Let the Sun Shine In

By Ralph Rossen
Director of Parks

The old saying "necessity is the mother of invention" has been proven true once again. In this instance the "necessity" for the Decatur Park District was the removal of their small deteriorating greenhouse from airport property in order that a new maintenance shop could be constructed. The "invention" was the creation of an actively solar heated 1,500 sq. foot double wing greenhouse complete with a 1,200 sq. foot headhouse and root cellar.

The completion of the greenhouse is a result of nine months of planning, engineering, and construction by the Park District personnel. It is a fine addition to the District's many other facilities that have been created and built by its maintenance staff.

The south side of each wing is angled at 60° and has 832 sq. feet of double thick 3/16" tempered safety glass that is separated by a 3/4" rubber gasket. The sun's rays enter from the south side striking the north wall and are reflected into six black aluminum water tanks (3' x 292' x 8') that hold a total of 2,600 gallons of water that has been dyed dark blue. When the air in the greenhouse cools, the water releases the heat energy it has absorbed during the daylight hours. During the winter nights a special canopy extending the full length of each wing is arched from the window sill on the south wall over the plants and water tanks to the north wall. This reduces the area that needs to be heated at night and prevents heat loss through the glass on the south wall.

If a backup source of heat is needed during periods of extreme cloudiness, a woodburning stove (designed and built by the staff) has been installed for each wing. The heat produced by these furnaces will be distributed to each wing by an 18" circulating fan that blows the warm air into a 50' long x 18" diameter perforated plastic duct that is located at floor level under the bedding tables. In case there is an extended period of extreme cold and cloudy weather, gas unit heaters have been installed in each wing. Last winter these units were never needed. During the spring and summer each wing will be cooled by its own 42" exhaust fan and two water evaporative coolers.

Does it work? An example of the potential for this type of system is illustrated by this fact. Last winter during construction on a clear day when the outside temperature was 8°F, the temperature at the peak of the roof in each wing was in excess of 110°F and the floor level temperature was 80° F. Throughout the winter months the water in the tanks ranged from highs in the 70's to lows in the 50's.

Sun and save!

The Decatur Park District plans to make use of this facility on a year round basis. It will no longer be necessary for the District to purchase flowers for any of its landscaped sites and it will be able to expand its planting program with many new "home grown" products.

At the present time the greenhouse has over 14,000 plants of several varieties that were planted in March when the facility was first put to use. They will be planted this summer in existing flower beds as well as on 20 park playgrounds utilizing the services of neighborhood volunteers, senior citizens and summer playground leaders. The Decatur Public Schools have been invited to use the greenhouse for their horticulture science projects, and special classes for senior citizens are being planned for this fall and winter. Various youth groups including Boy Scouts and Girl Scouts have been encouraged to develop programs whereby they could make use of the facility on a year round basis.

Yes, the Decatur Park District is quite proud of its new greenhouse. The $45,000 spent on materials and the hundreds of man hours needed to finish this project will be returned to the community many times over thanks to the beauty it will provide in the parks throughout the District and the educational benefits it will offer to the people of the community.

Illinois Parks and Recreation 7 July/August 1981