Dear Jim: I have a slow-moving cat and a hyperactive dog. Holding the door open for them allows a lot of hot humid air in, not to mention mosquitoes and flies. Would a pet door kit be an effective energy saver? – Clay W.

Dear Clay: Holding a door open for a pet, until it finally makes up its mind, increases the load on your air conditioner in the summer or your furnace in the winter. Summertime is particularly bad because the humidity that comes in may force you to set the thermostat lower for comfort.

Installing a pet door kit can be not only a significant energy saver, but a time saver too. There is a huge array of kit sizes, styles and features available to meet almost any pet’s size and habits. They all have locks of some sort to provide control over your pet and security from break-ins.

One of the most convenient pet door kit designs has four-way door settings with a magnetic sensor. I use one of these in my own sunroom. A tiny magnet, about 1/2-inch cube, slips over your pet’s collar. A sensor in the door opens only when it senses the magnet, so no other animals can get in.

In addition to the magnet sensor, the typical four-way lock settings are: “in-only,” “out-only,” “locked” or “both ways.” If your pet does not wear a collar, it will take only about one minute to remove the magnetic sensor-lock so the magnet is not required for your pet to pass through.

Sliding glass door-mounted pet doors are becoming increasingly popular. The tall panel, with a pet door in the bottom, fits into the sliding glass door track. It has security locks that are often better than the original ones on the door. The most efficient ones use double-pane thermal glass.

If you prefer not to disturb your existing sliding glass door, the same type of panel is made of screen and fits into the screen track. Smaller horizontal pet door-screen panels are available for double-hung windows.

Since cats tend to jump up on windowsills, consider installing a pet door kit through a window screen. These pet doors have two halves that snap together over the screen. Once you cut the hole through the screen, tap the halves together to lock them in place. It handles pets up to 30 pounds.

Most pet door frames are made of tough plastic or anodized aluminum. The aluminum ones, some with carpeted tunnels, are more attractive, but also more expensive.

It is important to size the pet door properly so that your pet will use it and that it is strong enough to support your pet. For example, a 5×7-inch door will handle cats up to 15 pounds and dogs up to 7 pounds. An 8×11-inch door will accommodate all cats and dogs up to 40 pounds.

Write for (instantly download – www.dulley.com) Update Bulletin No. 593 – buyer’s guide of 10 automatic pet door manufacturers listing features, prices, door sizing-pet chart and instructions for building a do-it-yourself insulated pet door. Include $3. and a business-size SASE. Send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244.