With a greenhouse, the idea is to have as much light as possible. If you have light only on one side, you may very well end up with those spindly plants you get on the windowsill. Unless, of course, the greenhouse will be heated if attached to the garage, and also get more than half a day of sunlight, in which case I'd say go for it as an attachment.
If one side of your garage (where you place the greenhouse) faces east, southeast, south, or southwest, you should be OK, providing you don't have large trees throwing it in deep shade during the summer.
If your garage wall faces north, you'll have too much shade to grow many plants, year round. You'll still get a good amount of sun during the summer as the sun is so high overhead. However, for the most of the rest of the year you'll have to deal with a lot of shade.
A west facing wall will absorb a lot of heat during the summer and will be hard to keep within the temperature range that's good for growing most plants. (Most plants like the same temps that people enjoy.)
East, southeast, south are usually the best. My small greenhouse is oriented north and south. The long walls face east and west. I have a large shade tree to the west that blocks the sun during the summer. Plus I put corrugated metal on the west side to reflect heat. East wall is corrugated fiberglass. North wall has plywood inside/outside and is insulated to help with winter's cold. South wall is more fiberglass.
The Solar Greenhouse Book by James C. McCullagh. It has all the answers to any questions you may have - and more. It deals with design, construction and crop production. Do it right from the beginning.
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I'll take a liberty and give another answer----go for a drive to where there are a fair number of greenhouses and do a count of those running on an east/west axis and a count of those running on a north/south axis.
You will probably find them running both ways, but my money is on the north/south axis to have the higher count.
No Way. You see you already have varing answers so this is far from decided. Your situation may dictate more than anything else.
IMHO, I think if you wish for maximum summer sun than a north-south orientation would be best. But since the sun is lower in the sky during the winter, an east-west orientation would be better for trying to grow then and may help reduce summer overheating if that is a problem.
If the grass looks greener it is probably over the septic tank. - troy n sarah tx
Generally they are free standing and to gather the most light they run north and south. Morning, afternoon, and late afternoon sun providing sun from three general directions.
Since you are putting it against a building it should be on the south side and run east and west for maximum exposure.
i agree with this--i set up a green house in the spring on the west side of my house up against the house (i have done it for three years) and next year i am going to move it to free standing and facing n and s. where i put it now it only gets good sun in the afternoon.
well if you live in Kansas you probably wouldn't have to have it attached..but it is always nice..i live in Michigan and have a free standing..if they are freestanding it sure doesn't matter what way they face but make sure you have automatic venting.
i did face my opening away from prevailing winds so when i have to go in in cooler weather the wind doesn't blow in and chill the plants.
in the south the most important thing might be some summer shade..you might want to place it in the shade of a deciduous tree or vine..that way it won't overheat as much in the summer.
It depends on a number of things. Like, what are you going to use the greenhouse for? Will you be trying to keep it above freezing? If so, with heat or on pure solar? How big does it need to be?
If the south side of the garage is available and isn't shaded, and would make a big enough greenhouse, then that will probably be best. I can't think of a good reason to build freestanding if you have the north wall built. If you can make it as big as you need with one of the long walls taking up the south side of the garage, that will be cheapest and stay the warmest.
I have built 4 greenhouses. 2 were leanto's with the glass on the southside. 1 freestanding. and this last one is freestanding with a Heavily insulated northside. It was place near a tree that fills with leaves on the West.Black barrels willed with water stacked along the Northwall help keep if from freezing. Heat comes from a small elec. heater.
The scariest thing about owning a greenhouse is the heating bills in the winter, and I live in south Texas. My greenhouse is 12 by 16 feet and a 20 lb bottle of propane lasts about 3 nights on the lowest setting. My COLDEST nights are usually in the high teens.