Greenhouse Heating Options

[FourOaks]

March seems to be the Winter that wont end. Im looking out the windows, and its snowing, again. For my area, this is highly irregular. Usually during March we get a cold snap that is about a week long, and its over. Not this year. Its really putting everybody to the test.


My poor little plants are suffering. Dont know for sure, but im guessing the combo of gray days and overnight cold is doing its damage. In about a week and a half I should start selling, and its not looking promising. Ill have some flats, but not a lot by any means. Which is really disheartening. On a side note, I was at my Wholesaler a couple days ago, and even some of their plants have some stress. So it can happen to anybody.


So, I have come to the point that to build my plant business, I have to seriously consider real heating options for when the weather gets like this. Im not looking to keep the GH's at 75 degrees, but warm enough that seedlings dont become damaged when the temp. bottoms out.


3 realistic options. Propane, Nat. Gas, and Wood. I left electric out, because that would cost a bloody fortune. Especially considering Duke Energy is wanting a 16% increase, to pay for a mess that they made and are being forced to clean up... But thats another topic for another day.


Natural Gas. I have natural gas already piped to my house. We have a gas furnace and a gas stove. Thats it. We have the bill set up to average out over the course of the year. Mainly because we were tired of paying the minimum in the summer for the stove, and then getting hit with a high bill in the winter. It just makes sense.


I could trench a line, about 150 feet, out to the seedling house, and install some sort of gas heaters. The additional cost would obviously just factor into the average bill. Im not sure there is a way to estimate how much that would add.


Propane. The people at Tractor Supply have kept me going. Or maybe I have been keeping their propane business going. The young lady at the register yesterday actually said "you sure do buy a lot of propane". Luckily they charge by the gallon. The current price is $2.69 a gallon. I have used all sorts of propane heaters. I prefer the blue flame over radiant.


Bulk propane is available. Last year when I checked, it was actually more expensive per gallon to have it delivered. Plus, a lot of complaints from folks who have home delivery. My understanding is to read the fine print, very carefully. I would probably be better off to purchase 100 pound tanks and haul them to TSC. I could strap them to a dolly and roll right up into my cargo trailer. It has a ramp to lower down. Would be much easier then lifting into the back of my truck.


Wood. I have an unused Wood Insert. I could drag it out there and start feeding it. Couple of draw backs to wood. Its a semi-permanent install that takes up a fair amount of space. And, you have to keep feeding it, all night long. I like sleeping myself. But on a positive, I currently have a metric ton of free firewood on my own property. That is a bonus.


Yesterday I went to Lowes and bought 2 more propane heaters. These were on clearance for $45. Had been $135. The reviews were mixed, but for the price its worth a shot. Plus if these do work out, they are duel fuel. Propane OR Nat. Gas.


https://www.lowes.com/pd/Thermablast...ater/999977962


I mounted both on the West wall of the seedling house. Each has its own propane tank. They are spaced about 8 feet apart. Although a combined 20000 BTUs isnt that great, Its doing the job. The current temp. outdooors is 33 degrees. Inside the seedling house its 46 degrees. As I have typed this, its warmed 2 degrees. I do have a fan at the peak that is running very slowly, just to keep the air stirred a bit.


Are there any other realistic options that I have missed?

[FourOaks]

A crappy pic, but you can see how the heaters are mounted. This was quick and dirty yesterday afternoon, but it got the job done. I screwed scrap 2x3s to the upright supports. The heaters have keyhole mounts on the backside.

[Salsacharley]

You propane system looks good to me, especially if you only need it for March. How are you venting it?

[Cole_Robbie]

Heating a greenhouse is a difficult endeavor, to say the least.

At the moment, I am able to heat a 4' x 40' section of greenhouse bench with just a small electric space heater. The cost is maybe $1 per evening. I put hoops over the benches, cover those hoops with plastic each evening, and place the heater underneath. The middle bench is about a foot higher than the others. The heater is under it, and the warm air flows upward out each end, and then fills the plastic tunnel of benches. I'm getting about a 20-30 difference in temperature, which is huge in terms of greenhouse heat. To make the entire greenhouse that warm would take a colossal amount of energy.

I do have to make sure to get up in the morning and remove the plastic, especially on sunny days, so I don't cook everything. And this method does not work as well when my plants get bigger, because the leaves really hate touching the plastic, but it will get me through March, when I have my coldest spring weather. I will have plants to sell this Saturday, March 24th, at my first market of the spring.

[Rockandrollin]

I recommend using a online heating fuel comparison calculator or downloading the app Heating Fuel Comparison. Enter your cost for electric, propane, and natural gas and it will tell you what will be most economical for you. Most likely it will be natural gas.

Many people think electric is so expensive, but in our neck of the woods, it is much cheaper than propane.

The vent free heaters can be a concern, if the room is fairly tight, eventually you run out of oxygen. If they don't burn correctly, they will produce carbon monoxide.

[FourOaks]

Originally Posted by Salsacharley

You propane system looks good to me, especially if you only need it for March. How are you venting it?

The heaters are vent free. Even if they werent, the GH is leaky enough that it doesnt really matter. This is an area that I could improve in as well. I need to get more wiggle wire and track, in order to seal down the edges of the plastic better.


In the long term, I plan to be utilizing at the seedling house all year, so heat needs to be available as needed. Some flowers take forever to grow, as well as keeping potential Mother Plants for cuttings. But that is later on, not a high priority this second.

Originally Posted by Cole_Robbie

Heating a greenhouse is a difficult endeavor, to say the least.

At the moment, I am able to heat a 4' x 40' section of greenhouse bench with just a small electric space heater. The cost is maybe $1 per evening. I put hoops over the benches, cover those hoops with plastic each evening, and place the heater underneath. The middle bench is about a foot higher than the others. The heater is under it, and the warm air flows upward out each end, and then fills the plastic tunnel of benches. I'm getting about a 20-30 difference in temperature, which is huge in terms of greenhouse heat. To make the entire greenhouse that warm would take a colossal amount of energy.

I do have to make sure to get up in the morning and remove the plastic, especially on sunny days, so I don't cook everything. And this method does not work as well when my plants get bigger, because the leaves really hate touching the plastic, but it will get me through March, when I have my coldest spring weather. I will have plants to sell this Saturday, March 24th, at my first market of the spring.

Im sure you can appreciate the problem of running out of room. Because you will eventually. Especially with getting into Hanging Baskets, Potted Flowers, etc. There is only so much bench space.

Originally Posted by Rockandrollin

I recommend using a online heating fuel comparison calculator or downloading the app Heating Fuel Comparison. Enter your cost for electric, propane, and natural gas and it will tell you what will be most economical for you. Most likely it will be natural gas.

Many people think electric is so expensive, but in our neck of the woods, it is much cheaper than propane.

The vent free heaters can be a concern, if the room is fairly tight, eventually you run out of oxygen. If they don't burn correctly, they will produce carbon monoxide.

You bring up some interesting points. Thanks for the advice on the app.

[bower]

Cole Robbie's trick of heating below the bench / under cover is a really good one. I tried running a space heater in my greenhouse once and it was useless. Wasted energy and nothing got warm. If I had to try again, I would follow your example Cole.
Can't do that with propane though. The heaters look good FourOaks but I would be concerned about venting. Better safe than sorry!

[FourOaks]

Well, its a good thing I have 2 heaters with 2 seperate tanks in the seedling house, cause 1 tank ran dry.


This cold needs to move on out of here. Next 2 days are supposed to be sunny, around 60 degrees. Then more gray days.


Least the sun has been shining since sunrise. Its already 62 under the plastic.

[Cole_Robbie]

I'm out of space now, and of course the weather has turned unseasonable cold, with lows right around freezing for several nights this week. I bought a diesel/kerosene salamander/job site heater last fall. I have problems with it shutting off, so I put it on a timer, and that helped a little. But I can tell from the fuel consumption that it is not running enough. So I just now built a fresh air intake for the heater, which is a blower connected to a wall so that it draws in fresh air. The idea of pulling in cold air into a structure I am trying to heat is counter intuitive, but if it keeps the heater running, then it will more than compensate for the cold air it draws in.

I am probably going to have to stay up and watch it. If the heater shuts off and the blower continues to run, that would be bad.

[ScottinAtlanta]

I am switching next year from electric to kerosene. Much cheaper in Georgia.

[Cole_Robbie]

Back to the drawing board, the intake blower does not help at all. The heater still shuts off after about five minutes, and the little light on it blinks. It makes the greenhouse smoky on the inside. I don't know what else to do except place it outside.

[AlittleSalt]

From old school thinking and experience:

Cole, not that I know anything about greenhouses, but the kerosene salamander should work better outside blowing in. If it is anything like the ones we used in the 1980s and 90s - the thermostat kicks in by the temperature of air going into the unit - causing it to shut off when the intake air is warm enough. In theory, that works, but it can get too cold before the unit turns back on. Keeping it outside blowing in could also cause it to never shut off. You're going to need to do some math on using that timer.

Like I wrote in the beginning of my post - it comes from old school thinking and experience.

[joseph]

I've been using a kerosene heater this spring. It's about a 10000 BTU unit. I'm loving it. It's just right for my 10' X 12' little greenhouse. My greenhouse could benefit from a fan in the peak, and additional draft-sealing.

[PhilaGardener]

Battery-powered carbon monoxide alarms are inexpensive and readily available.

If you are using a fuel burning unit in a GH, particularly one that is not vented to the outside, it will be the best $20 you ever spent.

[Worth1]

We had a diesel powered Webasto heater in our box van, the darn thing was always breaking down.
Not good at 30 below.

Worth