To start on your light dep project, we will focus first on greenhouse construction. There are several questions that you must ask yourself. First, do you want to use wood, metal, PVC, or a prefabricated steel design to create the structure that will provide support for your greenhouse? Second, once you have determined which materials to use, do you wish to design a polyethylene tunnel greenhouse out of steel and polyethylene or Visqueen sheeting, or do you want your greenhouse to have more of a hoop house design of PVC piping anchored into the ground using rebar? Do you want the floor of your greenhouse to be an earthen floor, or are you planning on measuring out, constructing, pouring and leveling a cement slab on which your greenhouse will sit?
All of these factors are essential to making your decision and doing a correct install for your greenhouse.
If you are going to build your greenhouse instead of opting for a prefabricated structure, then you will need to know its dimensions first and foremost. First, measure how long you want each greenhouse building to be, after clearing a large enough and flat enough area for modification. Most greenhouses are anywhere from 20 to 60 feet in length, excluding the larger commercially built ones seen on nurseries and tree farms. Determine your building's length that you want and stick with it.
Next, you will need to measure the width. Most greenhouses are from anywhere between 12 and 24 feet wide, with wider designs being acceptable in regions not subjected to inclement weather.
Finally, you will need to measure the length of the hoop or roof section. This is done by using a bendable tape measure and having one person hold it flush to one side of the proposed structure, up and over the hoop, and finally down snugly again on the other side of the foundation. If you need help to stick the measuring tape to the hoop to get a good measurement, this can easily be accomplished by affirming alligator clips at one-foot intervals along the hoop to hold the measuring tape in place. Typically using a foot to two feet of excess polyethylene will ensure that some overhang is left on the sides. Having the sides open on the bottom as a vent is also a variation on this hoop-house design. Make sure that your hoops are spaced by three feet or less, and that they are firmly attached to your base.
The next step is installing a hand crank with a horizontally situated crankshaft that spans the length of your greenhouse. This crankshaft is connected to a control arm that is just one foot longer than the length of your greenhouse. Using a pulley system that relies on the strength of your arms to move the crank, you raise and lower the roll of blackout canvas with the control arm until the blackout fabric is securely snug on the opposite side of the greenhouse. After checking to see that there are no other light leaks, the blackout is allowed to continue until a timer signals it to be removed.
