HORT 4253/5253
Greenhouse Management
Heating Problems

1. Calculate BTU requirements for a single A-frame greenhouse that is 60 feet wide and 320 feet long. The distance from the ground to the gutters is 14 feet. The house is of metal construction with the roof made of double glass and the sidewalls are constructed of FRP. The average outside temperature is 15F and desired inside temperature is 70F. Wind velocity averages 15 mph.

GH component Std. Heat loss K C or CW Corrected Heat Loss
gable 72 .77 .70 38.808
roof 1594 + 106 = 1700 .77 .70 916.300
Sidewall (760') 560 + 224 + 67 = 851 .77 1.00 655.270
         

                                                                                                                                                                                    1,610,378 BTU/Hr lost

 

                                                                                                   How many BTU/hr are required to heat this area? 4 @ 400, 000 BTU/hr or
                                                                                                                                                                                        8 @ 200,000 BTU/hr

 

2. Calculate the BTU's required for the following structure. A quonset house that is 30 feet wide and 100 feet long. Single poly for all coverings. Average low temperature is

-5F and desired inside temperature is 50F. Average wind speed is 20mph.
GH component Std. Heat loss K C or CW Corrected Heat Loss
end 23 .80 1.00 18.400
roof/top 237 .80 1.00 189.600
         
         

208,000 BTU/hr lost

How many BTU/hr are required to heat this area? 1 @ 225,000 BTU/hr or 2 @ 125,000 BTU/hr

3. Calculate BTU requirements for a ridge and furrow Quonset design, 2 greenhouses 34 feet wide and and 250 ft. long. The greenhouses are double poly covered metal house. The distance from the gutters to the ground is 8 feet (poly walls). Expected low temperature is 5F and wind velocity of 35 mph. Desired temperature is 75F.

GH component Std. Heat loss K C or CW Corrected Heat Loss
end (2) 29 * 2 = 58 1.16 .70 47.096
roof (2) (538 + 134) * 2 = 1344 1.16 .70 1091.328
sidewalls (636') 320 + 64 + 26 = 410 1.16 .70 332.920
         

1,471,344 BTU/hr lost

How many BTU/hr are required to heat this range? 8 @ 200,000 BTU/hr

4. A greenhouse is constructed as a A-frame ridge and furrow design. There are 3 houses, each with 50 feet wide and 125 feet long. The house is a loose house, wood with single glass. The side walls are 12 feet high including a 2 foot curtain wall (4" concrete block). The average wind velocity is 15 mph. Average low temperature is 25F and desired inside temperature is 55F. Calculate BTU/hr need to meet the conditions specified above.

GH component Std. Heat loss K C or CW Corrected Heat Loss
gable (3) 50 * 3 = 150 .41 1.25 76.875
roof (3) (443+88+22) * 3 = 1659 .41 1.25 850.238
sidewall (550' - 10' tall) 395+40= 435 .41 1.25 222.938
curtain wall (550' - 2' tall) 79+8 = 87 .41 1.25 22.829

1,172,880 BTU/hr lost



How many BTU/hr are required to heat this area? 6 @ 200,000 BTU/hr