QUESTION: My front door is wood with a window and the back door is metal. They are the original ones and neither is very efficient nor airtight. I cannot afford new ones. How can I improve their efficiency myself?

ANSWER: Energy losses from inefficient entry doors can account for a significant portion of your monthly utility bills. What makes things worse is that leaky doors can create drafts in your house. When this happens, people tend to set their furnace thermostat higher and this wastes even more energy.

There are ways to improve the efficiency of old doors, but don’t eliminate the possibility of installing a new one. Prices for some well-insulated steel and fiberglass doors, especially one for the back door without glass, are very reasonable. A pre-hung one is not difficult to install yourself.

Before you make a decision on what to do, inspect your old doors.

First, make sure the wood door is not rotting and it is not badly warped. Use a long straight edge to check this.

The most common problem with metal doors is rust, not warping. The first place to check is along the bottom by the weatherstripping on either side. Rainwater tends to collect there and it is not always painted well. Minor holes can be repaired with car body filler.

If the doors are reasonably sound, check for the location of the air leaks. At night, have someone shine a flashlight from outdoors around the seals and check for light indoors. On a windy day, move a stick of lighted incense around the seals and watch the trail of the smoke.

Often with wood doors, the majority of the problem is simply the latch plate is not holding the door tightly closed against the weatherstripping. Hold the door tightly closed and check for air leaks again. The steel door should have magnetic weatherstripping.

One solution is to reposition the latch plate. This will require filling in the old screw holes and drilling new ones. Chisel away some of the wood in the recess for the latch plate.

Another option is to install an adjustable latch plate.

Check the condition of the hinges and replace them if necessary. If the hinges and pins get worn, the door will not hang square in the opening, and therefore will not seal well.

It is almost certain the seal on the bottom of the doors against the floor threshold is worn. If it is not torn, adjust the floor threshold higher. There are generic replacement seals you can install. An add-on retractable threshold seal works well.

The following companies offer door improvement products: Duck Brand, 800-321-0253, www.duckbrand.com; M-D Building Products, 800-654-8454, www.mdteam.com; Pemko Manufacturing, 800-283-9988, www.pemko.com; and Thermwell, 800-526-5265, www.frostking.com.

Send inquiries to James Dulley, Butler Eagle, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.

James Dulley has a degree in mechanical engineering. His monthly column appears in more than 300 publications.