These come pre-packaged with nails or screws at all Sutherlands Locations. Weather stripping is to be installed with the resilient part sealing out the air by pressing against the window or the door. Don't make them too tight that the window or door won't operate correctly. You may have to adjust the door to hang straight before you begin the weather stripping by adjusting the hinges and then sanding or planing the edges until the doors can open and close smoothly. You need Insulation at the location that separates any living space from unheated areas because that's where heat loss happens and also where the sun's heat comes in during the summer months.
Heat rises and therefore is lost through the roof.
The floor of an unfinished attic and the roof above a finished attic are examples of critical insulating areas. See Attic Insulation below. It's a doubled over strip of springy metal and fits between the door edge and jamb. Some others will attach to the door frame so it presses against the door when it's closed. The bottom of the door crack is usually creating the strongest leakage.