Just insulating pipes alone won't help. Insulation of anything only slows heat exchange. What I would suggest is a recirculation system. The best ones require a return pipe, but if you have walls open running a return line should not be too difficult. There are several brands on the market that work well. I use a Laing and it has worked very well for several years. You can get them with or without timers. A recirculation system give virtually instant hot water. It is wise to insulate the hot water and return line to retain as much heat as possible.