A method of manufacturing an insulation mat from a raw material comprising grass plants, characterized in that: i. the raw material grass is mowed in the field, ii. the mowed grass is withered in the field meaning to pre-dry the grass to a dry substance content of 25-40%, iii. the raw material is being collected and pressed in a silo under the exclusion of air, iv. the raw material is removed from the silo, being loosened and moved to a metering device, v. the device moves the raw material into one or more hammer mills, where it is ripped apart 3 and reduced into parts of an approx. 10-30 mm in length and 1-3 mm in thickness, vi. by adding water to the de-fibered plant matter, a raw material suspension, which can be stirred or pumped, is manufactured, vii. the raw material suspension is moved to a mechanical de-fibering, viii. the fibers are withdrawn from the suspension, ix. then, the fibers are being mechanically drained, to obtain a first intermediate product made of moist, natural grass fibers which have a dry substance component of 30% to 50%, preferably nearly 40%, x. and a second intermediate product is obtained from a first intermediate product by implementing the following steps: • pre-drying of the grass fibers to a dry substance content of 60-85% of the total weight of the fibers or drying up to a dry substance content greater than 85 %, of the total weight of the fibers, • adding of binding fibers up to a content by weight of 4-25%, preferably 5-15% of the product's weight, • spraying of the additives. i. the raw material grass is mowed in the field, ii. the mowed grass is withered in the field meaning to pre-dry the grass to a dry substance content of 25-40%, iii. the raw material is being collected and pressed in a silo under the exclusion of air, iv. the raw material is removed from the silo, being loosened and moved to a metering device, v. the device moves the raw material into one or more hammer mills, where it is ripped apart 3 and reduced into parts of an approx. 10-30 mm in length and 1-3 mm in thickness, vi. by adding water to the de-fibered plant matter, a raw material suspension, which can be stirred or pumped, is manufactured, vii. the raw material suspension is moved to a mechanical de-fibering, viii. the fibers are withdrawn from the suspension, ix. then, the fibers are being mechanically drained, to obtain a first intermediate product made of moist, natural grass fibers which have a dry substance component of 30% to 50%, preferably nearly 40%, x. and a second intermediate product is obtained from a first intermediate product by implementing the following steps: • pre-drying of the grass fibers to a dry substance content of 60-85% of the total weight of the fibers or drying up to a dry substance content greater than 85 %, of the total weight of the fibers, • adding of binding fibers up to a content by weight of 4-25%, preferably 5-15% of the product's weight, • spraying of the additives. • pre-drying of the grass fibers to a dry substance content of 60-85% of the total weight of the fibers or drying up to a dry substance content greater than 85 %, of the total weight of the fibers, • adding of binding fibers up to a content by weight of 4-25%, preferably 5-15% of the product's weight, • spraying of the additives.