Poor RV insulation can be dangerous during the colder months. Anything you do to warm up your RV is pointless if you can't trap heat inside.
When you don't want to heat up your entire RV, set up a small tent on top of your RV mattress. Camping tent fabric has some built-in insulation, so the interior temperature will be higher than the rest of the RV.
Even if you have a bed in the RV, try climbing into a sleeping bag before you nestle under the covers. The extra layers and insulated material make a huge difference at bedtime.
You can raise your body's core temperature by eating warm foods and beverages. Stock up on appropriate snacks and meal ingredients.
As you move throughout the day, you will inevitably sweat a bit. This isn't a big deal as long as you're moving. But sweat can quickly lower your body temperature once you lay down for the night. That's why it's always a good idea to change into a fresh, dry set of clothes before bed.
The layer that's closest to your skin should be moisture-wicking. Polyester, wool, and nylon are excellent materials for a base layer. Next, add an insulating layer that traps air and warms it up. Fleece is a popular choice, but you can also use wool for this layer.
You can lose a lot of heat through your scalp. Hats keep your head and ears nice and toasty. Keep a beanie on hand for everyday use. You might want to sleep in that beanie because you don't want to get chilly while you're asleep.
Don't be tempted to wear bulky socks and tight-fitting shoes as a way to bundle up your feet. This combination actually cuts off circulation to your feet, making them feel even colder as a result. Wear loose-fitting shoes so you can promote a bit of airflow and reduce sweat.
Electric space heaters are a great way to warm up your RV, but they won't work if you have no power. Therefore, propane burners and heaters are good alternatives. Just make sure you keep enough fuel on hand to keep them running!
If you just need a small, personal heat source, try chemical hand warmers. These small packets can be tucked into your shoes, gloves, pocket, or anywhere else you're feeling chilly. You can also heat up a water bottle. They might not stay warm forever, but the water remains at a comfortable temperature if you keep it close to your body.