Designing an Aquaponic Greenhouse for an Urban Food

Appendix G: Heat Loss Calculations

For the heat loss calculations, the formula 푄=푈퐴∆푇 where,

Q is the heat transfer rate in Btu per hour.

U is the heat transfer coefficient U-value= 1/R-value, measured in Btu/h (F) (ft^2 ).

A is the surface area in squared feet.

∆푇 is the temperature inside minus the temperature outside.

If the greenhouse is entirely covered with transparent panels the heat loss will be the followings.
Assuming the greenhouse is fully insulated on the walls that are not transparent.

Insulation

(R-value)

Heat loss (U-

value)

Btu/(h*F*ft^2 )

Area

(ft^2 )

∆푇

(60F-

15F)

Q

(Btu/h)

Solexx 2.10-2.30 0.45 1760 45 35640

Multi-wall

polycarbonate

1.5-2.0 0.6 1760 45 47520

Single-wall

polycarbonate

2.0 0.5 1760 45 39600

If the greenhouse has one wall made of plywood

Insulation

(R-value)

Heat loss (U-

value)

Btu/(h*F*ft^2 )

Area

(ft^2 )

∆푇

(60F-

15F)

Q

(Btu/h)

Solexx 2.10-2.30 0.45 1496 45 30294

Multi-wall

polycarbonate

1.5-2.0 0.6 1496 45 40392

Single-wall

polycarbonate

2.0 0.5 1496 45 33660