Heating my Greenhouse

[Joe Bifano]

I had an idea on how to heat my greenhouse and wanted to know what you all think.

 

I was going to get a pellet stove insert from a friend for free and started to brainstorm. I have a greenhouse that measures 24x64' and it has 17' high ceiling in the center.  It is way to big to heat the whole thing so I had an idea on how to heat just some parts of it.

 

With the pellet stove I was thinking of making another room, inside the greenhouse, out of plastic and maybe a thermal blanket. I want to maybe put the plastic on some rafters that come across the greenhouse at 10' high and enclose a space that would be just for tomatoes about 8' wide and 64' long.  Put the pellet stove in that area and see what I get at night. I would roll up the thermal blanket during the day and drop it at night.  I could do the same thing above instead of using the plastic so I get a higher R-value.

 

Also if the thermal blanket idea would not get enough R-value I had another idea on using 2 pieces of plastic creating a air space. Then using a woodworking cyclone add static free peanuts to it creating a pocket of peanuts to make a high R-value filling in the walls and ceilings.  Then in the daytime vacume it all back out to a large container or feed siloh.

 

Your thoughts.

[TCLynx]

are you really up to opening things up every day after dawn and closing it back up before it cools off too much?

[Joe Bifano]

I would do anything to be able to have tomatoes growing all year long.  It gets to 20 degrees here at night and my greenhouse during the day is over 80 when the sun shines. It gets so hot I am wearing shorts working out there today and I am sweating like crazy.

[Chi Ma]

I wonder if you could heat up 55 gallon drums full of sand for thermal mass.

[clint miller]

geothermal heat I saw this british green family show.  Any way they lined a hole with styrofoam and filled it with rocks.  The hole had a 4in pipe .  During the fan would blow air down and heat up the rocks and the opposite at night. 

[TCLynx]

There are also some water wall bags you can install that can provide thermal mass that can be warmed up during the day and then they give off heat at night.

[Joe Bifano]

With my greenhouse being 1500 sq ft. I  don't think small amounts of thermal mass will help.  I have not filled my 2 1200 gallon fish tanks yet and also need to fill my rafts that will hold about 2600 gallons so I will have 5000 gallons of thermal mass and not sure what that might do.

 

That is why I was looking at the pellet stove and the smaller area to heat rather than the full greenhouse. 

 

I also read on this forum that having a heated greenhouse would put a lot of condensation on the top plastic and create a lot of humidity. I am in such a dry climate I am not sure that this would hurt me at all but if anyone can add to this let me know.

[Molly Stanek]

From what I've read and experienced, it's the combination of high humidity and cool temperatures that allow fungal problems to grow out of control incredibly quickly.  Towards the end of September here in Milwaukee we ran into a lot of powdery mildew on our tomato plants simply from closing up the greenhouses at night. Our greenhouses were not heated - we were just trying to extend our growing season a bit.

I'm not sure what your situation is, but if you're thinking about heating only part of your greenhouse with the pellet stove I would be a little concerned about the areas that will remain cool and will most likely have high humidity levels.

Joe Bifano said:

With my greenhouse being 1500 sq ft. I  don't think small amounts of thermal mass will help.  I have not filled my 2 1200 gallon fish tanks yet and also need to fill my rafts that will hold about 2600 gallons so I will have 5000 gallons of thermal mass and not sure what that might do.

 

That is why I was looking at the pellet stove and the smaller area to heat rather than the full greenhouse. 

 

I also read on this forum that having a heated greenhouse would put a lot of condensation on the top plastic and create a lot of humidity. I am in such a dry climate I am not sure that this would hurt me at all but if anyone can add to this let me know.

[Joe Bifano]

So are you saying then it is better to heat the whole greenhouse and then I will not have any condensation.

[TCLynx]

Well heating the air will definitely help against the high humidity problems.  If you were to heat the water and not the air you would wind up with major ice condensing onto the outer cold surfaces of the greenhouse.  As long as the air is warmer than the water, that will be far less of a problem.  However, condensation may still be an issue.

[Joe Bifano]

Wow so if I want 75 degree water in the fish tank I have to have a heated greenhouse to 75.  That would be expensive. I am thinking that my dry climate of maybe 5 to 10% humidity may not be that bad if my tanks are 75 and my greenhouse is maybe 50.  I guess I have to put the 2 55 gallon boilers in the greenhouse and see how much heat they make.  I will have one for each fish tank and maybe the pellet stove going too. A lot to work on in the next few weeks.

[TCLynx]

Try and see how it goes.  Might be worth it to you to stop into the greenhouse group and ask Rob some questions.

[William Morgan]

Heating the water is your best bet. There is condensation, but with air moving fans, the plants seem to stay pretty dry and totally dry by mid morning. When heating the water your air column gets colder as you get higher. You would need to build a small plastic hut for the tomatoes. The heat will rise and keep them warm enough.