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Sherry's own greenhouse specifications
Secrets of cooling in Sherry's greenhouse

From many visitors I've been asked to give the specifications of Sherry's Greenhouse (my own actual greenhouse), the equipment that I use and how I use it, etc. Here are the answers.

The greenhouse is free-standing on the upward slope behind our house (in order to catch the winter sun--well, what little there is of it). It is 8 feet wide and 12 feet long with a 10 foot roof peak. It has a traditional house shape with a steeply pitched roof. It was assembled from a Simpson Strong-Tie GardenHouse kit (see supplier's list below). (Warning: We had to do some redesigning and fabricate a few parts, and some pieces came from the factory incorrectly assembled. It is my understanding that Simpson Strong-Tie Corp. is redesigning that greenhouse.) Overall, though, I like this greenhouse very much.
Update: I have not heated the greenhouse & grown tomatoes during the winter of 1996-1997. Many of you have asked why. It is because I have had increasing trouble with the roof vents warping. It makes the greenhouse very difficult to seal against cold at night and still allow venting on clear sunny days. (Yes, we do have those kind of days even in Portland, Oregon, USA.)

February 1997 update: I now have renewed confidence in the Strong-Tie Corporation. When my husband and I first assembled my greenhouse, I spoke to John Herrera (who was managing production of the greenhouses) and told him of the difficulties we had. He said at that time that they--Simpson--would stand behind their product--old design or new.

This winter I finally decided to call John and see what could be done about the increasing problems with the roof vents. (I missed my winter tomatoes!) That one call was returned promptly by new production manager Ronnee McGee. She said that, while there were some problems with that older design, I was apparently experiencing the worst of it. She further said that she had been briefed by John regarding my greenhouse history, and that they would be shipping to me the necessary roof parts from the new design to fix my greenhouse problems--just in time for the serious growing season! My sincere thanks to Ronnee McGee, John Herrera... and to the Strong-Tie Corporation (without which, my husband's treehouse would fall apart).

12 February update: John called to see that everything had been resolved to my satisfaction (yes, indeed!) and to tell me that my roof parts are being gathered for shipping. It was very nice of him to make that follow-up call.


The house was erected early in the summer of 1995. (...and then the real learning process began!)

The glazing of the house is double-walled polycarbonate. All surfaces of the house are glazed. (Technically speaking, the glazing is Co-Ex Corp. Macrolux Coextruded Thermoglazing which is warranted against yellowing for 10 years.) (Another brand name for the same thing is Lexan Thermoclear.) I HIGHLY RECOMMEND this type of glazing for several reasons: 1. It diffuses the light extremely well while still allowing more than 90% of it inside, thus no hot spots to burn plants as with glass. 2. It is very tough and lightweight. 3. The double-walled channel structure of this glazing traps air and thus insulates. 4. That same trapped air also prevents dripping inside the greenhouse. 5. It's very clear (not as clear as glass, but much more so than fiberglass). 6. There is no rough surface (as with fiberglass) for dirt to catch on and moss to grow on. My glazing has stayed quite clean.

The frame is redwood (with a treated wood attached foundation). It has a dutch door. All seams in the house are sealed either with clear caulking or that foam sticky-on-one-side tape (can't remember what the stuff is called!).

The house rests on a simple gravel (1/4 minus) foundation (6 inches thick) over heavy duty weed barrier cloth. Underneath the foundation is a T-shaped trench filled with a perforated pipe and coarser gravel for drainage.

For venting, the center 8-foot section of the roof peak opens up (in two parts) with automatic vent operators. The cool air intake vents are in the lower wall opposite the door and also have automatic vent operators. The vent operators have within them a wax-like substance that expands when it gets warmer (thus opening the vent) and contracts when it gets cooler (closing the vent). I highly recommend these for any greenhouse. They work well, require no attendance or power, and they're adjustable. In winter, the lower vents are kept closed (vent operators disabled) and sealed with crushed plastic wrap that I stuff in around them.

Inside the greenhouse, hanging from the rafters, is a simple window box fan. It runs constantly, on low speed in winter, high speed in summer. It would be more efficient to have a fan installed in the end wall near the roof peak, but in my neighborhood I feel that solution would be too noisy and disturb the neighbors.

To heat the house in winter, I have used various means. The goal in heating it varies according to reality (outside). I would like to keep it no lower than 60 degrees Fahrenheit, but often this winter (1995-1996) I've been lucky to keep it above freezing. (The roof vents have been difficult to keep sealed as they are beginning to warp.)The tomatoes continued to produce (at least a little) so I guess we did alright. I use 2 (1500 watt) electric heaters which have thermostats.

When we had an ice storm, the power went out. I asked my husband Scott if he wanted to save the tomatoes. The decision was "yes", but we couldn't drive anywhere due to the ice. His idea was to use what we had on hand--the little barbecue! Well, the cure almost killed. We didn't realize just how hot that column of heated air from the barbecue would be. The tomatoes were at least 6 feet above it, but they got burned badly. So did the peas and the beans. The lemon tree was perfectly happy. The greenhouse was filled with very thick smoke. We had to hold our breath and run in each hour to check on the state of the coals. The greenhouse stayed warm, though, and the tomatoes did live on to produce more. A bonus was that the smoke killed the whiteflies.

When driving was possible, we purchased a small propane (9000 btu) heater for future backup (and we did have to use it--it's been a very hard winter here). Heating the greenhouse has been expensive, especially since it is free-standing. I may not heat it so much next winter UNLESS I do a better job of managing things and have the house packed FULL of tomato plants and can seal it properly. It is my dream to have abundant tomatoes in the winter to share with others.

I also have 5 large barrels full of water inside the house (holding up shelves on the south side) for the purpose of collecting and distributing what solar heat we get. Here in Portland, Oregon, USA, we have FAR more cloudy days than clear ones. This is really a disadvantage in the winter. It's amazing, though, what DOES happen when we have a clear, very cold day. This past winter several times it was 25 degrees Farenheit outside and 80 degrees Farenheit inside the house! That's the real magic of a greenhouse--walking into it on the coldest winter day and feeling like you just stepped into summer. It's warm and you can pick fresh tomatoes and a lemon or two.

Another winter problem is short days (and long nights). For that I have a 1000 watt metal halide light. It is on a timer set to go on for 2 or three hours each morning and evening. Now (in March) I am beginning to cut back on the supplemental lighting. (I have asked the nearest neighbors to tell me if my lighting schedule disturbs them. I've only had to make one adjustment.)

For cooling in summer (in addition to the constantly running fan and automatic vents), a mist system is a MUST! (See supplier's list below.) My mist sytem is a very simple 1/2" diameter clear reinforced vinyl hose with one gph nozzles preinstalled about 2 1/2 feet apart along its length. I have cup hooks installed for tying up plants, etc. and I just draped the mist hose around the upper part of the house using the hooks to hold it. Before the mist system was installed, temperatures inside the greenhouse were soaring above 120 degrees Fahrenheit. You can imagine what this did to the poor plants. Only a few survived. I had to start over with most of them.

The mist system is controlled with both a temperature sensor and a timer that activate a solenoid valve which in turn allows water into the mist system. My husband built all of the controllers for the greenhouse, but you can also buy them ready-made. I can set the sensor control for the maximum temperature to be allowed in the house (usually 85 degrees Fahrenheit). The temperature sensor constantly monitors the temperature.I can also set the timer for two things: 1. Interval before mist sytem is charged with water ("wait"). 2. Interval that mist system "mists".

We began by setting the maximum temperature to be 85 degrees Fahrenheit, the "wait" (delay) interval at 15 minutes, and the "mist" interval at 3 minutes. Scott hooked up a chart recorder and set it up outside the greenhouse so we could "see" what was happening during the day. The peaks were high and the valleys low on the chart, indicating drastic changes in temperature. With a few adjustments, we arrived at a setting that produced a fairly even line on the chart recorder. The settings for success (in my greenhouse, that is) are: Temperature maximum 85 degrees Fahrenheit, "wait" (delay) interval 3 minutes, "mist" interval 20 seconds. It is, of course, very helpful to have a smart husband with two shops full of tools and gadgets who knows a lot about electricity and machines and little computers. I married a "techno-nerd" and I love him.

Another summer cooling must is shade cloth. I don't know what "percentage" mine is, but I use it to cover the lower half of the roof and the upper half of the wall on the south side. This year I also plan to allow my passionflower vine "Incense" to grow along the south side for shading.

Wiring in the greenhouse (also done by my husband) is set up with GFI (Ground Fault Interrupter) so that I won't get shocked. Everything is enclosed with liquid-tight plastic conduit as well. The panel upon which all controls are mounted is protected from the mist system overspray with a large plastic cover. He also ran wires for a controller, a telephone, and a video camera. Eventually we would like to have live video pictures and all pertinent physical data for the greenhouse up on the web. (I will reserve the right to throw a cloth over the camera if I'm in there working... OK, I'll be a sport about it.)

Plumbing (by Scott, of course--Hey, I DID dig all the trenching for the plumbing and wiring!) includes two solenoid valves (only one being used now, but eventually we would like to set up automatic watering so we can leave for a weekend in the summer without Sherry WORRYING about the fate of her plants). (I often talk about myself in the third person.) I also have three spigots inside the greenhouse. The pipe running out to the greenhouse is in a fairly deep trench, but we still had to shut the water off for a couple of months when it was coldest. During the winter, I keep about 20 gallon-size milk jugs full of water at all times to warm the water to greenhouse temperature. That way, I don't have to water with the very cold water straight out of the tap.

Update summer 1996: Sherry's greenhouse now has an optional automatic watering system controlled by a timer and solenoid valve.

Many people helped me get this greenhouse up and running. First of all the initial construction stage involved cutting into the bank behind our house to make a flat place for the greenhouse up high enough to catch the winter sun. Our nephew Grant took on this heroic job. In the summer heat he dug and moved MANY YARDS of hard heavy solid clay soil to make a place for the house. Without him, it probably still wouldn't be up (and Grant doesn't even like tomatoes!). That heavy digging was too much for me (and that's saying a lot because one of my husband's nicknames for me is "The Rototiller" because I do so much digging around here). Grant also dug the drainage trenches under the greenhouse. Sherry did dig the trenches for the plumbing and wiring and also hauled about half of the gravel (uphill) to the greenhouse site. One day as we were beginning to haul gravel for the foundation and fill the trenches, Grant's parents, Don (Scott's brother) and Joanne appeared. Don got us organized and Grant (who was already there working, of course), Joanne, Don and I hauled lots of gravel and filled trenches. It went very quickly with their help. Many thanks to them all. My husband Scott did lots of things mentioned above and much more. He also is the one who actually erected the greenhouse and fabricated parts for it. I helped as best I could.

I have worked for a professional grower (of perennials) and have toured professional greenhouses, several of them quite large. Mine is very close to "state of the art" for its size. (One of my former employers was even envious of my greenhouse, and--not surprisingly--wanted to hire Scott to make modifications to his house!)

I'm sure I have forgotten something here. I am amazed at how long it has taken me to type all of this out!

Finally, the goal this year is to get the greenhouse into FULL production and keep it that way. You can continue to help by giving me your suggestions through my home page. Thanks for reading through all of this.


--- Sherry

Greenhouse & Cleaning Services Information

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Charley's Greenhouse Supply
1569 Memorial Highway
Mount Vernon, WA 98273

Telephone 1-800-322-4707

Fax 1-360-428-0310

If you have a greenhouse, you MUST get their catalog. Great service, wide variety of greenhouses AND supplies and equipment. Knowledgeable and nice people, too.


Simpson Strong-Tie GardenHouse

Telephone 1-800-999-5099

This company makes the greenhouse that I have. They have redesigned the roof of the 8' x 12' GardenHouse. Call their number to ask where you can buy it locally if you're interested.

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Revised 14 July 1997, Copyright 1997, Sherry's Greenhouse, all rights reserved.