Tech solutions: What style of greenhouse is best?

Q. What style of greenhouse is best?
Planning for a new greenhouse is one of the most important steps a grower has to take. Proper site selection, orientation, size, glazing material and many other factors enter into the decision.

Generally for someone starting out in the business or expanding a small operation, the free-standing greenhouse is the best choice. For a larger established business that has good markets, the gutter-connect is preferred. Here are some considerations to help you make a decision.

Free-standing greenhouses are less expensive to build as site preparation and erection costs are less.
 

Free-standing greenhouses
A free-standing greenhouse can have a hoop (gothic or Quonset) or gable roof shape. The gothic shape is the most popular today as it sheds snow easier than the hoop shape. The square foot cost of a free-standing greenhouse is usually less than a gutter-connected house.

Width
Hoop house designs are available in widths from 12 to 34 feet with the wider widths usually having a collar tie or truss to support more of the roof load. Gable designs are built to about 60 feet clear span. The wider the greenhouse, the greater is the efficiency in the use of space with less influence from sidewalls.

Length
Hoop houses are available with 4- or 5-foot hoop spacing. Gable houses are usually 8 or 10 feet between frames. If the greenhouse is to be covered with polyethylene film, 48, 96 and 144 feet are standard lengths to better utilize the available plastic sheet lengths.
Gable houses can be built to any multiple of the frame spacing. With rigid glazing (polycarbonate, acrylic or glass) length is less critical.

Non-level sites
Although it is best to select a level site or have it leveled, free-standing greenhouses are commonly built on sites with one house lower than the adjacent one. Avoid this if possible as it makes materials handling and walking more difficult.

Expansion
With individual greenhouses it is easier to add to the growing space. Some growers add one greenhouse every year as the business expands. Adding space can also be done without disturbing plant production.

Before beginning, plan on where future greenhouses will be built. Also, if possible, arrange the greenhouses so that they can all be attached at one end to a head house. This improves labor efficiency.

As the glazing area to floor area ratio is less in a gutter-connected greenhouse, heating costs are as much as 25 percent less than an equivalent floor area of free-standing houses.

Gutter-Connected Greenhouse
A gutter-connected greenhouse is a series of gable or gothic arches connected together at the gutter-level. Post lines support the gutters and drains are provided inside to carry the water away. Gutter-connected greenhouses are usually most economical when built greater than 20,000 square feet.

Advantages of gutter-connected greenhouses include:

Less land is needed
About 30 percent more growing area can be placed on the same amount of land area as free-standing greenhouses.