Sealed vs vented electric cost

Hi all,

I have a grow tent that lives in a cold space. I'm spending a load of money heating it with a fan heater and then I'm venting a lot of that warm ait out. It seems like a mad thing to do and I was thinking of sealing the tent.

To do that I will need to run co2 and a dehumidifier.

Heater is 1200w on full power but it's half power so 600w fan heater. It's probably on all the time at the moment.

Dehumidifier which I own already consumes about 0.3 kW per hour. So its about 300 w.

I think if I sealed the tent it would be on 1/4 the time so I would save a load.

Anyone done this and it it worth it... does it save money?

Or you can hook your exhaust to run only when a high temp parameter is hit/humidity parameter is hit?

Inkbird controller or get a ac infinity fan set up

bk78 said:

Or you can hook your exhaust to run only when a high temp parameter is hit/humidity parameter is hit?

Inkbird controller or get a ac infinity fan set up

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Yes I have a day night fan controller. It has a temp sensor. But it sits at 25% minimum idle speed. It increases to max speed at 30c.

I'm just thinking that even at 25% I'm still pushing a lot of heat out.

if you use an "EC" fan and appropriate controller you can run as slow as 1%.

grotbags said:

if you use an "EC" fan and appropriate controller you can run as slow as 1%.

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Will I run into humidity issues though?

oill said:

Will I run into humidity issues though?

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in general 1% is too low it was more to show just how controllable EC fans are.

1% might be ok for cuttings as you want the extra humidity and dont really need a load of co2, 5% might be ok for early veg with a little less humidity and a bit more co2. then onto maybe 10-15% for mid veg ect.
basically the more mass in the tent the more humidity is generated the faster you will need to run the fan, running a grow this way is always a trade off between heat and humidity, you just have to make the best of it.

this is all dependant on how big your tent is and how large your extraction fan is.

ec fans are all pwm controlled so more or less any pwm fan controller will control any make of ec fan, you might have to do a bit of rewiring the connectors but they should work.

i have used these https://www.hg-hydroponics.co.uk/can-ec-lcd-digital-fan-speed-controller-13180-p.asp with various makes of ec fan, they are great.
you can use 2 fans, you can set min and max run speed, max temp and max humidty, temp and humidity hysteresis, it also has a light sensor so you can have different settings for min/max speed, temp/humidity for day and night. if you use an intake and extection fan it also allows you to ballance them so you always maintain negative pressure.

obviously they aint magic and can only do so much but short of going sealed room and adding ac, co2, dehumidifiers ect it about as good as it gets.

oill said:

Will I run into humidity issues though?

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Probably. I grow in a cold space, and vent on temp rather than 24/7.
Lights out humidity spikes are unavoidable if venting solely on temps. If you dont have one, consider an oil filled heater. Much more efficient.

Boatguy said:

Probably. I grow in a cold space, and vent on temp rather than 24/7.
Lights out humidity spikes are unavoidable if venting solely on temps. If you dont have one, consider an oil filled heater. Much more efficient.

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The last one I had pissed oil everywhere... was a nightmare!

If you can find a good used air to air heat exchanger it will recycle some of your lost heat to the fresh air commimg in.
I use a temp+RH controller on the air to air and the same on the dehu. If it’s cold in the room the dehu runs. If warm the air to air runs. I bring in outsid air so it can be -20. The air to air warms it up. This only works if your outside air is dry which it usually is in winter. I just use the air to air fan to move the air. Restrict the fresh in to mach the warm out as the carbon filter will restrict a bit. I think this is about as efficient as it gets power wise.
I have a small veg room connected to my flower room. The air mover is in the flower room and takes care of both. Maintaining 52RH and 25c, use LED on all of it. Would like to get up to 28c need more light I’m thinking.

oill said:

The last one I had pissed oil everywhere... was a nightmare!

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Not sure how that even happens. Did it split?

I would just make room that tent is in the "lung room" and control the temp and humidity in it. Tent exhaust goes back into room. If room isnt insulated, may need to insulate.
Better option may be get rid of tent and get more light, to light and heat whole room.

Roguedawg said:

I would just make room that tent is in the "lung room" and control the temp and humidity in it. Tent exhaust goes back into room. If room isnt insulated, may need to insulate.
Better option may be get rid of tent and get more light, to light and heat whole room.

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It's loft space.... so its more complicated than that

A sealed environment is easier and less expensive to run and the gains more then pay for the electric. Never run a heater when you can add bulbs to your leds. The walls, floor, potts will retain the heat enough during lights off. Only vent at lights off & on then once every 2-3 hours for 30 min. During lights off once the smell gets strong. Maybe a 15min. Air exchange halfway through flower with the co2 shutting off 1 hr Prior.

I was thinking about trying a sealed room for the same reason as you, I vent to outside so I was constantly heating to blow it controlling humidity.

Now I use a dehumidifier and a small tube heater inside the tent with the fan running constantly slow in summer and thermostatic in winter.
A variac let's you turn down ac fans to 0-100% with zero buzz from the coils

The dehumidifier is much better/cheaper, watt for watt it takes care of humidity while giving of heat at the same time.

Turpman said:

If you can find a good used air to air heat exchanger it will recycle some of your lost heat to the fresh air commimg in.
I use a temp+RH controller on the air to air and the same on the dehu. If it’s cold in the room the dehu runs. If warm the air to air runs. I bring in outsid air so it can be -20. The air to air warms it up. This only works if your outside air is dry which it usually is in winter. I just use the air to air fan to move the air. Restrict the fresh in to mach the warm out as the carbon filter will restrict a bit. I think this is about as efficient as it gets power wise.
I have a small veg room connected to my flower room. The air mover is in the flower room and takes care of both. Maintaining 52RH and 25c, use LED on all of it. Would like to get up to 28c need more light I’m thinking.

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I wasn't even aware of these "air to air heat exchangers", I like this technology.

I’m in a shed, w two 2x4 tents.
One for veg w an led and optional cmh and oil filled heater when it gets to below zero outside.
One for flower with led and the dehumidifier.
This winter I’m circulating air from the tops of both tents ducted down to the bottom of both tents.
At a low circulation setting, I’m at 68-72 dark and 72-80 lights on
Humidity fluctuates but 35-50 in flower side and 50-80 rh on veg side.

finished a run like this, no co2 or meter and I open them up once a day for 15 min or so to check on them.
I am happy with the results.
Will be digging out my controller to monitor the heater and co2 levels.
I’ve ran a second tent as a lung before, worked well.
Now I’m spreading the gear between the tents to still use the floor to grow and a lung effect between them.

Last week -13 outside
Now it’s +10
I don’t want to cook them.
Weather changes fast here, sometimes before I can get to make changes.
-results are fried leaves drooping to the floor or straight up dead crispy leaves.

I don’t know cost totals yet.
We pay based on last years use; then make up or get back the difference.
But, it’s definitely saving costs to circulate and not vent.
This was the only way I could get both warm and dry enough.
Without two of everything.
-and paying to power them.

expensive weed

Star Dog said:

I was thinking about trying a sealed room for the same reason as you, I vent to outside so I was constantly heating to blow it controlling humidity.

Now I use a dehumidifier and a small tube heater inside the tent with the fan running constantly slow in summer and thermostatic in winter.
A variac let's you turn down ac fans to 0-100% with zero buzz from the coils

The dehumidifier is much better/cheaper, watt for watt it takes care of humidity while giving of heat at the same time.

Click to expand...

A fully controlled environment is essential. Need a de-hu, AC + Co2 in a sealed environment to do the best you can. When venting its Important to have a filtered intake come on with equal cfm's or close to neutralize pressure. A little negative air pressure is good but not to much and positive air pressure is not good. Vent high and intake low to the ground unless you're in a cold climate adjacent from your room. Then vent low and intake high because heat rises. Only need to vent 15min before & after lights out and on to exhaust the high humidity coming off the plants as they take there morning & eventing piss.
The only way I see someone needing a heater is in a situation like the guy above. In a shed outside below 0•. Even then, if it's a well insulated shed then he may not need it but if not then during lights out only. Leds are only efficient if you don't need the added heat. You can do just as well or better using bulbs enhanced with 30% leds of the right wavelengths.

If anyone is looking to really add some heat while getting light I recommend the Hortrilux SE-600 CHPS. Essentially a quality light heat bulb. But for heat and efficiency I recommend cmh. Both to be enhanced with some leds.

Comparator said:

If anyone is looking to really add some heat while getting light I recommend the Hortrilux SE-600 CHPS. Essentially a quality light heat bulb. But for heat and efficiency I recommend cmh. Both to be enhanced with some leds.

Click to expand...

It's generally cold and damp here I'm no stranger to hid

That said I refuse to ignore the benefits of led, i don't read technical stuff I've little interest in it so I'm not judging by anything other than the results.

I have an oil heater in my tent because the dark period starts at 11pm / 12am and the temp dips at night. I also have temp / humidity controlled AC Cloudline exhaust fans, so the heater isn't working very hard. I have one of two 6" exhaust fans set to a minimal of 1% to keep negative pressure. It was a bit tricky balancing the exhaust system with the AC / heater setup which are working in unison through an Inkbird controller. I wanted the exhaust to kick on before the AC, and that took a little tinkering.

I planned to go with a sealed system and bought a mini split about a year ago, but I haven't installed it yet because it seems like CO2 is going to be another expense and another layer of complication. I do hear that the heat pumps actually save money on electric though. I'm all electric, so my bill is huge in the winter months.

I basically wrote that to follow this thread.