My builder is about to proceed with building my home.They are not an energy star builder;however,many of the techniques are in line with enery star.(ie low e windows,vapor barrieron interior walls,foam at baseplates and electrical outlets,Honeywell programmable thermostats,zoned ac,thermal sheating over exterior walls,two 50 gallon water heaters)There is a major no show-12 seer air conditoning.12 seer would cost an additonal 2800 dollars. I live in the Dallas-Ft. Worth metroplex .It is not uncommon to have a 300-450 dollar electric bill during the hot summer months.(May-September).Radient barrier would cost an additional 2450.Should I upgrade at these prices? If so, which one of would you purchase over the other? Cool ply(tech shield) or the 12 seer. I can only pay for one!I do not want to finance either if they will not help.