derived from grams of material and tested in controlled conditions through calorimetry techniques when calculating fire loads. Micro-scale tests to obtain HoC, e.g., Bomb Calorimeter and Microscale Combustion Calorimeter, indicate that the specimens do not represent large-scale behaviors and physical factors such as end-use of the material, ventilation factors, layering of materials, etc. Additionally, it has been examined that the current literature values that are derived from Bomb Calorimeter tests are deemed outdated and report underestimation or overestimation when calculating permanent fire loads. The aim of the project is two-fold: carry out a theoretical examination of how permanent fire loads are calculated per country, and; utilize traditional and alternative approaches to obtain the Hoc for building envelope materials. By utilizing an increasing-scale testing approach, theoretical (Microscale Combustion Calorimeter and Bomb Calorimeter) and realistic values (Cone Calorimeter and 1/3-scaled room corner test) for the Heat of Combustion were derived. It was determined from the experimental design that the calculated fire load from the room corner tests results in the lowest fire loads, both permanent and temporary, because it considers systemic performance and material-to-material interaction. The presence of the non-combustible materials provided means to delay the burning of the combustible linings. Further, it was seen in the scaling of the tests from micro- to final form of the samples, that the Cone Calorimeter is an attractive starting point to accurately represent permanent fire loads since materials could be tested as composites or in larger sizes vs. microscale tests.