Method of manufacturing a composite filter media

A method of making a composite filter media, said method comprising:

• forming a nonwoven fabric mat comprising a plurality of synthetic bicomponent fibers by a spunbond process, the plurality of bicomponent fibers comprising a core material and a sheath material, the sheath material having a lower melting point than the core material;
• calendering the nonwoven fabric mat with heated embossing calender rolls having an embossing pattern, to melt the sheath material to bond the bicomponent fibers at contact areas of the embossing pattern the embossing pattern forming a bond area pattern in the nonwoven fabric mat having a bond area of the spunbond fibers of about 10% to about 16% of an area of the nonwoven fabric mat, said bond area pattern comprising a plurality of substantially parallel discontinuous lines of bond area to bond the synthetic fibers together to form a nonwoven fabric, the nonwoven fabric having a minimum filtration efficiency of about 50%, measured in accordance with ASHRAE 52.2-1999 test procedure;
• and
• applying a nanofiber layer by electro-blown spinning a polymer solution to form a plurality of nanofibers on at least one side of the nonwoven fabric to form the composite filter media, the composite filter media having a minimum filtration efficiency of about 75%, measured in accordance with ASHRAE 52.2-1999 test procedure.