Most Greenhouse Heating Conversations Begin With Equipment. We Think They Should Begin With Energy.
One of the first questions people ask us is usually straightforward:
"What's the best way to heat my greenhouse?"
It's a fair question. Heating is one of the largest operating expenses for greenhouse operators, especially during winter months and shoulder seasons when temperatures can change dramatically between day and night. Every year, growers look for better heaters, more efficient fuel sources, improved controls, or larger systems capable of keeping temperatures where they need to be.
But after spending years working around thermal storage, we've found ourselves asking a different question.
What if the biggest opportunity isn't creating more heat?
What if it's keeping more of the heat your greenhouse already receives every single day?
That may sound like a subtle distinction, but we've come to believe it's one of the most important mindset shifts happening within greenhouse design today.
Greenhouses are remarkably efficient at collecting solar energy. The challenge has never been getting warm during the day. The challenge begins after sunset, when much of that free energy slowly disappears and heating systems begin replacing what was naturally available only a few hours earlier.
The sun rises.
The greenhouse warms.
The sun sets.
The heat begins to leave.
The heater turns on.
Tomorrow, the cycle repeats.
For decades, most conversations have focused on the last step of that cycle.
We think they should start with the first four.
WHY GREENHOUSES LOSE HEAT SO QUICKLY
One of the remarkable things about a greenhouse is also one of its greatest challenges.
The same glazing that allows sunlight to pour into the structure throughout the day also allows heat to escape once outside temperatures begin falling. Every greenhouse is constantly exchanging energy with the environment around it. During daylight hours that exchange generally works in the grower's favor. At night, it begins working against them.
This isn't a design flaw—it's simply physics.
Heat naturally moves toward colder environments. As outside temperatures fall, the greenhouse begins giving back much of the thermal energy it collected throughout the day. Heating systems respond by replacing those losses, often cycling repeatedly throughout the evening and overnight hours.
Researchers have studied greenhouse heat loss for decades because it remains one of the largest contributors to energy consumption in controlled environment agriculture. Work from Cornell University's Greenhouse Engineering Program and other agricultural engineering researchers continues to emphasize that reducing heat loss is often just as important as increasing heating capacity. The most efficient greenhouse isn't necessarily the one producing the most heat. It's often the one that wastes the least.
That observation has shaped how we think about thermal storage.
WHAT PASSIVE HEATING REALLY MEANS
The phrase passive greenhouse heating sometimes creates the wrong impression.
It doesn't mean operating a greenhouse without heaters. It doesn't mean eliminating furnaces or boilers, nor does it mean hoping the weather cooperates. Passive heating simply means making better use of the energy a greenhouse naturally receives before asking another system to replace what has already been lost.
Growers have been experimenting with this idea for generations.
Water barrels became one of the most recognizable examples because they were inexpensive, readily available, and capable of storing solar heat throughout the day. Others incorporated concrete floors, masonry walls, insulated north walls, underground air systems, thermal curtains, and a wide variety of passive solar greenhouse designs. While the materials differed, the objective never really changed.
Capture available energy.
Hold onto it longer.
Reduce how much replacement energy becomes necessary after sunset.
The technology has evolved over time, but the philosophy has remained remarkably consistent. Every passive heating strategy is ultimately attempting to answer the same question:
How do we make better use of the energy we're already given each day?
WHY THE CONVERSATION IS CHANGING
One thing we've noticed over the last several years is that growers are asking different questions than they used to.
Years ago, conversations often centered around heater size, fuel type, or output capacity. Today, those discussions increasingly include insulation, environmental controls, energy efficiency, thermal storage, and temperature stability.
That's encouraging.
Because once the conversation shifts from producing more heat to managing existing heat more effectively, entirely new opportunities begin appearing.
Instead of asking,
"How much bigger of a heater do I need?"
many greenhouse operators are beginning to ask,
"Why is my greenhouse losing so much heat in the first place?"
Those are very different conversations.
One focuses on equipment.
The other focuses on energy.
We believe the second question is the more important one.
WHERE THERMAL STORAGE FITS
This is where thermal storage becomes particularly interesting.
We've never viewed phase change materials as a replacement for greenhouse heating systems. In our minds, they've always been another way to manage the energy already flowing through a greenhouse each day.
During daylight hours, excess thermal energy is available.
Several hours later, that same energy is needed.
The challenge has always been connecting those two moments.
Traditional thermal mass systems have attempted to bridge that gap for decades. Phase change materials represent another approach—one designed to capture thermal energy when it's abundant and release it later as temperatures begin changing.
That same philosophy is now being explored across commercial buildings, refrigerated transportation, cold-chain logistics, and energy-efficient construction. Across each of these industries, the conversation is becoming less about generating additional energy and more about making better use of the energy already available.
Greenhouses are simply another place where that evolution is taking place.
WHY THIS MATTERS
Passive greenhouse heating isn't really about replacing heaters.
It's about asking less of them.
A greenhouse that retains more of its daytime energy may experience fewer temperature swings, reduced heater cycling, more consistent environmental conditions, and potentially lower overall energy demand. None of those outcomes occur because passive systems create additional heat. They occur because less energy escapes before it can be used.
That distinction is important.
Efficiency isn't always about producing more.
Sometimes it's about wasting less.
Fore Energy Perspective
One of the biggest lessons we've learned is that the future of greenhouse heating probably won't be defined by larger furnaces, higher BTU ratings, or more sophisticated heating equipment.
We believe it will be defined by how intelligently growers manage the energy their greenhouse already receives every single day.
Every morning, the sun provides an incredible amount of thermal energy completely free of charge. Our job isn't to create more of it. Our job is to keep more of it working after the sun goes down.
That's ultimately why we've become so passionate about thermal storage.
— Brent Wiltz, Founder, Fore Energy
FINAL THOUGHTS
Passive greenhouse heating has been around for decades, and the principles behind it remain remarkably simple.
Collect energy.
Store energy.
Use energy more effectively.
What's changing isn't the philosophy.
It's our ability to execute it.
As greenhouse technology continues advancing, we believe the conversation will continue moving away from simply installing larger heating systems and toward designing smarter thermal systems that capture, retain, and reuse energy more effectively.
Because after years of studying thermal storage, we've come to believe that the best greenhouse heating strategy isn't necessarily creating more heat.
It's making better use of the heat you already have.
Research & Industry Sources Referenced
- Cornell University Greenhouse Engineering Program
- Passive Solar Greenhouse Research
- Controlled Environment Agriculture Research
- Greenhouse Heat Loss Studies
- Building Science & Thermal Mass Research
- Phase Change Material Thermal Storage Literature
Topics Discussed
- Passive Greenhouse Heating
- Greenhouse Heating Costs
- Thermal Storage
- Phase Change Materials
- Greenhouse Heat Loss
- Solar Heat Gain
- Energy Efficiency
- Controlled Environment Agriculture
- Environmental Control
Continue Reading
- PCM vs. Water Barrels for Greenhouses: Which Stores Heat Better?
- Why Greenhouse Temperature Stability Matters More Than Temperature Alone
- How Much PCM Does a Greenhouse Need?
- Phase Change Materials for Greenhouses: What It Is and How It Works