Taking Stock of Your Door
An easy way to find out if your door is letting in cold air is to stand outside the closed door on a dark night with a helper standing on the inside. Shine a flashlight all around the edges of the door and wherever your helper on the inside sees light seeping in, that's where the cold air is entering. Now, note the type of door you have. If you are using a door that is rated as an interior door instead of a proper outside door, it will be uninsulated without adequate gaskets. In those cases, it is best to just replace the door rather than try to weatherproof it. Also, if you currently only use an inner screen door in addition to the exterior door, consider installing a glass sealed storm door instead, which can reduce drafts up to 75 percent.
Alignment and Door Surfaces
Most doors will fall out of alignment over time. If you make the effort to ensure your door is straight and true before weatherproofing, this will cut down on any materials you may need to purchase. Reset the door and shim the edges to even out the gaps to make it easier to weatherstrip. Adjust the strike plates, hinges, latches, gaskets and tighten each. Consider using a door set if you have a warped door jamb or sagging door; these come in a variety of materials, colors and finishes, are easy to install and will not only stop drafts but cushion the door to prevent slamming. Fix any cracks in doors panels or around sidelight panels with wood filler or caulk.
Weatherstripping is a narrow piece of metal, vinyl, rubber, felt or foam that seals the gaps between door frames and moving parts. It is available from any hardware or home improvement store in rolls that you can buy by the foot or in kits. To determine how much you need, measure the sides of the door and add about 5 to 10 percent for waste.
There are five main types of weatherstripping. Metal spring tension seal is invisible and permanent but has to be nailed down and is difficult to install. Felt is inexpensive and easy to install but visible and the least effective at preventing airflow. Foam tape is good for blocking corners and irregular cracks but is not particularly durable. Reinforced vinyl is adjustable and comes in a variety of colors, but it is visible and may not adhere well to metal or during cold weather. Door sweeps are used on the bottoms only of the interior side of an in-swinging door or the exterior side of an out-swinging door. Sweeps are easy to install and adjustable, although they may catch on carpeting, in which case you can try a sweep which comes on a roller.
To install weatherstripping, clean the door jambs and surfaces thoroughly with an all-purpose cleaner and allow to dry thoroughly. Cut the weatherstripping to the appropriate length with scissors or tin snips, peel off the adhesive backing and tack the strips in place so that they are snug against the door. If using the metal spring tension seal, you will need to nail the stripping down. If using the foam tape, reinforce it with staples. To test gaps in weatherstripping, close the door with a dollar bill positioned across the weatherstrip. If the dollar falls out, the gap is too large, but if you cannot pull it out, the weatherstripping is doing its job by stopping air leaks.