Thermal Screen Calculator

Enter Greenhouse and Screen Details

Units are metric. Adjust advanced options for better estimates.

Length (m)

Long side of the greenhouse floor.

Width (m)

Short side of the greenhouse floor.

Average Height (m)

Used for infiltration heat loss.

Surface Area Multiplier

Typical range: 1.10–1.60.

Inside Temp (°C)

Target temperature near plants.

Outside Temp (°C)

Typical cold-night temperature.

Cover U-Value (W/m²·K)

Lower is better insulation.

Screen Reduction of Conductive Loss (%)

Common range: 20–50%.

Air Changes per Hour (ACH)

Tighter houses: 0.5–1.0 ACH.

Heating Hours per Day

Night heating is often 8–14 hours.

Season Days

Length of your heating season.

Heater Efficiency (%)

Include combustion or system losses.

Energy Price (per kWh)

Use your local electricity equivalent price.

Thermal Screen Cost (per m²)

Used for payback estimate.

Reset

Tip: If results look too low, raise the Surface Area Multiplier or ACH.

Greenhouse (m)	Inside/Outside (°C)	U-Value	Screen Reduction	ACH	Season Days	Estimated Seasonal Savings*
10 × 6 × 3	18 / 2	5.8	35%	1.0	120	Moderate
18 × 8 × 4	16 / 0	3.2	45%	0.8	150	High
6 × 4 × 2.5	15 / 5	6.0	25%	1.5	90	Low

*Savings depend on energy price and heater efficiency. Run your own numbers for accurate budgeting.

Effective surface area: A = (Length × Width) × Multiplier
Conductive heat loss: Qc = U × A × ΔT (watts)
Infiltration heat loss: Qi ≈ 0.33 × ACH × Volume × ΔT (watts)
With thermal screen: Qc_screen = Qc × (1 − Reduction%)
Total heat loss: Qtotal = Qc + Qi
Energy use: kWh = (Qtotal ÷ 1000) × Hours ÷ Efficiency
Cost: Cost = kWh × Price
Payback: Seasons = ScreenCost ÷ SeasonalSavings

These are planning-grade estimates. Real results vary with wind, humidity, gaps, and screen installation quality.

Enter your greenhouse length and width, then set average height.
Set target inside temperature and a typical cold-night outside value.
Adjust U-value and the surface area multiplier to match your cover.
Pick a screen reduction percent based on your screen type.
Add ACH, heating hours, season days, efficiency, and energy price.
Press Calculate to see savings and payback above.
Use Download CSV or Download PDF for records.

Heat loss profile and where screens help most

Greenhouse heat demand is driven by two main components: conductive loss through the cover and infiltration loss from air leakage. A thermal screen primarily lowers conductive loss, so benefits grow when U-values are high, surface area is large, and temperature difference (ΔT) is steep. If ACH is high, tightening vents, doors, and seams can deliver similar savings to a screen.

Interpreting U-value, multiplier, and ΔT settings

Use U-value to represent the cover’s insulation level; lower numbers indicate better performance. The surface area multiplier converts floor area into an effective skin area for walls and roof. ΔT is inside minus outside temperature, so small changes matter: raising inside setpoint from 16°C to 18°C increases ΔT by 2 K and proportionally increases both conductive and infiltration losses.

Infiltration, ventilation habits, and practical ACH choices

ACH represents how often greenhouse air is replaced each hour. Calm nights with well-sealed structures can be near 0.5–1.0 ACH, while windy sites and frequent door openings may exceed 2.0 ACH. Because infiltration loss scales with volume, tall houses can lose more heat even with the same floor area. Track drafts and adjust ACH until estimates match experience.

Seasonal energy, cost planning, and payback logic

Seasonal kWh depends on heating hours and the number of cold days. Heater efficiency converts delivered heat into purchased energy, so an 85% system needs more input than a 95% system for the same load. Payback compares installed screen cost against seasonal cost savings; use realistic prices and include maintenance or replacement in your budgeting.

Example data to validate your setup quickly

Try this reference case and compare the output to your baseline:

Size: 12 m × 6 m × 3 m, Multiplier: 1.30, U-value: 5.5 W/m²·K
Temperatures: 18°C inside, 1°C outside, Screen reduction: 40%
ACH: 1.0, Heating: 10 hr/day, Season: 120 days, Efficiency: 85%
Energy price: 0.20 per kWh, Screen cost: 12.00 per m²

1) What does the surface area multiplier represent?

It converts floor area into an estimated cover area for walls and roof. Use higher values for taller, arched, or multi-span houses, and lower values for compact, low-profile structures.

2) Does the screen reduce infiltration heat loss too?

This calculator assumes the screen reduces conductive loss only. Some installations may slightly reduce drafts, but infiltration is mainly controlled by sealing, vent management, and wind exposure.

3) How do I choose a realistic ACH value?

Start with 0.8–1.2 for a well-sealed greenhouse on calm nights. Increase toward 2.0+ for windy sites, frequent door use, or obvious leaks, then calibrate against observed fuel use.

4) Why is heater efficiency included?

Efficiency converts the heat load into purchased energy. Lower efficiency means you buy more kWh (or fuel equivalent) to deliver the same heat to plants, raising seasonal cost.

5) What if outside temperature is higher than inside?

For heating loss estimates, inside should be higher than outside. If your scenario is cooling, the physics differs and screen impact may change; use the tool only for heating planning.

6) Can I use non-electric heating prices?

Yes. Enter an equivalent cost per kWh of delivered energy. Convert your fuel price to kWh using the fuel’s energy content, then reflect system efficiency in the calculator.

7) How accurate are the results?

Results are planning-grade. Wind, humidity, thermal mass, gaps, and screen installation quality can shift real usage. Adjust ACH and multiplier to match your greenhouse behavior over several cold nights.