Greenhouse vs. Shed for overwintering tropicals

When starting from scratch, at what point does it become more feasible to build a shed compared to building a greenhouse? I've been thinking about this for a long time and would like some input. I would think that if you have an unused room in your house that's already heated during the winter, growing plants in that room with a sodium or mercury light would be cheaper than building a greenhouse and heating it. What if you don't have that free space with free heat?

Greenhouse pros:
free light forever
enhanced growing (almost free) during spring and fall because of daytime heat
construction cost (if using a hoop house or similar)

Greenhouse cons:
cost of heater
cost of heat
construction cost (if using twin-wall or triple wall, or some expensive sunroom glass)
ventilation costs

Shed pros:
cheap heat if constructed properly
shell is already built and available from many different sources
minimal ventilation required

Shed cons:
construction cost of added insulation
cost of lighting equip
cost of running lights

Let's keep this discussion focused on overwintering because if you wanted to do this all year long, you would have to pay for the light to be on in the shed which wouldn't make any sense. I would think that the further north you are, or the warmer you want to keep your growing area, the more likely the shed would start looking better. If you were growing coconut palms in zone 4 that shed would look pretty good, but where do you draw the line?

Stosh,

SB,
I must not have been clear. Yes, by shed I meant any well insulated structure with no glazing or any "natural" light.
No, definitely for growing, not dormancy. The whole reason this came up (and we've discussed this before) is how frustrating it is paying for heat when it's so pricey and also how low the r-factor is with glazing. I'm always thinking and searching for a way to conserve heat both from a capturing standpoint when there is excess and from an insulating standpoint when there is a deficit.

Why wouldn't it be cheaper to put artificial lighting in a well insulated building to grow plants?

Well, we could calculate it out...

We would need the hypothetical dimensions of the shed and GH, the glazing, the R-value of the shed insulation, the lighting details. It would not be hard to figure out. Let's give it a try!

This is a very interesting topic, and I would love to see the figures too. As a northern gardener with a large tropical plant collection, I have been wrestling with similar issues. I'm currently using many plant lights and adding around $80/month on to my electric bill with my "plant room." I've wondered about constructing either a sunroom or an attached greenhouse, but every which way I look at it, the cost of running lights even if I double the number I am currently using seems like a cheaper way to go. In addition, with lights there are no cloudy days, which in VT is most of the time. Any how, I would love to see some figures.

Stosh, the spousal Unit and I remodeled half of a building that had been used for pigs. It was our breeding/gestation building for our sow herd. When we discontinued the hog part of our farming enterprise the building sat empty for 2 years. The building dimensions are 30x120. We finished off half of the building to use as a greenhouse where I could overwinter tropical plants. I have made a business of this doing it for other people. I only take large plants, those that would be a real pain to try and overwinter in your house. The building was open to the south to begin with. We put double wall polycarbonage panels on the south roof and south wall. The rest of the building was sprayed with expandable spray foam insulation, over which we put foil-bubble-bubble-foil roll insulation. We have 2 vent fans (at least 36 inch, I'm not sure offhand) and 2-200,000 BTU LP heaters. We only need 1 to adequetly heat the inside, the 2nd is for insurance purposes in case one does a croaker. LOL And yes, there have been a couple times when I'm jolly glad we had it.

If you are wanting to overwinter tropicals, I wouldn't even CONSIDER a "shed" type building with very little or no natural lighting. I should probably add here that I am NOT into retail selling, I do not start or sell plants; mostly because I can't compete with Wal Mart and I DON'T want to compete with the local family garden center business that helped us get started in this venture. I also want to be done with it all by the end of May, since hubby and I operate a running farm business, I have field work to do in the summer and I don't want to deal with selling plants.

Before I had the greenhouse I tried to overwinter the tropicals I had in my basement. No natural lighting, so I used grow lights. the plants didn't do much all winter long. I think you would be disappointed if you did it that way. As far as the heat goes, my initial goal when entering into this venture was to have enough plants belonging to clients to pay my LP bill, essentially enabling me to keep my own plants in there for free. I have consistently been able to achieve that goal, except perhaps my first year when, as a new business, I didn't have alot of clients or plants. My building is now full; has been for the last 2 years. We have discussed enlarging the greenhouse portion; the way the original hog building was built, there are 16 foot increment/sections, so we could do 16 feet without much trouble. We have not, as yet done that.

When we first started talking making a greenhouse, a hoop structure covered with plastic was not even a consideration. Number 1, because of the wind and cold factor and having alot of plants that are not mine in there and Number 2 was the fact that we have cattle, and if cattle get out plastic film would be a great thing for them to see and say "WOW..........look at that plastic stuff, let's see if we can chew it off." And they would.

Somewhere on this greenhouse forum I have a thread showing what we did. I'll see if I can find it and figure out how to put a link to it here. If you have any questions, fire away; I'll be glad to answer them.

I don't know if this will work or not.........if it does, this is "Our Greenhouse Project".


http://davesgarden.com/community/forums/t/365081/

Would the size really make that much difference? I would have thought that everything would be in proportion no matter how big you go, but for arguments sake, let's start small, like 10x20.

I would consider May-Sept normal growing months around here even though "official" last frost is May 15th we hardly ever get frost in May. Average daily temps around here bottom out in the high 20s in Jan and get to the low 50s in April and Oct.

We could choose a common hobby glazing like twin wall polycarbonate or possibly 2 layers of poly. Let's make the shed's r-value similar to a house in this area - maybe walls in the 20s and ceiling in the 40s?

I know nothing about artificial lighting, except that I own one 4' fluorescent fixture with a grow light that I've never used. But if I were to use artificial lighting I would obviously go with the most efficient which is probably HID. I have tropicals including palms which means they need lots of light. I forget the numbers, probably 10,000 candlepower or is it 100,000?

On the lights, how many lights and how many watts?

Wow, I was hoping for some help in this area because I really have no idea. I guess I'll have to do some homework and find out how much light a single 600W HID light would create and whether it would be enough for the small 10x20 room. Just got in from shooting the eclipse and now it's time for bed.

You can find a lot more of this kind of information in grow room type forums. Lot of guys growing some really expensive tomato's ;-) If one was to build a well insulated shed without windows I'm sure the HID could provide all the heat. Just remember that this lights are not cheap to run. You can cover with less fixtures if you install a light mover.

Darn clouds ruined our view:-(

Yeah! Those "expensive Tomato grow rooms" make for some really interesting reading! The technology blows me away; CO2 injectors, carbon filters, ph controlers, and the like. Those have got to be some great "Tomatoes." To adequately light a 10X20 grow room, you would need a mininum of (2) 1,000 watt HID lights, maybe more, for high light plants.

Doug

Wow, I guess that kind of answers my question. I had no idea you'd have to have 2000W of light for such a small room. That seems crazy, but it sounds like you know what you're talking about.

If we base the discussion on that number, I can see why nobody grows things indoors. My 5000W electric heater would definitely take more $$ to run in the peak winter months like Jan and Feb, but the other months it may be tie. Somebody's got to invent a way to make more efficient light, like LEDs or something.

I really believe when the LED technology comes into its own, it will revolutionize the way people garden indoors in this country. It is really looking promising right now. If you do a search for LED UFO Light, you should find some interesting growing trials being done with a light that consumes only 90 watts of power, but outputs more than a 400 watt metal halide. The problem is that the light is too expensive right now - $600.

Doug

I'll check that out. Even at $600 the long term savings would have a fairly fast payback. Could you imagine the savings in oil and carbon output this technology could save a nation? It's nice to see emerging technologies with the promise of solving our most pressing problems.

Here is the link for the UFO Plant Light in case anyone wants to check it out. http://www.hydroponicsfarming.com/product-612.html

My bro is in the lighting business and he showed me a cool "fluorescent" LED, T8 size, no ballast, 300 little LED lights inside the tube, something like 14W, $300.

Anyway, stosh, do you still want to work through the numbers?

Don't know if this will help.......
I have a GH , all glass , this is my first winter using it . It is way too hot in the summer, great for storage but not plants. I have blocked out light from the north wall and that half of the roof with foam , all other glass has 2 layers of bubble wrap. Little light would come through the north side so the foam. I was thinking this fall of covering the whole inside with foam and only using my 'homemade grow lights' for light.
I'm using 2 1500W heaters on thermostat , Don't ask what it cost to run them.

Rentman, the heating costs is what drove me to start this thread in the first place. This year I made a special effort to seal every crack I could find and then I taped all the vents shut on the knee wall because it doesn't get hot enough for them to operate. I did significantly reduce my heating costs, but they're still very high. My wife asks me "Couldn't you just buy all new plants every year with what you spend on that GH?" Well, the answer is no, but she has a point - it's very expensive.

SB, I guess we don't need to run the numbers anymore because 2000W for 12 hours a day doesn't really sound like a deal either. It may be a little cheaper just by doing a few things in my head, but that's only if you already have the shed or spare room that's already insulated well. If you were starting from scratch, the extra building costs of the highly insulated building would be insane.

I had a room that I wasn't using, that was in the middle of the house and doesn't have any windows. I put a 4' x4' skylight in the ceiling and now there is tons of light. The guy opened up a lot of the ceiling, sloping it down away from the skylight and that makes a difference in light as well. I have a lot of tropicals and palms overwintering in there, and they seem to be doing well.