Greenhouse Heat Loss Calculations: 7 steps.

Step 1. List greenhouse dimensions in feet:
Wall height, A=
House width, B=
House length, C=
Rafter length, D=
Lower wall height, E=
Upper wall height F=
Gable height, G or H=

Step 2. Calculate the appropriate surface areas and perimeter. N is the number if individual house sections forming each greenhouse range. N= 1 for a single house.

Lower wall area:
2N(E x B) + (E x 2C) =

Upper wall area:
2N(F x B) + (F x 2C) =

Single material wall:
2N(A x B) + (A x 2C) =

Gable area:
N x B x G =

Curved end area:
1.3N x B x H =

Gable roof area:
2N x D x C =

Curved roof area:
N x D x C =

Perimeter:
2 [(N x B) + C] =

Step 3. List construction materials and U factors for each surface.

Table of Heat Transfer Coefficients (U-Factors): http://www.oznet.ksu.edu/dp_hfrr/Floriculture/index2.htm

Location Construction material U Factor
Lower wall U1=
Upper wall U2=
Single material wall U3=
End Area U4=
Roof U5=
Perimeter U6=

Step 4. Calculate appropriate conduction heat loss, hc.
hc = Area x U x .T
T = Inside night temperature - minimum
outside temperature

Lower wall area x U1 x .T =
Upper wall area x U2 x .T =
Single wall area x U3 x .T =
Gable or curved end area x U4 x .T =
Roof area x U5 x .T =
Perimeter length x U6 x .T =

Total = QC =

Step 5. Calculate greenhouse volume.

Gable house volume:
N [(A x B x C) + (B x G x C/2)] =
Single curved roof house volume:
2H x B x C/3 =
Multiple curved roof volume:
N[(A x B x C) + (2H x B x C/3)] =

Step 6. Calculate air infiltration losses, hinf.
Table of Air Infiltration in Greenhouses: http://www.oznet.ksu.edu/dp_hfrr/Floriculture/index2.htm

hinf = 0.02 x .T x Volume x Air exchanges/hour
=

Step 7. Calculate total heat loss, ht.

ht = hc + hinf =

Source: Greenhouse Engineering, 3rd ed. 1994. By R.A. Aldrich and J.W. Bartok.
Northeast Regional Agricultural Engineering Service (NRAES-33).

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