Most greenhouses are warmed by capturing heat from the sunlight during the day while using electric heaters to keep the nursery warm at night. However, electric heaters cause electricity bills to go up and can be very expensive to utilize.
You can heat a greenhouse without electricity by choosing the right location, insulating the greenhouse, installing thermal mass objects, using compost, or using propane heaters.
Based on geographical location, size, and types of plants grown within, greenhouses require heating solutions that are unique for them. What matters most is that you find the best system that works for you. For more details, please read on.
Choose the right location for your greenhouse.
The location of your greenhouse is the first step in heating your greenhouse without electricity. The sun provides most of the heat and light during the day, and it is a free and natural source of energy. Where you live and the amount of space your greenhouse requires plays a huge role in where you should build your greenhouse to get the most sunlight.
When selecting the location to construct your greenhouse, you want to find an area with the least amount of obstructions as possible. Select an area that is free of shadow producing obstructions like mountains or trees. This is important because when the sun rises into the sky during the day, you want your greenhouse to be in plenty of sunlight without shadows blocking it at any time. A lack of sunlight can reduce the growth potential of your plants.
Insulate the greenhouse.
Once you have your greenhouse in a large sunny location, it will need to maintain the heat that it gathers inside. Insulating your greenhouse ensures that the heat built up during the day remains for a longer period of time when the sun has set. The first areas to take care of are the windows and doors. Horticultural bubble wrap is an easy solution.
Horticultural bubble wrap is a special type of bubble wrap that is designed to absorb and hold in heat from the sun. The larger the bubbles, the more heat it can retain. While traditional bubble wrap is an option, it is not a good idea to use it for the long-term as it is weaker than horticultural bubble wrap and will not hold in as much UV light. Use duct tape to hold the wrap to the windows or staple the edges to the wooden posts of your door to keep the wrap in place.
Make sure to clean the windows and doors before you stick the wrap on them. To increase the effectiveness of the horticultural bubble wrap, place a layer of plastic wrap between the glass and the bubble wrap. This will add another layer of heat-absorbing material to your greenhouse. If you want to keep your plants warm during the night, place a large sheet of horticultural fleece directly onto the plants.
Remember to remove the horticultural fleece during the day so your plants can absorb the sunlight easier.
After you have insulated your windows, doors, and plants, inspect the structure of the greenhouse for areas that heat can escape through. Gaps in your doors and windows can be an escape route for heat. You can seal these gaps by placing foam tape, silicone caulk, or duct tape over the gaps to seal off the escape route. If your greenhouse has a dirt ground, placing concrete blocks or a mat over it, helps to minimize the amount of heat lost.
Install Thermal Mass Objects
Now that your greenhouse is secured and bringing in the heat, you will need something to absorb that heat. Having something to absorb the heat is important because when the sun sets, your greenhouse will need a way to get heat from another source. Thermal mass objects complete this task perfectly as they absorb the sun’s heat during the day and release it into the greenhouse at night.
Thermal mass objects you can use are bricks, concrete, clay, straw, water, and other heat-absorbing materials. Thermal mass objects that are dark in color work very well for holding in the heat because dark colors store heat better. If you decide to use water as a thermal mass object, store it in black 55-gallon drums. If you have a smaller greenhouse, the water can be stored in regular gallon containers painted black.
Place the thermal objects closer to the windows of your greenhouse, where they can absorb the most heat. You can use the bricks or concrete as a floor for your greenhouse, which will give it a strong foundation and help reduce heat loss through the ground. You can place straw in the pots of your plants to help reduce the amount of heat lost in the soil.
Compost is an odd but very efficient way to keep your greenhouse warm. Compost is organic material that has gone through the composting process. According to Rozie Apps, compost produces heat that ranges from 120°F to 160°F (49°C to 77°C) as it decomposes. Compost is also an excellent type of fertilizer to use for plants.
Some of the materials that make up compost are grass clippings, leaves, dead plants, vegetable leftovers, paper, eggshells, and other organic materials. Composts with darker complexions are better because they absorb more heat during the day. Compost decomposes over time, but if you would like to speed up the process, you can add some Earthworms, specifically red wigglers, to the mix.
Red wigglers are ideal for gardens because they help fertilize the soil by eating waste and expelling soil. Adding red wigglers to your compost can help it decompose faster, which will lead to more compost. Red wigglers need an ideal environment to thrive, so make sure that your compost is moist, warm, dark, and has lots of food for them to eat. Red wigglers eat most of the materials in the compost, but raw fruits and vegetables are the best kinds of foods to feed them.
Over time the compost will heat up your greenhouse on its own, and you will not have to do much to maintain it. The worms will mate and die within the soil, so no need to keep buying new ones. Once the compost looks like soil, you can use it for your plants.
Use Propane Heaters
Like electric heaters, the role of propane heaters is to heat up a large area of space in a couple of minutes. Propane heaters not only provide heat for your greenhouse but also provide carbon dioxide for your plants. One propane heater you can invest in is the ProComMG10TBF, which comes with a thermostat.
This heater shuts off automatically when it senses that oxygen levels are low and uses propane or natural gas. However, as with all heaters, make sure not to place the heater near anything flammable and monitor the temperature of the greenhouse in case the area gets too hot.
Location and insulating your greenhouse will ensure that the heat enters and stays inside the greenhouse. Adding thermal mass objects, compost and heaters can help circulate heat within your greenhouse. These methods are all great ideas for keeping your greenhouse warm, but it is up to you to find the best one that works for you.