Back Of The Napkin

of the
biggest consumers of energy in homes and buildings, which are heating

napkin
A napkin, or face towel (also in Canada, the United Kingdom, Australia and South Africa: serviette) is a rectangle of cloth or tissue paper used at the table for wiping the mouth while eating. It is usually small and folded.
a small piece of table linen that is used to wipe the mouth and to cover the lap in order to protect clothing
A square piece of cloth or paper used at a meal to wipe the fingers or lips and to protect garments, or to serve food on
diaper: garment consisting of a folded cloth drawn up between the legs and fastened at the waist; worn by infants to catch excrement
A baby's diaper

back
At a distance away
the posterior part of a human (or animal) body from the neck to the end of the spine; "his back was nicely tanned"
Toward the rear; in the opposite direction from the one that one is facing or traveling
in or to or toward a former location; "she went back to her parents' house"
back(a): related to or located at the back; "the back yard"; "the back entrance"
Expressing movement of the body into a reclining position