Shade Cloth Transmission and Solar Heat
Multiplies glazing and cloth transmission to the light the crop actually receives.
Example
You enter
- Outdoor DLI (mol/m^2/day) 45
- Glazing transmission (%) 65
- Shade cloth (%) 50
- Crop target DLI (mol/m^2/day) 20
- Outdoor peak solar (Btu/h per sq ft) 290
- Floor area (sq ft) 2880
You get
- System transmission (%) 32.5
- DLI at the crop 14.63 mol/m^2/day -- SHORT of target by 5.38
- Shade that lands on the target 31.6% cloth
- Under two layers 7.3125
- Two layer share of target (%) 36.5625
- Intensity through the envelope 189 Btu/h/sq ft glazed, 94 under the cloth
- Solar heat the cloth removes 271440
- Solar removed (ton) 22.62
Checked against published worked examples from: Virginia Cooperative Extension.
Details, formula, and sources
ScopeFinds the shade percentage that lands on the crop target, and prices the solar heat removed. A 50% cloth under 65% glazing passes 32.5%, and two layers pass a quarter of what reaches them (16.25% of outdoor light) rather than nothing.
Formula or tablesystem transmission = glazing transmission x (1 - shade fraction), multiplied again per layer; inside DLI = outdoor DLI x system transmission; solar removed = (glazed - shaded) intensity x floor area.
Source and editionCloth manufacturer transmission data measured on the installed fabric, and the crop's own DLI requirement, govern.
Free accessPublic arithmetic; transmission percentages are published by cloth manufacturers.
What governsEstimate. AHJ and licensed professional govern.
API field namesoutdoor_dli, glazing_transmission_pct, shade_pct, target_dli, outdoor_peak_btuh_per_sqft, floor_area_sqft, system_transmission_pct, inside_dli, required_shade_pct, two_layer_dli, two_layer_share_of_target_pct, glazed_btuh_per_sqft, solar_removed_btuh, solar_removed_tons
- Layers compound multiplicatively; adding shade percentages is wrongspec-v1756 method
- Heat real and the reason the cloth exists, but bought with exactly the light the crop lostgrower trade-off