The cold, cold ground

I notice my van seems to be a lot colder this winter, so far, than last winter. In particular, the floor of my van, which is pretty well insulated with a laminate flooring, foam underlayment, and PE film, is freezing cold, and I don't remember my feet being so freezing last year. Actually, I remember it being quite comfortable last year. What is going on?

Oh. Yeah. I forgot. My floor vent. I didn't have one last year. I put one in over the summer. So, this year, I do, and I'm in the habit of leaving it open. So freezing cold air from the ground is coming up and chilling my floor down, hard core.

I've been meaning to put in another vent from the cab, one that will take in warm air that has been solar heated by the windsheild and side windows. The cab is a lot warmer than the box, summer and winter. It's nice to be able too isolate the air in summer, but in winter I'd rather be letting solar-heated air from the cab come in to the van, than freezing cold air from the floor, at least during the day (I guess at night it doesn't matter).

I have a vent. I just need to find a place to put it.

UPDATE: I figured out a temporary solution that works well. I close the ceiling vent, and leave the floor vent open. Warm air comes up (when available) through the floor vent, but doesn't vent out the top. Cold air vents out the floor vent. It's not warm in here, but at least it's warmer than the outside ambient air, so that's an improvement.