Heating suggestions for this greenhouse

Hi all,
My greenhouse is finally done, I think....I am now in the process of getting a heater for the cold nights up ahead. It is a 12x14 with height of 7-8 ft. As you can see the lower half of the greenhouse is made of pressure treated wood and the roof is of corrugated polycarbonate panels. The windows are single pane glass (used) so doesn't really keep the heat as much at night. I have done some insulation on the wood part of the GH with fiberglass and reflective foil/bubble/foil sheets, however, haven't quite finished it yet as the budget is all gone. Just have enough leftover for a heater. ;-)
Any suggestions on what to buy/used to keep it warm on some freezing nights here at the Florida panhandle? Also, would covering the windows with a 6 mil plastic help keep the heat at night ? thanks and will greatly appreciate any feedbacks ;-)

Eileen

Covering the windows with plastic will surely help.

I have three electric heaters in each of my two greenhouses. One is at either end and a backup on another breaker in case the breaker trips on the other two. These heaters are all on GFI circuits and will automatically cut off if tipped. They all have 1200/1500W settings. I use the 1200W settings since it draws less of a load on my breakers. The heaters are not expensive and can be found at any big-box store such as Lowe's and Home Depot.

My greenhouses are both 10x12x8'. I have covered every square inch of them in outdoor bubble wrap, but I am using the bubble wrap "off label". I won't be able to tell you until next spring whether it was worth the time/effort/money to cover my greenhouses with it. The bubble wrap is 16 mil thick. So far, with nights getting into the 40's, the bubble wrap seems to be making a big difference in retaining heat and keeping out the cold, but I need to see the results after an entire winter to really know how effective it is and how it holds up to weather.

Ken in NE Mississippi

Ken thanks for the info. could you tell me which type of heater did you use? There are so many options and since it will be my first time to use a greenhouse I really don't know what to use. I have been to Lowes and found so many different ones from $20 to $100 for a heater.
I do appreciate your quick feedback. I will drive down to Lowes after work and see what I can find .

thanks
Eileen

I actually have four different heaters of the six I use. The listing begins with what I think (might be) the best, but is the most expensive. All of the below are working well though.

1. Holmes 1200/1500 - A taller unit that (perhaps) distributes the heat well.
2. Bionaire 1200/1500 - Rotating front to distribute the heat. This unit is 1/3 the size of the Holmes.
3. Utilitech 1200/1500 - Spartan and the least expensive.

The fourth is a specific wall-hung unit and was expensive. I am not crazy about this heater and have not listed it. It cost over $100.

I don't know what I paid for anyone of these three but it was somewhere between $20 and $40.

Ken

Ken thank you so much for the quick reply. I have checked out Lowes online and they do carry the Utilitech heater. Not bad for 1300-1500 . I could afford at least maybe 3 for now. Im just glad it hasn't been that cold yet. My plants are still doing fine outside covered with a blanket if it's a bit chilly night.

is this what you might be talking about?

Yep, that's the one.

ok, once again thank you so much for the info... now I can confidently buy the heaters and move in my greenhouse occupants ;-)

My pleasure. Enjoy your new greenhouse. You will soon have it packed with plants and it will enable you to expand your (tropical) plant varieties.

Another zone 8a greenhouse owner here, 10'x20'. I use a small wood burning box heater and also use a Honeywell electric radiant heater with a thermostat. When the wood heater burns down, the electric heater will cut on. Or if the cold is moderate I use only the electric.

The bubble wrap suggestion on the windows/door will help.

Most cold air comes in around the base of the greenhouse so if you can finish insulating the perimeter it will also help.

One thing you should do is determine cooler and warmer temperature zones in your greenhouse. I did that by placing thermometers in the different ends and monitoring them.

Once I determined that, I purchased a fairly inexpensive thermometer with a sending unit. I'd suggest placing it on the cooler end of the greenhouse so you can monitor the coolest temperature in the greenhouse from the warmth of the house. That way you will know when or how much heat is needed. It takes the guesswork out of it.

As a result of the temperature differences, I was also able to position plants that are more or less tender in appropriate places in the greenhouse. Of course everyone uses theirs for different types of plants and different seed growing than I do.

Moving plants in this weekend as the cold nights are ahead... low 30's and high 20's by Wednesday here. That is early for us.

I do wish you luck and hope you enjoy it this winter.

Getting cold here in NE Mississippi as well. The prediction is for mid-20's Tuesday and Wednesday mornings. That's really early for these low temperatures. Global warming I guess!

Not only are my two greenhouses each heated with three heaters (two primary, one back-up) but they are also fully wrapped with outdoor bubble wrap. This will be the first winter using this bubble wrap, and it will be interesting to see IF this wrap helps to heat the greenhouses and more importantly helps to hold the heat in and keep the cold out.

From what I've read, I believe you will be happy with the bubble wrap outcome.

One other suggestion to improve the temperature conditions inside FlaGardeners greenhouse would be a fan. Warm air rises and if the fan can be aimed to circulate it, it will retain the temp far better.

I have a ceiling fan in mine that I leave on low speed full time. It seems to help maintain a more even temperature.

Found this surprise while working in the GH today. I moved these in a week ago and was delighted to find a flower bud...

Looks like the 'Marbled Rainbow'. I have about a dozen also in bud.

Podster,

thanks for the input. I have been busy trying to insulate the greenhouse so i haven't had the chance to read the new posts ;-) I have blown up my budget for my greenhouse and doesn't really have a lot to spare for the bubble wrapping the windows so I used a 6 mil plastic sheeting for now. I did wrap all the windows with it except for 2 front south facing windows to air out during the day as it gets 100 degrees in there.
I do have a question for you Ken, how do you power your 3 heaters? I had a plug installed at my greehouse and now just realize I may not have enough amperage to support 2 heaters . The 10 gauge wires were tapped to an existing GFCI plug that has a 15 ampere and 12 gauge wire that was tapped on the outside break panel where the electric meter is. Im kind of worried that the 15 amperes may not be enough and I'd hate for it to trip all the time with 2 heaters running at 1500 watts for 6 hrs or so.
tonight's forecast is in the low 30's so I will definitely need 2 heaters in there as one only manages to keep it at 60 when the outside temps are in the 50's. also what temp do you keep the greenhouse for the plants to survive?
would appreciate your input on this.

eileen

Eileen, my situation is a bit different than yours since I have five heaters, three in one greenhouse and two in the other one. The third heater is only a backup in case a breaker trips. The third heater (orchid greenhouse) is on a separate breaker than are the other two heaters. All my heaters are electric, but I only run them at 1200-1300 W, rather than the 1500 max setting. That cuts down the load a bit. Also, I have my five heaters on two separate breakers and each are 30 amps. Keep in mind that I also have seven fans and eight, 4', 2-tube fluorescent fixtures on these two circuits. The fans only run from 8 AM until 5 PM and the lights are on from 3 PM until 10 PM.

Even though your heaters only will run intermittently, 15 amps is awfully small. I am not concerned about the wire gauges. Those appear adequate. Is there an outside plug close enough to your greenhouse that you can run an extension cord? If so, you can use that plug for one of the heaters. If you don't, give your electrician a call, explain your problem, and ask IF you can replace the 15 amp breaker with a 25 or 30 amp one. IF he does not think that would be safe you may just have to add another plug or two, running new wiring and adding another breaker. If you do this be sure your electrician understands that you want wiring that can handle a 25-30 amp load.

I hope some of what I said is helpful but keep in mind that I am NOT an electrician.

Ken in Mississippi

Ken,
thanks.. thing is it wasn't done by an electrician but just by a friend who is a handyman. I do have another plug at the backporch that I can run an extension cord to the greenhouse and connect the heater to that.I already knew I will have to change the breaker for a bigger one but the dilemma is , the wire used to install the 15 amp is just a 12 gauge wire . As I understand from reading , I will need a bigger wire to accommodate a higher amps and that will drive my hubby nuts. That will mean we will have to dig up the trench, unbury the pipes and change the wire to a bigger gauge ;-) he was already up to his wits end with the greenhouse project.
you said you have a separate breaker for your other heaters, does that mean installing a new breaker panel? ok that may not go well with hubby ;-). I didn't realize the work and cost it will involve having a greenhouse . the outdoor GFCI outlet was installed from the outside breaker panel so it was easier to run the wires and it was meant to just power Christmas lights and water fountain. I didn't know I was going to have a greenhouse built this year ;-) but im sure eventually I can get things done right. For now I will have to live with having an extension cord to plug the second heater. thank you so much for the enlightening reply ;-) I hope I didn't bother you so much with my questions

Eileen

I don't mind a bit. I am a Master Gardener and our main creed is to help others.

Your 10 gauge wire will handle 30 amps and your 12 gauge wire will handle 20 amps, and IF the wire length is not too long to your greenhouse plug, the 12 gauge will handle 25 amps. This is what my electrician wrote down when I was putting plugs in my two greenhouses.

When you run your extension cord, use a 50', 12-3 cord. It can easily handle 15 amps. Your heater will only pull about 10 amps IF you use the 1200-1300 W setting. Even on the 1500 W setting, you probably won't trip the breaker but that is getting closer to a 15 amps draw.

Again, if you are using an already installed porch plug AND your house has 10 gauge wiring, there should be no problem increasing that breaker to 20-25 amps if the breaker is only 15 amps. But I wish you would ask an electrician about doing that. My son is a certified electrician and I will ask him about doing that. You need to know what wire gauge you have though. Your handyman should be able to open up your breaker box and tell you the wire gauge for that porch plug.

Hi Ken,

I have called or hubby called our more experienced handyman and he said all that needs to be done is to re-wire the 12 gauge wire into a 10 and replace the 15 amps with a 30. let's see . btw do you have a picture of your greenhouse?

These pictures were taken in early summer, before I wrapped the greenhouses in bubble wrap.

Ken ,
thanks for sending the pictures of your greenhouse. Im quite curious as to what material the first greenhouse is made of? the door looks cool ;-) what do you use to stake them down ? I was afraid of buying a pre-fab greenhouse due to the storms we get here in the summer, you know;-)
I too am planning to keep my orchids in the greenhouse in the summer , do you have to cool your greenhouse for the orchids? right now they are inside my house for the winter and i take them outside by the front porch in the summer time. I miss my orchids from the Philippines. When i left Philippines , I had over 100 orchids that now my mom and dad are taking care for me. Orchids are pretty much the only flowering plant I have aside from the typical tropical plants we got there. They were soo easy to manage there but here I am having a hard time.

Both are polycarbonate but look totally different, coming from two manufacturers. Neither one looks like this right now. I have wrapped them both in very heavy bubble wrap, hoping to invite heat, keep the cold out, and retain the heat. Time will tell whether this is successful or not. It is another one of my experiments. LOL

The lean-to is anchored with large screw-like gadgets that were about 12" long and 4" wide. You simply screw them into the ground and attach the stems to the base of the greenhouse. I think I used six of those large screws. The screw anchors came with the greenhouse. The polycarbonate is translucent but you can neither see in or see out of this greenhouse.

The free-standing greenhouse is resting on 4"x4" treated lumber. The lumber pieces are all bound together with metal straps and I drove six, three feet long, 3/8" rebar at the corners and mid-way of the longest span. The greenhouse is 10x12' and its base (metal) is screwed into the 4x4" foundation, one screw every foot. I drove the rebarl at an angle and then strapped them to the 4x4's with metal straps, the kind used to tie down rafters used in home building. Nothing is going to move these two greenhouse from their foundations. They might blow away, but the bases will not move. We have had 40-60 mph winds, usually associated with thunderstorms and I have never lost a panel.

I have a single "typical" door on the lean-to, and that opening is 3'. The free-standing has two sliding doors and that opening is 5' with both doors open to their maximum.

The only thing that cools my greenhouses is fans. I have four fans in the orchid greenhouse and three fans in the "everything else" greenhouse. They are all on timers and run approximately 12 hours in the spring-early fall, and 8 hours in the fall/winter.

Other than my "baby" orchids (approximately 400 of those), all my tropical plants, including orchids go outside in the spring and don't come back in until the night time temperatures get around 60 F. My smaller orchids, what I call "baby" ones, in 2"-3 3/4" pots, stay inside the greenhouse year-round. I probably move about 200-300 tropical plants, including NBS and BS orchids outside during the warm months.

Ken

wow 400 orchids? do you propagate them yourself? do you sell them too? i have only a few pots and so far only one of them have been generous enough to bloom year after year. I have 3 Phalaenopsis that I acquired this year and seem to be doing fine. However I have a cattleya that is almost 4 years old and still hasn't bloomed. I have to admit I have quite neglected them and only been paying as much attention to them this year ;-) hopefully I can get it to bloom next year .

btw here is my greenhouse with its "tenants" right now. Still have a room for now but I'm sure it won't be long ;-)

You have a gorgeous greenhouse with lots of space for additional plants.

I don't grow my orchids from seeds, and don't have the knowledge or facilities to do so. I purchased my plants either as plugs (vast majority) or in flasks. Therefore the majority of my plants as still very small, very young plants. I have only been growing orchids as such for two years. My original dozen or so orchids were blooming plants. They were purchased for my own enjoyment, never thinking that one day I would be in the business of selling orchid plants. I have divided my original plants and most of them have been sold.

I actually have approximately 600 orchids now. 90% are NBS or smaller and 10% BS plants. One has to be patient when growing plants from seedlings, very small seedlings. I think that within a year I will have lots of plants that are now blooming size/age. That's when things get very interesting. I am a hobbyist grower and want to remain so. I delight in growing orchids and other tropical plants. Selling them only allows me to purchase more plants and growing media. I will never profit from my sales and never care to do so.

I hope that you will check out my website and give me some feedback. I don't know a lot about website development and depend on feedback to improve my site.

ken what is your website?

i found your website..will definitely check it out tomorrow as for now it is bedtime ;-)..

Bedtime here also. Sleep well.

Ken, I'm frantically reading as much as I can to "fix" my problem and this thread has helped considerably. Thank you! Much to my dismay, my Marley greenhouse heater on a designated 220 line, decided to stop working late yesterday. I'm in upstate SC and it's 11 degrees here this morning. I had a portable propane gas heater and placed that in the greenhouse last night, but need to make some big decisions today, as the propane tanks are not the answer. I'm guessing that we are a little cooler than you are, 7b. I'm debating on going with natural gas. In the meantime, I'm headed to the local big box store to purchase a couple of electric heaters. I searched on line, well into the night, trying to find a solution. I knew this day would come and obviously I'm not prepared. Loosing power would be worse, that's why I had the propane heater. I have a separate 110 line coming into the greenhouse, along with the 220 line. It seems that you have decided that smaller electric heaters are the way to go. Is natural gas available in your area? I'm perplexed as to what I should do? The infrared natural gas heaters look like a good option, as they don't require any exhaust system and will function if power is lost, and they are less expensive than the "flame type" natural gas heaters. My greenhouse is small, 10 x 12, glass and on a kneewall, so the top of the pitch is pretty tall, 16' or so. I have orchids and tropicals and try to keep the temperature at night around 50 degrees. Any help would be greatly appreciated. The propane tanks are running out! :) Cindy

Personally, I would only use propane in an emergency situation. I worry (perhaps unnecessarily?) about the fumes that the burned propane puts out. We do have natural gas in the house but it would be a really big job plumbing it into the GH's. If one loses power, natural gas heating would not work, at least not in my house, since we have central air/heat. My small, big-box store electric heaters are probably not the most efficient way to heat (small) GH's, and my two GH's are the same size as yours, just not nearly as tall. But I like the idea of having the two ends of the GH's on separate circuits', so that IF a breaker trips during the night, at least I have another heater still producing. That's my theory anyway.

Ken

cindy what did you end up with? gas is so expensive, and I'm with Ken on using on in emergency. Hope you didn't loose anything.

Jan