humidity in cold winter climate supposed to be below 40%?

kronicking420 · Feb 21, 2020

Hi, I am looking to start growing and I have purchased tents cmh lights day/night fan controller etc. I am wondering what you guys do in winter if you live in a cold climate where the humidity inside is supposed to be below 40%. During winter it is almost always colder than 20F usually stays around 0F or -10F according to this website and a couple others https://www.hvac.com/faq/recommended-humidity-level-home/ the humidity in your home during those temps is supposed to be no higher than 25% for -10F and 30% for 0f. I was wondering what suggestions you guys have? Is it okay to grow at those humidity levels because I have been reading about 40-60%. I don't know if it makes any difference but I have autoflowers.

Burned Haze · Feb 21, 2020

Follow/learn this (Vpd) and you’ll be okay

The Ultimate Vapor Pressure Deficit (VPD) Guide

"Why devote an entire guide to VPD?" you might ask. The answer is that the vapor pressure deficit (VPD) is extremely important for growing plants. VPD helps you identify the correct range of temperature and humidity to aim for in your grow space. With VPD you can achieve the best results while...

pulsegrow.com

PipeCarver · Feb 21, 2020

kronicking420 said:
Hi, I am looking to start growing and I have purchased tents cmh lights day/night fan controller etc. I am wondering what you guys do in winter if you live in a cold climate where the humidity inside is supposed to be below 40%. During winter it is almost always colder than 20F usually stays around 0F or -10F according to this website and a couple others https://www.hvac.com/faq/recommended-humidity-level-home/ the humidity in your home during those temps is supposed to be no higher than 25% for -10F and 30% for 0f. I was wondering what suggestions you guys have? Is it okay to grow at those humidity levels because I have been reading about 40-60%. I don't know if it makes any difference but I have autoflowers.

I'm there now with temps outside -15c - -20 c overnight. I can't keep my indoor humidity high enough. with out humidifier in flower room I was down to 17% I added a small 1 gallon humidifier and it only brought it up to 22% added another 1 gallon humid. I've got it up to 35%. My veg room with humid. is only 35% I'm having some leaf issues but they're surviving not thriving with slow growth.
I saw a video on building a swamp cooler I'm looking into making one but our cold snap is about to break with warmer temps all next week so by then I won't likely need it. We have radical weather changes and I think a swamp cooler should be in my arsenal of equipment to deal with these radical changes in temp and humidity

GNick55 · Feb 21, 2020

kronicking420 said:
Hi, I am looking to start growing and I have purchased tents cmh lights day/night fan controller etc. I am wondering what you guys do in winter if you live in a cold climate where the humidity inside is supposed to be below 40%. During winter it is almost always colder than 20F usually stays around 0F or -10F according to this website and a couple others https://www.hvac.com/faq/recommended-humidity-level-home/ the humidity in your home during those temps is supposed to be no higher than 25% for -10F and 30% for 0f. I was wondering what suggestions you guys have? Is it okay to grow at those humidity levels because I have been reading about 40-60%. I don't know if it makes any difference but I have autoflowers.

i live where it’s winter now and growing, get a good humidifier!
you don’t have to have the carbon filter hooked up, exhaust fan was though, sucking out a hole in roof, not as much suction as filter in tent.
till pretty much flowering and i did have humidity anywhere from 50 -65+ depending on what i was doing, i’m flowering now with humidifier still going and just hooked up carbon filter, humidity has dropped to around 40, so i spray the inside of the tent a couple times while lights are on for the first week or two of flowering, than all should be fine, 40 is good for buds.

GNick55 · Feb 21, 2020

Burned Haze said:
Follow/learn this (Vpd) and you’ll be okay

The Ultimate Vapor Pressure Deficit (VPD) Guide

"Why devote an entire guide to VPD?" you might ask. The answer is that the vapor pressure deficit (VPD) is extremely important for growing plants. VPD helps you identify the correct range of temperature and humidity to aim for in your grow space. With VPD you can achieve the best results while...

pulsegrow.com

yep! look for vpd chart.

GNick55 · Feb 21, 2020

GNick55 said:
i live where it’s winter now and growing, get a good humidifier!
you don’t have to have the carbon filter hooked up, exhaust fan was though, sucking out a hole in roof, not as much suction as filter in tent.
till pretty much flowering and i did have humidity anywhere from 50 -65+ depending on what i was doing, i’m flowering now with humidifier still going and just hooked up carbon filter, humidity has dropped to around 40, so i spray the inside of the tent a couple times while lights are on for the first week or two of flowering, than all should be fine, 40 is good for buds.

hole in roof is in tent roof.

Nugg · Feb 21, 2020

Bonus... propane heater...gives heat and humidity with extra co2...vent out excess..

Growing_Garbage · Feb 21, 2020

Nugg's got it. Probably not a beginner move but if you're buying stuff and getting setup where it seems to get real freaking cold might be worth the investment.

A good humidifier helps too, and also gives off heat!

MIMedGrower · Feb 21, 2020

I use a whole house humidifier so the plants and people live in above 45% humidity.

Dehumidifiers and a/c keep it below 60% in summer.

this humidifier:

AIRCARE 6-Gal. Evaporative Humidifier for 2700 sq. ft. 831000 - The Home Depot

With a large reservoir and extended run time, this humidifier is a customer favorite. Casters make the humidifier easy to move once filled. It has three fan speeds, an adjustable humidistat, refill indicator,

www.homedepot.com

kronicking420 · Feb 21, 2020

Hey, Thank you all for your suggestions. I will have to look and learn that vpd chart when I got some time. Just to clarify the temperature in my house (basement) is 62.6F and 70F in my tent but outdoors it is usually around 0F and when at those temps outside if I humidify my house I will be going over the RH allowable when those temperatures are outdoors causing condensation on windows on screws and in attic which will mold and cause structural damage. It says on HVAC site and others that the humidity should not exceed 30% with those temperatures outside. I would just humidify tent and pump air out of house but than I will waste a lot of heat. I am also willing to spend some money on heaters etc but I don't think I need a heater as my lights and fan control (controls fan speed to maintain temperature) seem to be able to get the temps up in the tent.

Growing_Garbage · Feb 21, 2020

Oh man I always grow semi outside so its less worry for condensation. You could get a few little temp/humidity meters and run a tiny 1 gal humidifier in the tent and see if it even brings the room up without venting outside. If it's normally really under 30 it will take a ton to bring it up much I bet.

Or just totally isolate the room from the house so it won't do structural damage. Look up lungroom grow ideas. That is how I have mine setup. Can grow with outdoor temps 0-110 pretty well with it isolated, like tent in a tent.

kronicking420 · Feb 22, 2020

hey, I will have to checkout some of the lungroom grows that sounds like a good idea. I was wondering I tried to get my vpd to 1 on the calculator and the only way I get close is if I lower my temperatures in the grow room to 62.6F which gives me 1.4 kpa (air). I was thinking about getting some heating mats for the pots (keeping soil warm) but I was wondering if growing at a temperature of 62.6F to get the vpd closer to 1 would be better than keeping my tent at around 70F. The temperature surrounding my tent fluctuates from 59F-62.6F so I am worried about keeping the tent too hot because I read that I should never let the temperature drop 15F at once because it will stunt growth and I really dont want a small autoflower.

visajoe1 · Feb 22, 2020

Im fighting the low humidity/VPD battle too. Just ordered this yesterday, 8g daily output, 2500 sq/ft coverage. $87. Only gonna be in a 150 sq/ft room

PipeCarver · Feb 22, 2020

MIMedGrower said:
I use a whole house humidifier so the plants and people live in above 45% humidity.

Dehumidifiers and a/c keep it below 60% in summer.

this humidifier:

AIRCARE 6-Gal. Evaporative Humidifier for 2700 sq. ft. 831000 - The Home Depot

With a large reservoir and extended run time, this humidifier is a customer favorite. Casters make the humidifier easy to move once filled. It has three fan speeds, an adjustable humidistat, refill indicator,

www.homedepot.com

That's probably what I need, I've been relying on cheap 1 gallon Humidifier /misters thinking this cold snap will disappear soon. We normally have a high humidity issue and I have a good dehumidifier for that but this low H stuff is stressing out my plants.

Munch517 · Feb 23, 2020

PipeCarver said:
That's probably what I need, I've been relying on cheap 1 gallon Humidifier /misters thinking this cold snap will disappear soon. We normally have a high humidity issue and I have a good dehumidifier for that but this low H stuff is stressing out my plants.

If you ever have the ability to run a sealed room you won't regret it. Maybe you could sort of run the room your tents are going in as a sealed space? I have a 6'x12'x7' space in Michigan and I can have it tightly controlled besides my window A/C being inadequate on the hottest days of the summer, a mini split is on the to-do list. I have a 50 pint dehumidifier, 5 gallon humidifier, a small 750w space heater that rarely runs along with the window A/C (8000 btus???). I keep things at 80F during the day, 74F at night. Humidity starts at 65% in veg and decreases to 40% by the end of flower. I can graph everything with my controller and when I don't let my dehumidifier run out it keeps things within +/- 7% of my target (it would do better with a "dumb" dehumidifier that could be controlled by my room controller) and temps stay within +/- 2F. I couldn't imagine trying to control things while venting the space, you're just blowing all your conditioned air out from where you need it.

visajoe1 · Feb 26, 2020

visajoe1 said:
Im fighting the low humidity/VPD battle too. Just ordered this yesterday, 8g daily output, 2500 sq/ft coverage. $87. Only gonna be in a 150 sq/ft room

View attachment 943693

Just to follow up on this unit performance:
-63db at top fan speed (relatively loud)
-in a 10x10 room with ~200cfm exhaust, can attain 70% rh
-unit RH auto settings MAX is 65%
-unit RH meter is about 5% above actual
-small footprint

humidity in cold winter climate supposed to be below 40%?

humidity in cold winter climate supposed to be below 40%?

kronicking420

Burned Haze

Guest

The Ultimate Vapor Pressure Deficit (VPD) Guide

PipeCarver

GNick55

GNick55

The Ultimate Vapor Pressure Deficit (VPD) Guide

GNick55

Nugg

Growing_Garbage

MIMedGrower

AIRCARE 6-Gal. Evaporative Humidifier for 2700 sq. ft. 831000 - The Home Depot

kronicking420

Growing_Garbage

kronicking420

visajoe1

PipeCarver

AIRCARE 6-Gal. Evaporative Humidifier for 2700 sq. ft. 831000 - The Home Depot

Munch517

visajoe1

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