Q - I want to plant some trees in my yard to reduce my utility bills and improve the resale value of my house. Is it worthwhile planting trees to save energy? Where and what types should I plant? S.T.

A - Energy-efficient landscaping, including proper selection and placement of trees, can lower your heating and cooling costs as much as 20 percent. In the summer, one large tree can absorb as much heat in a single day as running several window air conditioners and can lower air temperature by 10 degrees.Global warming (greenhouse effect) can also be reduced. The trees themselves consume carbon dioxide and produce oxygen. By reducing the need for air-conditioning, less carbon dioxide is emitted from electric generating facilities.

The goal of tree planting is to block the winter winds and summer sun, while letting the winter sun and summer breezes through. In general, this includes planting deciduous trees (ones that lose their leaves) on the east and west sides of your house and evergreens to the north.

When selecting trees, it is very important to consider the height and shape of the tree as it matures. This allows you to determine how many to plant and how far to locate them from the house to get adequate shading. The growth rate and hardiness (the coldest winter temperature it can survive) are also selection considerations.

Even deciduous trees, planted directly to the south, are not extremely effective for summer shading. The summer sun is very high in the southern sky it shines over the tree to your house. Also, the branch patterns of some trees is very dense and can block as much as 60 percent of the winter sun's heat even after the leaves have fallen.

The proper location to plant the trees depends on your type of climate. In cold climates, the main objective is blocking winter winds and collecting solar heat. A dense row of evergreen trees to the northwest and west are effective.

The goal in temperate climates is to block the winter wind and capture the winter sun plus to block the summer sun and channel in the summer breezes. A large row of evergreen trees from northeast to northwest is effective.

Low deciduous trees to the east and west block the morning and afternoon sun in the summer. A semi-circular row of deciduous trees from southeast to southwest, with a break to the south to funnel in summer breezes.

You can write to me for UTILITY BILLS UPDATE No. 268 listing 100 trees, their heights at maturity, shapes for shading, growth rates, and hardiness zones of the country where they will grow, and sample landscape layouts for the various climate zones in the U.S. Write to James Dulley, The Deseret News, 6906 Royal Green Dr., Cincinnati, Ohio 45244. Please include $1.00 and self-addressed STAMPED BUSINESS-SIZED envelope.

Q - Is it worthwhile to put insulation on the hot water pipes leading from the water heater? Whenever I turn on the hot water faucet, it takes a long while to get hot water. L.O.

A - Whether or not it helps to add hot water pipe insulation depends somewhat on your hot water usage patterns. If your family turns the hot water on and off often at various periods of the day, then the insulation will help.

However, if the hot water is only used occasionally by a couple of people, it won't help much. With or without the insulation, the hot water in the pipes will have time to cool off before the next use.