A passive solar greenhouse uses the sun for heat. It warms up in the day. It can hold some of that heat after dark.

The idea is simple, but the setup still matters. Sun, shade, airflow, and insulation all affect the result. In Alabama, you must also plan for hot summer days.

How the Heat Is Stored

Sunlight enters through the clear cover. It warms the soil, benches, and other parts of the greenhouse. Some items can hold that heat for a while.

Water jugs, stone, brick, and concrete can help. These items warm in the sun. They then give off heat as the air gets cooler.

Pick a Sunny Site

Choose a spot with good winter sun. A south-facing site often works well in Alabama. Watch for shade from trees, sheds, and fences.

If you plan to grow in the ground, check the soil first. Our Alabama garden soil test guide shows how to take a sample and use the results.

Hold Heat at Night

Clear covers let in light, but they can lose heat at night. Double-wall panels can help. Two layers of greenhouse film can help too.

Seal gaps around doors and joints. Put heat-holding items where the sun can reach them. Do not let them block your plants.

Plan for Summer Heat

Summer is a different problem. A greenhouse can get too hot very fast. Roof vents, side vents, fans, and shade cloth may be needed.

Good airflow can also help with damp air. Healthy soil helps plants handle stress. You can learn more in our guide to composting in Alabama heat and humidity.

Start Simple

You do not need a complex system. Start with sun, good vents, some insulation, and a small amount of thermal mass. Then watch the temperature each day and night.

Basic garden care still matters inside a greenhouse. Our Alabama home gardening guide covers soil, water, mulch, and simple plant care.