This calculator estimates patio surface heating from absorbed sunlight and cooling from air movement. It is designed for comparison between layouts, not for engineering certification.
- Measure patio length and width, or estimate averages for curves.
- Choose your surface material and color to reflect finish choices.
- Estimate shade coverage during the hottest afternoon period.
- Enter peak air temperature, humidity, and typical breeze level.
- Press Calculate Heat and compare scenarios, then export CSV or PDF for records.
| Scenario | Surface | Shade | Air temp | Humidity | Wind | Typical outcome |
|---|---|---|---|---|---|---|
| Sunny slab, low shade | Concrete, dark | 10% | 35°C | 55% | 1.5 m/s | Hot surface, higher heat score |
| Light pavers + sail | Pavers, light | 55% | 35°C | 55% | 2.5 m/s | Lower surface temp, improved comfort |
| Deck with plants | Wood, medium | 35% | 34°C | 60% | 2.0 m/s | Moderate heat with better margins |
| Turf corner zone | Turf, medium | 45% | 33°C | 50% | 3.0 m/s | Cooler touch, lower stored heat |
Why patio layout drives heat buildup
Patios behave like small heat islands. Dense finishes absorb sunlight, store energy, and re-radiate heat into seating zones. Layout decisions that increase shade, reduce reflected glare, and improve airflow can lower peak surface temperature and extend usable outdoor hours. For planting, irrigated beds along hot edges can cool adjacent air, and lighter furniture fabrics reduce radiant discomfort at close range. during summer.
Inputs that most change results
Solar irradiance, shade coverage, and surface reflectance (albedo) dominate the heat balance. Moving from a dark to a light finish raises reflectance and can reduce absorbed load. Increasing shade from 20% to 50% typically delivers a larger benefit than changing material alone, especially on west-facing spaces. Wind exposure also matters because higher airflow increases convective cooling.
Surface temperature and comfort metrics
The calculator estimates surface temperature by combining absorbed solar energy with cooling from wind and longwave radiation. A simple convective term increases with wind speed, so even modest breezes can reduce heating. Heat index is also calculated from air temperature and humidity to represent perceived strain on people and pets. Use the score to compare layouts, not to replace local safety guidance.
Design strategies for cooler patios
Prioritize shade where afternoon sun is strongest. Place sails or pergola cloth to cover dining and traffic paths, and leave open edges for cross-ventilation. Use lighter pavers or reflective sealers to reduce absorption, and choose permeable joints or gaps to limit heat storage. Planting borders add evapotranspiration cooling, while water features and intermittent misting can improve comfort when used in shaded areas.
Using exports for planning and comparison
Run multiple scenarios for the same patio: baseline, then adjust one variable at a time. Export CSV to compare heat score, heat index, net solar flux, and estimated surface temperature across options. Save the best three scenarios and share them with contractors. Export PDF to document assumptions, support procurement choices, and keep a record for seasonal maintenance planning.
1) What does the Layout Heat Score represent?
It is a 0–100 indicator combining estimated surface heating, heat index, shade, and wind relief. Use it to compare design options under the same weather assumptions.
2) Is the surface temperature an exact measurement?
No. It is a planning estimate based on simplified heat-balance relationships. Real temperatures vary with moisture, clouds, surrounding walls, and time of day.
3) Which change usually cools a patio the most?
Increasing effective shade often produces the biggest improvement. Pair shade with lighter finishes and better airflow for the best overall comfort.
4) How should I estimate shade coverage?
Think about the hottest afternoon window and estimate the percent of the patio covered by tree canopy, structures, or nearby building shadows.
5) Why include planting and water features?
Plants and water can cool air through evapotranspiration and evaporation. They work best when the space is also shaded and ventilated.
6) When should I export CSV versus PDF?
Use CSV for comparing scenarios in a spreadsheet. Use PDF when you need a shareable snapshot of inputs, results, and notes for a project file.
After you run a calculation, the latest result is stored temporarily and can be exported.
- CSV is ideal for spreadsheets and comparisons.
- PDF is a quick report for sharing with clients.