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To use less energy in a heated greenhouse, reduce heat loss before changing the heater: repair leaks in the covering and around doors and vents, then assess whether a well-fitted thermal screen suits your crop and structure. After that, improve heat distribution and tune the temperature schedule to the crop’s needs. Screens and lower night settings can reduce demand, but neither has one specification or setting that works for every greenhouse.
Start with the heat that is escaping
A heater must replace heat lost through the greenhouse covering and through air leakage. That makes the envelope—the covering, joints, doors, vents and foundation edges—the first place to look for avoidable energy use. A larger or newer heater will not fix a leaking door or damaged film; it may simply keep supplying heat that continues to escape.
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Inspect and repair the covering
- Look for visible damage. Check glazing or film for tears, cracks, loose sections and failed joints. Repair or replace damaged areas with materials appropriate to the existing covering and its installation.
- Check openings and edges. Inspect doors, vents and the areas where the covering meets the frame or foundation. Gaps can let warm air out and cold air in, so make sure closures fit and operate as intended.
- Recheck after repairs. Confirm that doors and vents close properly and that repairs remain secure. Include these checks in routine greenhouse maintenance rather than waiting for a cold spell to reveal a problem.
Farm Energy’s greenhouse checklist discusses double covering and insulation as additional ways to reduce losses. Whether either is practical depends on the structure and covering; historical cost or payback estimates should not be treated as current quotes.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteUse U-values as a comparison, not a guarantee
A U-value describes heat transfer through a material: all else equal, a lower value means less heat passes through it. The values below are illustrative figures reported by DPIRD, not measurements of every product or installed greenhouse. Real performance depends on the material, condition, assembly and installation.
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| Covering or layer | Illustrative U-value (W/m²·K) | Source and qualification |
|---|---|---|
| Single polythene film | 7.5–8.5 | DPIRD table value; actual installations may differ. |
| Double polythene | 4.0–5.0 | DPIRD table value; actual installations may differ. |
| Double-wall polycarbonate | 3.5 | DPIRD table value; actual installations may differ. |
| Glass, 3 mm | 7.0–8.0 | DPIRD table value; actual installations may differ. |
| Thermal screen | 2.8 | DPIRD table value; do not assume every screen or installation matches it. |
These figures help explain why adding a layer can matter, but they do not predict a particular grower’s fuel bill. Leakage, greenhouse geometry, weather, operating hours and the screen’s edge closure also affect the result. They are not a complete ranking of every covering assembly: the cited figures describe particular material categories, and installation quality affects how a real greenhouse performs.
Assess whether a thermal screen fits your greenhouse
A greenhouse thermal curtain, also called an energy screen, adds a barrier between the crop space and the roof or upper greenhouse volume. Depending on its design and how it is fitted, it can trap air, reduce the area through which heat is lost, and reflect some infrared radiation back toward the crop. At night, closing a screen can also mean less greenhouse air volume has to be kept warm.
The potential savings are meaningful but variable. University of Wisconsin Extension publication A3907-03 by Scott Sanford reports nighttime heat-loss reductions of 20–75% across curtain materials and says some growers saved 30–50% on heating bills. Those are different measures: a reduction in heat loss through curtain materials does not guarantee the same reduction in fuel use or cost. UMass Amherst’s Center for Agriculture, Food, and the Environment says heating-cost savings of 30–50% are common in many installations. These are source-reported ranges, not promises for a particular greenhouse.
Sanford’s publication states that “70 to 80% of greenhouse heating occurs at night” and argues that growers can realize substantial savings by using thermal curtains at night. Treat that share as the publication’s reported figure, not a current measurement for every greenhouse. Your own nighttime share depends on climate, structure, crop temperature requirements and operating schedule.
Compare screen characteristics that affect crop conditions
- Thermal performance and fit: Look at the screen’s intended thermal function and whether it can close across the greenhouse with minimal gaps. Edge closure and compatibility with the structure matter; a nominal material value cannot compensate for a poorly fitted screen.
- Light transmission and shading: Check how the screen affects the light reaching the crop, especially if it will be closed during periods when plants need light. A thermal screen should not be operated as if light were irrelevant.
- Humidity and permeability: Consider how the material and operating schedule affect moisture management. Some fabrics are permeable or combine functions, but suitability depends on the crop and greenhouse conditions.
- Function: Screens may be designed for thermal retention, shading, light abatement or more than one purpose. Government of Ontario guidance reports that some light-abatement curtains that also act as thermal curtains reduce nighttime heat loss by around 50%; performance varies by model.
- Operation: Decide whether manual or automated opening and closing is appropriate for the greenhouse. Controls should follow crop light and humidity needs as well as temperature, rather than simply closing as early as possible.
- Durability and installation: Account for the material’s expected use, greenhouse geometry and installation requirements. A screen that cannot be operated reliably or closed consistently may not deliver its intended benefit.
Do not choose a screen from a savings percentage alone. Compare its thermal purpose, light effect, permeability, fit and operating requirements against the crop’s needs and the way the greenhouse is actually used.
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Think through whole-season economics
A screen decision involves more than the fabric’s advertised performance. The relevant comparison is the screen and installation cost against the heating demand it may help avoid over the seasons it will be used. That outcome depends on local climate, greenhouse geometry, existing envelope condition, fuel prices, operating schedule and crop requirements. The cited publications do not establish a current price, standard payback period or guaranteed savings for a particular installation.
When comparing options, account for the screen, its fit to the structure, how it will be operated, and whether automation is needed for consistent opening and closing. A low-cost material that does not suit the crop’s light or humidity requirements is not necessarily the right value. Similarly, a high quoted savings percentage cannot substitute for understanding how the number was measured or whether the cited conditions resemble your greenhouse. Ask suppliers for specifications relevant to your structure and verify product-level claims; no independent current comparison of named commercial models is established here.
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Operate the screen around light, temperature and moisture
Closing a screen can conserve heat, but timing and operation affect the crop environment. Closing it too early may reduce useful light; operating it without regard to humidity can create conditions that do not suit the crop. The right schedule depends on the greenhouse, crop, season and available controls.
- Identify the crop’s requirements. Establish the temperature and light conditions needed for the crop and its current growth stage. Include production timing and local conditions rather than relying on a generic greenhouse setting.
- Choose a screen schedule that preserves crop conditions. Consider when the screen can be closed to limit nighttime loss and when it must open to provide needed light. A screen with more than one function may involve trade-offs among heat retention, shading and light abatement.
- Account for moisture. Consider whether the screen material and its operating pattern allow appropriate humidity management. Do not assume that a thermal benefit alone makes a material suitable for the crop.
- Review how the system is working. Check that the screen closes as intended and that its schedule remains appropriate as crop needs and growing conditions change.
Ontario’s approximate 50% figure applies to some combined light-abatement and thermal curtains, with results varying by model; it is not a universal screen specification or a guarantee of bill savings. No independent current comparison of named commercial models is established here, so evaluate product-level claims against specifications for the screen and conditions you intend to use.
Deliver heat evenly and operate equipment efficiently
Once avoidable losses and screen suitability have been addressed, look at how heat reaches the crop. DPIRD discusses hot-air and hydronic heating approaches and recommends even distribution, with heat applied low where suitable. The right approach depends on the greenhouse and crop; a general rule should not replace an assessment of the system’s layout and requirements.
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Check heat distribution
- Look for areas that receive noticeably different heat from the rest of the growing space.
- Consider whether the system distributes heat evenly at crop level, rather than concentrating it in one area or allowing warm air to remain high above plants.
- Where appropriate for the structure and crop, evaluate low-level heat delivery. DPIRD recommends applying heat low where suitable, not as an unconditional instruction for every system.
- Have system layout and changes assessed for the greenhouse and crop rather than assuming that adding heaters will solve uneven temperatures.
Maintain the heating system
Maintain heaters and use a system suited to the greenhouse. Efficiency figures reported for a heater category or older publication are not a substitute for the current specifications of a particular model, nor for local sizing advice. Multiple heaters may provide resilience, but selection, sizing and safe installation require qualified advice.
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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteWhen considering a change, distinguish equipment efficiency from whole-greenhouse energy use. A more efficient heater can reduce the energy needed to deliver a given amount of heat, but it does not eliminate losses through a damaged covering or a poorly closed screen. The envelope, heat distribution and operating schedule all influence the result.
Set temperatures for the crop, not a generic rule
A lower night set point may reduce heating demand if the crop and production schedule can tolerate it. DPIRD presents this as a possible strategy and discusses a 24-hour temperature regime; it does not establish one suitable temperature for all crops. Acceptable temperatures depend on crop type, growth stage, production target and local conditions.
- Define the crop’s acceptable conditions. Base temperature decisions on the crop and stage of growth, not on a single target copied from another greenhouse.
- Assess the production trade-off. Decide whether a lower nighttime target is compatible with the production schedule and crop outcome you need. Lowering a set point is not an energy saving if it compromises the conditions required for production.
- Consider the 24-hour regime. Evaluate nighttime temperature as part of the broader daily temperature pattern rather than in isolation, consistent with DPIRD’s discussion of a 24-hour regime.
- Adjust controls deliberately. Make changes that the greenhouse’s control system can implement and maintain, and check that the operating schedule remains aligned with crop needs.
There is no defensible universal night temperature in the available guidance. A crop-aware change is a decision to assess, not a recommendation to lower every greenhouse’s thermostat by a fixed amount.
Estimate savings without treating published ranges as promises
Published figures describe different outcomes and should not be combined as if they were one expected payback. The Wisconsin Extension publication reports a range for nighttime heat-loss reduction across curtain materials and a separate range of savings reported by some growers. UMass reports common heating-cost savings in many installations. Ontario reports an approximate nighttime heat-loss reduction for some dual-purpose curtains. None guarantees what a specific grower will save.
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| Reported figure | What it describes | Source and limitation |
|---|---|---|
| 20–75% | Nighttime heat-loss reductions across curtain materials | University of Wisconsin Extension, A3907-03, by Scott Sanford; not guaranteed fuel savings. |
| 30–50% | Heating-bill savings reported for some growers | University of Wisconsin Extension, A3907-03; publication date not stated. |
| 30–50% | Heating-cost savings described as common in many installations | UMass Amherst Center for Agriculture, Food, and the Environment; page date not stated. |
| Around 50% | Nighttime heat-loss reduction for some light-abatement curtains that also function as thermal curtains | Government of Ontario; performance varies by model and page date is not stated. |
| 70–80% | Share of greenhouse heating occurring at night, as stated in the publication | University of Wisconsin Extension, A3907-03, by Scott Sanford; not a current measurement for every greenhouse. |
The actual result depends on climate, greenhouse geometry, fuel prices, the condition of the existing envelope, screen installation and operation, and crop needs. A grower starting with a tight structure may have a different opportunity from one with damaged covering or major air leaks. Without those details, a published range cannot establish a greenhouse-specific saving, cost or payback period.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Use a practical order of work
Prioritize actions in the order that addresses the causes of heat demand and avoids buying equipment before understanding the structure.
- Repair avoidable leaks. Inspect covering, doors, vents and foundation areas; maintain tight closures and repair damage.
- Assess additional envelope measures. Consider double covering or insulation only where appropriate to the existing greenhouse, recognizing that historical cost estimates are not current prices.
- Evaluate a thermal screen. Compare fit, thermal purpose, light transmission, humidity implications, permeability, durability and operation against crop requirements.
- Improve heat delivery. Review whether the current hot-air or hydronic system distributes heat evenly and whether low-level delivery is suitable.
- Maintain and assess equipment. Use a system appropriate to the greenhouse; obtain qualified advice for sizing and safe installation, particularly if adding heaters.
- Review the temperature schedule. Consider a lower nighttime set point only when compatible with crop stage and production goals, and treat the full 24-hour regime as relevant.
This sequence keeps the decision anchored to the greenhouse: first limit unnecessary loss, then assess the screen and system, then tune operation around the crop.
Choosing products and getting advice
If you are shopping, the directly relevant product category is a greenhouse thermal curtain or greenhouse energy screen. Compare the material’s intended function, light transmission, permeability, fit, durability and operating requirements rather than relying on a headline savings claim. Greenhouse covering repair or insulation materials and environmental controls may also be relevant, but they are secondary choices and should be matched to the particular structure and operating needs.
For installation or equipment changes, seek advice suited to the greenhouse geometry, crop and local conditions. Heater sizing and safe installation require qualified advice. A supplier or installer may be able to explain whether a screen fits the structure and how it will operate, but individual product specifications should be checked directly; the cited guidance does not validate particular listings, current incentives or affiliate programs.
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Frequently Asked Questions
How much energy can a greenhouse thermal curtain save?
The figures vary and describe different outcomes. University of Wisconsin Extension publication A3907-03 reports nighttime heat-loss reductions of 20–75% across curtain materials and says some growers saved 30–50% on heating bills. UMass Amherst says heating-cost savings of 30–50% are common in many installations. These ranges are not guarantees; climate, fit, greenhouse condition, operating schedule, fuel prices and crop needs all matter.
Should I close the greenhouse screen as early as possible?
Not automatically. Closing a screen can reduce nighttime heat loss, but closing too early may reduce useful light. The schedule should also account for humidity, crop requirements and the screen’s permeability and intended functions.
What night temperature should I set in a heated greenhouse?
There is no universal night temperature in the cited guidance. A lower night set point may reduce demand only when the crop, growth stage and production schedule can tolerate it. Consider nighttime temperature as part of the crop’s 24-hour temperature regime.
Is double covering always more efficient than single covering?
DPIRD’s illustrative U-values are lower for double polythene (4.0–5.0 W/m²·K) than for single polythene film (7.5–8.5 W/m²·K), but these are source table values, not guarantees for every installed greenhouse. The structure, covering condition, assembly and air leakage affect actual performance, and whether double covering is practical depends on the existing greenhouse.
What should I compare when buying a greenhouse energy screen?
Compare thermal performance and fit, light transmission and shading, humidity implications and permeability, durability, greenhouse geometry, and manual or automated operation. Check that the screen’s function suits the crop and that it can close reliably; a savings percentage alone is not enough to judge suitability.
The Bottom Line
Use less energy by addressing heat loss in order: repair leaks and damaged covering, assess a well-fitted thermal screen for the crop, improve even heat delivery, and adjust the temperature schedule only within crop requirements. Published savings ranges can guide comparison, but they are not guarantees for an individual greenhouse.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
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