warm air blowing through vent on cold day with hvac off

[elin]

I've noticed that on cold days that my car automatically blows warm/hot air through the vents into the cabin even when I don't have the AC toggled on. It's very noticeable when I first get into the car. Has anyone else noticed this?

I figure something is turning on to heat the batteries, but is that warm air also supposed to be flowing into the cabin? Just wondering if this is a common occurrence or if I need to get this looked at. Thanks in advance.

And just to clarify, I do have the fan on, I just do not have AC on.