Linen sheets feel colder than polyester blankets primarily due to their lower insulation properties, as linen does not trap air effectively, allowing heat to escape from the body. In contrast, polyester blankets, being thicker and better at trapping air, reduce heat loss and feel warmer upon contact. The sensation of coldness from linen can also be compared to touching metal versus plastic, where metal conducts heat away faster. While polyester is a synthetic plastic, it is not the heat retention that makes it feel warm, but rather its ability to slow down heat loss. Overall, the difference in thermal transfer and air permeability explains why linen feels colder than polyester.