A method for manufacturing a fiber-containing element, said method comprising the steps of: providing fibers, at least some of which are first fibers, such as mineral fibers, polymer fibers, cellulose fibers, or other types of fibers, in an amount of from 3 to 98 wt % of the total weight of starting materials in the form of a collected web, providing a binder in an amount of from 1 to 30 wt % of the total weight of starting materials, subjecting the collected web of fibers to a disentanglement process, suspending the fibers in a primary air flow, mixing the binder with the fibers before, during or after the disentanglement process, providing a filler, such as a fire retardant, in an amount of 1 to 55 wt % of the total weight of starting materials, adding the filler at any suitable step of the method, such as before, during or after the disentanglement process, collecting the mixture of fibers, filler and binder and pressing and curing the mixture to provide a consolidated composite with a density of from 120 kg/m3 to 1000 kg/m3. With this method homogeneous composites can be produced.