Kathy b, welcome to iRV2.com. We are glad to have you join us here. As exrench has stated glass itself is a very poor insulator. If you can move the glass up and down, you may need to replace the felt seal. There is also a seal for the glass to glass slider. Good luck and keep us posted. Enjoy the website.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7