energy that would otherwise be used to heat the greenhouse during the night. According to a research
done in New Jersey, the use of thermal blankets during the night obtained a savings range of 22% to
58% on energy costs. (Roberts, Mears, Simpkins, & Cipolletti, 1981).
There are several important aspects of these blankets: it is important that the system covers all edges to
prevent the warm air from leaking out, it should also have a drainage system to prevent excessive
condensation; a material that allows water to pass is preferable, another criteria is the strength of the
material, to prevent damaging it. The blanket could also be made of multiple layers, more insulation,
and ideally with a reflective side, to maximize heat retention. (Patricia A. Rorabaugh, Merle H. Jensen, &
Gene Giacomelli, 2002)
(Roberts, Mears, Simpkins, & Cipolletti, 1981)
Figure 17. Curved Thermal Blanket
Figure 17 shows a movable curved curtain stalled inside a greenhouse, besides the thermal insulation at
night is could also serve as a shading area during the day.
2.3.1.5.2 Ground Insulation
Ground insulation is the insulation under the ground. It is normally used in the foundation to keep the
ground warm and prevent the bite frost from lowering the temperature inside of the greenhouse. As it
is intuitive, the insulating material has to be more resistant than normal insulation materials because it
is always humid and great part of the time wet, and therefore, it tends to be more expensive than a
regular insulation material.
There are many insulation materials designed for floors and foundation, but most of them are expensive
and/or made to be used in houses, like surface-bonding cement and pressure treated plywood. Because
we are dealing with water all the time, neither of these options works well for us. Ideally the floor of a
greenhouse has to be able to absorb water fast. Therefore we need an insulation that either absorbs
water of that goes around the foundation. (Gibson, 2010) (Fratzel, Foam Board Insulation R Values)
During a visit to a greenhouse in Massachusetts we were presented the Extruded Polystyrene Foam, also
known as blue or pink board. This material is a rigid foam board of varying thickness and sizes that can