The best orientation for most greenhouses in the Northern Hemisphere is east-west, with the long axis running from east to west. This alignment exposes the longest side of the structure to the southern sun, capturing the most light during winter when the sun hangs low in the sky. That said, your latitude, climate, greenhouse type, and surrounding landscape all influence whether this default rule applies to you.
East-West vs. North-South Orientation
These are the two primary options, and each serves a different goal. An east-west greenhouse has its ridge line running from east to west, meaning the longest wall faces south. A north-south greenhouse has its ridge line running from north to south, so the sun sweeps across both long sides over the course of the day.
East-west orientation maximizes winter sunlight. When the sun is low on the horizon from late fall through early spring, light penetrates the full length of that south-facing wall rather than just shining through one narrow end. This lengthens your daily light window and helps maintain more stable internal temperatures. If you plan to grow through winter or start seedlings early in spring, this is the stronger choice.
North-south orientation distributes light more evenly across the full year. As the sun tracks across the sky, both sides of the greenhouse receive direct exposure at different times of day, which reduces the hot spots and overheating that can become a problem in summer. For growers in warmer climates who are primarily concerned with spring-through-fall production, this orientation often makes more sense.
How Latitude Changes the Recommendation
Your distance from the equator is the single biggest factor in choosing orientation. Above roughly 40 degrees north latitude (a line running through Philadelphia, Denver, and northern California), east-west orientation is the clear winner. At these latitudes, winter days are short and the sun angle is low enough that an east-west greenhouse captures significantly more usable light during cold months.
Below 40 degrees, in warmer southern regions, the calculus shifts. The sun is already high enough in winter to deliver adequate light from multiple angles, and the bigger challenge becomes managing excess heat in summer. A north-south orientation provides better ventilation dynamics and more balanced light distribution, both of which help prevent overheating. John Biernbaum, a researcher at the Rodale Institute, notes that north-south orientation in southern latitudes provides good light along with the best ventilation.
Orienting a Lean-To Greenhouse
Lean-to or attached greenhouses follow a different rule because they only have one fully glazed side. A lean-to should be placed against a south-facing wall, whether that’s the side of your house, a garage, or a garden wall. This positions the glass to face the sun’s path for maximum light exposure. The solid wall behind it also acts as thermal mass, absorbing heat during the day and releasing it at night.
If a true south-facing wall isn’t available, southeast is the next best option. You’ll capture strong morning light, which is valuable because it warms the greenhouse after the coldest part of the day. A southwest-facing lean-to works too, but the greenhouse will stay cooler in the morning and may overheat on summer afternoons.
Keeping Shadows Away From Your Site
Orientation matters far less if your greenhouse sits in the shadow of a building, fence, or tree for half the day. The winter sun angle is the critical factor here, because shadows stretch much longer when the sun is low. At 40 degrees north latitude on the winter solstice, for example, the noon sun sits only about 27 degrees above the horizon. A 30-foot tree just 20 feet south of your greenhouse would cast a shadow nearly 20 feet up the south wall at solar noon, effectively blocking most of the light you’re trying to capture.
A practical rule of thumb: measure the height of any obstruction to the south, then place your greenhouse at least twice that distance away. A 15-foot tree needs at least 30 feet of clearance to the north. For taller obstructions or higher latitudes, increase that buffer to 2.5 or even 3 times the height. Keep in mind that deciduous trees lose their leaves in winter and cast lighter shadows, but evergreens block light year-round. When in doubt, visit your planned site on a winter afternoon and observe where the shadows actually fall.
Wind, Ventilation, and Structural Safety
Orientation affects airflow as much as it affects light. The most efficient natural ventilation happens when the greenhouse axis sits perpendicular to prevailing winds. If your area’s dominant winds blow from the west, for instance, a north-south oriented greenhouse (with its long sides facing east and west) would catch those breezes through side vents effectively. An east-west or northeast-southwest alignment also performs well for ventilation when combined with both roof and side-wall vents.
Strong prevailing winds can also be a structural concern. Positioning the narrow gable end toward the dominant wind direction reduces the surface area that takes the brunt of gusts. If your site is exposed and windy, this consideration may matter more than squeezing out a few extra percentage points of winter light. Windbreaks like hedges or fences set 15 to 20 feet upwind can reduce wind speed without casting problematic shadows, especially if you keep them on the north or northwest side.
Slope and Drainage
If your property has any slope, a slight south-facing incline is ideal. It angles the greenhouse floor toward the sun, improving light capture in winter and encouraging cold air to drain downhill and away from the structure. Avoid low spots where cold air pools on still nights, as these frost pockets can drop temperatures several degrees below the surrounding area.
Good drainage matters too. A greenhouse on flat, poorly draining soil will struggle with excess humidity, which promotes fungal diseases. If your best-oriented site is also your wettest, consider raising the foundation or installing French drains before building. The goal is to keep the floor zone dry while the plants get all the moisture they need from controlled watering.
When Perfect Orientation Isn’t Possible
Most home sites don’t offer a perfectly flat, shadow-free, south-facing plot with calm winds. The good news is that a greenhouse angled up to 15 to 20 degrees off true south still captures the vast majority of available winter sunlight. You lose very little by going slightly southeast or southwest of the ideal. Beyond 20 degrees off axis, the losses become more noticeable, but supplemental grow lights or reflective interior surfaces can compensate.
Light-diffusing glazing materials also reduce the importance of perfect orientation. Standard clear glass or film creates strong light and shadow patterns inside the greenhouse, but diffused glazing scatters incoming sunlight so it reaches plants from multiple angles. This helps even out the distribution, which partially offsets a less-than-ideal compass alignment. If your site forces a compromise on orientation, choosing a diffusing cover material is one of the easiest ways to recover lost growing performance.