I just became a new home owner. This home was build in 1956. In my walk up attic there's a vent on the floor. A frame with 1/2" mess covers the top of this vent (maybe to keep thing from falling in). Inside the frame is this tube about 8"dia. it has a flap on top, this tube sits in the floor of the attic. Can someone tell me what this is and the purpose of it?

Greetings and WELCOME to the site, SimpleTech! I just moved your question from the Introductions section of the site to Other Home & Garden so that your question will get more exposure. The Introductions section is for introductions only and not questions. That vent in your attic could be the vent for a fan in your bathroom. Hopefully, some others might have some ideas also.

Please do take some time to introduce yourself in that section also. We are glad that you have chosen to use this site!

I had suggested moving it heating and cooling.

Just what is under it? It could be a combustion air intake for the furnace.