I have built a greenhouse this year using 9 mil Polly and have fans to move the air inside and even a thermostat to regulate when they turn on and shut off. Everything appears healthy and stable but I can't get the temperature down. Very frustrated when I see amazing flower blooms then they fall or don't produce fruit. I test the water and have normal water conditions up to 6" into the soil and wet soil conditions at the bottom of the beds. Just curious to know if you have any suggestions. I feel like I should lay off the watering a little but with days spiking into the mid 90's I feel like I should at least surface water. Thank you for your time hope to hear back from you.
Clackamas County Oregon
Greenhouse temperatures can be 20+ degrees (F) higher than outside temperatures so summer time cooling is necessary. There are different types of cooling to consider:
Passive cooling just means to move that warm mass of air out and replace it with cooler outside air. This can be accomplished by venting and using fans. Adding additional ceiling vents or opening the end walls or side walls may be necessary. Not sure what your design is, can you describe or provide some photos? What is the area of the venting/open areas compared to the area of the greenhouse?
There are also other cooling techniques that might help, but may be cost prohibitive for a hobby type greenhouse. There are evaporative cooling systems (look for fan & pad systems affectionately known as 'swamp coolers'). Some of the commercial growers also use a fine mist or fog system as another for of evaporative cooling. Both of these systems work most efficiently in dry climates, so might not be worth the investment in western Oregon where we tend to be a little more humid.
Thanks for using Ask An Expert!