Your greenhouse may need to be kept warm at night as the temperature decreases. In order to keep your plants safe from the dangers of frost or subzero conditions, you must keep them warm. However, growing energy costs and environmental consequences may prevent you from heating your greenhouse adequately.
To keep your greenhouse warm at night without breaking the bank, we’ve compiled a list of ideas in this post.
How Can You Keep Your Greenhouse Warm at Night?
It is possible to keep your greenhouse warm at night using a variety of methods. Steps that are both basic and highly effective are as follows:
Add compost in your greenhouse
Keeping them in your greenhouse is a no-brainer due to the fact that compost is naturally warm. Temperatures in healthy compost piles can reach up to 104°F. If you periodically flip it to add oxygen, it can keep your greenhouse warm all night. Wood mulch on the ground can also contribute to the heat.
Use thermal mass objects
With only sunshine heating your greenhouse, additional thermal mass objects are needed to boost the overall temperature. When it’s hot outside, bricks, clay, rocks, and a concrete slab floor all absorb heat and release it when the weather cools down.
One of the cheapest ways to heat a greenhouse is to employ thermal mass objects. For optimal heat absorption, use stone or bricks when building raised beds. Water also makes a great thermal mass. It’s also a good idea to place water or black barrels around your greenhouse.
Strategically position your heaters
In the event that you have heating systems, make sure to place them in an area of your greenhouse that is completely open. To be safe, keep them out of the water. Additionally, position the heater above the plants that require the greatest attention.
Only heat the necessary areas
If you don’t need to, you don’t have to heat the entire greenhouse. A mini-greenhouse can be built inside your larger one. A heating system or horticultural fleece can help keep your little greenhouse warm even when it is completely enclosed with bubble wrap or other insulation.
Why Should You Buy a Mini Greenhouse?
Anyone who wants to grow plants in a greenhouse should buy a tiny greenhouse. In terms of cost and convenience, it’s a better option than a normal greenhouse. To help you make up your mind, here are a few reasons why a little greenhouse is a worthwhile investment:
Start early plant growth
You can start planting in a little greenhouse even before the cold season arrives in your area. It is possible to grow warm-season veggies in your greenhouse and then transfer them to your garden as the weather warms up. Once the crops have been harvested, you can begin planting for the next growing season sooner.
Compact and easy to handle
Toss out your preconceived notions about greenhouses being the size of a small house. It is possible to find greenhouses in a wide variety of styles and sizes. If you’re a home gardener who doesn’t require a large greenhouse, a mini greenhouse is a great option. A tiny greenhouse is less expensive than a standard greenhouse, yet it offers the same advantages.
Protect your plants from pests and animals
Bugs that want to devour your leaves and produce can be found, but so can beneficial insects. There are all kinds of critters and insects out there that can ruin the months of hard work you’ve put into your landscaping project. In addition, plants that are exposed to the elements are more likely to contract illnesses from nearby plants. Protection from insects, animals, and illness is provided by the greenhouse.
Great for gardeners with limited space
A tiny greenhouse is a great option if you want to cultivate crops but lack the room. Regardless of the weather, you can grow practically anything in a tiny greenhouse. As a bonus, you can position it wherever — balconies, patios, decks, and even on your dining tables. Smaller tiny greenhouses are available for people who want a more compact design, although the average size is roughly six feet.
Keep plants safe from bad weather
In the face of extreme weather conditions, it is difficult to raise healthy crops. If you live in an area where the weather can change at any time, a tiny greenhouse is the best option. When it’s pouring outside, you can still grow a wide variety of plants. A tiny greenhouse will keep your plants safe and healthy.
Ideal for beginners in greenhouse gardening
If you’re interested in learning more about greenhouse gardening, a small greenhouse is an excellent starting point. A little greenhouse is a fantastic place to start if you want to learn the ins and outs of greenhouses. It has the same advantages as a traditional greenhouse, but at a fraction of the price and time commitment. You may find information about your plants’ growing circumstances, the fundamentals of greenhouse cultivation, and much more.
Greenhouses Get Cold at Night
Greenhouses must maintain a temperature of between 80 and 85 degrees Fahrenheit in order for plants to thrive. Temperatures typically fall during the night. As a result, the greenhouse experiences a 20-30°F reduction in temperature.
How Cold Is Too Cold for a Greenhouse?
A greenhouse’s temperature can only be described as “cold” if we know what we’re growing in it.
Either a warm or chilly climate can be maintained in a greenhouse. It’s all up to you how you intend to make use of it during the course of the calendar year.
A temperature of 55 degrees Fahrenheit or higher is required for a hothouse, while a temperature of 45 degrees Fahrenheit or below is required for a cool house.
Temperatures below 55 degrees Fahrenheit for hothouses and below 45 degrees Fahrenheit for cold houses can therefore be considered “too cool” for greenhouses, according to this information.
When the temperature drops, you’ll need a strategy to keep your greenhouse warm.
Your greenhouse crops’ ability to resist different levels of cold also varies. Depending on the temperature at which they are grown, greenhouse crops can be categorized into three main groups:
- A base temperature of 39 degrees Fahrenheit or lower is required for these crops.
- Crops that thrive in temperatures between 40 and 45 degrees Fahrenheit are known as cold-temperate crops.
- Plants that can’t handle temperatures below 46 degrees Fahrenheit are known as “cold-sensitive” crops.
The coldest temperature at which a plant will not develop is called the base temperature (sometimes referred to as the minimum temperature). Unless the temperature rises above the basal temperature, plants do not produce leaves or blossom.
The base temperature of your greenhouse crops must therefore be taken into consideration when determining the ideal growing conditions in your greenhouse.
The ideal temperature for your greenhouse crops is just as important, and it’s well worth your time to learn about it. At this temperature, plant growth is the fastest.
Depending on the crop, this temperature might range from 70 to 90 degrees Fahrenheit. This temperature range is critical for healthy plant growth in your greenhouse.
It must be below zero degrees Fahrenheit outdoors before you begin to feel the chill in the greenhouse.
How Much Warmer Is an Unheated Greenhouse at Night?
The sun is the only source of heat in an unheated greenhouse, which is also known as a cold greenhouse.
Unheated greenhouses can have temperature differences of up to 30 degrees Fahrenheit from the outside.
Depending on the sort of greenhouse you have and the level of insulation in your greenhouse, this variance might be rather large.
A temperature variation of 5 to 10 degrees Fahrenheit is not uncommon in a single-layer greenhouse.
Outside, a 9 to 14 degree Fahrenheit temperature variation is typical for a double-layered greenhouse.
How do Cold Do Greenhouses get at Night?
Temperatures in greenhouses can fall as low as 50 to 60 degrees Fahrenheit at night in the northern United States.
Nighttime lows of 0 degrees Fahrenheit are not uncommon in the greenhouses during the winter.
Summer nights in the South can see greenhouse temperatures rise to between 60 and 70 degrees Fahrenheit. Temperatures in greenhouses can fall to as low as 15 degrees Fahrenheit at night during the winter months.
At night, greenhouse temperatures can reach 40 to 50 degrees Fahrenheit in the Mid-Atlantic region of the United States. At night, temperatures in greenhouses can fall to as low as 10 degrees Fahrenheit in the winter.
Do People Normally Heat Greenhouses?
Winter and particularly frigid nights cause greenhouse temperatures to plummet.
The growth of plants in greenhouses can be significantly impacted by cold temperatures, which can result in stunted growth. Plants may finally perish in extreme instances.
The ideal temperature for most growers is between 80 and 85 degrees Fahrenheit. That’s why greenhouses are heated when the weather becomes too chilly.
Should I Make My Greenhouse Airtight To Preserve Heat?
Airtightness is essential in greenhouses. Due to a lack of air-tightness during colder months and a corresponding increase in temperature, greenhouses are not ideal for growing plants.
As a result, you should ensure that the greenhouse is airtight. This will prevent your greenhouse from being too cold for the plants because it will keep the heat in and preserve it.
Yes, that’s correct! To save heat, you should construct your greenhouse such that it is completely airtight.
How Can You Heat a Greenhouse Without Electricity?
Electric heaters in greenhouses can drastically increase your energy costs.
Using energy to heat a greenhouse isn’t a viable option for the vast majority of farmers. This is due to the fact that the cost of electricity can often outweigh the value of the plants themselves.
If you want to keep your greenhouse warm without increasing your utility cost, you can do so with the help of a greenhouse heater. Here are some ideas for heating your greenhouse without using energy.
1. Using Compost
One of the best ways to generate heat is through the use of compost.
Nearly 160 degrees Fahrenheit can be generated by a compost pile. As a result, composting can be an efficient method of raising the temperature in your greenhouse. Additionally, the fertile soil will benefit from your efforts.
It is possible to compost hay, plant clippings, and even leaves.
Compost can be used to heat your greenhouse if it is placed in the center.
The heat generated by microorganisms breaking down the compost’s organic material is a byproduct of this process.
2. Using Solar Heaters
Solar heaters are a clever method to keep your greenhouse warm without relying on energy.
Solar panels and rechargeable batteries are all you’ll need to power your heater and keep you warm.
The sun’s energy is captured by solar panels, which provide electricity to power your solar heater. Batteries that can be recharged will allow you to store energy for when the sun isn’t shining.
3. Shared Heat
Using the principle of shared heat, you can heat your greenhouse without using energy.
Your greenhouse must be built in such a way that it is surrounded by another structure that it can exchange heat with. Typical examples include a chicken coop and a barn.
Your greenhouse will be kept at a comfortable temperature thanks to the chickens in the shared building.
4. Thermal Mass
Heat is stored as thermal mass, much like a battery.
Basically, the thermal mass heats up during warm periods like sunny days, and when it cools down, the thermal mass gently releases the stored heat.
Water barrels, stones, bricks, and straw are all examples of thermal mass. As long as it’s substantial and black, it’s a good thermal mass. These materials are ideal for capturing, retaining, and slowly releasing heat.
Water barrels are the finest thermal mass option. In order to keep your greenhouse warm, you should use water because it has a higher heat capacity.
If your greenhouse gets cold, you can use dark stones, which will absorb heat from the sun and release it slowly.
You should think about adding some thermal mass to your greenhouse in this regard. This will keep your greenhouse warm without the need for power.
5. Sink your Greenhouse
Basements are viewed as gloomy, cold places by most people.
The truth, on the other hand, is that temperatures below ground are frequently higher than those found above. The more stable the temperature is, the deeper it is buried.
Keep in mind that sinking the greenhouse floor below the frost line will help keep it warm.
As a result, your greenhouse’s temperature will be kept more stable by the earth’s heat.
The best approach to keep your greenhouse warm without using a lot of electricity is to insulate it.
Bubble wrap, glass, and greenhouse plastic are the most typical greenhouse insulation materials.
Greenhouse insulation made from any of the aforementioned materials will do a good job of retaining heat. Use plastic for the greenhouse’s outside and bubble wrap for the greenhouse’s inside as two types of insulation.
Bubble wrap is a good choice for greenhouse insulation if you’re just going to utilize one type of insulation material. More than three years is the average lifespan.
Avoid any gaps between the insulation layers and the sides while insulating your greenhouse.
To summarize, you should always maintain your greenhouse’s temperature at a comfortable level that is neither too cold nor too hot for your plants.
As a result, the plants will flourish and grow to their full potential.
Do You Need To Heat Your Greenhouse In Winter?
Before you begin the process of adding extra heat to your greenhouse, you should carefully evaluate this question.
It may not be required to heat your greenhouse throughout the winter in some regions.
Assume that the temperature at night in winter is rarely lower than 30 degrees. Your greenhouse can be used to cultivate a wide range of cold-tolerant vegetables from now until spring without requiring additional effort.
In contrast, no matter how tough your crops are, you will need to add some type of additional heating if you have a harsh winter with temperatures routinely falling into the single digits or lower.
Of course, if you want to grow warm-season veggies in your greenhouse in the middle of January, you’ll need to employ more than one of the techniques listed here to keep them healthy and productive. A more temperate climate does not exempt you from this rule.
8 Practical Greenhouse Heating Options
It’s time to have a look at your heating options once you’ve chosen whether or not heating your greenhouse is important for your environment and aims.
All of the solutions below are doable (i.e., they won’t take a lot of time and effort on your behalf), but their cost and environmental impact vary widely. As you go through the sections, think about how much each one might cost you and the world, and how it relates to your long-term objectives.
Both solar panel heaters and passive solar capture can be used to heat a greenhouse with solar energy.
Solar Powered Heaters
They’re exactly what they sound like: little solar-powered heaters.
It’s not as easy as you may think to get your hands on these types of heaters. The reason for this is because heaters utilize a lot of energy, which means that several solar panels must be installed.
Installing fifteen 100-watt solar panels, for example, would be necessary to power a 1,500-watt heater. For the light to get in, you would have to put so many solar panels on your greenhouse.
Even if you went with the more expensive, higher-wattage 500-watt solar panels, you’d still need three panels, which is still too much for a greenhouse roof.
To use a greenhouse heater powered by the sun, you’ll need to have solar panels installed on your property.
Passive Solar Heating
Do not, however, write off the sun’s value just yet.
One of the most cost-effective ways to raise crops in the winter is to employ passive solar heating in a greenhouse.
It was just 42 degrees outdoors when my greenhouse reached 101 degrees. An incredible amount of excess heat is created with no further work. In the depths of winter, you may grow nutritious vegetables without increasing your electricity cost by capturing and redistributing heat.
Increased heat absorption can be achieved by building raised beds with additional soil, using stone or brick to line greenhouse walkways, and using large flat rocks wherever available. The heat can also be collected by placing large tanks or jugs of water in the area.
These surfaces will begin to release this heat back into the atmosphere as the air cools at night.
A heat sink can also be used as a passive solar resource.
Dig a two- to three-foot-deep hole in the greenhouse’s middle to begin. The most efficient heat sinks should be about one-third of the greenhouse’s size. A 3 by 3 square foot hole, for example, is ideal for a 10 by 10 square foot greenhouse.
Backfill the pit with river boulders, gravel, bits of concrete, or bricks and place a tube, such as a wide PVC pipe, in the center. All day long, these high-thermal-mass fabrics will keep you warm. Afterwards, the heat will dissipate through the tube overnight.
Earth-source heat pumps are heat sinks optimized with a solar fan or pump to circulate air in and out of the ground.
Hot Water Heating
In addition to using the sun’s free energy, you may heat your greenhouse with hot water.
Solar water heating cells use the sun’s rays to heat coiled lines of water. In the greenhouse, a giant barrel of hot water is filled by these pipes. The greenhouse is warmed by the radiation of this water container’s heat.
Alternative (and more successful) heating methods include burying hot water pipes right in the flower beds.
So that your greenhouse can remain warm at all times, a water pump circulates the water via the solar panel.
Boilers, wood stoves, and electric heaters can all be used with solar water heaters. Compost bins can even house coiled water lines. Decomposition generates enough heat to warm the water pipes and a small greenhouse.
Setting up and maintaining this form of heating can be labor-intensive. However, simple solar choices are also available for those who don’t have a lot of money.
There are various basic choices available to you if you are ready to pay to heat your greenhouse. Electric heaters, such as this Bio Green greenhouse heater, are the most energy-efficient option.
You’ll need a power source in your greenhouse if you’re going to use an electric heater.
With an outlet or an extension cord, this form of heating requires absolutely no time commitment. However, keep in mind that greenhouse heating is inefficient.
The primary purpose of a greenhouse is to increase the amount of light that enters the structure. Insulation is often sacrificed in the process. So when the sun goes down, greenhouses begin to cool quickly. The structure of a greenhouse has very little to do with retaining heat.
As a result, the least efficient method is to heat the air in a greenhouse. An electric heater will run continuously if the outside temperature is below the set temperature, so plan accordingly.
However, this is still one of the simplest ways to get started with the process. It’s a great choice for locations that only have a few days of freezing weather each year.
Oil Filled Heater
Fuel costs can be lower for oil-filled heating systems than for electric ones, which makes them a preferable option for greenhouses that need to run continuously at night and on overcast days.
These devices, like an electric heater, need to be plugged into an outlet to function. The oil reservoirs must be heated with electricity. Oil heats up the entire apparatus as it circulates through it. Using convection, this heat is dissipated into the atmosphere.
In addition to not drying out the air, an oil-filled heater has another advantage over an electric heater.
It is important for plant growth to have a steady supply of humidity in a greenhouse. Blower-powered electric heaters tend to dry up the air, resulting in lower humidity levels. Heating greenhouses with an oil-filled heater, on the other hand, has only a modest impact on humidity.
The use of a kerosene heater in greenhouses where electricity is unavailable is preferable. The vast majority of these machines run solely on kerosine tanks that can be refilled. Therefore, there is no need for power outlets or extension cords.
They, too, like electric heaters, have the potential to dehydrate the air around them. These heaters, however, will likely need to be constantly running during the winter to maintain a stable temperature in your greenhouse. Kerosene, on the other hand, is less expensive than electricity.
They may produce a lot of heat, and the most concentrated portion of that heat is located directly in front of the flame element. A kerosine heater can melt polycarbonate or PVC sheeting if it is too close to it.
This will ensure that you have a safe and effective heating system, as well as keep plants and other flammable materials away from your heater at all times. Kerosene heater safety can be found here.
Use Germination Mats
Using germination mats in a greenhouse is an excellent way to heat a specific area. These mats are comparable to heating pads, which are commonly used to treat aches and pains in the muscles and joints. In order to promote better root growth, they are not effective in warming the air, but they can be quite successful at warming the soil.
It is not possible to use germination mats to heat in-ground or raised beds with these products. They’re not ideal for heating huge pots either. Because of this, they’re ideal for heating seedling trays and shallow pot heating trays.
You’ll be able to change over your beds more quickly if you plan to cultivate cold-season plants throughout the winter by using these mats. For unexpected cold bursts, you may even use them to preserve your flowers and greenery from freezing.
Those Vivosun mat and thermostat sets, for example, come with a programmed thermostat as part of the price of the germination mat. These varieties allow you to control the temperature of the soil to your exact specifications. The mat may also be used in spring to germinate hot-season vegetables with specific temperature requirements, giving you more control over changeable winter conditions.
It’s not as if we’re saying you should bring a cow into your greenhouse at night to keep it warm. If Bessie didn’t devour your plants, that would be an effective strategy.
Making a greenhouse that also serves as a home for tiny animals is the goal here. A common wall between your greenhouse and your chicken, pig, or rabbit hutch can assist keep the temperature steady at night.
The heat from the animals’ bodies, as well as their excrement, will help keep things warm. Putting the animal enclosure in the greenhouse helps you to improve your efficiency by utilizing the heat from the bulb heaters or other heater types you already have in the animal enclosure.
It all depends on what kind of animals you have and how well your coop and greenhouse are set up.
Use A Hotbed
Turning your planting beds into hotbeds is a very efficient and cost-free way to heat your greenhouse in the winter.
Plants in hotbeds benefit from the heat generated during decomposition. Making them will need some digging if you’re working with in-ground beds, but the results will be well worth your efforts. It is possible to avoid digging entirely by building raised beds and filling them with the necessary material.
Begin by adding two to three feet of horse dung and straw to the bottom of the bed (approximately three and a half feet deep for in-ground beds). Instead of horse manure, you can make compost out of decaying leaves and food scraps. Just like you would when making a simple compost pile, use the same ratios here.
Plant your vegetables in the six-inch layer of potting soil on top of the bed.
The manure or compost mixture will continue to decay throughout the winter. Roots will remain happy and healthy as a result of this heat rising through the soil. It’s possible that some of this heat will disperse into the surrounding air.
Other Greenhouse Heating Considerations
It’s possible that some of the methods outlined above will be more effective than others. Whatever approach you choose, there are things you can do to make it more successful.
Consider these additional factors in order to get the most out of your greenhouse’s heating capacity.
We all know that the temperature increases when the sun rises. This is the exact opposite of what you want to happen in the winter in a greenhouse, where plants are normally positioned on the floor. In addition, the greenhouse’s ceiling is where the majority of the air exits. In order to make the most of the warm air you’ve generated, you must maintain it closer to the surface of the ground.
Air circulation is essential in this process.
A fan placed near the greenhouse’s ceiling is a great way to keep rising warm air from escaping or cooling down.
Air that moves too quickly cools rather than circulates; this is undesirable. If you want to create a mild breeze, but one that doesn’t feel cool to the skin, turn your fans down.
If your plants are located near the greenhouse’s walls, this can be a beneficial thing, as it can help to level out pockets of cold air.
Eco House’s simple solar fan kit is a good option if you don’t want to contribute to your electric bill by running the fan all night.
Grow The Right Plants
The most important thing you can do to make the most efficient use of the heat you generate is to choose the correct plants. Tomatoes and peppers, which are summer annuals, need a lot of heat to thrive. Winter gardening necessitates the use of artificial lighting.
Heating and lighting costs will go up significantly as a result of this.
Instead, look for plants that thrive in cooler climates and with less light exposure.
The shortest days of the year are no problem for cool-season plants, which can endure temperatures as low as minus 40°F. In most areas, these plants may be grown year-round using the simple methods indicated above.
Here are a few of the most cold-tolerant plants to grow in your winter greenhouse with only a small amount of heat:
- Onion rings
- Onion bulbs
- Swiss chard
- Chestnut chard
- A vegetable known as Brussels sprouts
For the greatest results, choose frost-tolerant types of these vegetables.
Use Thermal Mass
Solar energy can be harnessed by thermal mass, which we discussed earlier. As a result, thermal mass can be used to its full potential in a range of applications to maximize heat retention.
If you’re using an electric or kerosene heater to heat your greenhouse, increasing the interior’s thermal mass will aid in retaining the heat that might otherwise escape. Running these expensive heaters less frequently will save you money in the long term.
Like thermal mass, hot water heaters and livestock can use thermal mass to store heat. Even hotbeds leak a small amount of heat into the air, which can be reclaimed by surrounding rocks or water bottles.
Here are some materials worth adding to your greenhouse to help capture heat and better regulate temperatures:
- Materials that can help your greenhouse retain heat and better regulate temperatures include:
- Blocks of cinder
- Water in drums or jugs
Building raised beds with extra soil, laying bricks instead of planks to line beds and putting water jugs in your planting beds are all strategies to maximize the use of thermal mass materials.
Insulate Where Possible
Insulation is a major factor in why you have to spend so much time and money heating a space that gets hotter than the outside during the day.
It’s important to note that this lack of insulation serves a purpose: it allows a lot of light into the space. You may still do certain things to help your plants retain heat without sacrificing the amount of light they receive.
Your greenhouse’s southern side is the only place where all of that sunlight ever enters. There is no effect on how much light your plants receive if you add insulation to your greenhouse’s northern walls.
Build a greenhouse with sturdy northern walls if at all possible. Some greenhouse kits are constructed this way, however the majority of greenhouses are completely transparent. Using styrofoam panels or bubble wrap on the north side of your greenhouse will provide an additional layer of protection.
Warmth and light are reflected back to your plants when they are on white or glossy surfaces, so keep this in mind when building these frigid northern walls. White should be the color of any solid walls in this area. Other types of insulation, such as reflecting or lighter-colored materials, should be used instead.
Insulating the walls isn’t the only way to keep the cold out; you should also seal and conceal any gaps around doors, windows, and vents.
Insulating your structure’s walls may not be as effective as insulating the soil, which has a naturally high thermal mass. This will restrict the heat absorbed by the soil during daylight hours from escaping as the air cools down.
Mulching is a simple technique to keep your soil (and the plants growing in it) warm in the winter.
The insulative properties of mulch vary greatly depending on the type. When it comes to insulation, straw is one of the best, and it’s inexpensive, especially in the fall. In the summer, cedar bark mulch, another common mulch, can serve as a bug deterrent.
Even dead leaves, grass clippings, and evergreen boughs can be used to save money in the garden.
Row coverings are another option for keeping your soil warm. Row coverings, as opposed to mulch, allow heat from the soil to reach the leaves of your crops.
Woven fiber sheets are commonly used for row coverings because they are thin enough to let sunlight through but thick enough to keep warm air trapped within the fabric. The same can be said for different types of materials.
Clear five-gallon buckets can be used for larger vegetables, while gallon milk jugs can be used for smaller crops. When it comes to covering vast areas, plastic row covers are ideal.
These types of row covers do not allow moisture to escape or allow for air circulation, unlike standard row cover material. Keep an eye on your plants to make sure they aren’t getting too saturated, as this might lead to fungal development issues. Remove the plastic coverings on hot days to prevent this.
Final Thoughts on How to Keep Your Greenhouse Warm at Night
After reading this article, you should be able to successfully nurture healthy plants and harvest high-quality produce in your greenhouse. You may get the benefits of growing plants in a greenhouse if you follow these guidelines.