"Seasonal" registers

Factual Questions
1

New house has forced air heat/air. Over the weekend we prepped the 3 bedrooms upstairs for painting walls/ceilings and refinishing floors. In the process we reomoved the registers along the baseboards, as well as one high on the wall in each room.

Now my understanding is that the wall register is to be opened/ closed during the summer/winter (I always forget which). Which way is it?

Also, we were surprised when we pulled the wall registers - they are not attached to any ductwork. Instead, when you remove the vent, you simply see the inside of the wall. Is this normal?

BTW - sure is sweet to be able to paint ceilings white when you know the floors are going to be refinished, the walls painted, and the trim redone. Sure makes the job easier! :cool:

2

What happens when you turn the blower on? The wall registers could be the returns going back to the furnace. Or the ones on the floor could be. Shoot, I can imagine the higher registers being the returns when the A/C is on, and the lower registers being the returns when the heat is on.

My old house has radiators. I like the heat more than forced air, but we don’t have central air, which would be nice a few weeks every summer.