What’s the best way to stay warm in my rooftop tent?

[OTH Overland]

Good info here. Liners are a great option, and layering know-how is key.

Avoiding sleeping bag compression is another good tip you mentioned. However, I've used a wool blanket draped over my O* sleeping bag to great effect to substantially INCREASE the overall R-value (I went from feeling quite cold to warm in fairly short order with no other changes). I've done this with my young children's bags as well to warm them up. One benefit over a liner is that you can easily add or remove all or part of it from you (while remaining in your bag) to regulate temperature. If it's large enough, you can even place half of it under your sleeping bag to improve the R-value of your insulated sleeping pad.

As a side benefit, wool maintains it's insulating properties when wet, which is a bonus. It's a very value piece of equipment to have in the cold weather kit.

We use the two person Dolomite One sleeping bag from North Face. I like that it has two top layers so you can unzip them separately and control how much insulation combined together it has a +15 degree rating and have found it to be comfortable down to around 20 degrees before Michelle digs out a wool blanket or down quilt to add to the mix. Not as much need for the extra insulation now we run a diesel heater, but nice to have knowing that one night the heater will likely cease to play nice (or when if forget to pack all the parts for it..lol)