Most of us use the same duvet cover all year round, then wonder why we sweat in summer and feel cold in winter. Yet the way a fabric handles heat and moisture plays a very different role from one season to the next.
Why does linen feel so cool in summer? Linen fibre absorbs moisture quickly and releases it just as fast. It draws sweat away from your skin and gives it off to the air, and it conducts heat better than cotton, so it carries body heat away rather than holding it in. It can feel a little stiff at first, but it softens with every wash. It is a fabric that almost grows old with you over the years.
In winter we want the opposite: to keep the warmth in. Flannel is cotton whose surface has been brushed to raise it. The air trapped between those tiny fibres acts as insulation. That feeling of touching something warm, rather than a cold surface, the moment you get into bed comes from there. Switching between two sets of bedding with the seasons is often smarter than fiddling with the thermostat.