Very often the wire available for an antenna will be wire intended for home electrical systems. This will is usually insulated which raises the question "should we strip off the insulation?" I took a very general look at this question using both experimental measurements and CAD modeling. Here are my observations: Download Insulated Wire and Antennas .
In addition to the base article there are several referenced articles which give additional information:
Download Qex-ground-systems-part-2
Download QEX Nov-Dec 2k antenna wire conductors