We've had condensation near the doors, bike door, front of the trailer (behind bunks), and under the rear slide mattress during cold weather. We often camp where it's cold; I know this is to be expected, but would appreciate some tips. It hasn't been a problem for us, we store the trailer indoors and it dries out well, but I'm worried about mildew later on. We keep the heat on and partially open at least one vent while sleeping, which helps. We prop up the rear mattress during the day to dry any moisture under it and along the bottom of the rear slide walls. I'm thinking of installing rigid foam insulation under and around the rear slide mattress, and maybe some removable insulation on the interior of the bike door. A small portable heater works well, but isn't practical without hook-ups. We often camp where it's cold.