Greenhouse Heating Options

[Cole_Robbie]

I started with an external wood furnace, which I still have, but I gave up that idea. Even with a huge fire, I could only get 7 degrees above the outside temperature with a single layer of poly and 15 with a double. It took up a lot of wood, and messed with my sleep enough to cut into the next day's productivity.

Old-timers here use a small wood stove inside the structure, but one needs s dedicated space for the stove and plenty of room around it so that the closest plants don't get too hot.

[FourOaks]

Im thinking that if I was to install the wood burner I have, I would be better off to build a structure on the end of the Tunnel, that would house the burner. Install a couple fans to help blow the heat.

Think of it like a small room. Maybe 6x6x6 or similar.

Decisions, decisons. No matter the choice, theres always pros and cons.

While im thinking about, I wonder about Coal. If one could get a better longer burn?

[Worth1]

Originally Posted by FourOaks

Im thinking that if I was to install the wood burner I have, I would be better off to build a structure on the end of the Tunnel, that would house the burner. Install a couple fans to help blow the heat.

Think of it like a small room. Maybe 6x6x6 or similar.

Decisions, decisons. No matter the choice, theres always pros and cons.

While im thinking about, I wonder about Coal. If one could get a better longer burn?

Coal is better
http://nepacrossroads.com/fuel-compa...calculator.php

[AKmark]

Originally Posted by FourOaks

2 Million BTUs! I have a 2.5 ton natural gas furnace on my house blowing around 100,000 BTUS. I know how much that costs. I couldnt imagine 20 times that amount. Maybe they would give me a price break?


Seriously though, I do run a fan at the peak of the seedling house on a really low speed. My thoughts are that it should help to circulate the air a bit.

Our friends who own a large GH business spend a 100k on heat every season, it is just part of the overhead.
I have had icicles on the outside of my GH at -10, have about a foot of snow still in the yard. We have to suck it up, we want perfect product when people are ready to buy in late spring. It all works out if you have a good business model, we spend a bit on heat, labor, supplies, and NEVER cut corners. When new people come in, many times they come back, that is the plan.

[FourOaks]

Originally Posted by Worth1

Coal is better
http://nepacrossroads.com/fuel-compa...calculator.php

Thanks for the link. Very interesting reading.

Originally Posted by AKmark

Our friends who own a large GH business spend a 100k on heat every season, it is just part of the overhead.
I have had icicles on the outside of my GH at -10, have about a foot of snow still in the yard. We have to suck it up, we want perfect product when people are ready to buy in late spring. It all works out if you have a good business model, we spend a bit on heat, labor, supplies, and NEVER cut corners. When new people come in, many times they come back, that is the plan.

Always going to have the cost of doing business, thats for sure. For instance, the cost of Credit Card Processing. Myself along with a lot of other vendors use Square. I laugh when folks want to scoff at fees, you pay no more then about $3 on a $100 worth of charges. Ill gladly give up the $3.


Your only statement that I will disagree with is the "perfect product". Obviously thats highly subjective. Around these parts, folks dont want perfect. "Perfect" is synonymous with factory farms, etc.


Once again, thats highly subjective, obviously you grow what your customers want.

[Dutch]

Hi FourOaks,
I heat my 10'x20' greenhouse with a Mr Heat Big Buddy propane heater. The heat levels are 4,000 on low, 9,000 on medium and 18,000 on high. I am able to keep the night time temps in the greenhouse above 40F with the heater on low if it doesn't get any colder than 20F outside and on medium when the outside temp gets to the low teens.
The key for me was using a dropped canopy ceiling inside. Without the canopy the most I could raise the temp in the greenhouse was a degree or two with the heater on high. I just took some pictures between the snow squalls. It is in the upper 20s outside and heavily overcast. The greenhouse is almost 60F inside with the heater on low.
MrHeatBigBuddy.JPG
InsideGreenhouseTemp4-9-18.JPG
InnerCanapy.JPG
Dutch

[FourOaks]

Dutch.. funny enough I do have one of those heaters. Mine is green. Think I got it from Tractor Supply.


What do you mean by "dropped canopy ceiling"??

[Dutch]

Hi FourOaks,
Its' basically an inner plastic shell. I use a 3mil 20' x 24' piece of plastic I buy at Menard's for a little under 20 bucks. I only use it for a couple months. I think it takes 3 or 4 months for the stuff to start to deteriorate. The framework that supports it is common 1/2 pcv pipe. The pvc pipe framework I leave up and reuse every year.
The greenhouse is in the back on a hill next to the garden. I'm going back up there to do some more transplanting in a couple of minutes. I just came down to the house to make my bladder gladder. I'll take some more picture when I go back up there and explain a little better in a post this evening.
Dutch

[Dutch]

The canopy creates an air gap between the outer wall which is exposed to the outside elements (temp, moisture, etc.) and the inner canopy wall which is exposed to inside elements (temp, moisture, etc.). In my case it also reduces the volume of upper area I needed to heat. If you had a tunnel, it would be a tunnel with closed ends in a tunnel.
My canopy or one piece sub-ceiling with walls is supported by 1” balls mounted on the outer wall. The round balls help to minimize tearing the inner plastic. The first year I made it, I had to run nylon rope across to keep the bows bowed. After a year of being bowed they now retain their shape.
My greenhouse is doubled layered with a 1” air gap between the layers, but the top has gable ends that open for cooling. I felt that the upper ceiling area was a waste to heat and making a sub-ceiling, the canopy, would reduce the area I needed to heat and solve my air leak problems on the gable ends too. It has done both.

The south wall of the canopy only extends down a foot or so because the door is there and the wall is already double layered. There is a plastic roll down door on the outside that I roll down at night as a storm door. The north wall which is the back wall and the side walls of the canopy extend to the floor. The ceiling and walls are all one piece of plastic draped over a pvc frame.
SouthWall2.JPG
Dutch

[PhilaGardener]

Nicely installed!

[Cole_Robbie]

I am starting to learn that the real point of the double-inflated poly layer that is a common covering is not the increase in r-value nearly as much as it is that you don't drop 5 to 7 degrees below the outside temperature due to atmospheric radiation cooling. On a cold night this week, my single-layer poly structure felt like a refrigerator inside. I could feel the temperature difference on my skin when I stood outside and reached in.

[FourOaks]

Dutch... I see what you mean now. Thanks for the pics and description.

Originally Posted by Cole_Robbie

I am starting to learn that the real point of the double-inflated poly layer that is a common covering is not the increase in r-value nearly as much as it is that you don't drop 5 to 7 degrees below the outside temperature due to atmospheric radiation cooling. On a cold night this week, my single-layer poly structure felt like a refrigerator inside. I could feel the temperature difference on my skin when I stood outside and reached in.

Interesting premise.

[biscuitridge]

Double poly doesn't prevent it from being colder inside,mine always is colder and I have inflated double poly.

[Cole_Robbie]

Originally Posted by biscuitridge

Double poly doesn't prevent it from being colder inside,mine always is colder and I have inflated double poly.

Interesting. Have you measured it? Cornell research found a 5-7 degree difference, but I think they only tested a single-layer structure. I would be curious to know if a double layer is the same.

The amount of energy required to heat my greenhouse the 7 degrees that it drops below the outside is huge. It is mind-boggling to think that a big heater would accomplish the same thing as just leaving the doors open.

[biscuitridge]

Usually around 3 to 4 degrees cooler.