Careful planning before beginning construction of a backyard greenhouse is a must. You must choose the best location based on available space and sunlight. You must also determine what size you will build.
There are many different materials to choose from. The floor plan must be laid out. Then you must decide whether or not you will include heating and ventilation or a watering system.
The most important decision that you will make in planning and building your greenhouse is the covering. The type of material that you select will directly affect the sunlight that hits your greenhouse.
Glass is the traditional choice. It is permanent. It is relatively easy to maintain. It is also attractive. Glass retains humidity, but it transmits heat and cold very quickly. It is a poor insulator. It can be made into a weather-proof tight-fitting seal, but these tight-fitting seals have been known to crack when the frame shifts or settles.
When choosing glass it is best to do so only when there will be a foundation. Glass can be made into any form. It is versatile, it will look great on any style of greenhouse frame. Tempered glass is stronger and also heavier. It can be difficult to install yourself. Glass also requires a heavier and stronger frame than other lighter plastics.
Fiberglass can also be used and usually comes in rolls or corrugated sheets. It’s corrugated form can be unsightly and the grooves are harder to clean than smooth glass. It is light-weight and strong. Although fiberglass is translucent it does transmit the sunlight the same as clear glass.
If you use quality fiberglass this light transmission will continue to be equal to glass. If you choose cheaper fiberglass the amount of transmission will begin to lessen over time. It diffuses the sunlight, so there is less chance of your plants getting burned from over-exposure to the sun’s rays. Fiberglass retains heat better than glass.
Polycarbonate sheets are UV treated plastic sheets that are available in single, double and triple sheet thicknesses. The single sheet is the most attractive, but with each additional sheet comes added heat retention, light diffusion and strength. The price also increases with each additional layer.
The initial added expense of multi-layered sheets is quickly recovered by the money saved on decreased heating costs. Polycarbonate sheeting is long lasting. It lasts about 15 years in most climates. It is flexible enough to conform to curves in the frame.
Polyethylene film is available in many grades and qualities. It is easy to use, although needs replaced more often than other covers. Because it is so lightweight, the frame need not be constructed so heavy. This will help cut costs for a tight budget. The light transmission of plastic film is equal to that of glass. This plastic film retains heat well.
Although treated with a UV-inhibitor, the life span is still very limited. There is very cheap plastic film available in hardware stores. This is not recommended for a greenhouse. It will rip and tear very quickly. The higher quality plastic film will last about 5 years before needing replaced. The average quality will last one to two years.
Galvanized steel pipe is an inexpensive, long lasting and strong material that can be used for framing your greenhouse. It is good for greenhouse frames because it requires little support, thanks to its inherent strength.
The less obstruction of sunlight the better. With steel, the frames can be thinner. This causes less shadow. The less shadow on your plants the better.
Aluminum is the most long-lasting of all greenhouse frame materials. It is rust-proof, rot-free and UV ray safe. It is also probably the most expensive. It comes in a variety of colors. It is low maintenance. It does not have the strength of steel, and because of this it requires thicker posts and membranes to support the weight of the cover material.
Wood is the most traditional of choices. It is very common in sunroom additions. It is versatile and can be painted or stained many beautiful colors. It is very heavy and will require more hardware than it’s lighter counterparts and this will result in more shadow space. Wood will start to deteriorate, which will be sped up because of the moist atmosphere inside the greenhouse.
PVC tubing is another common material chosen for greenhouse frames. This is because it is light-weight, portable and easy to install.
There are many shapes to choose from or you can design one yourself. The Quonset hut shape is common. There are lean-to shaped greenhouses and window mounted additions that are built onto your existing home. There are free-standing, post and rafter options.
You may choose to lay a foundation or not. Heating, cooling, air circulation, lighting and watering are all options that can be put on automatic or manual controls. The best advice is that it will be much easier and cheaper in the long run to start big, rather than expand later.