Provided is a multilayer thermal insulator and related method that use a non-woven core layer comprising non-meltable and flame-resistant polymeric fibers. One or more scrims are disposed on the opposing major surfaces of the non-woven core layer, and a peripheral edge of the one or more scrims is either edge sealed or capable of being edge sealed to substantially encapsulate the non-woven core layer within the one or more scrims. Optionally, a binder is provided on the scrims or non-woven core layer to facilitate edge sealing. The provided insulators are essentially dust-free and capable of passing stringent flammability standards.