Put in a misting system. I live south of Ocala,FL and that's how I keep all 3 of my greenhouses cool all summer. And believe me it gets hot here.Somethings I take out for the summer but there are still some plants that stay in. But a misting system during the day will make a big diference.

Mist will help, but I wouldn't think you would need mist in March in zone 6.

Is your exhaust fan sized appropriately? In order to cool to within 8*F of outside temp, it needs to exchange all of the air every minute (thanks, Cuestaroble).

Get the shade cloth, it makes a huge difference. With an appropriate exhaust fan and shade cloth you shouldn't get more than perhaps 4-5 degrees over the outside temp.

SB

Just how hot is tooooo hot, darrin? Did the temps reach 110 degrees inside?

Two auto vents? That auto vent should close at night, it may need adjusting, a bit at a time. What about the other two vents that came with the kit? Are you opening them in the daytime?

Did you put in a heat sink? That should help, too. I'm about 400 miles south of you and not having a problem with daytime temps yet.

If he has the Harbor Freight vent opener it will not open until it is too hot and if you adjust it to open at 80F it will not close at 60F these units are a P.O.S. I bought four of them after seeing have flimsy they were and how they worked I threw them in the trash.

LOL welcome to the wonderful world of Greenhousing. This is one reason little greenhouses are worthless. If you have a 6 foot roof, your going to have a hothouse come spring.

I may only have a rinky dink 6'x8' el cheapo HFGH but not all of us can afford or have room for anything bigger at this time. I may be new to this forum but if you can't be helpful in your comments keep them to yourself. I review this forum to learn and not to be insulted

Good Lord, belleville rose gr, you must have had a hard day at the job. I dont believe anyone was insulting you or your greenhouse. I just made a blanket statment about small greenhouses. Your'll learn, we all do. I learned and moved on, you will too. Welcome to the forum, its a great place and I am sure you will agree with my blanket statement in time. :-)

Hope tomorrow is a better day for you.

Just ignore those who haven't anything pleasant to say, Belleville, and their grammar. We all have different goals.

Darrin, the HF openers will work if you keep fiddling with them. We had one of the four that had to be returned because it was actually defective. They replaced it and FINALLY all are working as they should. It helped to read the directions aloud, LOL.

About the heat sink, I think you said that would be one of the things you'd do later. Not only does it help with nighttime lows, it seems to mediate daytime highs. There have been several opinions on that in previous posts here.

Darrinky, I'll ask again...Exhaust fan...how big is your exhaust fan?

The roof vents are fine, but they will be inadequate in warmer weather. Additionally, having roof vents open decreases the efficiency of your exhaust fan air exchange. In the summer, I generally unplug my ridge vent; the cooling from the exhaust fan is much improved this way.

Shade cloth + mist + exhaust fan will generally work in z6.

I have already place an order for a shade cloth and a misting system from Charley's. I won't make it through the spring without frying my plants. I had 80 degrees inside the other day when it was 45 outside I opened the vents and it dropped to 70. The shade cloth I order will let me reverse it during the winter and will act like a solar cover. I believe its called Chill out

Hi, I have a 6x8 home attached greenhouse I built last summer. So I am still working everything out. I bought an aluminet shade last year, it is pretty much the same thing as the chill out shade. It did help alot to keep the temps down. I suggest you mount it outside the greenhouse during the summer. I found this worked better. In the fall I mounted one inside and I liked that, but i took it down in the middle of the winter as I wanted more light.
Since my greenhouse is home attached I don't have an exhaust system like yours. I have a roof vent and fans though. I didn't have any heat sinks last year and my greenhouse would get maybe 130 somedays, that is if I forgot to open the glass door in the morning. I am still trying to figure out what to do about that this spring. In the morning, before work I usually open the glass up and then close it in the evening when I get home, but it sure would be nice to have it automatic.
Our greenhouses are smaller but with work they will be fine. It will just take more work than with a large greenhouse, of course it is cheaper to heat our greenhouses ;) so they do have their benefits!

I also have some really tolarant plants that I am growing that will be perfect for shading other plants in my greenhouse. I have some hoya, and they are doing SO well in the greenhouse. I hope that when they are slighty larger that they will help shade some of my orchids. It is going to take some work and I know I will lose some plants, but I knew this when I bought the greehouse.

My exhaust fan pushes 1320 cfm so it should be adequate. I was on duty at the fire station yesterday so i was really worried about my few plants inside cooking...
High temp inside yesterday was 87 so i was so relieved. The doors were shut all day and everything seemed to stay fairly cool. IT was really nice outside yesterday with a high of 60. I have to get my shade cloth on order.
Can someone describe the misting system in breif and tell me how it is controlled. Timer or what??? Two more heat sinks go in today. You guys are the best.
PS> If a mister runs all the time what keeps all electrical components from rusting/shorting out? DO they just mist the plants. I picture misters like in the produce aisle at Krogers or Wal-Mart? PS I have no intake vents for my exhaust fan. How i overlooked it I do not know. Suggestions for that as well will help. I was wanting to use passive peak louvers from lowes that open when air from a fan pushes them and just reverse them. Will this work? Seems drafty when wanting to hold in heat.

I don't think Orchiddude was trying to aggravate anyone. He's basically saying that small greenhouses are very difficult to maintain an appropriate temperature/growing conditions...and he's right! This applies to many things...a 4' pool table is a major compromise, a ten gallon saltwater aquarium is a zillion times more challenging to raise fish or corals. It's a simple truth...unfortunate but real. I'm glad Orchiddude has a big greenhouse and I know he must enjoy it. I hope for the same thing for myself.

I think all of us that enjoy or dream of having a green house need to recognize that our goals should ideally be to have a BIG greenhouse. In the meantime most of us will have to make do with smaller ones and all the inherent hassles associated with them.

I purchaed the following from Charleys
http://www.charleysgreenhouse.com/index.cfm
#6076 Greenhouse Watering System
#3320 Hose Y Timer
#2122 Chill-Out Reflective Shade 10 ft x 12 ft

Darrinky, I think we found your problem...no intake vents. Your exhaust fan is just pulling air in through the roof vents. I don't know, but I strongly suspect that they aren't big enough. Even if they were, you aren't moving air all the way across the GH.

Put in one or two adequately sized intake vents on the wall opposite your exhaust fan and you'll likely drop another 10-15 degrees. The passive ones will work. Motorized ones can be set to come on at a lower temp than the exhaust fan. You'll want to seal them up in the winter. I use 1" rigid foamboard insulation.

I would recommend the electrical components be protected from moisture as a general measure. This means using "waterproof" wire nuts, GFCI protection, "in-use" outlet covers, and so forth. With this, you won't have to worry much about mist, watering, condensation drips, or anything else.

There are all kinds of mist systems out there. Many people use the misters you can get in the lawn care sections at Lowe's or HD. They sell timers, tubing, and such. I found the mist from these systems a little coarse and so I went with a mist kit from Hummert. Most people I have seen install the misters overhead. I positioned mine over the aisles so that any drips when they shut off did not land on the plants.

There are a variety of timers available. Just make sure that the mist goes off at night, preferably a couple of hours before dark, so the foliage has a chance to dry off a bit.

SB

Thank you lilies4me, your right, I wasnt trying to piss anyone off. The smaller they are, the harder they are to work with. The person that makes these little greenhouses doesnt want the buyer to know that. I am also amazed at how they advertise these little houses. If you look in the magazines, you see these little greenhouse out in the open with what looks like a pretty day. The pictures usually have people in them working with plants or something. You never see fans or misters running in the ads. Its like a perfect little house, until you get them, then its a nightmare. Its to hot or to cold etc...

I guess I would be pissy too, if I bought something that didnt work....LOL. I am joking, dont beat me up.... :-)

orchiddude
I know you were just trying to help but some times the truth is hard to accept.
What you said is true just like what I said about the HFGH vent openers. Several took offense but I was just trying to keep someone from wasting $80.00 like I did.
If someone has them and with a lot of fiddling as one poster put it he made them work and he is happy with them fine but I stand by my statement. In my opinion you would be better off buying a Bayliss rather than the HF opener.
In the past I was using a 6x8 GH to grow plants from seed in the spring. In the summer my GH is empty but on a 60F day I could not keep it from overheating.
Today it is near 60F as I write this and my exhaust fan is not running and I only have one of the three windows in the back open along with the front door about half open.
I just could not believe what a difference a 10 foot ceiling makes.
I have a alumni shade cloth but have not put it on yet probably won't use it until it goes into the 70's

Box fans are versatile and can be easily used and moved. You can hang them to fill a doorway and move lots of air.

Folks, I've been swapping gardening stories and advice with Orchiddude for a number of years. Let me assure you that Rob is a very nice guy and would not insult anyone on purpose.

You guys wouldn't believe it but I rarely if "ever" see a greenhouse in a yard in my city. I can keep a Harbor Freight 6 x 8 Greenhouse at 63 degrees (note: I read from stressbaby in a thread this week that plus or minus 3 or 4 degrees F was possible with a shade cloth) when the temperature outside yesterday was 56. I open the one little vent, have my "system" for exchange running and a shade cloth covering the entire thing. That's it:)

Dax

Should or if anyone would like to know more, I'm using two sections of 8 feet running feet length of Heat Mats, Have less 'open' square footage within the confined cubic feet space due to the use of poly tenting chambers for simple propagation (grafting) and naturally I wouldn't be writing an answer to some of these questions if I didn't have information to share.

No thermal mass, no nothing. In fact and one of the other reasons I answered is because not only all this, I caulked the entire thing shut as solid as a drum. And it's in full sun till mid afternoon.

One 'lucky' advantage is that a large 30 foot Red Maple (for reference to branch structure) rests directly south of my greenhouse and only 15 feet away should I imagine... so when it really warms up and these red maples begin leafing out, I instantly shift to afternoon partial sun.

My shade cloth is stretchy and I bought it from Gemplers. This way I can always open 'that' vent.

Have a wonderful day everyone!

Dax

2 things I did, one I used black weed control that comes in rolls and put them on ceiling on the south side with the julianna clips. Second, I didn't caulk the 2 middle panels on both sides and put screen on them. That way I can clip the panels off from the outside and get the breeze. Then I made a big screen for the doors, so I could leave them open, and keep out the bugs. If it still gets too hot in my greehouse, I water everything and that will bring the temp. down.
Hope this helps, I will try to post pics of my screens.

How about this beaut of a door:

{{gwi:292991}}

Bring it up and with a spring-loaded clamp, add a screen door built out of 2 x 4's and you have more area as touched upon by the poster above.

Dax

Watch out!

I am finally planning to start construction of my HFGH 10x12 this weekend, and have been thinking about the number of automatic vent openers necessary. This seems to be an appropriate thread to discuss it. Only one poster here mentions having four openers (or ordered 4). Most everyone seems to have only two, from the reading I've done. Why wouldn't it improve Darrinky's situation to increase them--or do you have two on automatic and two manually opened?? Or would this interfere with the exhaust vent/fan system, as Stressbaby maintains? I am just about to order 2 of the Bayliss Mk 7 S's, but perhaps 3 or 4 would be better? I plan to install all 4 vents on the leeward side. Any advice or explaination why most folks are only using two is welcome. Thanks,
Ann

I started out with two just as a trial. I should get four. Honestly i didn't think they would hold up so I am still waiting for the wind to rip one off. My Harbor F. models open well. IT is the vent mounts on the greenhouse that are weak. I reinforced mine with some aluminum I bought at a home improvement store. I will try and post a pic. It chaps me that when my new shade cloth comes in I will have to cut it in order for these vents to open. Brand new and I have to CUT it!!!! I am sure there are other brands that work better but for $20 I can't complain about the HF model. The metal piece is under the mount on the greenhouse. It is hard to tell but it helps hold the weight and keep the original strip of aluminum from twisting. Once you mount one it will make sense.{{gwi:292992}}

PS... temps have not been too bad even when we had a warm spell last week. One day when I was on duty it got up to 92 degrees. (70's outside) I have a big oscillating floor fan that I set up on a timer to run from 2 to 5 when it gets hottest. It will not help when temps get in the 80's and up but hopefully my new shade cloth will be in place next week. ONe thing I have learned... there are no hard and fast rules to this... you just have to try things and see. Bad part is... you may kill prized plants figuring it out. I waited a few days before anything real nice went in. I did all my digging/renting buying and reinforcing for under $1400. I still need a mister. I plan on buying tees and nozzles from ACF greenhouses and building my own system from PVC. I bought a six series digital timer from Home Depot for under $50. I like it. It can run from one minute to 10 hrs. per series.

Last year I started my plants in the portable GH that I used for two years and in the spring I worked on my 10x12 HFGH but did not put it into operation until this year.
This gave me a year to play with it before I actually used it.
I bought 4 HF vent openers but the operation of them was erratic they would open late or close way too late and the heat was going out the top. Those problems along with the flimsy construction caused me to junk them.

For those who have not yet bought vent openers here is something to think about. If you use vent openers they will only work while it is cool when it reaches the 80's you must force ventilate.

With operational vents you need to cut you shade cloth if it is not hemmed it will probably tear.
Do a search on this forum and read about all the problems people have trying to keep a thermal blanket on in cold weather. If the wind don't tear it off it will get under it and while blowing through under it you have no dead air space. READ NO INSULATING VALUE.
In the FAQ under 10x12 HFGH I outlined how I installed my thermal blanket it absolutely will not blow off or let air under it I leave it on year round. If I use shade cloth I don't cut it because the vents are non operational.
For what it cost for 4 quality openers like Bayliss I got a exhaust fan rated at 2350 CFM put a speed control on it and a thermostat and set it for what temp you want to maintain. Warm in the winter cool in the summer and none of the hassle of removing the cylinders from the openers every winter no problems with shade cloth or trying to keep thermal blanket on keeps GH at lower temps and no worrying about a wind storm blowing the open vents off while they are open.
I'm at the age that I don't want to be putting a pool cover on and off or be out side in the middle of a wind storm trying to save it. I set the thermostat and leave knowing that it will be fine.
Only risk is if the electric goes off it won't work but if it is hot and the power fails your roof vents are not going to cool it anyway and when the exhaust fans is on you need the vents closed.
I did away with the roof vents and I have no regrets

I have Aluminet, so I cannot comment on any other kind of shade cloth...but the Aluminet is quite rip-resistant. I made a hole for the arm of my ridge vent motor, and there has been no change in 3 years. The hem failed before the cloth tore any further.

Like Gardenerwantabe, I disable (unplug) my ridge vent in the summer. The exhaust fan is more efficient that way. I do use the ridge vent in spring/fall when it is not REALLY hot.

I have purchased a 20-inch motorized shutter and a 12-inch 1/10HP fan which should produce a 1150 CFM flow. This seems considerably less than what gardnerwanabee has installed, although at the time I bought it I believed it would be sufficient. Maybe I will need the supplemental vents after all? I don't think hemming a shade cloth for vent cut-outs will be a problem for me.

gardnergal
If you go by the calculation charts your fan is large enough but you can drop the temp on a hot day with a bigger fan. The one that I bought was only $20.00 more than a 1150 I got more than twice the CFM for another 20 bucks. I do have a speed control on it so in cooler weather I can set it at a lower speed so as not to cool too fast.So far it works very well.

It's only 10X12, right? Move it to a place where it gets shade in the afternoon, like the east side of your house. Problem solved.

Where I live we get a breeze nearly all the time in the spring.
Since I installed three Windows in the back I can raise the windows and open the door and get cross ventilation.

So far this spring we have only had a high of 80F and I did not need to use the fan at those temps.

Only thing that my GH is used for is to grow plants from seed.
We have a large water Flower garden and we grow everything from seed.
Most of the year the GH will sit empty.
I won't be fighting the really hot weather. Last summer I just left the doors and windows open it got pretty hot on some of the really hot days but since it was empty it didn't matter.