There are many cost effective ways to heat a greenhouse. Greenhouses lend themselves well to heating depending on their size. Obviously, the smaller the greenhouse, the easier it is to heat.
Since most greenhouses are made from plastic or glass they are ideal for allowing the heat into the greenhouse. This is a great way to get plants started and keep them safe from the elements of the weather such as wind and spring rain storms.
However, glass and plastic won’t provide enough insulation for the greenhouse. While they allow the light in and will overheat the greenhouse during the day, they won’t hold the heat in at night. Left uncontrolled this can be very dangerous to the plants.
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Ventilation
The key then is to insulate the greenhouse and allow proper ventilation to help encourage the plants to grow properly and keep the greenhouse at an optimal temperature. Ensure that there are some windows or screens that can be opened and closed to ensure plenty of ventilation during the heat of the day.
Fans can also be placed strategically to ensure that there is plenty of air circulation. Most people use fans and ventilation to encourage their greenhouses to remain at the same temperature. Solar energy is plentiful for greenhouses and should be utilized as often as possible.
Install A Good Thermometer
First, install a good thermometer in the greenhouse. You’ll want to monitor the temperature of your greenhouse and try to keep it at the same temperature during the day and night.
Place a few different thermometers in the greenhouse and learn where the “hot spots” are. You can then place the plants that require more heat nearer those areas.
Solar Energy
There are many ways to utilize this solar energy. If the solar energy is stored in thermal mass it will be easy to level it out and maintain the temperature.
Thermal mass is the means of storing the energy. You do that with any material that will store the energy. You can use water, solar batteries that will store the energy and other materials like a heat sink.
Water Barrels
Many greenhouse owners use water barrels to store the heat for the greenhouse. They set these around inside of the greenhouse positioned where they will get the most light and absorb the most heat during the day. At night, as the water begins to cool down it is releasing the heat in the greenhouse. You can think of the water barrels as a solar battery. They will work very well if you have enough and the greenhouse is small enough.
They will stack a few 55 gallon water drums in the green house and move the plants around so that those that require more heat are nearer to the water barrels. This is a great way to utilize solar energy.
Aquatics
More than one gardener utilizes aquaponics in a greenhouse. By growing fish and plants together they have taken care of the issue of heat. The water is always in motion and as the fish excrete their excrement they are feeding the plants.
Many of these gardeners also use a lighting system for the fish tanks and thus take care of the heat issue in a round about way.
Concrete Or Brick Barriers
Another great method is to use concrete, flag stones, bricks or something to absorb the heat. Place these in areas that the sun will heat during the day and at night they will release the heat back into the greenhouse.
Again, as in the water barrel method, place plants that require more heat nearer to the flag stones, bricks or concrete this will ensure that they are receiving plenty of heat.
For any light colored bricks, flag stones or concrete, consider painting them black so that they will absorb and hold more heat.
Raised Beds
Raised garden beds in greenhouses will get plants up and off of the floor. You can use such things as wooden structures or planters, shelving units or some other means to raise the plants off of the floor. The plants can then be placed near walls or other structures that will help to keep them warm.
Raised garden beds will help to retain heat and keep plants warmer for longer. By using this along with one of the other mentioned methods you’re ensuring that your plants stay nice and warm during the cooler nights.
Compost Bins
Compost generates heat by the very act of composting. You can set up a compost bin in your greenhouse and this will also help to keep that area warmer.
Place your compost bin on the ground and put some cinder blocks near it. Set a water barrel on the cinder blocks and the compost will help to heat the water barrel.
Caution, keep an eye on the compost bin, you don’t want it to suddenly combust. Be sure that you’re turning your compost several times per week to keep it heating evenly.
Simply add fallen leaves, vegetable trimmings and any other compost materials to your compost bin and work it just like you do your outdoor compost bin.
Horse Manure
While it may not sound like a glamorous way to heat your greenhouse, it will work. As the manure breaks down in composition, it will produce heat.
Simply place horse manure in some large sized crates and place these in and around the greenhouse. You can put a screen on top if you wish and set some of the plants on these to give more warmth.
When the manure breaks down and ages, you can use it as fertilizer for your plants or add some to the compost.
Flooring
The floor of your greenhouse should be made up of bricks, flag stones, concrete, mulch or something that will absorb heat as well.
Again, if you’re using concrete, bricks or flag stones, be sure that they are painted black to absorb more heat.
You could also use river rocks or pebbles on the floor. The rocks will absorb heat during the day and release it at night.
Photo by terriem 