Spring plans - Greenhouse/Hoophouse

[GoneFish'n]

I am planning to build a greenhouse or hoop house come spring. I was wondering what others are using? What preferences and experiences you are willing to share? Pictures would be nice too.

Thanks,

Lynn

[KentUB]

Our plans got stalled a bit by the cold weather, but we purchased a tool just for building Greenhouses and I recommend it to everyone that wants to avoid the high cost of greenhouses kits or prefer to do the DIY thiing.

Lost Creek Greenhouse Systems (http://www.lostcreek.net) sells a bender to bend chain link fence top rail into hoops for hoophouses. It is very inexpensive, easy to use and can save you a ton of cash over a kit. One caution on purchasing, if you do not need it right away, troll eBay for this thing. It is $89 off his web site and he also sells on eBay. I got it from him with an eBay auction for $49! Just make sure you buy it from Lost Creek as there is someone that is selling knock-offs that are junk.

They recommend driving 1-5/8 inch tubing into the ground for anchors. In the Uintah Basin your chance of hitting a cobble rock with an 18 inch stake is 100%, so we decided to drill holes and cemet ours in due to the wind out here. First snow occured the week-end we were to pour the cemet and everything has been on hold until it warms up enough for the cemet to properly cure before we pour. I am praying for a very early spring.

[nwestwood]

I've liked my hoop greenhouse. I've seen that the taller greenhouses have better humidity and air control (and more usable space along the sides), such as the one at Nelson and Pade, but they cost significantly more, more than I could justify for my hobby. My double poly covering has lasted 5+ years each time I've changed it. It's still cheaper than therapy... (oh maybe it is therapy).

[GoneFish'n]

I have one of Lost Creek's benders as well. Mine is for a 12' hoop. I haven't tried using it yet. I have been toying with the idea of putting a sharper bend at the apex to create a steeper side to shed the snow. I want to bend a 5' piece in the center with maybe a 1' radius then straight sections connecting to 10'6" pieces down to the ground. I want to put 3' straight up sides before the bend starts to give a little more room along the sides of the house. The idea I have seen for the stakes and figured to use was using 30" stakes of 5/8" rebar into the ground 24". Place a 3/4" PVC piece over that, enough to cover it, and put the ribs down over that. I also figure to space my ribs every 3', which is closer than most sites I have seen use, for increased strength. What is the spacing on your greenhouse Neal?

[KentUB]

If you go to Lost Creeks web site and look at Clairs success story you can see a greenhouse that was over engineered to no end (the guy is an Aeronatical Engineer if I remember correctly). He is only about 100 miles north of me where they get even worse wind than I have to contend with and when I talked to him he said he went back a checked his figures and realized the structure would probably survive a Cat 4 Hurricane!

Your thought on the PVC is probably not the best since during the cold of winter any movement is very likely to shatter the brittle PVC due to pinching action, then you will get even more movement which wil cause additional failures and everything goes downhill from there. The 1-5/8 EMT they recommend is cheap and cheap insurance.

[nwestwood]

I've used PVC for mini greenhouses covering my giant pumpkin plants in early spring. The PVC stresses and will bend and break over time, I don't recommend PVC. My greenhouse is a commercial variety from Cropking, it's now 15+ years old. There are many other good suppliers as well. It is primarily 1" galvanized hoops on 4' centers with cemented posts and cross bracing. Every year we have 50+ mph winds (Check you my weather data at www.utahcountyweather.com) and the greenhouse hardly notices that.

WIND SPEED (mph)
DOM
YR MO AVG. HI DATE DIR
---------------------------------
09 1 3.2 48.0 8 NE
09 2 3.8 45.0 27 NE
09 3 6.3 56.0 29 N
09 4 6.5 55.0 28 N
09 5 5.1 43.0 13 N
09 6 3.5 48.0 20 ENE
09 7 3.8 36.0 19 ENE
09 8 4.1 47.0 15 ENE
09 9 3.9 51.0 18 ENE
09 10 5.4 51.0 19 N
09 11 4.3 46.0 22 N
09 12 2.5 45.0 5 N
---------------------------------
4.4 56.0 MAR N

[GoneFish'n]

You are right about PVC, it does get brittle with the cold. I had thought about the brittleness caused by UV with sun exposure, but it wouldn't be exposed to the sun. I hadn't considered the cold. Maybe I will use some galvanized pipe to beef up the rebar to near the internal size of the top rail. I will have to look into it.

My understanding is if you cement in posts, it becomes a permanent structure and you may need a building permit. Or, I would. You may not where you are.

My CD that came with my bender only suggests 1-3/8" 16 - 17 gauge top rails, even for 20' wide greenhouses. I know commercial fence companies have the 1-5/8", but they would be much more expensive. Do you plan to go wider than 20'?

I looked at CropKing's site. Their tubing is 16 gauge for up to 20' wide and 4' spacing. I would think 1-3/8" top rails from Lowes or Home Depot at 3' spacing should be enough.

[nwestwood]

You are right about a building permit, and with all the water, power, and gas lines, I did get a permit when I installed mine.

[KentUB]

I would take a look at the manual again. You do use the 1-3/8 16 or 17 gauge for the hoops, the 1-5/8 is for the posts. The 1-3/8 slips right into the 1-5/8 and is realativly tight fitting, especially when it is through bolted.

I went back and forth on the permit issue. The standard in Utah is that a greenhouse does not need a permit, unless it has services going to it like electricity, gas, etc. We have a garden center here that has over a dozen greenhouses with water and power in them and they have been through the process over and over. They suggested that the best approach is to build a greenhouse, then get a permit for your services, otherwise you have to have a county approved engineer design your greenhouse. Adding the services to an existing agricultural structure is very easy, however I would talk with your local planning people to check on that.

[GoneFish'n]

I followed your advice and looked at the manual again. I also emailed Loy at Lost Creek about mounting my bender vertically and found out I had an old manual. Loy sent me an email with his latest manual. Dated October 2009. Both manuals used the 1-5/8" posts though. I had read somewhere else about using rebar stakes. I can see this way would be better so I plan to use the 1-5/8" posts now. Hopefully I can get them in the ground without having to dig post holes to put them in. I have gravel starting about 2' down and some of the rocks are pretty large. Right now there is still 2 ' of snow where i plan to put the hoop house. I am anxious for Spring. Thanks for the advice Kent.

[KentUB]

Yeah I am so ready for the weather to warm up. We litterally missed out on pouring cemet by less than 12 hours before it snowed the first snow which was quite a pile of snow. When it has warmed up since then for a day or two where we could pour, our schedule has conflicted.

[KentUB]

I attended the first day of the Diversified Agriculture Conferece in Vernal today put on by the USU Extension Service. One thing I learned about today is they have a new project going in Logan using unheated high tunnels. In this case they build a tunnel within a tunnel, they have a 1 foot seperation between the tunnels. This gives effectively R-12 insulation (Edit: um, no! I got this from a source that was not quoting complete info)

USU ran these tunnels, unheated with tomatoes until the third week in November! I will get the chance to speak directly with the extention agent running the project (who happens to be the State Vegatable expert as well). This has the possibilities to save a huge amount of energy and I can hardly wait to get some concreate info on their experiment.

Everyone with the extention service was very keen about what we are planning to do with Aquaponics and the complete different direction from the normal agricultural activities. It was very nice to see a lot of very forward thinking farmers and ranchers at the conference, so willing to share their info and work together.

Edit Note: I had been quoted by an HVAC guy a while back that one unit of R-Value was equivilant to 1 inch of still air. This is wrong and comes from simplified information on air space with other materials surronding it. However it still does present a large insulating space as air is a very poor conductor of heat other than radiant. Does anyone have the ASHRAE Handbook to lookup air space insulation? Since my added cost for the additional frame calculate out to about $220, a saving of an average of $10 a month means less than 24 month payback.

[GoneFish'n]

Speaking of USU and high tunnels, there are a couple of interesting videos about USU's testing of hoop houses. Here are the links, if you are interested.
Hoop House I

http://video.google.com/videoplay?docid=4555704608768330618&ei=a5KKS5TTIZeeqQPTtuylBw&q=utah+state+university+hoophouse&hl=en#

Hoop House II

http://video.google.com/videoplay?docid=4555704608768330618&ei=a5KKS5TTIZeeqQPTtuylBw&q=utah+state+university+hoophouse&hl=en#docid=7497554495921114830

The double hoop sounds interesting. I have tried to find R Factor information for dead air space, but haven't found anything authoratative as yet. If dead air space was all that insulative there wouldn't be a need for insulation. I guess there would. My exterior walls are R30, that would mean I would need 30 inch walls to have the same R Factor with just dead air. Now if we could leave enough space to add a couple senators or congressmen we would have enough hot air to easily heat the green house.

[GoneFish'n]

I just found something in a book entitled House Warming by Charlie Wing: "True is the R 4 per inch of still air; but equally true is the reluctance of air to stand still!. Air within or in contact with the thermal envelope is constantly picking up heat from the warm side and losing heat to the cool side." He has a chart showing the effective insulation R value of a 3-1/2" of still air. Theoretically R 14, accounting for the direction of heat flow the R value up is 0.84; sideways, 0.91; and down, 1.22. Dead air space is not much of an insulator at that. The real value of insulation is stopping the circulation of the air within the space.

It may not be economically advantageous to build a green house with double walls. It would be interesting to see USU's test results on this.

[KentUB]

We had planned on building a High Tunnel where our garden is at, just to extend the season. Here you are almost certain to have frost on Memorial Day and Labor Day! Last year we got a a few dozen squash, but only a dozen tomatoes.

However while at the Ag Conference I got my County Extention Agent and USU together to talk and we are sponsering a full day high tunnel workshop here on our farm and as a result we will have a 14 foot by 92 foot high tunnel at the end of the day! We a pretty jazzed about this as it will give us so much more growning space that we had not expected to start utilizing via Aquaponics for a long time. We could put 15 of these on our property and still have 15 more of the 20x40 Aquaponics houses as well so it does not interfere in our primary plans. The high tunnels are dirt cheap and easy to put up in 1/2 a day. We do not expect it to be as productive as an Aquaponics system.