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Entry Date
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Nick Name
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Location
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Sunday, June 21, 2026
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Richmond Dave
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Richmond, BC, Canada
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Entry 18 of 18 |
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I've been playing with VPD. This is the yesterday's graph of my best VPD readings to date. It's all to with temperature, humidity and transpiration. The greenhouse is 60ft x 35ft. Along one of the long walls I've installed 9 - 5000 cfm exhaust fans . The opposite long wall is open to create a cross draft. By adjusting the temp at which the exhaust fans and misters come on, I can raise or lower the VPD. This has been a challenge because we installed new poly and the new poly is so much brighter than the old. The greenhouse gets hotter faster. On top of better light transmission we're doing this with no shade cloth to try to achieve maximum photosynthesis. In addition to all of the above we have had some record breaking hot days. We have had only minor leaf burn issues with this system. In addition we have installed some serious LED grow lights to give 3 hrs of extra light at dawn and dusk.
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