Steel back with glass

Good afternoon all,

I am currently renovating my brownstone and opening up the back. I want to do steel with glass however I have heard that it’s not the most ideal when it comes to insulation and during winter time (cold draft ). Has anyone went the steel route and if so I would love to hear some feedback. I am currently installing central air/heat and there will vents coming from the floor right infront of the steel/glass back. To help counter act any cold drag . Will that help ? Other option will be to go with aluminum which I’m not the biggest fan of since I’m limited in a certain design that I want to go with. But if steel is not ldeal , I’d go with aluminum. Any input is greatly appreciated.

Sal