Improve Energy Efficiency in Greenhouses
Energy is one of the top operating costs for more greenhouse growers. One of the best ways to help reduce costs is to make your operation more energy efficient. Here we will show you ten of the most common successful measures that you can use to reduce your energy use and save money.
- [Voiceover] Top 10 Things Greenhouse Growers Can Do To Improve Energy Efficiency.
- [Voiceover] Operating a commercial greenhouse is one of the most rewarding ways to make a living, but it is not an automatic or easy task.
It requires horticultural expertise, business savvy, and an understanding of equipment.
Like greenhouse growers across the country, growers here in Pennsylvania are facing pressure to lower costs to stay competitive in the market.
- [Voiceover] Energy is probably one of the top operating costs for most greenhouse growers, so one of the best ways to help reduce costs is to make your operation more energy efficient.
Energy-efficient greenhouses cost less to operate, and, in some cases, perform better than less efficient facilities.
When you think about the changing, and, often, rising costs of energy, it makes sense to ensure that your greenhouse is as energy efficient as possible.
Today, we are going to tell you about 10 of the most common successful measures that you can use to reduce your energy use without compromising the performance of your greenhouse.
- [Voiceover] Number one, tighten up the house.
- [Voiceover] Many greenhouses are extremely leaky.
There are cracks, holes, and openings in the walls or roof that allow warm air to escape, and cold air to leak in.
This infiltration process can account for a significant portion of a greenhouse's winter heating bill, but they can often be eliminated with the help of a sharp eye, a can of spray foam, and, maybe, a tube of caulk.
Some of the benefits of tightening up the house are that it can reduce heating bills by 5 to 10%, it can improve air flow patterns, and it can make temperature and humidity more uniform throughout the greenhouse.
- [Voiceover] Heat can also leak through metal posts and frames embedded in a greenhouse's walls or roof.
Even if there is not a physical opening that allows hot air to escape, as shown in this picture, the metal, with its high thermal conductivity, provides an easy pathway for heat to move from indoors to outside.
Cover these structural elements with insulation whenever you can.
It's a great way to retain the heat inside the greenhouse.
Your plants will thank you.
- [Voiceover] Number two, add a thermal screen.
- [Voiceover] Clear greenhouse coverings play an important role in allowing sunlight in the house, but, unfortunately, the panels are poor insulators.
Movable thermal screens can help minimize heat loss at night in the winter, without making any permanent changes to your panels.
The screen can be drawn across the roof and the walls of the greenhouse.
They can even serve double duty, providing shade from excessive sunlight in mid-summer, as well as that thermal insulation during winter nights.
The reduction in heating costs will vary, but it can be as high as 30 to 40%.
- [Voiceover] Number three, seal the fans.
- [Voiceover] The fan's louver is supposed to automatically close the fan opening when the ventilation fans are turned off, but bent or malfunctioning louvers are far too common in greenhouses, as shown by the red arrow.
Make sure that the louvers fit flat and tight, as shown by the green arrow.
Gaps or drilled holes around the fan housing can also contribute to air leakage during the winter, leading to higher heating bills.
- [Voiceover] You can seal the fans by repairing malfunctioning louvers, and, also, by covering any holes and cracks, as you can see in this picture.
You can also cover the fan inlet with a sheet of foam insulation board, which you would only need to do during the coldest months, when the fan is not needed.
- [Voiceover] Number four, insulate the perimeter.
- [Voiceover] One of the spots where heat is lost in the winter is along the perimeter of the greenhouse, through the ground, and through the bottom part of the side wall.
The arrow here shows how light below the benchline is wasted anyway, so you might as well insulate that space.
- [Voiceover] You can reduce energy losses by installing an insulated board that extends from the height of the greenhouse's benches, down into the soil along the greenhouse's perimeter.
Typical savings will vary, but are on the order of about 5% for Pennsylvania conditions.
The purple arrow shows how foam insulation can be installed outside during construction or reskinning.
The green arrow shows proper placement of the foam insulation, relative to the greenhouse exterior.
- [Voiceover] Number five, insulate the north wall.
- [Voiceover] The north wall of a greenhouse lets in, surprisingly, little light.
This is especially the case in the winter, when the sun is low in the southern sky.
Because of this, you may find it's cost-effective to cover the wall with insulating board, to reduce heat losses.
This picture shows an insulated north wall with some of the insulation broken away, showing how it is mounted to the greenhouse wall.
Painting the insulation white will enhance light levels in the greenhouse because it can reflect back the winter sunlight that would have, otherwise, passed through the north wall.
- [Voiceover] Number six, upgrade your fans and screening.
Ventilation fans vary in their performance.
If you purchase the cheapest ones available, chances are they're also pretty inefficient.
Now might be the time to upgrade to a higher-efficiency model.
Larger fans are often more efficient than smaller ones, but there can be a lot of variation in efficiency from one to another.
You can find the ventilation efficiency ratio of particular fan models online, or ask the manufacturer.
- [Voiceover] Number seven, upgrade your lighting.
- [Voiceover] While not all greenhouses use electrical lighting, those that do should consider the possibility of upgrading their system to something more efficient.
The cost of lighting can be quite high, especially if lighting systems are kept on for long periods of time.
Here are a few strategies for improving energy efficiency in greenhouse lighting.
Let's go over each strategy.
- [Voiceover] First, consider replacing light sources and using higher efficiency luminaires.
Efficiency ratings for different luminaires are available from the manufacturer.
- [Voiceover] The use of timers and occupancy sensors can help improve efficiency in the area of lighting.
Make sure to use precision controls, to limit overuse, for plant lighting.
- [Voiceover] Are you losing light in your greenhouse?
The use of light-colored curtains can reflect more light back into the greenhouse during night hours.
- [Voiceover] Number eight, clean your fans.
- [Voiceover] Do you care about the fans in your greenhouse as much as you care about your plants?
It's okay if you don't.
Caring about your plants makes you a good grower, but it does pay to care enough about your fans to check them out from time to time.
Make sure they're in good operating order, and see if they need a good cleaning.
Even just accumulated dust on a fan's blades and safety screen can increase your ventilation energy use by as much as 20%.
- [Voiceover] All you really need to fix that is a rag and some elbow grease.
Just don't forget to deactivate the electrical circuit for the fan before you start.
- [Voiceover] Number nine, upgrade your motors.
- [Voiceover] Electrical motors operate most efficiently if they're running at full capacity, so a motor that's bigger than it needs to be will use extra electricity, just to keep itself going.
That leads to additional energy costs, so it's worth it to figure out if that's the case with your motor.
A good electrician can take electrical measurements to determine if it's oversized or not.
The savings from replacing oversized equipment can be significant.
You could also look into switching to energy-efficient motors, which cost a bit more upfront, but use less electricity than the standard motors.
- [Voiceover] It's important to pick the right motor, and a couple of things to consider are the efficiency, the available voltage and phase, and the size, or capacity.
Standard efficiency motors are, typically, 75 to 80% efficient, whereas, high-efficiency ones are closer to 85 to 90%.
If it's practical, switch from single phase to three phase motors.
You should also replace oversized motors with smaller motors that run at 80 to 100% capacity.
- [Voiceover] Number ten, tune the control system.
- [Voiceover] Would you take in your truck for a tuneup?
You need to do the same for your greenhouse's control systems.
Whether you use mechanical controls or a fancy computer system, it's still worth it to check to make sure everything is running properly.
A thorough inspection of the control systems requires a bit of technical knowledge, but, really, anyone can catch some simple problems.
For example, if your ventilation fans are going while the heat is on, there's probably something wrong.
If the lights are on with no plants in the house, it's worth figuring out why.
- [Voiceover] Making your greenhouse more energy efficient is a really great way to reduce your operating costs and improve profitability, but, keep in mind, that not every one of the measures is appropriate for every greenhouse.
Sometimes, an energy conservation measure is simply too expensive to install when you compare it to the expected savings.
A careful energy assessment is the best way to determine which measures are really worth it for your operation, however, there's a good chance that some of these suggestions will help you make your greenhouse more energy efficient and cost-effective in the coming years.
- [Voiceover] Contact your Penn State Extension Office if you have questions, or take a look at Extension's energy efficiency website at energy.extension.psu.edu/efficiency.
Frequently Asked Questions