You’d think it goes without saying but you need to build your greenhouse in the right location on the first try. I’ve watched dozens of YouTube videos of people building a greenhouse but none of the ‘home inside a greenhouse’ videos go into detail about how to site the structure. If you don’t get it right you will either struggle with unhappy plants or have to go through the time, effort, and expense to move it. The stakes are even higher when your home is inside the greenhouse. A few considerations are 1) potential for falling leaves to become a maintenance issue, 2) tree limbs that might fall and break a panel, and 3) the sun exposure on the structure. Those of us who are not blessed with wide open spaces should study the sunlight patterns for a full year before building, if possible.
Sun exposure is the amount of sun light on the greenhouse based on the angle of the sun throughout the year, and cloud coverage, and shade from trees or other structures. Understanding the sun exposure on the specific location for the greenhouse is important for both heating by passive solar gain and to provide the optimal light for the specific types of plants you want to grow. The sun exposure can vary widely throughout the year.
I purchased my property in the spring after the trees had leafed-out and was fortunate to find only 2 deciduous trees that had to be removed because they were within the greenhouse footprint. There were also a few trees that were either dead or had an ominous lean, that were taken down for safety. Otherwise, the entire perimeter of the property is ringed with mature fir trees. Through the spring months, there is barely dappled sun between the trees. By April, however, the sun is high enough to crest the trees from noon until almost sunset when it goes behind the sheds which cast their long shadow onto the greenhouse’s location. This should provide sufficient light and warmth for early vegetables like peas, kale, leeks, artichoke, radishes, and lettuce. I expect this will also provide enough solar gain to be warm enough to have my home’s doors and windows open starting in late March or early April.
During the summer months the entire location of my greenhouse gets full sun for 10 hours or more. Now the concern is not getting enough light, it’s about providing some protection from too much solar gain. Ventilation is critical to let out excess heat. I’ve seen a lot of people use shade cloth to filter the light being magnified through the ‘glass’ but I think that may not provide much help for temperature control. I hope to provide some measure of temperature control by using frosted panels on the roof. I think this will also provide a more pleasant, less harsh, light in the house. Unfortunately the frosted panels will mean no star-gazing from inside the greenhouse.
Early fall can be glorious in the Pacific Northwest. The sun’s angle over the trees may be similar to spring but with less overcast or rainy days so there is, overall, more sun exposure through September and October. Late October to early November is when the wind storms start. After one particularly bad wind storm where 2 trees fell on my neighbor’s property, I was glad I’d taken down those trees in the spring. Not even any large tree limbs came down but closer inspection revealed a couple ‘widow makers’ too close for comfort to the greenhouse location. I’ll be sure to have the tree service take care of those before construction starts. Otherwise, the planned greenhouse location looks good for fall for both plant and human living conditions.
During the winter months there is barely dappled sun at ground level due to cloud cover and/or due to the sun’s low angle. Lack of any sun on the ground during winter is what reminded me to look up! Even when the sun’s angle isn’t high enough above the trees to shine onto the ground, there is, however, much more sun coverage at 10′ or 12′ above the ground. This means that whenever the sun is not hidden by clouds, it will shine on the greenhouse roof, even if it does not reach the sidewalls. If the sun shines on any portion of the greenhouse there is good potential for passive solar gain to raise the inside temperature enough to be able to have the house’s doors and windows open in the middle of winter!
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