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Heating a hoop house/green house.

Started by pinebugsrus, April 04, 2012, 09:52:27 PM

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pinebugsrus

I'm new to the Forum and the outside wood boiler experience.  Spent a lot of time reading many of the strings in an attempt to get schooled up on the subject.  What a tremendous resource this forum has been for me as a rookie boiler operator.  I'd like to thank all the members for their contributions to past strings and the humor is priceless.  Thanks guys.  Better get to my question now.  My boiler is big enough to heat my house and garage with plenty of Btu's to spare.  I'm thinking of building a greenhouse and to grow veggies through the winter so does anyone here have experience heating one with an owb?  Do you employ a combination of heating the soil beds and direct air/space heating?   
Don't know what I wanna be when I grow up.  She says....GROW UP ALREADY!!

Clam77

I don't own one but I'd think if you had the in-floor radiant heat and a reznor style forced draft heater you'd be as warm as you'll ever need to be..

Just my 2¢..   :D
Andy

Stihl 009, 028, 038, 041, MS362
Mac 1-40, 3-25

red oaks lumber

i think you could heat  a green house even in the winter. at night if you had a retractable heat blanket that you pulled out at night to keep you heat confined to a lower level in the g.house and pull it open in the morning to allow sunlight to provide the heat for the day.\ my thoughts on the heat blanket could be something like cables strung down both sides of your g. house maybe 4 ft. off the floor your blanket would have grommets so as the cable would be strung on it ,kind of like a shower curtain is strung.
if it still required more heat maybe just dont have veggies growing in the coldest month of the winter
the experts think i do things wrong
over 18 million b.f. processed and 7341 happy customers i disagree

Holmes

Welcome to the Forestry Forum pinebugsrus.  Seeing you are in Maine you should figure 60 to 80 btu's per square foot to heat a green house. You should have no problem heating a small green house.  Radiant floor heating will only deliver 30 to 40 btu's per sq. ft. You will be better off to use a modine type blower heating unit.
Think like a farmer.

doctorb

I have no experience with what you propose, so take my opinion for what it's worth.

The problem, IMO, is not heating the greenhouse, but the loss of heat from the greenhouse.  So I am in line with Red Oaks, as that's the problem his post addresses as well.  So the design / construction of the greenhouse matters a lot in this decision.  How big a space do you need?  The title of your thread makes me picture one of those structures with metal hoops holding up a thick plastic cover.  I envision that the heat loss from such a structure would be huge.  While that type of design may be less expensive, it will cost you a lot more in wood and wood prep time than a more conventional building with windows, etc.  And since you can't have heating mistakes in mid-winter with veggies, I would investigate other more insulated types of greenhouses before I put up the hoop type in Maine.  I would also ask about the forced hot air heat's effect on the plants.  It's a very dry heat, and the humidity in your greenhouse may also need to be supplemented with a FHA heating system.  Just my thoughts.
My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

thecfarm

 We use to have a greenhouse before my OWB days. We had a forced hot air oil furnace,90,000 btu. Start it up about the end of Jan. We was on a first name basic with the oil guy. I myself would put a heat exchanger in,the one with a fan behind it,this will help move the air too. Will also need fans in there too to help move the air around too. don't want mold problems. We use to use regular box fans,mounted upside down so the controls was easy to get at. Kept them running for at least 2 years,24/7,for the season. I thought they would die in one year,but they worked fine. Really need 2 layers of GREENHOUSE plastic. Pricey,but will last a long time until it starts to get cloudy. Also should have a blower to blow air between the 2 layers too. This helps as insulation. When it's dark out,that heating system will be running to keep the greenhouse up to temp. I kept a big plastic tote,probably held 250 gallons of water,right in the greenhouse. This way the water was at room temp. Well water is really too cold for the plants.We would fill this tote than pump water out of it. I can see this idea working,but will cost to get it going,but need to make it a long time investment. Need to remove snow away from the green house when it snows too.The inward pressure can collapse the sides.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

blackfoot griz

There is some good information on you tube.  One worth noting is "Sustainable Energy: Thermal Banking Greenhouse Design" This could give you some ideas of how you could incorporate your extra BTU's from your OWB. The basic premise is that you use the ground under the greenhouse as a heat sink.

We have a 16x60 hoop house. In this part of Montana, there is no way we can grow tomatoes if they are not under cover. Two years ago, our spuds had their leaves frozen off in June, July and August!
We have a "min/max" thermometer in our hoop house and the extremes are incredible. It can hit over 125 during the day and go below freezing at night. I like the idea of storing the heat gain of the day and releasing it at night.
One of these days, I am going to build another greenhouse and incorporate the heat sink concept!








pinebugsrus

Many thanks to everyone for the thoughtful input.  I may be talked right out of this, forget about all the expense and work a hot house would bring and just find a cheap, used hot tub to bleed off my extra Btu's.  It's just that we are really feeling the pinch with the rising cost of fresh produce up here so why not tap into some of this free heat to grow it?  I know ....it's never free but I have vowed not to buy any wood for as long as I can keep feeding this beast with blow down, thinning out my house lot and clearing for other people I pick up handyman work from, etc.  I even pick up the crumbs left on the side of the road when the tree trimmers come through to clear the growth hanging over the power lines.  Blackfoot, our growing season is probably about as short as yours so I'll look into this a little more before I buy that hot tub.  16x60 is impressive.  Is that a commercial operation or just for your own dinner table?  Thecfarm....looks like you have a serious operation and you mention a veggie stand in a couple photo captions.  You said your former greenhouse was heated with oil but do you have any idea how much oil to get through our Central Maine winters?  I could estimate how much extra wood I might have to plan for with that info.  By the way....I will get up your way sometime soon as we are too close not to stop by, shake hands and introduce myself.  You have contributed much to my greenhorn intro to owb operation.  My Central Boiler dealer knows you I think and I have an idea where the farm is so we should talk sometime.  Isn't there a big hot house operation up in Madison, growing tomatoes year round?  I think they heat with wood boilers up there.  Anyway, I have as much experience gardening as I do operating this owb, getting it on line 1-5-2012, but got to start somewhere.  Doc and Red....you guys might be onto something with the thermal blanket or just shutting down after a well timed harvest for the coldest 2 months.       
Don't know what I wanna be when I grow up.  She says....GROW UP ALREADY!!

pinebugsrus

Holmes, thanks for your input as well.  I did some math using your numbers and it looks like I would have plenty of Btu's to add a 12x30 greenhouse.  Thinking I'd start even smaller and expand if it worked out OK.  Clam77, I think you're right about the combination.  You guys are gonna talk me right into it.  Thanks again.   
Don't know what I wanna be when I grow up.  She says....GROW UP ALREADY!!

Taylortractornut

I had an  old plant man tell me that  bottom inbed heat is the best for alot of veggies.    I have a 13 by 20  hoop house I made from trampolines.  You can grow alot of Brassicas and cole crops in that mall of an area and still heat it to. 
My overload permit starts after sunset

albirk

about 5 years ago i hooked a green house up for guy we put infloor (in the bed) and a hanging unit it cost about $1000 for parts and labor (pex,manifold,2 pump,2" foam to line the beds and fittings) he sold at the farmers market all winter and said he payed it all off within 2 months he now has a stove to heat 6 hoop shed some are all in bed and some are a coil and fan and the wood used in a year is not bad he said compared to gas

DR_Buck

This is a topic Robert (Onewithwood) can answer.  I think he heats  couple of green houses with a Central Boiler Classic.
Been there, done that.   Never got caught [/b]
Retired and not doing much anymore and still not getting caught

thecfarm

Yes,in bed heat in better for plants. I have no idea how much oil we use to go through,it would scare you. Just in one season I know we went through 2 tanks and probaly more like 4.When it was cold in Feb we would go through a alot of oil. I would go to bed and mark the gauge and get up in the morning and it would be down by just about a ¼ inch and that was a 250 gallon tank. We had alot of hanging plants too. We had a 25 by 75 foot green house.I really have no idea about how to save heat mass on a small scale. We had our greenhouse full of plants so not much room to fill up 50 gallons barrels of water or to have rocks in it. I've read about digging the greenhouse down 3-4 feet into the ground too. Lots out there,check it out.Yes,there is a BIG tomato greenhouse operation in Madison. We have been by it,but never been on a tour. We are having new signs this year,per order of the state. The C Farm, Biscuits and Jam. These will be on Route 17,at 12 Corners,heading towards Livermore Falls. Than I can put my produce sign below that. But we can not put biscuits or jam unless it's a state approved sign. But anything grown on our land is fine.I am just about to start on a building for the veggies. We also sell bread,small pies,whoopie pies,pot holders,aprons, biscuits,jams,jelly.Please stop by and see me. Where about in Readfield are you?
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

LAZERDAN

Where have I been ?                             
A whoopie pieThe whoopie pie (alternatively called a gob, black-and-white, bob, or "BFO" for Big Fat Oreo) is an American baked good that may be considered either a cookie, pie, or cake. It is made of two round mound-shaped pieces of chocolate cake, or sometimes pumpkin or gingerbread cake, with a sweet, creamy filling or frosting sandwiched between them.[
                                                                   Yumm  Yumm                           

Clam77

We have a large greenhouse here at work (don't know exactly how big but I'd say close to 75x200) - they have a thermal blanket in it they roll across the top to conserve heat/shade from the sun.  It works VERY well.  We use steam heat here though - there's a couple large forced-draft heat exchangers hanging in there.
Andy

Stihl 009, 028, 038, 041, MS362
Mac 1-40, 3-25

thecfarm

By the way if you want to grow just the cold crops,like lettuce,spinach that makes a big diffeance on the heat too. Probaly cost wise,the greens are the way to go.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

downeast

Quote from: thecfarm on April 06, 2012, 09:31:38 PM
By the way if you want to grow just the cold crops,like lettuce,spinach that makes a big diffeance on the heat too. Probaly cost wise,the greens are the way to go.

Great idea. Think a little out of the box.....
Look up Eliot Coleman on growing "cold crops" like thecfarm mentioned as well as many root veggies. Coleman has written many books on growing in a Downeast Maine winter with NO heat since our light latitude is similar to southern France. The Coleman operation a few miles from us sells gourmet produce year-round to restaurants in this region.
Heavy insulating will pay off as above.
Spending that kind of $$$ on winter tomatoes ( a summer crop) makes little economic sense IMO.
Good luck.

mrcaptainbob

Many years ago, during the dead of winter here in Michigan, the company I worked for saw fit to have the sidewalks in front of the main building repaved. Terazzo. To keep the 'crete warm a tent was built to span the path for it's length. 2x4's were used for framing. Heavy visqueen was used on both sides of the lumber and securely fastened. Propane tanks were at either end feeding the stoves in there. That they had the sheet plastic on both sides kept a sizeable air pocket in there and acted as a pretty good insulator. Maybe something like that would work for your green house? Solar would still make it's way through during the day....

pinebugsrus

Quote from: Taylortractornut on April 05, 2012, 11:55:59 PM
I had an  old plant man tell me that  bottom inbed heat is the best for alot of veggies.    I have a 13 by 20  hoop house I made from trampolines.  You can grow alot of Brassicas and cole crops in that mall of an area and still heat it to.

Great idea Tractornut!  Insurance companies hate those things and will cancel your homeowners ins. around here if they catch you with one set up in the yard.  Maybe I can get a couple throwaways.  Is the radius tall enough to walk in or do you extend with additional pipe?  That inbed heat seems like it would be the best , keeping the dirt warm, more like the natural growing season.  I may find it too expensive to set up though, with insulation board, pex pipe, etc.  Cost my decide it for me and just go with a cheap water to air heat exchange setup.  Dad works for an HVAC contractor so I can get a used unit heater cheap.  Got a 60,000Btu Trane unit for $100.00 and put that in my garage.  Works great just running my return line through it before I go back to the OWB.  I'd have to set up a dedicated zone for the fantasy greenhouse though as I've maxed out the capacity of the single 1" pex to the house.  So a 2nd circulator, pex run and unit heater will be a big expense so I better start saving my bottle return $ now.  The Eliot Coleman Cold Crops method may be the way to start this adventure and if successful, get the boss on board to invest the big$ to go heated.  Thanks everyone, for the input.
Don't know what I wanna be when I grow up.  She says....GROW UP ALREADY!!

OneWithWood

Sorry I am late to the party...
We heat a 30x90 hoop house using hydronic heat (hot water loops in the slab) as well as a smaller 16x16 Farmtec greenhouse.  Keeping temps above 40°F during the winter has not been a problem.  The heat source is a Central Boiler CL 7260.  During a normal winter we will use 20 cord (60 rick) of firewood.  This past winter was so mild we used half of that. 
The heated slab provides good layered heating zones so we can move plants up off the slab onto benches to control the soil temps. 
One With Wood
LT40HDG25, Woodmizer DH4000 Kiln

Al_Smith

Depending on the situation a green house structure can gather a lot of passive solar heat during daylight hours .As such more often than not it's neccessary for exhaust fans under certain conditions .

One gent I know built a large south facing semi underground house .He simplely used plastic barrels full of water to act as a heat sink for the excessive amount of solar heating.The water retained the heat which was expelled during periods of no or little sunshine .

I have one experiance with a commercial green house which had a large Kewanee coal fired boiler .At zero degrees it burned a ton of stocker coal in 24 hours .The heat was radiated by a long series of piping using 180 degree return pipe fitting and circulation fans which used plastic ducting .

In days of full sun the inside  temperature could shoot up to over 90 degrees in just a few minutes even at sub freezing condtions of maybe 10 degrees outside .However just 10 minutes of cloud cover would drop the temp causing the big boiler to kick in .

bandmiller2

As Al mentioned probibly the greatest danger in a greenhouse is overheating and cooking your veggies.Thermostatic controlled fans are a must.For a noncommercial personal greenhouse i think half burried with two pane insulated sliding glass doors set at an angle south would turn the trick.Some heat from an outside boiler would help through the long cold nights.Frank C.
A man armed with common sense is packing a big piece

Al_Smith

I've always had a notion to build a small hot house just never got a round tu it .Some rather ingenious ideas have been used for small units .Such as attaching said structure on a south facing wall of a house to capture the solar heat and by use of recirc fans blow the excess out into the house both making use of the passive solar heating plus not cooking the plants .At night time reverse the fans .

Like most things a person could get real fancy like I think it was Arby's that had thermostatically controlled shade curtains to regulate the passive solar on the solarium type rooms they had during the mid 80's .Worked great most of the time just cost -a- plenty .They were a tad tricky to work on and preform maintainance which I found out after working on several that failed and about cooked the dining patrons .

Those were early electronic type integrated circuitry and not well thought out at the time .I'm certain by now improvements to the systems have been corrected .Still costly though .

Al_Smith

While on the subject a slight detour .

Now if you're ever in Nashville and a country music fan or not take a tour of the grand old opry .There in lies the most elaborate system of a green house type thing I've seen .It' s a multi million dollar set up but they have the nicest botanical garden type setting  I believe I've ever seen .Huge recirc fans and damper controlled upper windows to regulate the temperature .I'm not certain what the heat source would be but it's really something to see in addition to the rest of the place .

muddstopper

Better late than never i guess. I would go with a solar collector with a insulated water storage tank. The collector is simple to make, some copper pipe, a little aluminun flashing, can of flat black paint, a few 2x4's and a sheet of lexan. You can build what ever numbers of collectors you need to heat your water capacity, The use of a low voltage water pump will allow the use of a small solar panel to circulate the water thru pex tubing under the plant beds. Thermostats will control heat. Its basicly trouble and maintenance free. I have gotten 180*F water temps in Dec and Jan, (norm is closer to 130*F) but of course NC winter isnt as cold as Maine

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