Sometimes you don't have any choice about where to put a garden or greenhouse. There is only so much room in the backyard, after all. But, you'll be spending time and money so taking the time to consider the factors that will affect how well the site will meet your needs will be worth it in the long term.
Start by choosing a site that has protection from strong winds and good southern exposure. Although buildings or trees will cause shadows, you can determine if a site is suitable by plotting the the height of buildings or trees and superimposing the shadow drawing on a chart showing the angle of the sun at different times of the year.
Start by choosing a site that has protection from strong winds and good southern exposure. Although buildings or trees will cause shadows, you can determine if a site is suitable by plotting the the height of buildings or trees and superimposing the shadow drawing on a chart showing the angle of the sun at different times of the year.
Calculate solar south
Calculate solar noon, the midpoint between sunrise and sunset, by checking the weather site for times. From this site, we can also see that, on April 23rd, the sun is at an altitude of 42.1 degrees.
In Whitehorse, on April 23, the sun rises at 6:16 and sets at 9:43 (a total of 15 hours and 26-1/2 minutes of daylight). 7 hours 13 minutes plus 6:16 means solar noon here occurs at one minute before 2 pm.
Ideally, site the greenhouse so that for two hours before and after solar noon, it receives full sun. At exactly solar noon, the shadow cast by a stake will lie directly north. Hammer in a second stake in the shadow of the first and this line can be used to orient your greenhouse to maximize southern exposure.
In Whitehorse, on April 23, the sun rises at 6:16 and sets at 9:43 (a total of 15 hours and 26-1/2 minutes of daylight). 7 hours 13 minutes plus 6:16 means solar noon here occurs at one minute before 2 pm.
Ideally, site the greenhouse so that for two hours before and after solar noon, it receives full sun. At exactly solar noon, the shadow cast by a stake will lie directly north. Hammer in a second stake in the shadow of the first and this line can be used to orient your greenhouse to maximize southern exposure.
Plot sun path and shadows
A protractor and hollow tube can be used to plot the trees, buildings or other objects that will cause shadows on the greenhouse.
From the weather site, plot the sun altitude for the solstices and equinoxes.
Adjust your location or direction if necessary to maximize exposure during the darkest months. A greenhouse can be as much as 30 degrees off true solar south with only a 10 percent loss in performance. Over 30 degrees, though, the performance drops quickly.
(adapted from: Gardener's Solar Greenhouse: How to build and use a solar greenhouse for year-round gardening; Ray Wolf, Rodale Press, Pennsylvania, 1984.)
From the weather site, plot the sun altitude for the solstices and equinoxes.
Adjust your location or direction if necessary to maximize exposure during the darkest months. A greenhouse can be as much as 30 degrees off true solar south with only a 10 percent loss in performance. Over 30 degrees, though, the performance drops quickly.
(adapted from: Gardener's Solar Greenhouse: How to build and use a solar greenhouse for year-round gardening; Ray Wolf, Rodale Press, Pennsylvania, 1984.)