Why are two thick cotton sheets warmer than one single blanket?

Two thick cotton sheets can be warmer than a single blanket due to the air trapped between the layers, which provides insulation. This trapped air acts as a barrier to heat loss, helping to retain body warmth. Additionally, the overlapping fabrics can create a denser layer that reduces drafts and increases overall warmth. The combined thickness also enhances comfort, contributing to a cozier sleeping experience.