Don’t all greenhouses use solar sunlight? Yes and no. Many greenhouses use sunlight to grow plants, but add electricity, gas, and other power devices during cold winter months to keep the plants from dying. Growing crops in northern latitudes where winter months freeze, and sunlight is minimum, is traditionally done by installing light fixtures and/or greenhouse heaters. This may sound like a simple solution, but when you get the monthly electrical bill, you’ll find it’s no solution at all.
Fortunately, growers have developed greenhouse designs that get around this problem- We call it the Solar Greenhouse (AKA, passive solar greenhouse). A pure solar greenhouse creates energy by optimizing sunlight and positioning (facing) the grow-plant wall toward the south. This way the greenhouse will capture heat during the day, then let it back into the environment at night when it’s cold. Along with the orientation positioning; proper insulation, thermal mass, and clever glazing practices combine to creates a greenhouse that uses little if not any outside power .
- Orientation is positioning the greenhouse plant area wall towards the south to maximize sunlight. Pointing it directly at the sun can overheat the building and harm plants, especially in the summer. It’s best to alter the south-faced wall marginally to the east at roughly 45° due south. This provides plenty of sunlight for plants with morning sun, and avoiding the heat that increases in late afternoon.
- If you can’t point southeast for whatever reason, orienting slightly to the west will suffice, though you may have to shade the plants in midday when the heat rises. *Tip, For optimum sun exposure, build the south-faced wall sloping at 45°. The north facing wall will be sloping at roughly 80° giving the south wall an expansive surface of sunlight.
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