Q. My old noisy refrigerator is on its last legs. I want a new super-efficient CFC-free model with more convenience features. What is the best type to buy and how much electricity will a new one save? — R.T.

A. After your furnace, air conditioner and water heater, an old refrigerator is the largest energy consumer in a home. Installing a new one will cut the electricity costs and noise in half and provide many new convenience features.

Some of the most efficient new full-sized family models cost less than $50 per year to operate. This is due primarily to improved insulation, seals, compressors and controls. These improvements also greatly reduce noise.

Many of the new convenience features also end up saving electricity. For example, a door-within-a-door model includes an another small door for frequently used items like drinks or snacks. Using this small door reduces the number of energy-quzzling times that the large main door is opened.

Convenient slide-out sealed shelves are also an electricity saver. These reduce the length of time that the door has to be opened to find and get items. If there is a spill, it can be cleaned up much faster.

Optional storage/serving dishes also save energy. Specially-sized dishes slip into designated slots inside the refrigerator. A meal can be prepared early and stored in the dishes. Just slide a dish out and pop it in the microwave. Serve the food in the dish and then put it in the dishwasher.

If your family uses a lot of cold drinks and ice, a through-the-door beverage station is ideal. It reduces the frequency of the door being opened. If you do not drink many cold beverages, then avoid this. It is an expensive option, takes up space and reduces efficiency unless used often.

Several top-of-the-line models use two separate compressors — one for the refrigerator and one for the freezer. This provides precise temperature control of both sections for more efficiency and better food preservation.

A design with the compressor and vent on the top of the unit is efficient and convenient. Since heated air naturally rises, it makes engineering sense not to locate it under the refrigerator. This design is more common in expensive built-in models.

Although you may still be able to buy freon-type models, new CFC-free designs are best. There are no CFC gases (ozone destroying chemicals) in the compressor system or used to make the wall insulation. These will also be less expensive to repair in the future when freon becomes more scarce.

Write for Update Bulletin 535 showing a buyer’s guide of the 15 most efficient refrigerator/freezers listing annual operating costs, sizes, convenience and design features and refrigerator efficiency tips. Please include $2 and business-size SASE. Send to James Dulley, 6906 Royalgreen Drive, Cincinnati, Ohio 45244. To rush bulletin delivery or read all previous columns — http://www.dulley.com.

Q. I have a greenhouse/porch attached to the back of my house. The roof leaks in a hard rain. My budget is limited. How can I permanently fix it myself without special tools or equipment? — G.H.

A. Greenhouse roofs take a terrible beating from the weather. They are usually exposed to the full sun, have little pitch and the humidity level inside, which reaches the roof, continually changes.

Installing a flexible mobile home “roofover” is one of the easiest ways to fix it yourself. You can buy the tough flexible skin and trim at a mobile home repair shop. Choose a light color to reduce overheating in the summer.