I don't know where "here" is, but I hope you are not under the NEC, because if you are, unless you have a SPECIFIC amendment, it IS quite illegal. ARTICLE 394 Concealed Knob-and-Tube Wiring 394.12 Uses Not Permitted Concealed knob-and-tube wiring shall not be used in the following: (1) Commercial garages (2) Theaters and similar locations (3) Motion picture studios (4) Hazardous (classified) locations (5) Hollow spaces of walls, ceilings, and attics where such spaces are insulated by loose, rolled, or foamed-in-place insulating material that envelops the conductors