Morning Snow
A small storm swept through this morning. Here's a great shot of the storm clouds over the valley as a light snow falls. The grow light in the greenhouse makes for an interesting contrast against the muted colors of the storm. Click for the full size image.

Fungus Gnats

My new enemy:

(Not to scale, thank God. They're about 1/8th of an inch in real life)

When I started growing my first few crops I had major problems with fungus gnats. They were everywhere in the greenhouse - flying around at soil level and swarming anytime a pot was disturbed. The primary cause is too much water (my kids really enjoyed water the plants several times a day...). Cutting back on water didn't help. I tried:

• Yellow pest strips. They caught plenty of gnats but never seemed to put a dent in the population. About once week I'd forget about the strips, only to have the gnat-infested pest strip stick to my head. Yuck.
• Apple cider vinegar. The gnats are attracted to the vinegar, fall in, and drown. It was rewarding to see a few dozen gnats floating in vinegar but it really didn't work.
• A mini bug zapper, capable of "...keeping 1000 square feet free from flying pests". Nope.
• Various organic insecticides, including pyrethrins and neem oil.

Nothing worked. I was getting really discouraged until I discovered  mosquito dunks. 

Mosquito dunks are cakes made from dried bacteria (Bt-israelensis). BT-i is ingested by the fungus gnat larvae while in the soil, where it kills the larvae before they mature into flying gnats. I ground up several cakes into a fine powder and sprinkled on the soil of all my plants. I also sprinkle a bit on any new pots I prepare for planting. Seven to ten days after applying it absolutely wiped out the fungus gnats, and I haven't had any major problems since. When I discover a gnat, I simply sprinkle a bit of powder on the soil of the affected plant to prevent an outbreak. Nothing like a bit of biological warfare against your enemy.

Laptop + USB + Old PC

I bought a wireless thermometer so I could monitor the greenhouse temperature from my kitchen. The unit displays temperature and humidity, plus high/lows for the day. It's great, but I was really curious to see how the temperature changed through the day/night cycle, and how modifications like bubble wrap, grow lights, or circulation fans impacted the temperature and, ultimately, heating costs.

The setup:

• Old laptop running Windows XP
• Wireless, so that I could view the temperature from any machine
• A TEMPer2 USB temperature probe ($15)
• ThermoHID software (free / supported by donations)

Here's a picture of the TEMPer2 USB probe. It has two temperature sensors - one in the plastic housing, the second as a remote probe. I figured I could use this to take the temperature in two different areas of my greenhouse, such as the floor and ceiling.

The software that came with the USB stick didn't provide the basic features that I needed for my project. I considered setting up a Linux box since I found drivers for the TEMPer2 probe, but as I dug into the solution I figured it was going to be a lot of work. In my googling I found the ThermoHID software - it provided everything in one single app, including a few extras, like a buit-in web server and the ability to read temperature for my city from an Internet source.

Here's a typical snapshot of the last 6 hours of my greenhouse:

Let me explain:

• The green line is the air temperature at 5' level. Right now it's in the middle of a plant
• The yellow line is the remote probe, currently at 18" from ground level
• The dark red line (bottom of the graph) is the outside temperature. The software connects to an outside source for local temperature and humidity for my area.
• The bright red line (top of the graph) is the outside humidity, also from an outside source.
• Temperature axis is on the left, humidity axis is on the right, time is on the bottom.
• In the lower right-hand side is the current outdoor weather conditions (partly cloudy)

The lines are a bit squiggly - that's the heater cycling on and off. It's a bit hard to see on this graph, but a grow light turns on at 6:00 am, slightly raising the temperature. The light cycles off by 8:30 am. My house is up against the mountains, so sunlight doesn't hit the greenhouse until about 10:30 am - that's when the temperature starts to climb.

Here's another shot showing the last 24 hours:

See the two dips in near the left of the graph? That's when the greenhouse got too warm (about 95) and the automatic vent fan turned on for a few minutes - just enough to take some extra heat out of the greenhouse. As night arrived the heater turned on, keeping the temperature around 50 degrees. It's a bit hard to see with all of the squiggly lines, but that's because I'm recording the temperature every 30 seconds. If I sampled less frequently the lines would be a bit smoother. 

I sample frequently so that I can estimate cost. Follow along for a bit. Here's the current temperature trend for the last thirty minutes:

Starting on the left side, you can see the ramp up for 7 dots. Each dot is a 30 second period, so the heater ran for 3.5 minutes, turned off for a while, then came back on for another 3.5 minutes. So, over the past thirty minutes, the heater has run twice, for a total of 7 minutes.

Right now the heater is running 14 minutes per hour, and it's a 5500watt (5.5kW) heater. My local electricity rate is $.07 per kW/hr. Thus, I'm using ((14/60) * 5.5kW) = 1.28 kW per hour, at a cost of (1.28 * $.07) = $.09 cents per hour. If I assume that the heater runs approximately 16 hours per day, that's a cost of $1.44 per day, or $43 per month. 

But that's just an estimate - the actual cost varies with the weather. We had colder temperatures in December, where lows were around 10-15 degrees at night. On snowy days the sun doesn't heat the greenhouse, so the heater runs more frequently. I figure that during the coldest, darkest part of the winter I'm probably adding $80-$100 to my electric bill. I'm also running a 1kW high pressure sodium light for a few hours in the morning and at night so I can get 15 hours of light per day.

Enough geeking for now. If you want to see the current six hour trend for the greenhouse, click here.

Salad Anyone?


I've been planing lettuce and radishes in these planters, which measure roughly 2' long by 8" wide. I start the seeds inside where it's a bit warmer, then move the planters out to the greenhouse. Early on I had problems with fungus gnats but I've figured out a remedy that worked very well (more on this later).

Here's a shot of the planters about 3-4 weeks after planing. I trim a bit of lettuce for dinner when we need a salad. Mixed greens on the left, red and green lettuce on the right. I had assumed that fresh greens would be crispy (why, I don't know...) but these aren't - they're almost silky or have a wilted feeling even though they're completely healthy. I've also noticed that the fresh lettuce doesn't spoil as quickly in the fridge.

Heating

I knew that I'd have to heat the greenhouse if I wanted to use it year round. My goal wasn't to keep it at a balmy 80 degrees, but make sure that it didn't freeze, or better, lows around the 50 degree range. I figured that plants do fine in the spring with cooler temperatures, so it's OK to let the greenhouse dip a bit at night. So how does one go about sizing a greenhouse heater and determining cost?

ACF Greenhouse provides a very useful heating calculator. I had to figure out some of the variables for my area, such as the average low temperature and cost per kilowatt-hour, and the external surface area of the greenhouse. I also assumed that I'd be a bit lower than the maximum estimates on heater size and operation cost, as I have an insulated slab floor (see earlier posts) and I was planning on insulating with bubble-wrap (more on this later).

If I recall the heating calculator estimated a maximum heating capacity of about 20,000 BTU (approximately 5800 watts). For comparison - small indoor space heaters are rated at a maximum of 1500 watts, so the 11'x15' greenhouse would require four heaters during the coldest winter nights. Ouch!

Space heaters convert electricity into heat (duh). Household space heaters are limited by the voltage and current supplied by the 110v / 15 amp circuit - roughly 1500 watts. For the greenhouse I planned on a 220v / 30 amp circuit.  I selected the the King Pic-A-Watt heater.

Originally, I had it mounted about six feet above the floor. Here's a picture of the bracket, now used as a plant hanger. You can also see the 220v socket in the back.

And here's a picture of the heater resting about a foot above floor level.

I also have a fan up near the ridge of the greenhouse which helps circulate warm air back down to floor level.

Have you noticed the bubble wrap? One of the tricks I've picked up along the way is to put bubble wrap on the inside of the glass during the colder months. I bought 2' wide rolls from Amazon - I think I have 1" bubbles but I can only find 1/2" bubble examples on Amazon. Installation is very easy - simply cut to the height of the window. Mist the window with water and place bubble side against the windows. I figure this will give me an r=1 insulation value, similar to using double-pane windows in the greenhouse. At the end of the winter I simply roll up and save for the next season.

I also researched water barrels for storing and releasing heat into the greenhouse. You can Google to find out information about the amount of heat stored per gallon - if I recall, by definition, a BTU is the amount of heat required to raise one gallon of water one degree F. So, a 55 gallon water take will absorb or release 5500 BTUs for every degree difference in air temp. When I calculated for my greenhouse it turned out that I would have needed about 12 55 gallon barrels - too much. But I do have one barrel, mostly so that I don't have to cart water to/from the greenhouse in the winter (the greenhouse water runs on our sprinkler system, which is drained during the winter months).

Next up - geeking out with an old laptop, a USB temperature monitor, and some free software...

Assembly


Assembly was pretty straight forward, but there were some challenges. ACF and BC Greenhouse provide .PDF and video files for assemble. The instructions were pretty clear, but there were one or two steps that we had to either figure out or improvise during assembly.

I bolted the walls and portions of the ends together in the comfort of my basement. I hired a carpenter to build a sill plate (pressure-treated wood between the base of the greenhouse and the cinderblock wall). Note that you may see a pink foam strip; the metal of the greenhouse cannot rest directly on the treated wood due to corrosion.

After several days of snow and temps in the 20s, we finally got the main structure up. We had to do it in one shot as a partially-assembled structure was more vulnerable to a wind storm.

Here's another shot, with me installing the poly carbonate roof panels. It was tough - I had to stand about 12' in the air, put a bead of caulk down and then fit the panel in place. The panels are approximately 2' by 8' so it was a bit difficult getting everything lined up, especially on the ladder. You can also see the glass is in the east wall.

I don't have many more shots of the construction at this point as it was my wife and I finishing all of the glass (glazing). At the very end we discovered a mistake in the glass for the front wall; a call to ACF quickly resolved the problem and we were able to complete the job.

I spent one weekend caulking the top of the inside glass. After assemble there was a 1/4" to 1/2" gap between the glass and the top of the structure. With even the slightest breeze I'd feel cold air rushing into the greenhouse. Caulking (silicon) sealed it up and helped reduce my heating bills.

More on heating next...

The Greenhouse

We looked a several styles and types of greenhouses. Our selection criteria:

• Must withstand high winds. We've recorded wind speeds in excess of 60 mph. High winds are common, especially before storm moves into the valley. 
• Size: must be less than 250 square feet, and cannot be over 12 ft high at the peak. Anything bigger or taller would require zoning approval.
• Powered ventilation. Ridge vents were deemed too risky with high wind.
• Must tolerate heavy snow, or have a steep pitch so that snow will not pile up on the roof. Some storms have dumped up to three feet of snow in 24 hours. 

After searching through the web I landed at ACF Greenhouses (www.littlegreenhouse.com). This site turned out to be extremely useful for calculating heat loss, finding speciality parts, and for providing an easy place to compare greenhouse models and features.

Several greenhouses seemed too flimsy to withstand the weather. We finally settled on a Cross Country Cottage model. I liked the classic look of the Cape Cod, but the pitch would have put the roof peak over 12'.

We settled on a 10' 8" wide by 14' 9" long. Total height was 12' accounting for the 16" knee wall. I choose single pane glass but a polycarbonate roof, as the polycarbonate is a bit stronger, hail and snow resistant, and provides a little more insulation than glass. 

The greenhouse was actually built by BC Greenhouse but resold by ACF. Same price from either vendor, but ACF greenhouse included several extras.

Lead time was about 6 weeks. I placed the order in early October, 2010, and the greenhouse arrived on November 23rd.

The total weight was over 600 lbs. It took my wife, neighbor, and the delivery guy to get this off the truck and into the garage.

I thought I could get this up quickly - maybe 1-2 days with a few friends. Ha! It took almost a month, due to bad weather, a part-time carpenter, and work.

The Before Pictures

Here where it all began - the corner of our lot. The small wood and chicken wire cage was used for a small garden, but not much really grew in the sandy soil. The care kept deer and the birds out, although occasionally a Scrub Jay would get trapped in the enclosure.

This picture was taken from the top of the hill, looking northwest. You can see the Oquirrh mountains in the distance. If you follow the mountains to the right you'll wind up in the Great Salt Lake.

Here's another shot, taken from the kitchen window. The hill is pretty steep, so we'll need some rock to create a terrace big enough for the greenhouse.

Granite, taken from the west side of Utah Lake. Luckily the rock matches the rock in the rest of our retaining walls. When the landscaping company was finished it was a perfect match. Here you can see the flat patch for the greenhouse's slab foundation.

The foundation was sized to accomodate the greenhouse plus a small knee wall. Insulation under the slab helps retain heat within the greenhouse. A drain was placed in the middle of the floor near the back wall. Conduit was left in the slab for water and electricity.

Concrete arrives. Note that the very front slab of the greenhouse is not insulated.

A crew arrives to build the knee wall. The knee wall is cinderblock, but the outside will have red brick that matches the brick on the front of our house.

Kneewall is done!

Next up - ordering the greenhouse!

The Utah Greenhouse

Greenhouse, January 2012

We talked about building a greenhouse for at least 10 years. Gardening at the new house is tough - lots of deer, the soil is very sandy, and there's not a lot of flat space.

In 2010 a house started on the lot just north of us. We decided to re-landscape that section of the hill, planting trees and flattening a space large enough to accommodate a greenhouse.

t's been a little over a year and the greenhouse is up and running. I've learned a lot - including heating, cooling, insulation, pest control, and basic gardening. The first year has been rough as I'm learning something every week, but it's finally come together into a nice, relaxing space. Hopefully I can share some of the things I've learned along the way in case you're thinking about a similar project.