greenhouse design.. temperature - Orchid Board

rezi · #1 01-11-2015, 10:47 PM

I'm new to orchids and have been researching them and greenhouse design.

Curious what factors besides economics went into choosing the temperature range of your greenhouse?

If you have multiple greenhouses lol, sounds like many of you do, what temperature range would you choose to enjoy the species you like best?

Thanks!

Ray · #2 01-12-2015, 08:22 AM

I'm only speaking for myself, but I think you've got it wrong. Decide what plants you want to grow, then design for them.

Then, when you find you're killing yourself in heating bills, you consider adjusting the collection.

I run my business out of my home, and my local inventory is in my basement, with the plants in the greenhouse. Considering heating costs, I've thought about moving the plants indoors under lights, and using the greenhouse for product storage.

There's a nearby grower who specializes in Andean species, so he purchased a 40' refrigerated shipping container, and outfitted it with lights to grow them.

rezi · #3 01-12-2015, 02:10 PM

I guess what I'm trying to ask is, given all your experience in the hobby, what temperature/light range would provide you the most interesting growing environment? Either species wise or a particular climate or locale you would want to replicate.

I was a little stunned by the general inefficiency of greenhouses and was reconsidering a notion I had about how I envisioned mine--hot humid tropical like. I suppose one's palette for orchids/micro climates evolves until one day your putting together a javanese cave stream orchidarium, or a high andean waterfall.

The Catasetum genus was the first to really capture my imagination but since I have stumbled across many colder growing plants that are enthralling as well. There is a pretty major temperature differential between warm growing orchids and my local climate of Seattle.

For whatever reason the thought of a heater humming away out there all nights, and constantly 9 months of the year, is a little uncomfortable. Electricity in quite cheap here, running NG is an option but seems overkill for a 10x8 greenhouse.

My girlfriend thought it was a little ridiculous to spend nearly what we pay to heat our 1800q/ft hardly update historic house to heat a 10x8 greenhouse.

I wonder how much of a difference careful planning and construction can make. Solid walls and insulation wherever I could. Digging the foundation a foot below grade etc.

There is surprisingly little journals of thoughtful greenhouse construction I could find on the inter webs.

Ray · #4 01-13-2015, 08:11 AM

Quote:

Originally Posted by rezi

I guess what I'm trying to ask is, given all your experience in the hobby, what temperature/light range would provide you the most interesting growing environment? Either species wise or a particular climate or locale you would want to replicate.

Again, that's a personal choice, and not something you can get from others. For example, there are lots of cold-growing plants that are interesting, but that's not my preferred segment of orchids.

Certainly there are things you can do to maximize the efficiency, but it's never going to be as energy efficient as a thick-walled structure with insulation.

Shape: minimize the surface-to-volume ratio. A geodesic dome, being close to hemispherical in form, would be the best.

Forget one foot below grade - deeper is better. A 4' tall roof over a 6' underground structure (an extreme example) would likely require no additional heating or cooling.

Glazing options: Thermopane, Low-E windows would be the most efficient, but also the most expensive. Very thick, multiwall polycarbonate is the next best thing.

The north wall of my greenhouse, as it'll never see light passing through it, is thick and insulated.

Then you can also consider the means of heating and cooling. A long time ago I read an article about an interesting take on geothermal heating - I don't think the term had even been invented yet. The author dug a trench below the frost line in his area (northern Michigan or Minnesota, if I recall correctly), and placed unglazed clay sewer pipe in it. One end entered the greenhouse below grade, the other - a few hundred feet away - was open to the air, screened and filters in a small enclosure above ground. By running a small exhaust fan, dry, frigid air was drawn underground, where it was heated to the mid-sixties and humidified before entering the greenhouse. In summer, the blistering, saturated ambient air was cooled underground, and some of the moisture would condense, before cooling the structure.

Electricity to run a fan (with adequate power backup, of course) is a damned sight cheaper than the cost of heating! If I didn't live on top of rock, I'd have done that a long time ago.

dabblin-n-orchids · #5 01-14-2015, 11:01 PM

the "4' tall roof over a 6' underground structure" is not actually that extreme. there are a number of people creating passive greenhouses that match those parameters. They also tilt the south facing windows to be perpendicular to the sun at it's lowest angle (winter solstice) for maximum light penetrance aan solar gain in the winter and maximum solar deflection in the summer. They are called Walipinis and some of them really are a hole in the ground with a small roof overhead. here is one built for $300: Build a $300 underground greenhouse for year-round gardening (Video) : TreeHugger

Ray · #6 01-15-2015, 08:33 AM

I agree, Michael.

Going with the fact that most of us don't live on hillsides, there used to be nursery in southern NJ whose greenhouse was an 8' tall concrete block "box" structure - insulated and covered with nicer-looking siding externally, painted white on the interior - with a polycarbonate-glazed roof.

Very energy efficient, and all they did was arrange the brighter plants in the middle, and the shadier ones on the perimeter.

silken · #7 01-15-2015, 10:33 AM

We have what I guess you can call a greenhouse attached to our home. It is heated right thru our winters which are as cold or colder than most people here on Orchid Board will ever see. It is not uncommon to have a week or more at a time of -36C or colder and we have fairly long winters. We didn't have a choice of choosing which way to orient it since we attached the long 30 ft. wall to our home. So the wide part faces west and the short end of windows faces south. It is 11 ft. deep and one short end attaches to a heated garage. Our landscaping made it possible to dig it into the ground 3 ft. We poured a heavy concrete pony wall with good foam insulation in it. The windows are triple glazed and able to open in the summer. The roof is triple glazed poly carbon panels. The frame is aluminum with foam insulation in the hollow parts. We have an energy efficient NG furnace in there that heats the greenhouse and 1/3 of our home. I am sure our gas bills are higher than if we didn't have the greenhouse. But the house wall it is attached to is all window anyways, so we don't feel that the bills are outrageous for what we have. Natural gas here is more affordable than some parts of the country. We do have to run a dehumidifier in winter and I usually don't have as much humidity as I would like. In very cold temps, it will collect on the windows and run down and just make a mess on the ledges and cause mold if it is sitting wet for too long. But it is around 40 to 45% in winter and I keep it cooler at 65F in the day and 55F at night. So extra humidity might not be real good anyways. I have been using this greenhouse or it's predecessor that had a fir wood frame for about 25 or 30 years. Not always for growing orchids, but for keeping tropical plants and growing many bedding plants.

We get the other extreme in summer of hot and sunny. We use a shade cloth in spring and on the short southern end there is a large exhaust fan that cuts in when the temp reaches 90F. We have 3 hanging ceiling fans that run 7/24 year round. and an intake fan for summer that runs when the exhaust fan runs. I often open windows in summer also. We have a misting line that runs the length of the ceiling that comes on several times a day in summer.

So that is a rough Idea of what I do to grow my orchids in a fairly harsh climate that sees both extremes in summer and winter. I do supplement lighting with T5's in winter since days are short and there is usually snow on the roof, which probably acts as a good insulator.

With some imagination and some research, anyone can build a greenhouse and make it work. It's just a little easier for those in a climate more friendly to the idea

By the way, I grow Catts, Oncidiums, Phrags, Paphs, Dendrobiums with a reasonable amount of success. I need to create small microclimates with heating mats for some tender ones in winter, and find the cooler shady spots for others in the summer.

AuGrower · #8 01-25-2015, 06:46 PM

Rezi,
You would be amazed at how much difference the sun makes in heating a GH. I had done months worth of research when I was looking into mine, but I still am surprised at how quickly my GH will warm up on a sunny day. I am planning on trying to run a Intermediate to warm GH. Partially because it covers a wider range for my favorite species, and also because it is closer to our natural weather.

Where you are going to run into heating issues is going to be your lack of sun. Even in the dead of winter here we have bright sunny clear days, but again we have subtropical weather here. I recommend trying to find an affordable heating alternative. One of the University GH here uses a corn fed heater to keep some of its aquaponics going through the winter, but I don't know how efficient or affordable something like that is.