dehum ac and so on

now i’m planning a grow room with dimensions of about 360cm to 160cm (roughly 12ft to 5ftish). i will not utilize whole area but rather do 3 individual screen for 3 different cultivars. in my mind the selection is dinachem destroyer and northern lights. 1m2 for each cultivar should be plenty of space for me atm.

anyway i’m also planning on using the adjacent room as a lung room and i’m trying to figure out which way would be the best. now i have big dehum uses about 1100w and the fan on it is rated at 760m3/hr (if i’m not mistaken thats 423cfm). there are two options:


the first option which i use 2 soler palaus i have at my disposal to move the air from the grow room to the exhaust room and then to the lung room to be conditioned and then into the grow room again.

now right off the bat i dont exhaust outside for safety reasons and thats why i have a huge dehum and an overpowered ac.

the problem with this setup is that the lung room will get cold because of the ac and in cold weather dehum goes into defrost mode more often which causes humidity spikes which i want to avoid.

when i was working on what i can do about this i came up with the second setup which uses the dehum as an actual exhaust fan. i’m not sure if dehums are meant to be used this way but my exhaust fan in the grow room which feeds air to the exhaust room is definitely lower cfm than the dehum so i dont think dehum will loose efficiency due to positive pressure but i’m not so sure about doing just a single pass of exhaust air will remove enough moisture or be 100% effective.

so advantages: i’m calculating an obvious negative pressure in the exhaust room which should work well for dehum. secondly the exhaust room will be hot in summers and pretty warm in winters which should prevent the unit from going into defrost mode.

do you think i can use a powerful dehum as an exhaust fan?

and how much moisture can be removed with a single pass of air by the dehum?

do you have any other ideas on how to solve my lung room predicament?

i feel like were over complicating this. you already have a mini split a/c thats the biggest cost, and a huge dehumidifier. i would just knock the walls down scrap all these fans and a scrap that lung room. your just losing sq footage for nothing. seal it up and do a co2 enriched room. what outdoor temps is the condensor on the a/c rated for? if you can run it all year round your golden. my nat gas co2 generator completely installed was like $400. can always do co2 tanks as well if your not wanting to get a gas fitter involved just make sure the co2 controller works with tanks.

I run my ac and dehumidifier in the room and have an exhaust fan on a timer. Really only need the dehumidifier when it's raining here

xox said:

i feel like were over complicating this. you already have a mini split a/c thats the biggest cost, and a huge dehumidifier. i would just knock the walls down scrap all these fans and a scrap that lung room. your just losing sq footage for nothing. seal it up and do a co2 enriched room. what outdoor temps is the condensor on the a/c rated for? if you can run it all year round your golden. my nat gas co2 generator completely installed was like $400. can always do co2 tanks as well if your not wanting to get a gas fitter involved just make sure the co2 controller works with tanks.

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Gemtree said:

I run my ac and dehumidifier in the room and have an exhaust fan on a timer. Really only need the dehumidifier when it's raining here

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thanks for the input dudes.

ok little background info is missing on my part. i live by the sea and the typical rh is 75+ around here and i even need to run a dehum in the house even without plants.

also the wall that divides the 2 rooms might be a loadbearing wall and in either case its an old house so i’m not really very excited about knocking walls down haha.

i’m not worried about losing ft2 because i dont plan on using this whole area even and no one lives in this house atm so its just not a problem to use two rooms to grow in half of one.

plus with lung room design i’m planning to use the lung room to dry aswell. i got a 4x4 tent which is gonna be free after i move into the room so i can put a small inline fan on a timer and dry in this cold lung room winter and summer.

oh also yeah ac works winter and summer all year around without problems. though i’m gonna have it swapped with a new 18000btu unit just to have peace of mind.

growing in the room which is supposed to be the lung room also crossed my mind @Gemtree but that would deprave me from a dedicated drying area in my setup. because the big room doesnt have an ac so it would get too hot in summers. i’m trying to maximise quality over anything else. the quantity will surely increase too but i really want a dedicated dry area because i am tired of drying in the grow area with 35%rh haha

ok i kinda wanna go with this 3rd idea i guess. which should work better than the previous drafts.


now there is another question on my mind. and this maybe a silly question but i just have no idea how to go about it. now i kinda figured that to calculate my btu needs i multiply the led wattage with 3.5 and this gives me the btus needed to cool the energy from the leds.

is this calculation the same for dehum too?

i mean watts are watts in the end so i’m guessing dehum watts and led watts are the same in calculations so there is no reasonable explanation in my mind that would suggest otherwise but i just want to confirm it with guys who already built their rooms succesfully.

so i’m between 12000btus and 18000btus. now since this is less than a legal grow if 12000btus would cut it i will not push for 18000btus to keep the bills down eventhough 18000 would be sweet and perfectly overpowered probably.

there will be 1200w of leds not sure if i’m gonna run them at 100% but lets say that i’ll, 1200w of dehum (1160w nominal-1400w max) and various fans and gizmos with a total of 500w guestimation

which one would you go with in my situation? 12K or 18K?

crimsonecho said:

i mean watts are watts in the end so i’m guessing dehum watts and led watts are the same in calculations so there is no reasonable explanation in my mind that would suggest otherwise but i just want to confirm it with guys who already built their rooms succesfully.

so i’m between 12000btus and 18000btus. now since this is less than a legal grow if 12000btus would cut it i will not push for 18000btus to keep the bills down eventhough 18000 would be sweet and perfectly overpowered probably.

there will be 1200w of leds not sure if i’m gonna run them at 100% but lets say that i’ll, 1200w of dehum (1160w nominal-1400w max) and various fans and gizmos with a total of 500w guestimation

which one would you go with in my situation? 12K or 18K?

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You dont mention co2?

thumper60 said:

You dont mention co2?

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bc i‘m not planning on using co2. my rooms are not sealed so atmospheric co2 is just ok for me atm and if in the future i decide to add co2 i will more than likely go with tanks instead of burners so i dont take co2 into consideration for btu calculations.

what is the outdoor temp range through the year, or during the time of the year that you will be growing? I ask because if you can use whole room and use air exchange along with the dehumdifier and AC it would simplify everything.

crimsonecho said:

bc i‘m not planning on using co2. my rooms are not sealed so atmospheric co2 is just ok for me atm and if in the future i decide to add co2 i will more than likely go with tanks instead of burners so i dont take co2 into consideration for btu calculations.

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Ok so your running ac an dehuy while venting? Good luck with that.

Roguedawg said:

what is the outdoor temp range through the year, or during the time of the year that you will be growing? I ask because if you can use whole room and use air exchange along with the dehumdifier and AC it would simplify everything.

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Running ac an dehuy while venting is not smart.

Roguedawg said:

what is the outdoor temp range through the year, or during the time of the year that you will be growing? I ask because if you can use whole room and use air exchange along with the dehumdifier and AC it would simplify everything.

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dips down to 0°C from time to time in winter and shoots up to 35°C in summers. air exchange in general is not something i prefer because again this is a stealth op so i have air purifiers, dehum and ac to keep the air clean dry and cool and since these areas are not sealed co2 replenishes naturally but dont have a sensor so i’m not sure about the ppms. gonna look into getting a co2 meter and see if i’m lacking on that end and if so i can use tanks to provide extra but it’ll just be a huge waste too as its not sealed.

thats why instead of tanks i was using aquarium reaction bottles in my 4x4 tent. citric acid baking soda water and provides 300g of co2 in one tank. refill every week and its golden. maybe i can use those tanks too as its much more inconspicuous to buy baking soda and citric acid than refilling tanks etc. but thats neither here nor there atm for the btu calculations haha

thumper60 said:

Ok so your running ac an dehuy while venting? Good luck with that.

Running ac an dehuy while venting is not smart.

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no i’m not venting at all. the air at most gets distributed inside the house but houses are not sealed either so air exchange and co2 replenishment does happen.

crimsonecho said:

dips down to 0°C from time to time in winter and shoots up to 35°C in summers. air exchange in general is not something i prefer because again this is a stealth op so i have air purifiers, dehum and ac to keep the air clean dry and cool and since these areas are not sealed co2 replenishes naturally but dont have a sensor so i’m not sure about the ppms. gonna look into getting a co2 meter and see if i’m lacking on that end and if so i can use tanks to provide extra but it’ll just be a huge waste too as its not sealed.

thats why instead of tanks i was using aquarium reaction bottles in my 4x4 tent. citric acid baking soda water and provides 300g of co2 in one tank. refill every week and its golden. maybe i can use those tanks too as its much more inconspicuous to buy baking soda and citric acid than refilling tanks etc. but thats neither here nor there atm for the btu calculations haha



no i’m not venting at all. the air at most gets distributed inside the house but houses are not sealed either so air exchange and co2 replenishment does happen.

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Ok i see now I though you stated 12 x 15 full of plants my bad you should be fine.

thumper60 said:

Ok i see now I though you stated 12 x 15 full of plants my bad you should be fine.

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no i’m just looking to create ample space to walk between my plants and be more hands on with a more open space to improve air movement and so on. i basically think of dedicating 1m2 area per each cultivar. ofc 3 1m2s will be bigger than my 2 2x2s and 1 4x4 combined but not looking to cover this space wall to wall with plants.