We have had our hybrid nearly 14 years and camp almost year round. Winter camping is always a great time. We have camped in below freezing temps many many times. Our aproach to keeping warm is somewhat unique. We use popup gizmo bunk covers though a tarp is comprable. What we use is electric or propane heaters while running an electric water collecting dehumidifier. This circulates and dries ALL condensation from the air and keeps us warm even in the bunks. Yes, the bunks may run ten degree's cooler. We keep the trailer interior around 70+. We have collected two to three gallons of water in twelve yours during super cold temps. Works well for us. We even dry cloth's in the bathroom over night