Since, We have figured out the Volume of the Greenhouse we are know able to Determine the Cooling and Ventilation Requirements
Since, We have figured out the Volume of the Greenhouse we are know able to Determine the Cooling and Ventilation Requirements
Step One: Determine the volume of the Greenhouse. ( Formulas are Given on https://environmental4.tripod.com/enviropage.htm)
Step Two: Determine the fan requirements to have one complete air exchange of the greenhouse volume every minute. For example you need 4 fans because your greenhouse is 100 feet long and 20 feet wide. (The Pictures Below will Explain to you how you Determine This)
Step Three: Multiply by the larger of the two correction factors for elevation or fan-to-pad distance.
Correction Factor to be applied when the Fan-to-Pad Distance is Less Than 100 feet
| Distance from pad to fan (ft) | 20-30 | 30-45 | 45-60 | 60-85 | 85-100 | Above 100 |
| Correction Factor | 1.7 | 1.56 | 1.42 | 1.28 | 1.14 | 1.00 |
Correction Factor to be applied for Elevations Above Sea Level
| Elevation (ft) | Sea Level to 1000 | 1000-2000 | 2000-3000 | 3000-4000 | 4000-5000 | 5000-6000 | 6000-7000 |
| Correction Factor | 1.0 | 1.04 | 1.08 | 1.12 | 1.17 | 1.22 | 1.27 |
Step Four: Select fans from the chart below, (This chart is one of many with a certain brand of fan: I will be using Windmaster fans) Keeping in mind that fans should be no more than 25 feet apart. It is generally better to space fans approximately 15 to 20 feet apart. This insures for a complete air exchange every one minute. Since you have already figured the volume of your greenhouse all you have to do is divide the total volume by how much each fan can move in one minute. Look in the .05" column and it shows how much air you can move.
For example the total volume of your greenhouse is 48,562 feet cubed. You have already determined in Step Two how many fans you need to have a complete air exchange. We will use four fans as an example. All you have to do is divide 48, 562 by 4 which equals 12,140.5. This means you need a fan to average at least that many RPMs. Then you have to look under .05" column and find a fan that gives at least 12,140. 5 RPMs. So I determined from the chart below that Fan model DC36H which gives out 13,200 RPMs. This fan gives out more than the required, but it is better to have more than enough, than not enough.
Step Five: Determine the area necessary for the evaporative pads. This done by dividing the corrected volume in the 3rd step by 250 for 4 inch pads or 350 for 6 inch pads. This number will give you the total area pad that is necessary for the greenhouse.
Here is an Example Problem Going Through all the Steps: You have a single ridge greenhouse which is 80 feet long with a width of 35 feet and a height of 15 feet. The greenhouse is located at an elevation of 2500 feet and the distance from the fan to the cooling pad is 24 feet. Using 6 inch cooling pads to control evaporation.
Step One: Volume: 80 ( [ 35 x 15] + [ (35 x 10) /2] ) = 56,000 feet cubed
Step Two: 4 Fans are required to get a complete air exchange
Step Three: 56,000 x 1.7 = 95,200
Step Four: Select Fans which circulate the corrected volume, Fan Model DC54J can move 25,100 times 4 fans is 100,400, which is more than enough.
Step Five: 95,200 / 350 = 272 So you need to have 272 square feet of cooling pad.
To Search the Internet about Questions on Greenhouses click here.
As long as you follow the steps and check your calculations you just determined what cooling requirements you will need, without paying anyone to do it for you