Depending on your location and the type of plants you grow, you may need to shade your greenhouse in the hottest part of the year. If you find the greenhouse reaching unhealthy temperatures for your plants, and the ventilation isn’t keeping temperatures cool enough, providing shade is a must.
But it’s also important not to over-shade. You don’t want your plants in the dark, of course; nor do you want them to get too cold. Some environments, and certain plants, require permanent shading, so non-temporary solutions are needed.
The most common method of shading a greenhouse is simply draping a special sheet over the top of the structure. Depending on your plants and local climate, you will need to select different material to block different amounts of light from entering the greenhouse. In temperate climates, forty to sixty percent is usually just right, but in hotter areas you may need 70 or more. In some cases you made need to fully block direct sunlight, or use even reflective material for shade.
If a tidy appearance is not one of your primary needs or desires, then liquid shade material may be the most convenient for your greenhouse. These are paint-like compounds which are mixed with water and then painted or sprayed onto the desired panels of the greenhouse. These can be washed or scrubbed off when no longer needed, or there are permanent compounds available if it’s needed year-round.
Many, many varieties of greenhouse shade cloth materials are available, ranging in colors, durability, light transmittance and even texture. Shade cloths can block as little as 22 percent, or as much as 100 percent. Reflective materials are available as well, and they also can block a varying amount of sunlight, while increasing temperature reduction over non-reflective shade materials. The reflective shade curtains also help to retain heat in winter under certain circumstances. The color of the sheeting will also affect the greenhouse environment to some small extent, white or black is probably the best choice, as other colors can possibly affect the plants negatively.
Blinds or curtains:
Another popular way of shading a greenhouse is with blinds. Typically, outdoor patio blinds would be attached to the outside of the greenhouse. Then can be raised or lowered as needed. Depending on the angle of your greenhouse’s roof, these may or may not work for shading the roof.
You can also even use some types of indoor blinds on the inside of your greenhouse, functioning just like the inside of your home. Just be sure they are not made of materials that are susceptible to the harsher environment of a greenhouse.
In some situations, it may be easiest to use rigid materials for shade. There are polycarbonate panels of varying light blocking ability available which can be temporarily or permanently attached to the outside or inside of your existing windows.
Alternatively, if 100% blocking is needed on a portion of the greenhouse for part of the year, even ordinary materials like plywood can be used. Just affix a large enough board over the sun-side windows for the summer.