Inside, keep your body off the ice or ground (the Inuit put their sleeping blankets on top of a bed of sticks and reeds) and create heat-trapping "loft" (it's what keeps you warm in a sleeping bag) by layering a few small blankets or big trash bags, with leaves or crumpled newspapers in between.
On nights when they have different bedtimes, Ms. Ellis may take an Ambien sleeping pill, which keeps her from waking up when Mr. Ellis comes to bed later.