So relative humidity is the measure of how much water the air can hold. it called relative because warm air can hold a much greater volume of water than cold air. That’s why its measured as a percentage. The volume of water the air can hold doubles with every 20 degree rise. For example, 50% RH at 50 degrees would only be 25% RH at 70 degree assuming all other factors stay the same. To put it another way, a cubic foot of air can hold 1 cup of water at 60 degrees and 100%RH then it could hold up to 2 cups at 80 degrees and 100%RH and 4 cups at 100 degrees 100%RH. Those aren’t the actual volumes, just the first thing that popped in my head to demonstrate the concept.
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So what ideal humidity and temp for cold environments, do you gotta reverse everything to make it what it would be if it were hot or just accept and let the plants tell you want it needs and wants
Over 60 ish degrees is best. Much lower than that and it can get be hard to keep enough moisture in the air. They can handle lower temps for shortish periods without much ill effect other than they slow down while its cold and speed back up when they warm up, It’s not the end of the world if you just can’t keep them above 60. Warmer is better but we do what we can with what we have. Adding a heater can be a double edge sword because you have to replace the humidity you lost and the heater itself dry the air too. I’m not saying don’t add a heater. I run one in my grow room. I’m just trying to make you aware of some of the challenges that can come with it so you’re prepared.
For ideal RH for a given temp we look to another concept called VPD(vapor pressure deficit). This describes in Pascals the difference in vapor pressure between a leaf and the air surrounding the leaf. It describes how hard the ambient air is sucking water out of the stomata of the leaf. This is what we are trying to actually control when we adjust temp and RH. In order to measure VPD accurately you need a infrared thermometer to measure leaf surface temp the you would calculate based on the difference in leaf temp and ambient temp. This chart assumes that they are the same which almost never happens, but it’s a decent guide to get started. All that being said VPD doesn’t need to be perfect. You don’t need to go out and buy an infrared thermometer or anything. Just understanding the concept and attempting to get close is good enough. Perfect VPD wont make the plant grow any faster unless near every other input is perfect. It’s effectiveness will be limited if the plant doesn’t have just the right amount of water, food, CO2 in the air, O2 around the roots, and light. I hope that’s not too much info at once. I try to break it down so it’s easy to understand.
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Your meter is out of probably out of calibration. I never had good luck with the cheaper meters. Do you have any calibration solutions?
Nope I just got it and didn’t all 3 solutions they all popped up correct. I have the apera too but gotta grab batteries for that this weekend, this is a back up, don’t need it yet but just wanted to test my water.
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The first two are probably within margin of error for that meter(usually 0.1 I think), but the bottled water throws me a little. Most of the bottled water I have tested comes in very close to 7.
Did you use the salt packs that came with the meter? Did you use fresh distilled water to mix them?
Nope, used the bottled water , oh well I’ll get some and get it all squared away before I truly need it, no worries.
Update on temp and humidity with mini heater added. I’m sitting comfortably at 80-85F 55-60H! Think we are all good for awhile til the next hiccup.
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That stubborn kid ever show up to the party🙃
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Great to see😁
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Do you have a way to record temp and humidity over night? I think that is going to be the real question.
Yep I have. Camera and got my new thermostat with wifi capabilities so I check it
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One is probably using water a little faster than the other. have you given them water since the runoff the other day?
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I did tonight cause the droop was sad so I thought maybe thirsty, we’ll see what tomorrow holds
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that was after you took the pic?
