Greenhouse help

I would recommend freestanding, as the structure will get SOME light from all directions. If you can orient it to be north-south lengthwise, you'll get the maximum light levels possible.

Also, minimize the surface to volume ratio by making the structure as cube-like as possible, rather than long and low, as that will offer the most thermal stability.

 

I'll add my experience. I have a 14x25 foot self built. I agree the long side needs to face south. I built mine like a pole building. 4x4 pressure treated posts on 8' centers. 2x4 pressure treated walls 24" OC. Always understand the standard sheet stock typically is designed for 4 foot widths. This method then allows me to expand long ways in the future if I decide to do that or replace walls if a problem arises.

I covered with 8 mill double wall polycarbonate. The triple wall was significantly more expensive and the supplier indicated that energy savings was not worth it. I have had no condensation problems. It was 20 below last year and no problems.

One critical piece no matter what......insulate or extend the covering down to frost depth to break the cold transfer. This will save you a ton on heating. I have the polycarbonate down to frost depth and then inserted 2" styrofoam insulation in between the 2x4 studs.

I use a gas fired Modine hot dawg heater. The greenhouse versions are all too big for a hobby greenhouse, so the garage version works great. I am pretty sure mine is a 60.000 btu version. I run it with a programmable home thermostat to allow for the temps to brought up slowly in the morning and drop at night.

I also contracted with my home alarm company to install a min max sensor. It goes off at 45 and at 95. It costs me $5 a month but great piece of mind to know I will get called if one of these extremes is hit.

I can share photos if you like. I also have plans that I used to build the frame.

I like things a bit simpler to control and not spend the money on automation that is difficult to repair.

 

Depending on the slope you can build a low cement block wall that is level on top and then fill with gravel. Then do like Kelly with J bolts sticking up with a wood sill plate.

 

Mine, too. Right front is at grade; left rear is over 4' off the ground.

 

Another thing to think about....use the roof to harvest the rainwater. Tanks in the greenhouse create a free source of great water and act as a temperature regulator and heat sink. I have two 300 gallon tanks and love the results. A friend installed hers partially buried to help take up some of the excavated space. There are lots of ag tanks that are designed for this. Rain brothers.com is a great site that sells all kinds of rain barrels and connection kits as well.

Here are a few photos of mine after it was built.

 

I could never find anything I wanted for a price I liked in a kit.

 

I got a very small kit (6 x 8) because it is what I could afford. I realized immediately that it was way too small for my existing collection. I dug down about 3 feet and used some insulated panels that I had to create deeper walls. Framed them in with treated lumber and put the kit on top of it. We have real winter here so as it got colder I knew it wasn't going to do for the deep freeze. I had been collecting glass panels for eventually building a real greenhouse. I had several 4 x 8 sheets of tempered glass. Framed them up and put them to the outside of the kit. Built a little breeze way for the front with lumber and plastic sheeting and it did great all winter. When it was 20 below or colder I could go out and sit in 80 degrees or warmer on a sunny day. I used an old electric garage heater to keep it warm, the extra depth made it possible to have more shelves, put 3 inches of gravel on the floor and would wet down the gravel to keep up the humidity. I had a small fan going 24/7 for circulation. Had the best growth of my orchid growing life last winter. Lots of blooms and then they went to the $20 dollar shade house this summer and exploded some more.

 

I built my own greenhouse... 9x36 9x18 is open and the other half is inclosed. I tried to copy a Pacific Coast greenhouse made of redwood and using twin poly roof and sides. Building your own greenhouse gives you many options... how high do you want the roof (are you hanging lots of plants), how wide do you want the benches. I have really gotten into building a wire carousels to hang my mounted plants... Marnie has many of these! Also, figure out how large a greenhouse you want then build it twice as big!!! Also, make sure you leave room to add on because you will need it!

First picture is putting a roof on the lath house, (the plants were not happy getting rained on during the cold wet winter).
Second picture is of the inclosed greenhouse and the third is the lath house. The pictures were taken awhile ago and there's LOTS more orchids and plants in there!!!

Dexter

 

Dexter, How are you building the carousels? I need to do something about my mounted plants.

 

Hi Liana... Making carousels is very easy... Figure out how high you want them and what diameter you want,,, 3 or 4 feet high (or less) and what ever diameter you disire. Make sure you add length for the wire to hang the carousel. You will need a swivel connector so the unit will spin.... You will need to figure out the diameter of the carousel also and that will depend on the space you have and how many plants you want to hang! Then you just go to the hardware store and purchase the materials... Wire mesh, galvanized wire to hang the carousel and a swivel... I like the 1" square wire but you can get what ever is available... When I cut the wire mesh I leave the "tails" on the wire and when I put the two ends together I bend the wire back on itself to told the cylinder together... Make sure you do not make the carousel too big... I can become VERY heavy if you have lots of wet plants. I learned that the hard way! The pictures are of a 3' x 1' carousel using 1/2 wire mesh.

Dexter

 

Thank you Dexter for the response, with pictures no less! I will have to make some of these today. I have hardware cloth left over from a build we did for our chickens and tons of wire I use to make pot hangers.
This is a great idea, thank you very much!

 

I have self built 3 greenhouses, 2 leantwo and a 12 x 35 hoop house [12' heated] My current 10 x 14 leantoo facing south east has a block foundation with a drain system under the floor, gravel with cement pavers over it. I used 2x4 with a preservative used by the Canadian Parks Dept. called LifeTime it is advertised as a finish but the park service uses it as a preservative on all it's outdoor wood. It seems to do a terrific job. with out the negative aspects of pressure treated wood, it is available from Log Home Supply Co. I found thermopane windows and a door at Habitat at a very good price but ordered double walled polly for the roof.

I have an Empire Direct Vent heater [propane] so I have no gas fumes inside, they are supposed to be for heating playrooms ect. Have used this for over 30 years, first one lasted about 25yrs. it does a great job, even installed it in a unheated garage window in one move. I have a duct fan to blow the heat down to the floor and box fan to circulate the heat across the floor. in addition I have several small fans near the top of the house to circulate the air in a circular pattern around the space. I use a commercial thermostat from Granger but would like to get a programable one that can handle the moist air. I installed 3 automatic roof vents that are adjusted so they open when the heat is too high near the roof, First I had an intake louver panel and a big commercial exhaust fan [they were from the old hoop house] but found I did not need them so removed them.

I have always have used 55gal. drums full of water under my benches to help stabilize the heat, the newer plastic ones don't have the rusting problem of the old metal ones. The use of tanks for storing rain or RO water, this is the same good idea. This summer I put together a fogger unit using a pond fogger from Mainland Supply Co. controlled by a Dayton humidistat from Amazon. It functions great and keeps the humidity up nicely, we had temps. in the 90's this summer, very unusual of here. Temps. here can range from -5 to the 90 but usually run from 5-10 to the mid 80's. Next project is some of overhead misters to mist my Vandas automatically every day.

Building your own greenhouse cuts costs so that there is more $ for plants to fill it and is why greenhouses are never big enough. Freestanding ones are really best but at 82 got tired of the show shoveling and climbing over snow mounds left by the plowing of the lane. Didn't want a broken hip either. Have fun with what ever you decide to get.