What type of heaters do you have - gas, electric?

My fan runs all the time. It is used to circultate the air for both the plants health and to distribute the heat. My heater is gas - Modine - so it has a built in heater that goes on when the funace goes on.

Also what fans are you taking about - interior circulating or exhaust

Hi Plantman,

I've got a Harbor Freight Greenhouse with no exhaust fan. The environment in the greenhouse that I know needs to be met for my special situation is this: The humidity in the greenhouse needs to be very high (95-100%) all the time while the temps need to be cool (In that 45-50 degree F range)... all the time

These are the components Im dealing with. Let me mention one more thing. IÂve already decided to buy another fan thatÂll be plugged into a thermostat control like the one I mentioned above, so IÂll have two fans plus the vent opener, which opens the single vent The Harbor Freight Greenhouse comes with Â(plus shade cloth as needed). ThatÂs as best as IÂm going to get I believe. I realize to control heat issues I can also spray down the walls and floor of the greenhouse with water to help as well. Other than that, I have the Autovent which opens at 60 degrees F and that will be my ÂexhaustÂ. And so you get an idea of placement for the fans, both will be placed in the upper corners opposite the Autovent/Vent aimed aimed directly at it. Then of course my heaters will be on the floor. IÂll also show you a few photos.

Model DFH 480M DeLonghi fan heater - The Heater Shop

Bayliss XL II Model

7" Clip-On Compact Fan (Scroll Down)

Gempler's Shade Cloth's I bought the 12 x 20 so I could just throw it on as needed and anchor it with bricks.

Photo 1: My Autovent which is partially open because the current temp is 62 F
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Photo 2: The Fan in the corner pointed toward the vent.
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Photo 3: The Side of the greenhouse with the Vent and my Sand Box which I will be burying my grafted plants in just above the union and budding strip and scion.
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Photo 4: The opposite side of the greenhouse. You can see how the fan is in the corner where the benches make an ÂLÂ shape.
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Photo 5 the last photo: The opposite corner for the other fan IÂll be ordering to also aim toward the vent.
{{gwi:308255}}

ThatÂs what I have to work with and I "believe" thatÂs the best I can do with this style of greenhouse. Thanks for your suggestions and for your help.

I'm learning HTML codes...obviously I don't have it quite right yet. Thanks again for your help.

Dax

Hi Dax,

Good to see you got your electrical worked out.

Based on your other picture, my guess is that you are talking about HAF fans, not exhaust fans.

I also run my HAF fans 24/7.

An advanced system will turn of HAF fans when, in the summer, the exhaust system is activated. You don't need the HAF when you are moving that much air through the GH in summer, so you can save a few $ this way. But I don't know of any controllers that do this automatically and I would guess it would be a little tricky to set up on your own.

At home I have an excellent link to a site discussing HAF. I can post it if you want.

SB

Dax, we posted at the same time.

It sounds like you are using this fan sort of like an exhaust fan.

You may want to consider another fan that just runs 24/7. There are formulas for calculating the size of HAF fans (in cfm) just like calculating heater capacity. They are contained in the link I mentioned above, but I'll have to post it tonight, I don't have time right this minute to google it up.

SB

Thanks Stressbaby. I'm not familiar with the abbreviation HAF so you'll need to explain what that is as well. I'm also starting, however only starting to understand that since my grafts will always have the humidity they need, I could in fact run a fan at all times. This is just yet another step in my mind that I just couldn't see until now.

To control the heat issue then (let me ask) would it be wise to keep my other fan on this thermostat device I have programmed for 45 degrees. Just guessing as an answer to my own question, I would think that's the way it should be set up. Then as SB suggested I could run the other one at all times. Please correct me if I'm wrong in my thinking.

Until then, I'm going to order another one of those fans right now because I like the way they clamp and because I really think I need two instead of one and then lastly, I'll wait to hear from you guys as to what you think I might need to do otherwise to help keep my greenhouse as best-suited for my growing needs as I can possibly manage.

Thanks again everybody (a lot),

Dax

Dax,

HAF is horizontal air flow.
Here is the link. Your fan is rated at 210cfm, so using the formula, one alone should be enough for HAF.

But even optimally positioned (in the wall) this cfm rating may be too low to act as an exhaust fan. Move it that far from the vent and you basically have an HAF fan on a thermostat. If I were you, and I really wanted to keep it cool, I would use your current fan for HAF and instead of buying another clipon, I'd buy a fan you can frame into the wall and use that one on the thermostat.

SB

i use an indoor/outdoor ceiling fan,and 2 cheap walmart box fans.they stay on 24/7.the thermostat for the vent fan is set for 82 degrees.

Hi Stressbaby,

I read the link and also took into consideration your thoughts for an exhaust fan but I really know nothing of exhaust fans either. For my Harbor Freight, what size would you recommend and where should it be placed? About the only panel I have that has room to do such is the panel directly behind the wooden box I constructed. Also, I know nothing about these and wonder how when not in use the greenhose is sealed up ? I really don't know whether I'd be able to do such a thing right now because #1 I don't know what size or how much it would cost, and #2 I don't know the cheapest place to buy it or how it fits and stays in place. Could you tell me a little more about these exhaust fans, please?

My other option is to simply include another one of those clip-on fans, which I already purchased, and hopefully between wetting down the walls and floors and using my shade-cloth, I may be able to keep the temps where I need to be at...however, it doesn't seem like I'm going to be able to. That Harbor Freight greenhouse sure seems extremely efficient in terms of not releasing heat, which will be good in winter, but bad when the temps begin warming up...thus your recommendation for an exhaust system. I feel like I definitely need the exhaust fan but I also hope that there's a possibility that the clip-on fans will do the job.

About HAF... You notice that I have my fan in the corner aimed at the roof vent. From what I understood from reading the link, the fans need to be positioned a certain way to create air-flow that is circular in pattern. If I were to not do/get the exhaust fan system as of yet, should my other fan be positioned to push air toward my other fan then? I need to make sure I understood this.

Then here's the newest scoop to my project at hand: I emailed a conifer hobbyist grower who's been successful in his own domain of zone 3 Canada and he recommended that I use heating cables as well. So I'm going to put those in as soon as I get them/it. I already dug out some sand and placed hardware cloth in place so I'll be ready to tie-wrap the cables to the harware cloth. Then I'll add a few inches of sand and then I'll bring in my understock. He told me this: "I may even add bottom heat and keep the sand damp so the roots push sap and the moist air rises off of the sand past the scions." He also went on to say, "For pines it is very important to keep them under 50 degrees and not below 45. (45 sor sure but 55 is tolerable) What you are trying to do is supress new growth from happeing while getting good push and healing from the roots. Pines tend to 'bolt' early if it gets too warm up above and the healing graft canot support the new growth. Slow spruces (the more dwarf like the slower they are) also need more time and cooler temps for about 6 to 8 weeks. I would start warming up the roots soon and graft in a couple of weeks most pines and spruces around 20th of Dec. or so. Keep everything cool until late Jan. at the earliest."

He also says, "If you start getting too much sun in late Jan. it would not hurt to throw a small piece of shade cloth 30-50% over the grafts until new push is showing and even then you have to be careful. Sometimes the new push is simply because things got too warm too early. If your fans are cutting in too much you have to be there to kkep the humidity up by misting a bit now and then."

Lastly, I think he just forgot to realize that the grafts themselves: the union the budding strip and all will still be under moist sand so misting won't be necessary on the grafts themselves. I am however planning on throwing the shade cloth over the entire greenhouse should it get too warm and I also plan to spray down the walls and floor as necessary in addition to try to bring down the temps.

So that's where I'm at currently.

Let me know what you think. Thanks, Dax

If I were to cut a circular hole in one of my panels and goop if up with silicone to hold one of those fans (Inductor Fan?) that can be purchased at a home improvement store that normally used to force air in heating ducts... and then attach this product Non-insulated Aluminum Air Duct or something else you guys might suggest that could be placed outside the greenhouse and attached so that it is curved down or to one side.....Would this be an example of an exhaust system?

I don't know what size inductor fan I'd need, but something tells me to go with the eight in versus the six inch. I remember seeing both 8's and 6's at the home-improvement store.

I would of course hook this up to my Plug-In Thermostat Ductstat as Stressbaby Recommended I do

Thanks for your feedback and expertise!

Dax

I would make sure it could stand up to the moisture from the GH...

Hi again,

I'm writing now to explain what I'm dealing with. All morning and currently it's been 22 degrees F and very sunny. The greenhouse with the door closed still got up to 70 degrees with the fan running before I decided over an hour ago to open up the door and place a stand-up fan to bring the air out of the greenhouse. I've now got a 50 degree temp and I'm waiting till it gets to 48 so I can reset my Thermostat Module the fan is set on. Then I've decided to run the heater at 45. I think even with an exhaust fan, I'm going to keep one of the heaters also on that Thermostat Module and then the other constantly running on low or maybe even high.

That link I provided above has a lot of exhaust information that I didn't see until I scrolled down the entire page. I'm thinking now that I can use parts identical to what they're selling but to buy them at my home-improvement store...still silicone caulking it up and then having some sort of Air Ducting "tube" to channel the air being removed from the greenhouse to the outdoors.

My only and last question still remaining is: Are these the right types of exhaust products I should use and should I use an 8 inch inductor fan?

Thanks again and Happy Turkey Day!

Dax

Hi Weebus,

Would you please explain about why an inductor fan may or may not stand up to the moisture? Or are you talking of something entirely different? Also, what do you recommend I do all things considered. I am willing to cut into my panel...

Thanks very much,
Dax

An inductor fan is for use in cool and heating a house. Like a fan that I use in my attic to keep it cooled off up there. It isn't made for moisture.

An exhaust fan is a fan that sucks the warm air out of your GH. It is mounted in framing and a hole, the size of your fan is cut in the glazing. The air inside your GH has a lot of moisture in it. The exhaust fan is made to endure the moisture, unlike an inductor fan.

It is very unwise to cut corners on electrical items concerning a GH. Spend a couple of busks and get the correct item, it wll save you money in the long run. I know money is tight, so you can't afford to replace your fans every couple of years. I know, I too am a disabled vet...

Can I use the Inductor to vent outside air?
The Inductor has to be protected from rain and excessive moisture. See link

Ok Weebus. I read everything on that link at least 3 times... I'm so stupid that I can't figure out if you provided that link for me to find what I need or if you provided that link to show me what I shouldn't use!!!
Please forgive my ignorance.

I also linked above a webpage about "inductor fans" that I thought were for greenhouses but I can't now tell if this "Greenhouse Supply Store" is selling an "inductor fan" or an "exhaust fan". Their link again for easy access: Home Harvest Garden Supply They do have a real nice part that "an exhaust/inductor fan" fits in...Please let me know if this part: 736255: 495CFM Intake 6 inch duct adaptor for use with 495CFM Dayton blowers under the section: EcoPlus Blower Duct Adaptors

In the meantime, my father came over to discuss this matter and about the only thing that came from the conversation was that we needed a 6inch hole saw (or if you think I could get by with a 4 inch hole, he already has that size hole saw. Other than that I guess he did come to another realization and that was this: that there are coverings that fit on the outside of these 'fans' that open and close for when the fan is running. He explained to me that these "shutter-like" openers and closers are used on the outside of homes for when a dryer is running in order to "open up" at this time and to close when the dryer isn't running.

So, I need to ask you...... where do I buy the correct exhaust fan that I'm looking for. Does 'Suncourt' as mentioned in your link above have something for my use or if not........I need a source, please! And not necessarily cheap...but within reason. I'm on disability too, yes!!!!!!!!!!! And yes!!!!! I bought a cheap greenhose!!!!!!! But Yes, Currently I do have the funds!!!!!

Once again...all things considered...I need exact recommendations for help.

Please help me I'm begging at this point! I at least want to see my options and I don't necessarily need to be a cheapo...if you know what I mean. However, I don't need a 200 dollar 6" exhaust fan either. Or like I said, we already have a 4" hole saw blade with a mandile so if a four inch exhaust fan will do the job then I'll simply go with that. I need advice and your sources for the "correct" exhaust fan And yes, I need my hand held on this one!!!

Thanks very much for your help.

Sincerely,

Dax

Here is a link that you can use for reference. I don't know if you need the intake shutter or not. You may be able to just leave your door cracked...

Look at the pictures to give you an idea of what we are talking about.

The prior link was so you know I wasn't talking out my behind about not using the inductor fan. Not good with moisture...

The 8" circulation fan you see on the link is also what is called an HAF fan. They run continuously and are a seperate function from an exhaust fan. You don't need anything like that, just some info for you to learn by.

Now I need to go and have a Thanksgiving dinner with some friends.

Hope everyone enjoyed their day!

Hi Dax, and Happy Thanksgiving everybody.

Weebus has given you good information. Generally speaking, you want a fan with a cfm rating roughly equal to the cf of your GH. This way the fan will exchange all of the air in the GH once every minute.

Again, generally speaking, you want the fan placed high on the wall so that you exhaust the hottest air. You want the fan to draw air all the way across the GH, and this means intakes low on the opposite wall. And finally, it helps to draw the air across in the same direction as the prevailing wind.

A screen door can serve as an intake. Alternatively you could frame in an intake shutter just like you would frame in an exhaust fan.

I don't think you'll get it done with a 4" hole saw. I've never seen a HFGH in person, so I can't give you precise details about how to do the installation. But basically you would cut out some of the glazing, frame a square out of metal or wood, and bolt/screw the fan in place. You may caulk around it if you want. You might find it easier to take out the whole piece of glazing, frame out and install the fan, and then cut up your PC to fit around the fan and reinstall it.

The fan (and shutters for that matter) leak some air. In the winter you may want to cover it up. I use a wooden box with old towels stuffed inside.

Technically, you don't need HAF fans running when the exhaust fan is on, but designing a system that shuts off the HAF fans when the exhaust kicks on is tricky (I'm working on it).

The fans listed in Weebus' link didn't go any lower than 12 inches, 1000 cfm. Below is a link to Charleys where you can get a 10" exhaust fan, rated at about 500cfm. I think it is a more expensive, though. There may very well be smaller or less expensive fans out there, you'd have to do a search.

Here is a Farmtek 10" fan rated at 600+ cfm for $137.

First off thank you folks for helping me.

I'm going to stir a bit of controversy but I'm going to do what I feel is right.

The link Weebus provided me 'for what not to use' is the same company that I bought my 'Plug-In Thermostat Ductstat' from. I just got off the phone with them.

This person explained to me that 'inline-inductor fans' are being sold by their company to remove heat from Artificial lighting in greenhouses, and that they are constantly being exposed to humid conditions. He told me that a 4" Inline Fan would remove the air from my greenhose which is approximately 322 Cubic Feet every 8 minutes. He also told me I could hook that up as well to my 'Plug-In Thermostat Ductstat' with no problems whatsoever. He said these products are rated for greenhouse applications and that I should have no fear of using them for the application I'm needing. He also said that modification of these products for uses such as mine are very much within reason and that simply modifying them for this application can be and is being done all the time.

I thank you guys again. I'm sure you think otherwise but I know the small 4" fan will do the job...or at least the job I need to have done.

I'm going to mount a board on my polycarbonate wall, drill the 4" hole out, keep most all of the inline fan unit inside the greenhouse and install a lightweight aluminum shutter guard on the outside of my greenhouse.

I'll let you know how things work.

Many thanks,

Dax

Hi Weebus,

I just want to thank you because of your comment about 'keeping my door open' and as a stroke of luck on my part, I built a simple screen door from 2 x 4's I had lying around and purchased a large hand-clamp to attach the upper right corner of my 2x4 door to the track my door slides on and I simply placed a large concrete block on the bottom left corner. Now I have a portable door!

The temps are 54 degrees F presently and with my shade cloth on and 2 fans running, and my vent open, and my screen door..... The temperature in the greenhouse is currently 59 and dropping! Plus, it's extremely sunny outside.

This addition plus the inline duct fan (dare I mention it!!!) plus my shade cloth and my second clip on fan that's on it's way outta leave me plenty of 'play' to keep my temps as close to or about where they need to be.

Thanks again...inspiration comes from out of nowhere at times!

Best,

Dax

That's what we are all here for! (Well besides giving Chris someone to argue with)

"Well besides giving Chris someone to argue with"

Was that really required on a thread I had not posted to?

OK, now I feel obligated to add something to this thread so that weebus can tell me how wrong I am and how I make myself look foolish yet again.

Use the fan to blow air INTO the greenhouse. In/out same CFM but a big difference in the "wetness" of the air that is passing over the motor.

If you are blowing air into the greenhouse you can also make some sort of device that adds humidity to the incoming air. a mini swamp cooler.

As to high humidity air passing through a non-greenhouse type of fan. The motors run warm, the moisture does not condense on it when it is running.

This thread is "suck it out".... "blow it in" gets exactly the same results but what passes through the fan is a totally different kind if "air"

Oh by the way conifers if you use that inline duct fan to blow air INTO your greenhouse you don't have to cut holes in it at all. You just have to dig a hole under the foundation.......

Chris you have lost your sense of humor. IT WAS A JOKE.

He can't dig a hole in his driveway, hey plus the guy said he would be fine...

OK, shiny happy people, let's put aside the moisture issue for a second.

Dax, for what part of the year will you need to maintain the 45-50*F temps? If you will use the GH spring, summer, or fall, I am more concerned that your system is undersized.

Is anyone else concerned that Dax has an undersized system? He's turning his air over EVERY 8 MINUTES.

SB

Yes, but he talked to the guy who probably doesn't own a GH, who said it was OK to use the 4" inductor fan. I can only advise, and I am tired of arguing with the "Experts".

Hi guys!

I'm only using the greenhouse from right now until I have no worries of spring frost's...so up till Mother's Day.

I too was a bit concerned about the turning over of air but in all reality, I'm only using this fan on the thermostat device so it will be running at times and at other times not. You know, it's basically just to help a little. I also have shade cloth, my new screen door which I can attach in seconds, a new wireless thermostat I ordered with an alarm feature, and also another clip-on fan. I'll admit I'm here for help and am no expert which I certainly believe Weebus is, Stressbaby, and others which I just haven't had much conversation with as of yet. I do agree now that Chris has a good point about bringing air in but unfortunately at the time I dreamed all this up I didn't have the expertise or knowlege at my disposal. I'll try what I've already done and if it doesn't work well, I'll turn the inductor fan around and bring air in instead. Currently, I bought some real nice stuff besides the fan which is a tapered unit that keeps outside rain, snow, etc from entering to the fan. It's actually really nice...I'll go take a photo and show you right now.

You guys have to realize also that in my mind when you spoke about exhaust I of course thought of air leaving the greenhouse.

Here's the photos:

This is the outside piece that I just silicone-caulked this afternoon. There are two identical pieces of painted wood on both sides of the panel that were silicone-caulked yesterday. Today we used a hole saw to create our hole to do the work.
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Then a photo of how this piece has a 'flap' that opens and closes depending of if the fan is running...it's feather-light.
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Then lastly the inside of greenhouse where the outside piece comes in and where tomorrow after the silicone dries, I'll place the fan into which will be screwed to this 'duct piece' and then plugged into the same thermostat device that I have programmed to turn my other fan on at 46.5 degrees F.
{{gwi:308258}}

Now even though Chris may be correct, which I don't deny, I would have had to put the inline-duct fan in the middle of the hole between the two painted boards, caulked it, and put (2) of the above photo pieces (Photo 1) on both sides of it...which now leads me to think I may still do that now...ahh, better slow down here a little before I get in over my head again.

Anyways, as you guys see, The hole will always be there and I can always turn the inline fan around if I need to, but I still think I may be ok.

Well, start telling me what you guys think again. As you see, I made it this far with your help, and I can always change some things around as well. I'm always open to suggestions and good advice.

I think I mentioned this but...the fan will be installed tomorrow after the silicone has dried. And I just remembered something else that I'd like to mention (if I still have your attention); Even though I'm sure the humididty will naturally always be there from having flats of other stuff like seedlings and cuttings in the greenhouse as well as the grafted material, the grafting material itself (the conifers) will be buried in sand to compensate me having to spray the walls down all the time to increase the humidity.

What else can I say...I'm trying, I'm learning, and I'm as I mentioned willing to change anything else and to continue learning.

...Dax

I'll also mention that I've found with trial and error that if I keep my heaters programmed to run at 48 degrees on one and 50 on the other and then having that thermostat device my clip on fan is running off of....I've learned that the temperature at night is always between 46-48 degrees F. Now this is still trial and error but the temps got as low as 22 the other night and have also been as warm as the 40's and 50's and with how things are currently set, the temp at night was still within that 46-48 range for this extreme fluxuation.

This I believe to be a miracle in progress thus far!!!

Dax

Well, Dax, you may be OK if you are not trying to cool the GH beyond May. Do a temp record and post it. Maybe we can learn something from you. SB

I am glad you are writing your own book Dax. I may grow impatient with he said she said, BUT this is how we learn and, we will never know if your set up is going to work unless you try it.

We did try and turn our fans around at work and it didn't work. You may have better luck, but we were able to cool the GH several more degrees by pulling the warm air out rather than trying to suck the cool air in. Just a thought.

It's in progress then...

Thanks again guys,

Dax

I didn't make myself really clear. I was thinking about using a non-greenhouse type fan in a greenhouse. If you suck out the wet air then you are not using your el-cheapo fan in a situation it is designed for. However if you use it to blow in normal air type "air" then at least you are trying hard not to get the fan "wet"

For three years I was a sucker not a blower, This time I am keeping my options open. (counting down the days to Feb 15th............)

This is a little off subject and perhaps you have already taken care of this in some way that I can't see in your pictures....but I was wondering about your electrical outlets in your greenhouse. Had you considered using GFI outdoor outlets instead of household ones because of the high humidity and chance of getting wet? You said you would be spraying down the walls of the greenhouse to cool it and I'm concerned about your outlets being so exposed. We used outdoor application GFI's in my greenhouse and placed them all about 6 ft high on the wall so that they would not be in the direct line of any spraying water. That way I can drag a hose in to water plants if I want or to clean out the greenhouse and not have to worry about water hitting anything electrical. It is only a tiny bit inconvenient to have to reach up to plug or unplug things in but seems so much more safer that way. Don't want anything burning down after all our hard work to build these greenhouses! :)

Good point. Dax might have the GFCI protection on the breaker. If not, Dax, you can just get a GFCI outlet and switch out. Get the same amperage as on the breaker. And an "in-use" outlet cover is a good idea. Then you don't have to unplug anything. SB

Hi Wyndyacre - Hi Stressbaby

Here's another area of what my father thinks is unimportant. I explained to him that "everyone" else has 'covered outlets' in their greenhouses. As always his reply is: 'I've been plugging things in like fountains all my life and have never used any of this equipment.' He just doesn't have any fear of problems nor any fear of electricity... What can I say other than thank you.

Today, we're putting in another in-line exhaust fan. This time it's a six incher with a converted duct-piece adaptor to allow for a four inch hole to be used for a six inch fan. I've been keeping track of various data and even on very cold days with the sun shining brightly, The temps have soared up into the 60's a few times. In addition I received my other clip-on fan so I just added it moments ago. It's now extrememly sunny, I have the shade cloth on...both fans running and the 'home-made' exhaust...and the vent open. I sure hope this second larger inline fan does enough work to keep this thing cool.

I'll be back...

Dax