greenhouse question

Tiger;
When you say you run yours at 60, does that mean you keep the temp there? How do you do that when it gets really cold outside? I guess your GH is sealed & insulated really well? That first cold night we had when it said it was 30 something outside, it said the samething inside. Granted I haven't put plastic up yet either. All I can picture is the temp being 32* and the heaters running like crazy in the GH "trying" to keep the temps at 60.
Thanks for all the feedback everyone. This helps a lot.

I use bubblewrap for insulation on the inside of my small greenhouse 6 x 8. I use a small space heater set at 70. It comes on as needed. Last year when the outside hit 20, it was 38 in the greenhouse. Without the bubblewrap I think it would have been a lot colder. I put the bubblewrap up over the weekend and its stayed about 60 overnight with outside temps in the 40s so far. I still have to plug up some air leaks around the framing. Some people use pool covers or foam boards as insulation.

I have the hoophouse type of grhouse. Two of them are over 65' and one is 100'. I have two layers of plastic on them with a fan blowing air between the two layers to get an extra 10 degrees of warmth. I have large vented propane heaters that are anywhere in size from 100 btus to over 200 btus ( I think-maybe larger). I have the thermostats set at halfway down the grhouses, so it is actually warmer nearer the heater -which is where I start all my seeds. I use the forced hot air from the heater to blow under the seed flats and on a cold night it can be 70 degrees right there. I say on a cold night, because the heater runs more.
If the night is really cold ( under 28 or so), I may turn the thermostat down a few degrees to conserve propane. On warmer nights, like last night (low of 51) I turned it up a few degrees to push some cuttings that I have in there. I also have fans down the grhouse at the top to help push the warmer air down there, and they run all the time. Keeps the air circulating as well.

The grhouses are sealed very well. but the space between the two layers of plastic is the only insulation that I have. I could not give up any light that I would lose if I started to put up other kinds of insulation. This is very thick, treated plastic that I use as well. I buy the most expensive, best plastic for grhouses that I can get, as I hate changing out the plastic-very time consuming. We are in the process of it right now. The plastic has been off all summer, and I am replacing any rotted wood, fixing leaning gables etc and today I hope to get two of the grhouses covered.

I do burn some propane-thats for sure! lol but it is a business expense for me, and I have to have a certain temp in order to keep on schedule with germinating seeds and growing them out. On the larger grhouse, if it is cold, I can blow thru a 350 gallon propane tank in 10 days or so. They finally attached a 500 gallon tank to that, and now they don't have to deliver gas as often...took them over 5 yrs to do it!

I am confused-if you don't have the plastic up-what are you taking measurements of? I am picturing a grhouse structure without the plastic-so its exposed to the outside air...in which case, it would show the same temps.

My GH is made of the clear panels (like the green wavy ones used on porches) They were ALOT cheaper than the polyC ones. I want the extra thermometers to take temps of various areas in the GH. I do keep a fan running 24-7 to keep air moving. Last night I didn't run the heater as it only got down to 50. I will prolly plug in 2 heaters tonight and keep the thermostat on them at 65 or so. It is supposed to start getting cold. We are going to line the inside of the GH with plastic. There will be a about a 4" gap between the panles and plastic. I am hoping this will help keep heat more. DH has gotten a heavy duty plastic to use. MY GH is only 12 x 24. A mere fraction of yours! Thanks for all the advice.
Dawn

lol I only told you the size of the grhouse to explain the size of the heaters-which is why it keeps it warm inside. These are big heaters.

To get that extra warmth from adding the plastic-keep the space between the two plastics anywhere from .5" to 4" . Anymore than that and you will lose the advantage.

Thanks Tiger. I can't imagine trying to keep yours heated. I knew you had to have a big heater for a GH that size. Do you think with the plastic lined on the inside and the 2 heaters my Gh will do OK? You don't keep stuff up near the walls right (in winter)? I would imagine that it is cooler the closer you get to the walls. I'm thinking too that things that are more cold sensitive will be placed closer to the heaters and things that can tolerate more cooler temps will be placed further away.
GH will be put to the sturdiness test today. 50-60 mph wind gusts today and this weekend from that hurricane out there.
One more thing please. B/C of the type of panels I used, do you think I will need to keep a shade cloth all year round? I had to put something up when I first started putting plants in there b/c it was too intense(blue tarp). I'm thinking I can gradually take it off for the winter. The plastic will be on top also so that will difuse the light also.

I do keep plants up against the plastic, but only because the houses get so full. I have shelves in all of them and they get packed. I try to keep the smaller plants on the wall closest to the sun so as to not block the sun. Last year, I had a huge heliconia at the far end of the grhouse farthest from the heater and the temps went down to 17 at night, and it was not happy so close to the plastic and so far from the heat. But there is no other place for them right now.
I would definitely take that shade cloth off. You don;t have to do it gradually either-not with the sun being so weak now. Just take it off!! lol Plants tend to stretch under it (depending on the thickness of the cloth - what % shade it is), but in the fall, winter, spring I would not use one. And in the summer, in the middle of May I take out all the plants and don't use the houses anymore.

here are some pics

I have a lot more plants than this in there now

I had to put some kind of shade up b/c my plants were burning while it was warmer. I think I can take it down now

edited: the wire shelves were added up top. They free curtesy of our local WalMart dumpster. All DH did was cut them to fit around the post. Will post new pics tomorrow.

This message was edited Nov 2, 2007 8:49 PM

Thanks tiger, I just read your last post, dont know how I missed it. The cloth is coming down tomorrow morning. I can't get over how many plants I have.

Great job there pdoyle. Things are looking very good. You should be proud,

I too was amazed when I brought my houseplants in a few weeks ago. I have more than I remembered too, ha-ha Oh well, can never have too many plants, Keep the pictures comiing, they are inspiring,

Ruby

today 11/03/07

(Spoken with a latino accent.) Looking good, looking good.

Finally got some pics of the GH with it lined/insulated

#2 It was getting so hot in there during the day I had to take the plastic off the fan and turn it back on (on a thermostat) to keep it cool in there.

#3

That looks wonderful. I wish I had that much space. You need an orchid or brug addiction to fill it up. Hehe... Mine gets very hot (over 100) even on very cold days when the sun shines! I don't have an automatic fan, wish I did. I had an auto window opener, but it stopped working. I go out about 10 am on sunny days and open the window. If I remember, I close it about 3pm. Otherwise DH says "did you close the greenhouse" and I say Oh No and run out there at 10 pm or later. LOL.

lol leclu727. I would LOVE to grow orchids out there. I think I need to really work on keeping it warmer at night to do that though. If I can get through this winter w/ no major incidents I'll have more confidence in growing things out there. I want to start seeds out there, we'll see.

Dawn, that looks great and very cozy. Like beclu727. I am envious of your space! This is my first winter too. What a learning curve, huh? So far I'd be lost without my exhaust fan/thermostat to keep up with the heat in there on sunny days. I did cover the fan up with plastic for a few brief days, but looking at the forecast I'll bet I'm yanking that plastic off again soon.

Open doors, close doors. Up ladder to open vents, up ladder to close vents. Cover fan, uncover fan. Shadecloth panels up, shadecloth panels down. LOL, I'm sure getting my exercise as I figure out how to work this greenhouse! I'll be skinny by spring! ;-)
Sheri

Sheri-it shouldn't be that hard! Do you have shutters behind the fan that close when the fan is not running? Also, the shutters at the other end of the grhouse should automatically open when the fan is on and close when the fan turns off. Just reread your post-you didn't mention the shutters opposite the fan-maybe you don't have them? If not-how does the fan pull air from the outside into the grhouse? By vents-do you mean a ridge vent? Aren't there thermostats for that? Also, I think you get better pull with two shutters and no ridge vent. Shutters are pretty cheap and easy to install and you would not have to deal with anything-just set your thermostats and walk away!

Thanks Sheri. I love it. I hope to use it to it's fullest potential. My biggest fear I thought was going to be the cold at night but i think I'm going to be OK on that front. Now I'm working on getting the day temps right. That sun is intense. On a 48* degree day in was everybit of 90 + in there. When the nights get down to 35 the green house gets pretty cool too. I'm thinking i need to keep the Tstat on a little lower setting to that it comes on sooner. Not good for the drastic jumps in temps right?

Hi tigerlily, and thanks. I do have shutters that close behind the fan when it's not running, but we can see tiny air gaps between the louvers even when closed, so that's why I covered the fan. Maybe those very small air gaps aren't enough of a problem to worry about in cold weather?

You're right, I don't have shutters opposite the exhaust fan. Mine is a little Harbor Freight 10x12, and we're in the process of building sliding screen doors to use as the air intake opposite the fan. The HF has two sliding poly doors (which are almost always open now.) I figured I'd be able to control air intake by exposing one screen door, or two, as I experimented to find what worked best.

I may need to install shutters opposite the fan. This was our attempt to keep things simple (greenhouse newbies here.) I thought that a screened door might work just as well...but of course, screen doors are not automatic, and I guess that's the big downside to our idea. On most days I do have the doors open and the thermostat on the exhaust fan kicks the fan on. But, I have to be sure to scoot out there early on sunny mornings to open up the doors, and to close them before it gets cold. Hmmm.

Another thing I did was to build screens out of Aluminet shade cloth (very open weave) and I replace 2/3 of my south wall panels with those screens in hot weather. So, then it's more like a screenhouse (well, sort of.) But now the nights are so cold that I have the panels back in...which is making me work harder (and think harder.)

There are four small roof windows on the HF and they are not automated with vent openers. Frankly the roof windows don't work smoothly at all, and I'm not sure that auto vent openers would work well...I kind of hate to spend $200 and find out they won't work for me. I've also read what you said...a good fan and air intakes can sometimes work better than ridge or roof vents anyway, especially in really hot climates like mine.

I think my ignorance about how air moves through greenhouses made me cautious about getting too elaborate too fast. But I see the point that comes shining through your good questions...there is a reason that people build in automated shutters or vents. My light bulb is starting to go on, LOL. Sometimes I have to do things the stubborn (dense) way the first time. I'm still fiddling and learning, and I really appreciate your thoughts.

Dawn, I have the same question. My gh has been going into the mid 90's during sunny days, and my heater thermostats keep it at mid 40's at night. I could set my exhaust fan to kick on at a lower temp during the day, as you said, so it wouldn't get as hot in there. I don't know if I should or not. My plants (cactus and succulents) won't blink at temps in the 90's or even 100, so I didn't think it mattered. But....are big temp differences between day and night too hard on plants? Maybe Tigerlily or others will have comments?
Sheri

sheri-I know what you are talking about with the small gaps on the shutter behind the fan-they are too small to worry about and they were never meant to be covered with plastic-so thats one that you can let go! lol

If I were you, I would lose the vents at the top-permanently shut them. Theres another not to worry about!
Go buy two small intake shutters-like 12" across (not motorized-when the fan comes on, it will pull them open, and they will shut when the fan turns off) They should cost about $ 30 each, and put them up high on either side of the door. Forget about the screen door-use a glass door and keep it closed, you will get much better pull and air movement thru the grhouse if you just let the shutters and the fan have their little relationship going! lol The one thing that you have to watch for, is that when the fan comes on, it will slam that door shut if you leave it open, and its the one drawback (small one) to the design. I never let people just go wandering around the grhouses alone because they don't know and I have had doors ruined because of it. Or they open the door when the fan is on and don't guide the door shut themselves-just let go and the door slams shut. I usually use my butt or foot and let the door hit either first and then pull my foot out and the door shuts the last few inches by itself if my hands are full-if that makes sense.

As for the differential temp between night and day-usually growers aim for around 15 degrees or so, which is attainable if your heater is set at 60 or so. I set my fan thermostat at 75 and the heater at 60. Just turn your fan thermostat down to 75-thats the best that you can do. On a hot sunny day, it will be warmer than 75 anyway.
I think that cacti go thru high differentials out in the desert? Really hot during the day and cold at night? do they go dormant out in the desert in the winter? what does a dormant cacti do/look like? lol Maybe you should keep the fan at a higher setting. Isn't there a cacti forum you could ask in?

Thanks tigerL, great info. I appreciated you checking back on this thread and giving advice/tips(anyone who has). I am learning a lot.
dawn

Same here Tigerlily, thanks so much. (And Dawn, thanks very much for allowing me to temporarily borrow your thread for some good help.)

GOOD, I won't worry about the little louver gaps.
GOOD, I have told my husband 50 times I wanted to abandon those annoying roof vents.

I thought about this all night and decided you're right. Small air intakes would allow me to stop letting the GH doors run my life. Heck, I could even go on a trip sometime during cold parts of the year! (LOL.) Only thing is I thought air intakes needed to be low in the wall instead of high...that doesn't matter?

I do understand the door slamming issue. The two Harbor Freight polycarb doors slide on a track, so that should not be a problem. I just need to make sure the doors aren't slid into a position that blocks any air intakes I install (should be fine when the two doors are closed.)

My weird plants would find 60 too warm at night (many need to go down to 40's in winter to bloom well in spring) so I will take your advice and post a question to some C&S folks about the temperature differential question. It's probably OK (most of my plants have nasty tough personalities anyway) but that would be good to find out. I am sure missing that 15° differential goal by a long shot!

Thanks so much for taking the time to help. As Dawn said, I'm learning a lot!
Sheri

Glad we both can learn something Sheri

automate your roof doors
I purchased the Harbor Freight
GREENHOUSE WINDOW VENT OPENER $20 each
http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=92192&CategoryName=&SubCategoryName=
Gas charged cylinder and piston rod, opens and closes window
Opening temperature range 59 degrees to 77 degrees Fahrenheit
Max. operating temperature: 122 degrees Fahrenheit
Lift capacity: 15 lbs.
90 degree maximum opening angle
1-3/8'' travel, max.
Adjustment knob allows setting

Steel and aluminum construction; Overall dimensions: 10-3/4'' L x 3/4'' diameter; Weight: 1 lb.

ITEM 92192

Jim, I'm glad to know those Harbor Freight vent openers have worked for you. I know two people who bought them and were unhappy, and replaced them with more expensive versions by other manufacturers. Looks like you're doing well with them. :-)

You are welcome guys. I remember on another thread that someone had both the shutters and the roof vents and wasn't getting good air flow until he closed the roof vents. If you have any leaks, (including the roof vents) then the pull from the fan is lessened. I have also heard bad things about the automated roof vents.

I put my shutters up high for a few reasons, and most commercial growers with my size grhouses do too. Up high gives you the clearest path for the air to travel through the grhouse. If you put them low, then the plants and shelves will block the air. In the winter, the air coming in can be cold (!) and you don't want that air blowing on your plants. My shutters are about 4.5-5.5' off the ground and they line up with my two aisles.
I am just wondering if you have room on the sides of the doors if you have a sliding door? You want the shutters to be away from the absolute sides of the gables, so you can get the air towards the middle some.

I did quite a bit of research before I chose my GH and how I would heat/cool it. It was very clear to me that you either used a ridge vent system, or exhaust fan with intake shutters, but none of the manufacturers recommended both.

I am sure where one is located makes a difference on which system to use. I am glad I went with the exhaust fan and shutters, it has worked very well for me. My shutters open up 3 degrees before the fan comes on. I also use a speed controller on the fan. I have it set at the slowest speed now that it is cooler out so that I don't shock the plants with a blast of cold air.

I needed my system to be automated as much as possible as I have to gone too long at times. (Like now. :-( Ugh. ) But I think you need to have something that works whether you are their or not. I would hate to lose a lot of plants because I could not get there in time to keep them from scorching, or freezing.

Nautical

I agree Nautical, a roof vent system alone would definately not work with my hot climate. I love my 16" exhaust fan (it has three speeds, and can exchange the air twice per minute at the highest setting.) I think I just need to get the air intake more automated, add shutters of some type, and give up on the screen door idea.

Tigerlily, thanks for the clarification on the shutter height question. The two doors are about 6' wide when closed. The GH is only 10' wide, so that leaves about 2' of space on each side for shutters. A 12" shutter could be placed about a foot away from the corner, but that's as central as I can get. I keep thinking it's still doable though...it's a small greenhouse and I tried not to undersize the exhaust fan. I'll kick it around some more.

I do know that the roof vents
plus a 3,000 cfm evaporative cooler does keem my GH
http://www.rader.org/garden/cooler.htm
below 80 degrees when it is full sun and outside temp 95 degrees

In my case (Sacramento California hot summers)
Keeping it cool and moist is much harder than keeping it warm

in a cold year we get a few days near freezing
many in the 40s
but nothing like feezing ground and temps below zero

Jim-I think its the swamp cooler that is keeping your grhouse more cool than the ridge vents. Does it run on electricity? Have you run it thru a summer yet?

yes it has a 1 hp motor and an electric pump which runs water to the pads
the water falling thrrough pads cools the air as it is sucked through the pads
It lowers the air temp 20 degrees 1500/2200 CFM (based on motor speed)

the thermostat determines the speed it blows at

Follow the steps below to properly size your residential cooler.

1. Consult area zone map to find correct zone

2. Consult table to find correct "Minutes per Air Change" for your zone.

3. Determine area to be cooled in cubic feet (building length x width x height).

4. Divide cubic feet (step 3) by minutes per air change (step 2) to determine Cooling Feet per Minute (CFM).

5. Refer to the Specification Charts in the cooler brochure for the units CFM ratings and expected static press to select a cooler model. If CFM falls between models, choose the larger model.

Graphic: Minutes Per Air Change Chart

*Interior Heat Load: High means places with unusual heat sources from hot equipment or processes, crowded conditions, etc. Normal means no unusual heat sources - typical home or office.

*Exterior Heat Load: Exposed means walls, roof exposed to sun, poor insulations, etc. Insulated means walls and roof well insulated and/or shaded.

Example - A house in Bakersfield, CA, 40 feet long by 30 feet wide with 8-foot ceiling. Well insulated, no unusual heat sources.

1. 30 x 40 x 8 = 9,600 cubic feet
2. Zone 2
3. Minutes per Air Change = 3
4. 9,600 (divide by sign) 3 = 3,200 CFM
5. Referring to the CFM inside the Champion Residential brochure, cooler model 4001DD with a ½ h.p. motor is indicated, assuming a typical static press of 0.2".

Well, we had our coldest night yet here. The thermometer this moring on the way to work read 16*. It doesn't get that cold often thank goodness. When I got home I went to the GH and checked the lowest temp reading... it said 28*. Everything looks good in there so far. I hope everything makes it alright. I have an osculating fan going and 2 heaters going. I will have to say that the Geraniums are doing wonderful. I had some in pots w/ ivy that i just stuck in there after the summer (hate the throw anything out) and just cut them back & then forgot about them. I've just given them a little water a couple of times. They have been blooming straight on for the las two months. It is so nice to walk out there and see something blooming. Everything is green and looking healthy. Now I hope it stays that way!

Good to hear that things are going well with the greenhouse. Oh yes, I understand the nice feeling you would get walking in and seeing the blooms on the geraniums. Freezing temperatures and blooms don't usually go together. I hope that things continue to go well for you.

Keep us updated.

Ruby

One of the most educational threads ever, on DG! I just discovered this one, so I had to read all 100 Jillion posts just to catch up. Beautiful GH, PDoyle! Good luck with it (it's a constant learning process!). Most everything posted here matches my experience with my (first)GH. Lawsy, what a learning experience!! I located my heat-demand thermostat smack dab in the middle of the greenhouse under a bench (water-protected), and I've never had the GH temp drop more than 2 degrees below demand temp (50 degrees). I have min/max thermometers at various places in the GH, and they stay within 3 degrees of each other. This was a good thing. It also may be beginner's luck.
Tigerlilly's observation re the strength of the winter sun vs summer sun's effect on house plants mirrors my own.Same with the vents. I'm growing Impatiens, Begonias, Pothos, Sanseveria,Columnea, Schlumbergera, Anthuriums, etc., happily side-by-side with Clerodendon, multiple Citrus, Datura, Aglia Odorata, Cestrum Nocturnum, Malphighia,,, And all seem happy at this point. But it will change as the days grow longer. I'll have to change when they do. That's what the key is...recognizing when conditions have changed, and you have to respond...and quickly! Even 1 week can make a difference (as I've unfortunately found out!). And as far as "touching the glass", don't worry about it. Consider it a form of "natural pruning". Although I haven't suffered any damage yet this year, I KNOW it's coming...in some form or another...

Thanks StonoRiver. This has been a fun experience - Albeit nerve racking at times b/c of temps getting so cold at night. Everything looks to be holding their own pretty well. The banana's have gone dormant though. Which is fine as I can't afford to keep it a toasty 70*... yet:) Everyting else is still nice and green. I absolutely love the fact that the Geraniums have kept on blooming. I hope to find other blooming plants that can take the temps like they have done. Even my Crown of Thorns are still blooming. I have kept my more sensitive plants like the orchids and hoyas in the house. We are going into our coldest part of winter so....
dawn

I was reading back through this and thought I'd mention somethings I've learned so far. I took down my shade cloth I used when I first put my plants in there( took off around first part of Nov) The plastic I have covering the walls and ceiling is difusing the light well enough I think.
I have not noticed a huge jump in my elec bill so far either. Now that is not say I wont see it now that we are getting into more colder days...
Aslo, I learned the importance of paying attention to how much you water in the GH too. Water does not evaporate in the winter like it doesn in warmer months or even in the home. Especially in the GH where it is cooler than my home. I have learned to water everything VERY little in the GH. I give everything the "just enough to keep alive" amount. When we went through a period of warmer days and nights I noticed alot of things needing more water sooner but that was it.
I also learned that just b/c you think your plants are "bug free' when you put them in the GH, KEEP CHECKING for them. I thought I had done right when I brought my plants in and had made sure they were sprayed and checked for bugs and all that stuff. Well I missed one or two and noticed spider mites one day. I sprayed everything with a dormant oil spray and that seems to have worked as i haven't seen anything other than a little spider once in a while. I KEEP CHECKING though.
I have also rearranged some of my plants a few times too. I have been following the sun and moving plants to match it. The ones needing more direct light(CoT, cactus, fuschia...) I have on the side the sun seems to be more direct on.
I watch the weather ALOT for warm spells to open the GH up some too. Wont' be getting them for while now as the high for Sunday is supposed to be 30*

I appreciate everyone's input on this thread. I am learning quite a bit and hope others are too!
dawn