A question about VHF/UHF antennas?

I have a dual band yaesu (144,440mhz) with 50 watts output. I was planning on installing a single antenna just for 440mhz operation (2m is going to relatively unused for my purposes) I plan to put a half wave dipole up at about 30 feet for 440mhz. I am using #16 copper antenna wire fed with 50 ohm coax (probably rg-58).....i want to shield the antenna from the elements by encasing it in 1/2 inch pvc pipe (i will feed at the center through a small hole in the pipe and cap both ends)........what i am wondering is will thus hurt my performance at all?......the radiating element will be completely encased in pvc...... i know some pvc manufacturers add metal filings to the plastic to meet strength requirements but i will be sure to get pure plastic....so hoe much would this design hurt my performance?