For commercial growers, heating a glasshouse through the colder months can come with significant operating costs. Maintaining the right temperature is essential for crop performance, but every unnecessary degree of heat produced – or lost through the structure – has a direct impact on the energy bill.
Creating a more energy efficient greenhouse does not necessarily mean replacing the entire structure or investing in completely new technology. In many cases, significant improvements can be made by looking at where heat is being lost, how effectively it is being distributed and whether existing systems are operating as they should.
With energy costs continuing to put pressure on growers, improving efficiency should be considered as much a part of routine glasshouse management as crop care itself.
- Keep the heat you have already paid for
One of the first principles of an efficient greenhouse is simple: reduce unnecessary heat loss.
Commercial glasshouses have a large external surface area, so heat can escape through the roof, sides and gables. Gaps, damaged glazing, worn seals and poorly insulated areas can all make the heating system work harder to maintain the required internal temperature. The harder the glasshouse heating system has to work to maintain the desired temperature, the higher the energy bill.
Therefore, it’s vital to carry out regular inspections in commercial greenhouses. Broken or slipped panes, damaged polycarbonate, gaps around doors and vents, deteriorated seals and other defects should be dealt with before cold weather places greater demand on the heating system.
UK government guidance for protected horticulture specifically recommends insulating walls, roofs and heating pipes where appropriate, alongside maintaining boilers and burners and controlling temperatures accurately.
Improving insulation is particularly valuable in parts of a site where maximum light transmission is not essential. Packing areas, workspaces, storage areas and other sections of an existing glasshouse can, for example, potentially be converted using insulated sandwich panels to create a comfortable environment for everyone on site.
Rather than continually heating a poorly insulated space, improving the building envelope helps retain more of the energy being put into it.
- Make better use of thermal screens
Energy screens are one of the most established methods of reducing heat loss from commercial glasshouses.
When closed, a suitable screen creates an additional insulating layer between the crop and the colder glasshouse roof. This reduces heat transfer and thermal radiation losses, helping retain warmth around the growing area.
Wageningen University research has demonstrated substantial savings from energy screens, although the exact figure varies according to the screen material, glasshouse, climate strategy and crop. This is why choosing the right screen system is so important. At GVZ Glasshouses, we work with Alweco as our screen supplier because we trust the quality of their systems and the breadth of options they offer. With a wide choice of screen materials and configurations available, we can help specify a solution that suits the individual glasshouse, crop and growing requirements.
However, simply relying on your glasshouse screen installation does not automatically make the glasshouse efficient.
Its condition and how it is controlled are equally important.
When carrying out an inspection of your greenhouse climate screens, look for:
- tears or damaged screen material
- gaps around the sides and gables
- poor closing or alignment
- worn drive components
- dirty or ageing material
- outdated control settings
Modern screening technology can also use outside temperature, radiation, humidity and crop requirements to determine when screens should open and close rather than relying purely on fixed times and operating screens manually.
When screens are worn or perform poorly, have gaps and/or outdated operating systems, their effectiveness is greatly reduced, and the risk of heat loss in your greenhouse increases.
- Avoid heating unevenly
An energy efficient greenhouse is not simply one that uses less heat. It is one that uses the heat it produces as effectively as possible.
Poor air movement can result in hot and cold areas throughout a glasshouse. If sensors are positioned in a warmer area while part of the crop is sitting in a cold spot, it becomes difficult for the climate computer to represent what is actually happening across the growing area.
The result can be additional heating, inconsistent crop conditions and areas of higher humidity or condensation, all due to uneven heat distribution.
Air circulation can help distribute heat and moisture more evenly. Ensuring there is good air movement in your glasshouse is one of the ways to reduce temperature variations and minimise cold spots, potentially reducing the need to use additional heating purely for humidity control.
Temperature and humidity sensors should also be correctly positioned, maintained and calibrated. Data is only useful when the information feeding into the control system accurately reflects conditions around the crop.
- Maintain the heating system
Efficiency improvements do not always require new equipment.
A poorly maintained heating system may consume more fuel simply to achieve the same result as a properly serviced one, unnecessarily increasing your glasshouse energy bill.
All components of your greenhouse heating set-up like boilers, burners, pumps, valves, pipework and control systems should therefore be part of a regular preventative maintenance schedule rather than only receiving attention when something stops working. In attempts to reduce spending, regular maintenance and servicing is often delayed until something breaks, leading to more costly repairs and equipment replacements than if it had been tended to regularly. So, in an effort to save money, energy efficiency is compromised and the grower’s business is at risk of experiencing undesired downtime.
Our general good-practice guidance for growers recommends regular servicing and maintaining of boilers and burners, and ensuring precise control of the required temperature regime.
Pipework outside areas where the heat is useful should also be properly insulated. There is little benefit in generating heat efficiently if a proportion of it is then lost before reaching the area where it is actually required.
- Look carefully at your climate settings
Small changes to temperature strategy can have a surprisingly large effect over an entire heating season.
That does not mean simply turning the temperature down. Crop requirements must always come first.
Instead, look at whether heating set points, ventilation, humidity control and screen operation are working together efficiently.
For example, simultaneously heating and ventilating excessively can waste significant amounts of energy. Similarly, unnecessarily opening an energy screen to control humidity can release valuable heat.
Research into energy-efficient greenhouse growing repeatedly shows that heating, humidity, screens and ventilation need to be considered as a connected climate strategy rather than as separate systems.
The right strategy will depend on the crop and the glasshouse, which is why accurate monitoring is so important.
- Use your data
Before investing heavily in glasshouse heating upgrades, you need to understand where your energy is currently going.
Conducting an energy audit can help establish:
- total heat consumption
- when peak demand occurs
- energy use by glasshouse or growing zone
- unusual changes in consumption
- differences between similar compartments
- whether improvements have genuinely reduced energy use
Capturing data and energy auditing are important tools for identifying, quantifying and prioritising glasshouse efficiency improvements.
Without a baseline, it can be difficult to know whether a change has actually delivered the expected saving.
- Consider heat storage and alternative heat sources
For some sites, improving the way heat is generated and stored can offer further opportunities to achieve energy efficiencies.
A thermal buffer or heat store can allow a heat generator to operate for longer, steadier periods instead of repeatedly switching on and off as glasshouse demand changes. This can reduce inefficient cycling and allow stored heat to respond to fluctuations in demand.
Larger commercial glasshouse sites may also investigate technologies such as heat pumps, biomass, CHP or other lower-carbon heat sources.
However, because no glasshouse environment is the same, there is no universal answer how to achieve the ultimate energy efficient environment. Crop requirements, site infrastructure, electricity and fuel costs, heat demand and capital expenditure all need to be considered before choosing a new heating technology.
Start with the glasshouse you already have
When businesses think about creating an energy efficient commercial greenhouse, there’s often an immediate assumption this requires investing in major new equipment.
However, the first question should be:
Are we making the best possible use of what we already have?
A well-maintained structure, correctly operating screens, accurate sensors, efficient heating equipment, good air movement and preventative maintenance and regular servicing can all contribute towards reducing unnecessary energy consumption.
Only after understanding the existing system is it possible to make an informed decision about where further investment will provide the greatest return.
At GVZ Glasshouses, we work with commercial growers, nurseries and garden centres across the UK on the maintenance, repair and improvement of existing glasshouse structures. From screening systems and ventilation equipment to polycarbonate roofs, insulated sandwich panel conversions and general glasshouse maintenance, there are many ways an existing site can be upgraded to perform more efficiently.
Want to discuss ways to improve the efficiency of your glasshouse before the next cold spell?
We’d love to have a chat.
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