Method for manufacturing a lightweight structural trim part consisting of the following steps: inserting a plurality of layers into a moulding tool with a first moulding half and a second moulding half, which second moulding half comprises a plurality of cup-like indentations, characterised in that the plurality of layers at least comprises: - a first air permeable skin layer of thermoplastic felt, facing the first moulding half, - a second air-tight skin layer, consisting of an outer air permeable cover of a thermoplastic felt as the outer layer and an inner airtight film, facing the second moulding half and - an air permeable film layer, between the first and second skin layer (3,4); closing the moulding tool (6, 7) and discharging gas from a first space between the film layer and the first moulding half, or charging a second space between the second mould half and the film layer with pressurized gas, in order to press the first air permeable skin layer against the first moulding half, shaping and consolidating the first air permeable skin layer, then charging with pressurized gas the said first space via the first moulding half and through the formed first air permeable skin layer and the air permeable film layer, in order to press the second skin layer (3,4) against the second moulding half, shaping and consolidating the second skin layer, meanwhile bonding the first and second skin layer to each other in the area between the cup-like indentations, in order to form a lightweight structural trim part comprising a plurality of cup-like cavities, opening the moulding tool (6, 7) and taking the lightweight structural trim part out of the moulding tool (6, 7). inserting a plurality of layers into a moulding tool with a first moulding half and a second moulding half, which second moulding half comprises a plurality of cup-like indentations, characterised in that the plurality of layers at least comprises: - a first air permeable skin layer of thermoplastic felt, facing the first moulding half, - a second air-tight skin layer, consisting of an outer air permeable cover of a thermoplastic felt as the outer layer and an inner airtight film, facing the second moulding half and - an air permeable film layer, between the first and second skin layer (3,4); - a first air permeable skin layer of thermoplastic felt, facing the first moulding half, - a second air-tight skin layer, consisting of an outer air permeable cover of a thermoplastic felt as the outer layer and an inner airtight film, facing the second moulding half and - an air permeable film layer, between the first and second skin layer (3,4); closing the moulding tool (6, 7) and discharging gas from a first space between the film layer and the first moulding half, or charging a second space between the second mould half and the film layer with pressurized gas, in order to press the first air permeable skin layer against the first moulding half, shaping and consolidating the first air permeable skin layer, then charging with pressurized gas the said first space via the first moulding half and through the formed first air permeable skin layer and the air permeable film layer, in order to press the second skin layer (3,4) against the second moulding half, shaping and consolidating the second skin layer, meanwhile bonding the first and second skin layer to each other in the area between the cup-like indentations, in order to form a lightweight structural trim part comprising a plurality of cup-like cavities, opening the moulding tool (6, 7) and taking the lightweight structural trim part out of the moulding tool (6, 7).