Increases in costs of energy during the next five years will be sizable enough to force people to undertake practical efforts to increase the efficiency of their heating and cooling systems, according to William R. Nelson Jr., professor of horticulture and landscape architecture, University of Illinois.

With appropriate landscaping, insulation, storm windows, and weather stripping, it is estimated a savings of 20 to 25 percent of the energy required for heating and cooling can be achieved, he said.

Speaking before the recent convention of the American Association of Nurserymen, at Atlanta, Ga., Nelson said that until the present there has been a lack of interest in energy conservation because energy was cheap and readily available.

Trees, shrubs, vines, ground covers and truf can be used to create aesthetically pleasing yet energy conserving designs. He said. A landscape that uses the sun in winter and shades the sun in summer involves three basic principles:

1) It must be designed to accept or reject solar heat when called for.

2) It must be designed to shelter outdoor areas and the structure from winds as much as possible during cold periods, but to admit and use prevailing breezes and pleasant winds during hot periods.

3) It must be designed to provide cooling and relief from high humidity.

Deciduous trees are the major plant element to use to minimize summer radiation. After the leaves drop in the fall, the warmer rays of the sun heat the building during the colder months.

Evergreen trees, on the other hand, block the sun's radiation in all seasons. This precludes their use close to the house in areas where you wish to take advantage of solar heating during the cold months. Their chief value lies in breaking winds during the winter.

Shrubs along with trees can establish wind control plantings. Depending on how you arrange them, the wind can be blocked, channeled or deflected.

Vines can be both versatile and effective. They can provide overhead shade with proper structural support and reduce the amount of heat on building walls.

Ground covers and turf can modify solar radiation and reradiation. Land forms, surfacing materials and water features also make energy conserving landscapes.