In heated glasshouses across the UK, energy accounts for a significant portion of production costs. For conventional glasshouse operations relying on gas boilers, energy expenses can climb to 30% of variable costs—a figure that makes energy efficiency not merely advantageous but essential for business viability. Understanding where heat is lost and how to retain it can transform operational economics without requiring complete system overhauls.
Where heat escapes in glasshouses
Heat loss in glasshouse structures occurs predictably through several pathways. The roof and side walls, particularly in older construction, allow substantial heat transfer to the cold external environment. Ventilation—necessary for crop health and disease prevention—represents another significant avenue for heat loss, as warm air is deliberately exchanged to manage humidity and CO₂ levels. Infiltration through poorly sealed cracks and gaps around doors, vents, and roof ventilators compounds the problem, especially during winter months when temperature differentials are greatest.
Understanding heat loss patterns is the foundation for targeted intervention. Many growers fail to recognise that small improvements across multiple areas accumulate into substantial savings.
Thermal screens: reducing nighttime energy demand
Thermal screens have emerged as one of the most cost-effective energy-saving technologies available. These materials—typically constructed from polyester or polythene—are deployed over crops during periods of low light or overnight, then retracted during the day to maximise photosynthesis.
Research published by AHDB demonstrates the substantial savings achievable. Tyvek thermal screens achieve approximately 60% reduction in nighttime energy consumption when drawn, translating to an overall 39% reduction in energy use during the period of deployment. Anti-condensate polythene screens, whilst offering slightly lower performance, deliver 22–26% reductions when used throughout day and night cycles.
The practical appeal of thermal screens lies in their dual benefit: significant energy savings coupled with minimal capital investment and straightforward installation. Many operations recover their investment within a single heating season.
Buffer tanks and combined heat and power systems
More substantial energy infrastructure investments target improved heat management and generation. Buffer tanks—large thermal storage vessels filled with hot water—decouple heating generation from immediate consumption. When a boiler or combined heat and power (CHP) unit produces more heat than the glasshouse requires at any given moment, the excess flows into the buffer tank for later use. This approach smooths demand fluctuations and allows heating equipment to operate at optimal efficiency rather than cycling on and off repeatedly.
Combined heat and power systems generate both electricity and usable heat from a single fuel input, typically natural gas. According to AHDB guidance, a glasshouse operating a CHP unit produces its own electricity whilst capturing waste heat from the engine to warm the greenhouse. Surplus electricity may be sold to the grid, creating an additional revenue stream. The capital investment in CHP is substantial, making it viable primarily for large-scale operations or operations where alternative heat sources justify the infrastructure investment. Heat pumps and CHP systems can be integrated within the same facility to optimise year-round energy production and storage.
Heat pumps and alternative heating
Industrial heat pumps, increasingly deployed in UK horticulture, extract heat from air, water, or ground sources and concentrate it for greenhouse heating. Whilst the electrical energy required to drive compressors represents a significant operating cost, heat pumps excel when renewable electricity is available or when waste heat from other processes can be recycled. They produce substantially less CO₂ than direct gas combustion and align with decarbonisation strategies.
Heat pump economics depend heavily on electricity prices and system design. Pairing a heat pump with a buffer tank optimises the arrangement: the pump operates during periods of lower electricity demand or peak renewable generation, storing heat for later use.
Climate control optimisation: setpoints and ventilation
Fine-tuning heating and ventilation setpoints delivers energy savings without capital expenditure. Minimum pipe temperature settings—the threshold below which circulating heating fluid is warmed before entering greenhouse heating pipes—are frequently set higher than necessary. Reducing these settings from typical values of 45–50°C to 35°C or lower, adjusted dynamically based on solar radiation, cuts energy input whilst maintaining adequate crop protection.
Equally important is coordinating ventilation settings with heating targets. The ventilation temperature setpoint must remain at least 0.2°C above the heating setpoint; allowing this gap to narrow forces vents open at lower temperatures, wasting heat. Permitting greenhouse temperatures to rise naturally through solar gain before raising the ventilation setpoint, rather than opening vents to dump excess warmth, captures free energy.
Accessing technical guidance through GrowSave and AHDB
The knowledge required for effective energy management need not be sourced from consultants alone. GrowSave, a long-established initiative now independent of AHDB funding, provides free or subsidised technical information on energy-saving techniques. The programme supplies guidance on screens, ventilation, CO₂ dosing, and alternative energy technologies through articles, quarterly newsletters, and training courses. AHDB continues publishing detailed technical guidance on minimum pipe settings, humidity control, and system integration, with research supporting evidence-based decision-making.
Key points
- Energy costs represent approximately 30% of variable expenses in heated glasshouses, making efficiency improvements directly profitable.
- Thermal screens deliver 22–60% nighttime energy reductions depending on material and deployment strategy.
- Buffer tanks and CHP systems improve efficiency by matching heat generation to demand and creating additional revenue through electricity sales.
- Fine-tuning temperature setpoints and ventilation logic saves energy without capital investment; minimum pipe temperatures can be reduced from 45–50°C to 35°C with proper controls.
- Free technical resources from AHDB and GrowSave support evidence-based energy management decisions.
Related service: Agricultural consulting services