Over the last five weeks we’ve made steady progress on the greenhouse. The big catalyst was the builders showing up one morning to get the greenhouse plastic on. Never mind that we had 12 m.p.h winds and it was really cold….we got it done anyway. With six of us hanging on for dear life, in windy conditions, it didn’t take more than an hour to get the double poly on using the wiggle wire system. That is a super slick way to install the plastic and there’s still room in the track if we want to put some shade cloth on the greenhouse this summer. We initially left about 12” of excess plastic around the edges in case we want to tighten up the plastic at some point. Since we’ve been working in less than ideal conditions, we haven’t had the luxury of working on a warm day to get things exactly the way we want them as far as getting all the slack out of the plastic. It may just be me seeking perfection, whatever that might be. We did trim the excess plastic on the west wall recently because that is where all the wind comes from and it was stressing this flap of plastic like crazy to have it flapping frantically in the wind (let alone driving me crazy listening to it).
Once the plastic went on, I was able to paint the interior on sunny days. Within an hour or two of direct sunlight hitting the greenhouse, the temps would be in t-shirt zones and I could paint. Two coats of Benjamin Moore latex enamel Moor-Glo were put on everything. After that was done, the electricians showed up to get the receptacles installed that would run the water and air pump, fish tank heaters and inflation fan for the greenhouse roof. Since there are two layers of plastic, an inflation fan is needed to inflate the space between the two layers. You’d be amazed at the amount of insulation that this creates. The other day when we unplugged the fan to get some of the slack out of the plastic and re-do one of the wiggle wires, the roof was still inflated. It was a cold but sunny day and the warm air stays trapped between the two layers. Even when I took a 3” piece of PVC conduit and plunked it on the roof, it wouldn’t deflate…it was insane.
In four days the electricians had the receptacles and lights installed. I found used 350 watt metal halide lights on Craigs list for $35/each. These are low bay warehouse lights and are typically used in ceiling heights of 10-15’. They also make a high bay light that works with taller ceilings. Metal halide lights give off light that is in the growing/blossoming spectrum and are excellent “grow” lights. They can have either an aluminum or acrylic shade on them or in this case they have the safety tempered glass style of cover with cage around them. I picked this type of light because they also give off a little heat when they are on and the only time I want to use these lights is during the gloomy winter months when plants won’t have enough light to grow. In our aquaponic training, Tim had given us a great article on choosing lights (if you decide to get them), how to size them for your trough size and how much they cost to buy and operate. On Thursday they had hung the 16 lights I bought and were set to finish wiring them on Friday morning. I pulled out the article Tim wrote and ran the calculation again (had done it early on in the planning process of building to know it was a viable option for us) and about had a heart attack. By my calculations, it would be an astronomical cost to operate them. When I met with the electrician Friday morning I discussed my concern and he took all the lights (except for two) down before his brother, the owner of the company arrived at the job site. When he got there he re-ran the numbers and we discovered that instead of using .0641 x kilowatts, I used the number as it is shown on the electric bill 6.41 cents. Let me tell you it makes a huge difference in the final number that you come up with. Before I go over how you calculate it, let me say here that I had started looking at fluorescent fixtures as a back-up to these but at $250/ea for new ones (hadn’t gotten to the point of trying to find used ones), it didn’t make financial sense for us with the amount we would need. My electricians recommend using T-5’s if you want to get fluorescents because T-8’s and T-12’s are being phased out. LED’s are still too rich for most people’s wallets even though they are an awesome light for growing. The metal halide made sense for us for the heat benefit (remember it reaches –25 here on a regular basis in the winter) and for the excellent grow spectrum plus they cost less than $600 for 16 lights. So to figure out what your cost would be to configure your lights or run anything, here’s the calculation:
1) Add up your total wattage. (In our case 350 watts x 16 lights = 5600 watts)
2) Divide that number by 1000 to give you number of kilowatts. (5600/1000=5.6)
3) Multiply that number by the amount your electric company charges per kilowatt hour (here’s where I goofed up…5.6 x .0641=.3589 or 36 cents an hour
4) Multiply that number by the number of hours you expect to use them per day. (let’s say we use them 12 hours on cloudy days so 12 x .36 = $4.31
5) Multiply that number by the number of days in the month that you’d use them. (say 20 days are crappy each winter month so 20 x $4.31 = $86.15. That would be your lighting cost each month in the winter to keep your veggies growing. Even at 12 hours a day x 30 days a month, you’re only talking around $129….that number is way better than the one I came up with and one that I can live with.
Ok, moving on…electrical is done. Painting done. I installed insect screen over the vent openings. Next is the building of the troughs that the plants grow in. Since the building is super insulated, I don’t have to allow for rigid foam insulation in the sides of the troughs, only on the bottom. So instead of the trough sides being 12” tall , they need to be 14” high (allowing for the 2” foam sheet that will lay in the bottom of each trough). This will insulate the water in the trough from the cooler ground temps. Since I’m using 14” pieces you get some waste off each 4’ x 8’ sheet of plywood or hardie board. I found six pieces of 14” x 8’ pieces of exterior plywood in the lumber pile (how lucky was that ). They must have been trim pieces from something but that built one row of troughs (when your row is up against a wall, you only need one “side”) I have built all of the sides and am now finishing up the ends of the troughs. Since one row of troughs goes from wall to wall, I don’t need any end panels there. Only for shorter rows of troughs. Next will be the assembly of the troughs and installation of the liner, then the plumbing. We will have 116 linear feet of troughs or 464 sq feet of trough space (each trough is 4’ wide). We also want to have a 4’ x 40’ trough outside the greenhouse that will operate in the summer time for the heavy, sprawling plants like summer & winter squash, tomatoes, cucumbers, and pumpkins. This trough will be drained in the winter and covered to keep leaves out of it.
Before I can proceed with putting the troughs together, we have to get some
While winter drags its’ feet, I am trying to get as many little projects done around the farm as I can. Things are taking shape and I’m trying to exercise patience. I keep telling myself that I’m way ahead of schedule. Originally I wouldn’t have been home until May to get anything done so I am way ahead of the game but I still feel the sense of urgency and excitement to get things growing. We’ve got 20 organic blueberry bushes and potatoes arriving in April. We just need Mother Nature to cooperate by sending us some warmer weather. I won’t be greedy….just give me something in the 50 degree range. I’ll take that at this point.
