Calculator Inputs
Example Data Table
| Scenario | Source (W×H) | Temp / Ambient | Distances (S→P, P→Shield) | Recommended Shield (physical) | Notes |
|---|---|---|---|---|---|
| Patio grill near pots | 60×40 cm | 180°C / 28°C | 1.8 m, 0.6 m | 34.0×25.0 cm (tilt 15°) | 10 cm margin; reflective foil face |
| Outdoor heater by bed | 45×80 cm | 140°C / 24°C | 2.2 m, 0.7 m | 33.1×50.2 cm (tilt 10°) | 12 cm margin; keep airflow behind shield |
| Sun-heated wall edge | 120×120 cm | 65°C / 30°C | 0.9 m, 0.3 m | 58.0×58.0 cm (tilt 0°) | Use larger shield if afternoon sun is direct |
Formula Used
-
Blocking geometry (similar triangles)
Required projected width at the shield plane is:Wreq = Ws × (a ÷ d) + 2 × margin. Height follows the same pattern withHs. -
Tilt adjustment
A tilted shield has a smaller projected area. The calculator uses:Wphysical = Wprojected ÷ cos(tilt). -
Radiant heat estimate (simplified)
Radiant power uses the Stefan–Boltzmann form:P ≈ σ × ε × A × (Ts⁴ − Ta⁴), then spreads asflux ≈ P ÷ (4πd²). Shielded flux is reduced using coverage and reflectivity.
These are planning estimates for gardening layouts, not a substitute for product specifications.
How to Use This Calculator
- Measure the visible hot face width and height of the source.
- Measure distance from the source to the plant canopy edge.
- Pick where the shield will stand between plant and source.
- Add an edge margin so shifting angles stay protected.
- Enter tilt if the shield won’t face the plant directly.
- Use downloads to store your settings for future moves.
Practical Notes
Material suggestions
- Reflective foil-faced boards reduce absorbed heat.
- Metal sheets can work, but keep an air gap.
- Avoid foam near high-temperature sources.
Placement tips
- Keep ventilation around the heat source.
- Anchor shields against wind and watering spray.
- Increase margin if the plant area is wide.
Heat exposure patterns around common garden heat sources
Radiant heat travels in straight lines from a hot surface to nearby leaves. Grills, patio heaters, dark walls, and metal sheds can create short bursts above 120–200°C at the source face. Even when air feels mild, direct line-of-sight radiation can dry leaf edges and raise canopy temperature. Scorch is common within 1 m during sustained use.
Inputs that most influence shield dimensions
The calculator uses three measurements to set the blocking size: the visible hot face width and height, the distance from source to plant, and the distance from plant to the shield. A larger source increases required area, while placing the shield closer to the plant reduces the projected size needed. The edge clearance margin adds a safety buffer, typically 5–15 cm, to cover sway and canopy spread.
Projected size versus physical panel size
The required projected size is what the plant “sees” at the shield plane. If the panel is tilted, its projected width and height shrink by cos(tilt). That is why the physical panel must be larger than the projected requirement when you angle it for mounting or wind stability. At 30° tilt, plan roughly 15% extra width.
Estimating heat reduction with reflectivity and coverage
Reflective faces reduce absorbed energy and re-radiation toward plants. In practice, clean foil or polished aluminum often performs in the 80–90% reflectivity range, while dusty or painted surfaces are lower. The result panel shows a coverage percentage so you can compare your planned panel with the recommended size. If coverage is low, enlarge or reposition the panel.
Planning materials, sheet counts, and safe use
After sizing, the sheet plan converts panel dimensions into full sheets using the best orientation to minimize count. Add a per-sheet cost to estimate materials and stay consistent across projects. A 1.22 × 2.44 m sheet often matches common board sizes in stores. Maintain airflow behind the shield, anchor it against wind, and follow manufacturer clearances for heaters and grills.
FAQs
1) How close should the shield be to the plant?
Place it close enough to block the view of the heat source, but not touching foliage. Many setups work well at 20–80 cm from the canopy edge, with extra margin for growth and wind.
2) What reflectivity value should I enter?
Use 85% for clean foil or shiny aluminum, 70% for dull metal, and 50–60% for painted or dusty surfaces. If you are unsure, choose a lower value to stay conservative.
3) Why does tilt increase the recommended panel size?
A tilted panel presents a smaller projected area to the plant. The calculator divides the projected requirement by cos(tilt), so the physical panel grows as the angle increases to keep the same blockage.
4) Do I need a margin around the blocked area?
Yes. Margin accounts for leaf spread, pot movement, and shifting angles. A 5–15 cm margin is common for containers, while wider beds often benefit from larger margins along the edges.
5) Is the temperature rise estimate exact?
No. It is a simplified planning estimate based on radiant heat assumptions and a typical convection coefficient. Wind, humidity, leaf angle, and intermittent heat cycles can change real temperatures significantly.
6) How should I orient the reflective face?
Aim the reflective face toward the heat source so it reflects energy away from the plant. Keep an air gap behind the panel when possible, because ventilation reduces heat buildup and improves durability.