The Plastic Greenhouse - Greenhouse Technology and Management - page 89

• Availability of labour. greenhouse is not appropriate complemen-

tary facilities and equipment for climate
control will have to be considered.

• Closeness to transport networks (roads,

railways), communication (telephone)
and energy (gas, electricity).
The orientation, besides avoiding shad- •

ows from hills or neighbouring build-
ings, must be considered in relation to
the dominant winds, depending on the
shape and slope of the greenhouse roof.
Normally the orientation would be
selected that captures the maximum
amount of light in the greenhouse (see
Chapter 3).

4.9.2 Criteria for the design of plastic-

film greenhouses

Greenhouse design is very much influenced,
in practice, by the local climate and the
latitude of the site (Von Elsner et al ., 2000a),
and in many cases is limited by the availa-
bility of materials for the construction.
No design is perfect, thus it is necessary
to prioritize in each case, the criteria to fol-
low, these being: (i) the maximization of the
light (the main goal to be achieved; Bailey
and Richardson, 1990; Giacomelli and Ting,
1999; Swinkels et al ., 2001); (ii) minimizing,
if possible, the structural elements to avoid
shadows (Briassoulis et al ., 1997a); (iii) ensur-
ing good insulation which decrease the heat
losses (Swinkels et al ., 2001); and (iv) afford-
able costs (Bailey and Richardson, 1990).
Greenhouses with retractable roofs were con-
ceived to maximize light (Photo 4.6).
The physical and mechanical proper-
ties of the covering materials and their

4.9 Criteria for the Design and
Construction of Greenhouses

4.9.1 Introduction

Depending on the local climate and the bio-
climatic requirements of the species to be
cultivated, once the proper site has been
selected, it will be necessary to choose the
cladding material, the type of structure and
the architectonic shape of the greenhouse. If
the predictable climate generated by the

Photo 4.6. Retractable roof greenhouse (Cravo type) that permits the complete retraction of the plastic
cover to maximize the solar radiation.