A unitary, pre-insulated pipe clamp/hanger has a conventional C-channel section clamp/hanger-receiving body portion 1 with a pipe receiving mouth 2, a fastening nail receiving mounting portion 3 integrally formed along the exterior of one wall with the nail penetration direction extending in an opposite direction to a pipe insertion/receiving direction of the mouth, A lining strip of thermally insulating, closed cell, polyethylene foam 4 is adhered to line the entire interior of the channel with respective foam end portions 5,5′ thereof protruding from the channel across the pipe-receiving mouth. One end portion 5′ is longer than the other end portion 5, forming a mouth closing, flap. The resulting assembly has an R-value of at least 5. The adhesion can be by double-sided adhesive tape attached between the clamp channel portion and the foam. respectively.