Your woollens are pervious to the cold air.
"Travels in the Great Desert of Sahara, in the Years of 1845 and 1846"
James Richardson
One of the large windows facing toward the farmyard had been permanently closed, and in the wide embrasure was placed a portion of Mr. Saul's library-books which he had brought with him from college; and on the ground under this closed window were arranged the others, making a long row, which stretched from the bed to the dressing-table, very pervious, I fear, to the attacks of mice.
"The Claverings"
Anthony Trollope
One reason for this is, that clay-rocks are much less pervious than sandstone, and their imbedded fossils have consequently escaped in greater measure the solvent powers of percolating water.
"Geology"
James Geikie