Energy losses from inefficient entry doors can account for a significant part of your monthly utility bills. When leaky doors create drafts, people tend to set the furnace thermostat higher, which wastes even more energy.
There are ways to improve the efficiency of old doors, but don’t eliminate the possibility of installing new ones. The cost of some well-insulated steel and fiberglass doors, especially those for a back door without glass, are very reasonable. And, a pre-hung door in its own frame is not difficult to install yourself.
Before deciding, carefully inspect the old doors. If they are in very bad condition, it will be difficult to improve their efficiency by a meaningful amount. First, make sure the wood door is not rotting, and then place a long straight edge across it to see if it is badly warped.
With metal doors, the most common problem is rust, not warping. Check along the bottom by the weather stripping on either side. Rainwater tends to collect there, and it is not always painted well. Try to determine why the water is collecting. If you find small holes rusted through, they can be repaired with car body filler and then painted.
If the doors are reasonably sound, check for the location of air leaks. At night, have someone shine a flashlight from outdoors around the seals while you check for light coming indoors. This will highlight significant leaks. On a windy day, move a stick of lighted incense around the seals and watch the smoke trail to locate minor leaky areas. Check the astragal (a half-round overlap that acts as a seal) between double doors.
Often with wood doors, especially ones with compression weather stripping, the main problem is simply the latch plate is not holding the door tightly closed against the weather stripping. One solution is to reposition the latch plate, which requires filling in the old screw holes and drilling new ones. Chisel away some of the wood in the latch plate recess. Or, install an adjustable latch plate that you can reposition for summer and winter as the door and frame expand and contract from temperature and humidity.
Steel doors should feature magnetic weather stripping, so this is not a major issue because the stripping is drawn against the door edge. Just make sure the door surface and the weather stripping are clean and smooth. Paint on the door edge can also come loose and create gaps that leak air.
Also check the condition of door hinges, and replace them if needed. If the hinges and pins are worn, the door will not hang square in the opening and not seal properly. There are many different hinge sizes, so take an old one with to the store for an exact match. Don’t just buy the cheapest ones, because there are many to choose from and quality varies.
It is almost certain the door seal on the bottom is worn, but if not, adjust the floor threshold higher. There are several height adjustment screws across the threshold, but they may be filled in with dirt, so poke around to find them. If the seal itself is bad, there are many generic replacement seals you can install.
Another option is an add-on retractable threshold seal, which is effective if carpeting is near the door. This seal is mounted on the inside surface of the lower door edge and is easy to adjust and install. When the door opens, a pin against the door frame is released and the seal automatically lifts to clear the carpeting.
Companies offering door improvement products include Duck Brand, 800-321-0253, duckbrand.com; M-D Building Products, 800-654-8454, mdteam.com; Pemko Manufacturing, 800-283-9988, pemko.com, and Thermwell, 800-526-5265, frostking.com. Also visit dulley.com for more information.