Complex sentence: Originally, headboards were made of wood, which is less conductive than stone or brick, and constructed to allow space from the wall (via thicker end pillars) to allow falling colder air to sink to the floor rather than onto the bed.
Split into simpler sentences: Originally, headboards were made of wood, which is less conductive than stone or brick. Constructed to allow space from the wall (via thicker end pillars) they allowed falling colder air to sink to the floor rather than onto the bed.