Anyone exhausting their dehumidifier outside (through window) outside of lung room to the outside? Does it work to reduce the RH in the room even though the dry air would be exhausted out of the house? (This is in my garage)
I have an A/C unit in my garage and a dehumidifier. As you can imagine they’re working against each-other. AC pumping cold air in and dehumidifier pulling in the air, condensing it and sending warm air back in the room.
Dehumidifiers do pump out a lot of heat. They also put out dehumidified air, so there’s a loss of effectiveness doing so.
My recommendation is to avoid venting outside as much as possible. This can create imbalances, and it costs more. You paid for the treatment of the air to have it pumped out.
When you move dry air out, whatever temperature air with whatever the RH is outside is now coming back in.
Now you’re paying twice for the same air.
These work well to control humidity. The air conditioner is essentially a large dehumidifier also, but with the benefit of cooling the air after dehumidification. I don’t feel it’s necessary to run both, unless you have a serious humidity issue.
The dehumidifier does put out heat, and can cause temperature issues if you’re unable to cool your room.
Yeah, I figured it is counterintuitive to run both but I’m already worrying about the RH and temp this summer. First warm days and already facing issues.
I may need two A/C units which is not optimal. Not sure what else to do.
Faced with a conundrum…. Higher heat or higher RH….
Are you flowering or still in veg?
As long as temps stay below 85°F you should be okay. High humidity is a problem if you’re in flowering, veg not so much.
Flip to flower this week 
4x4 tent. I did order another blower and hose to pump air in so I will have a 6” blower forcing air in and a 6” exhausting outside (through window). Maybe that will help somewhat.
I would relocate the dehumidifier to the room you draw air in from. It will dry the air, and reduce tent temps.
Sorry, maybe incised confusion. My tent is set up in my 1 1/2 car garage. Windows are blacked out, I insulated the garage door yesterday. The A/C and Dehumidifier are in the gargae. A/C unit is venter to the outside through window, the tent ventilation system is also exhaust to the outside.
System is struggling to keep up. Today will be 88 deg outside and we’ll see how high it gets.
When the new ventilation fan comes in I will pump air in from gage to the hole on the bottom, and close the vents.
I would try using only the air conditioner to maintain temps reasonably.
Another option might be to operate the lights at night, when it’s the coolest, and have lights out during the day. I get it if that schedule doesn’t work for you, everyone has a different one, and only available certain timeframes because of work.
I think the AC unit is undersized. Need to look at it more in detail to check the SACC rating. BTU rating doesn’t mean anything…… 
I hooked up an ac unit in my lung room. Vents outside, and i have it elevated to drain into a bucket. Keeps my humidity at 50% steady in the grow closet and temps stay between 75-77° lights on. I just hooked it back up, so after i dump the bucket a couple times to clear out dust or anything in the lines, I can use the water to feed with.
Humidifiers work great, as well, but you’re combating the higher temps. If i run the dehumidifier, I have it as far from the closet as possible, though not much help.
It can be tough finding the balance.
Had to look that one up… got it now, I only used the BTU rating as guideline, because at the end of the day, when it’s 90°, it’s going to run for a hot minute… I look at the BTU rating and I double it to get the proper cooling for the space. (Basically all window units suck, and their measurements for a room to cool, aren’t accurate especially with a heat load.
So after further review, my first problem is my portable air conditioner IS undersized. I will have that rectified this weekend. Current unit is 8000btu / 4000sacc, new one is 12000btu / 8300sacc. Garage is 15x21 (315Sqft), according to DOE this should be sized appropriately.
I feel confident this should help rectify the majority of my issues by reducing the temperature and humidity, thus reducing the need to constantly run the dehumidifier and the systems fighting eachother.
I covered my windows and insulated the garage door to help but didn’t see a huge difference. I also noticed that with the clothes dryer running it was increasing the tent temp by 3-4 degrees in the garage.
Tent Exhaust - I have a 6 in exhaust with carbon filter sucking the air out of my 4x4 along with fans inside the tent. As a safety measure I ordered another 6” to add to the incoming side to force air in. I’m a little worried about them fighting each-other. I did this to assist with airflow but to also allow me to close the vent flaps to keep it dark inside because I am flipping to flower tonight.
We’ll see what happens…… AC arrives Saturday.
This climate control is plaguing me.
As stated above, I got an inline blower to force additional airflow into the tent but that caused too much positive pressure and I couldn’t find a balance.
So, next I replaced my portable 8000btu/4000sacc A/C unit with a 12000btu/8200sacc A/C unit.
I’m running both the A/C and the dehumidifier in my 21x15ft garage. All windows blacked out and garage door insulated. Now, I can reduce the temperature in the garage but the new AC is causing the humidity to increase. If I just run the dehumidifier the RH reduces and the temp rises.
Chasing my tail here. You can see in the graph below, last night I ran the dehumidifier only, all night. Steady temp and average humidity level around 55% (week 1 of flower). This morning at 6:30 I turned in the AC and you can instantly see the temp begin to slowly cool (or maintain) and the humidity begin to creep up.
What am I doing wrong? Driving me nuts.
Warmer days ahead this week too. I will add that the RH outside yesterday and today has been at/over 75% RH outside.
I’m against that I’m wasting $ running them both for something that may be out of my control.
If your state is legal, just get some polyfoam board and put reflective side out on the windows. If not legal, hang white blinds between the reflective surface and the window. Seal the foam board to the sheetrock. Cut a three inch wide strip of the foam board to make up the difference in thickness for the window molding. Lots of hot air comes in around window framing.
From your pic it looks like a black towel on the window, that will increase your heat if the sun hits it at all.
If you haven’t yet, seal the garage door the same way. The only way air should enter the garage should be from the doorway into the house which I hope is A/C.
With the exhaust fan running in the tent, you’ll be amazed at where air will be drawn from. I used a cig lighter and watched for the flicker of air moving. I was shocked I had multiple places it would blow the lighter out. EVERY little crack matters. Caulk, aluminum duct tape, whatever is easier for the application.
Is your attic access in the garage, a lot are, it will suck hot attic air in the room.
I wouldn’t use a stand alone A/C. They generate a bunch of heat even when exhausted outside. Consider a window unit, the “hot” part of the A/C is outside of the room. Most are sealed pretty good to keep cooled air separate.
You can run massive A/C and dehumidifiers and run in circles if you don’t prevent the draw of outside air.
It may be easier to cut the garage space in half and build a smaller lung room which can be sealed much easier. Keep anything generating heat, out of the room, and duct what you need into the room.
The house is all under trees (0 sun whatsoever, I did that for the light) so even though I have black towels blacking out the window it doesn’t seem to have any extra noticeable heat.could be, but don’t think that’s the main problem. But I’m going to get solar reflective blackout curtains to put in place. Garage door is insulated, did that last week.
Yes, there is a crawl space above. I’ll have to check to see how much air is getting sucked in and insulate as needed. Good point there.
I can/will insulate the exhaust hose to prevent that heat, that was on my list. Buying a window unit is not in the table at the moment.
As I fought my battle, I didn’t find any one thing, just bunches of little things.
When you say you insulated the garage door, does that mean it’s “sealed”, no air leaks. I Insulated a window with polyboard, but had to go back and caulk because it was sucking air between the polyboard and the sheetrock. I had it screwed down with fender washers, it was still suck’n air.
Where I ran the exhaust from the tent into the attic I had to fight to get the duct hose through the hole, I still had to fill in around it because it was suck’n air from the attic. I even had to open the window A/C and tape the assembly seams on the styrofoam duct separating the cool from hot air. Where I ran the RO supply and drain lines through the base board to the laundry room I had to seal that hole up. All these I found by using a cig light and watching for air movement.
Sounds like your on the right track, just keep chipping away at it and you’ll get it.
