I HAVE A LIGHTWEIGHT CURTAIN between the cab and the back of my van. I use it mostly for privacy, which isn’t very often, because I usually camp far from others. Sometimes I use it to block sun on hot days. And sometimes I use it to hide the contents of the van when I’m in a store. It’s better not to tempt anyone. The rest of the time it’s stuffed behind the driver seat. There are a few gaps around the sides, but it has served its original purpose well.

Why is the cab colder?

One reason the cab area gets cooler is the lack of insulation on the windows, which I could fix with panels covering the glass. That’s not too hard, but I haven’t had previous reasons to address that problem. Another reason for cooler cabs is drafts via the air vents. And if this were an older van with dry, brittle door seals, I’d have another source of drafts.

Now it’s cold

I had heard that the rear of the van would stay warmer with a curtain separating it from the front, but since I avoid cold weather I never had any cause to use my curtain that way. However, this year I’m committed to wintering at almost 6,000 feet, and although it’s still autumn, we’ve started having sub-freezing nights. So I’ve been doing the curtain thing.

Some people use heavy curtains, like packing blankets or sleeping bags. Some people have complete walls. My curtain is thin because, as I said, I originally wanted it just for privacy. I was curious to see whether that light fabric barrier could keep out cold to a noticeable degree.

Test 1

During a few cold nights I would stick my head into the cab to see if it was colder there. Yup. But I wanted something more factual than what my face and ears were telling me. I wanted data. So I put my thermometer’s outside temperature sending unit in the cab. And crawled back into bed. When I woke in the wee hours I compared the readings:

Well yeah! Eleven degrees is a significant difference. 

Test 2

Okay, now what would happen if I used a thicker curtain? For the next night I doubled up my late spring/early fall blanket and rigged it into position. I also kept the lightweight curtain in place as it had been the previous night.

According to a weather app it was 25°F in our area when I checked my thermometer at 5:17 AM. Whoo, that’s… that’s c-c-c-c0ld to me. Good thing I have a warm bed.

The front and back were only eight degrees different this time. That might have been because it was colder outside than the previous night. Still, it’s proof that separating the cab from the rest of the van helps keep the back a little warmer — and we need all the free warmth we can get.

Of course, this isn’t just a van thing. The same principle works with SUVs, minivans, cars and RVs — any rig where the driver compartment is open to the rest of the vehicle.