One of the most common questions we get about wool insulation is what about fire resistance? It’s a crucial factor when considering any building material, especially insulation which sits inside your wall cavities. Not only does common sense dictate that your insulation resist fire but it is also part of building code. In this blog, we’ll dive into our testing process and why wool is fire resistant.

If it’s not E84 rated, then it’s not home insulation

We put our wool through the ASTM E84 test which is the industry standard for assessing the surface burning characteristics of building products. The purpose of this test is to observe the flame spread and determine the relative burning behavior of a material. Through the E84 test, both Flame Spread Index (FSI) and Smoke Developed Index (SDI) are reported. FSI is the measurement for the speed at which flames progress across the interior surface of a building, while SDI measures the amount of smoke a sample emits as it burns. Here is a video showing the test in action, pretty cool stuff.

Havelock Wool conforms to Class A of the ASTM E84 test

There is no pass or fail for the E84 test. Rather, materials get a relative rating and certain codes and regulations define required FSI and SDI values. If a material doesn’t meet code directives, then you may not be able to use it. With a Class A rating for both FSI and SDI, Havelock Wool conforms to strict building code measures. 

How does wool resist fire?… and not support a flame below 1,100 Fahrenheit?

Its interior composition explains why wool is fire resistant and its ability to self extinguish. Wool has high nitrogen and water content so it needs higher levels of oxygen to burn than the surrounding environment provides. In addition, wool’s cross-linked cell membrane structure will swell when heated to the point of combustion, forming an insulating layer that prevents the flame spread. This also means that wool produces less smoke and gas than synthetic fibers and synthetic insulation. To see wool’s fire resistance in action, check out this video from the BBC

This characteristic of wool is one of the reasons it is used across all types of applications where fire resistance is important. It’s an ideal fiber for interiors such as carpets, curtains, upholstery and bedding, helping to reduce the risk of fire spreading within a house. Wool textiles are also used widely in personal protective equipment (PPE) to protect fire and military personnel. The fact that wool only smolders and doesn’t melt or drip onto skin, is itself a lifesaver.

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