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Rainfall Collection Equation:
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The Rainfall Roof Calculator estimates the amount of rainwater you can collect from your roof based on rainfall amount, roof area, and collection efficiency. This helps in planning rainwater harvesting systems and water conservation efforts.
The calculator uses the following equation:
Where:
Explanation: The equation accounts for the volume of water that falls on your roof and the percentage that can actually be collected, accounting for losses due to evaporation, splash-out, and first-flush diversion.
Details: Rainwater harvesting reduces demand on municipal water supplies, lowers water bills, provides an alternative water source during droughts, and reduces stormwater runoff that can cause erosion and pollution.
Tips: Enter rainfall in inches (check local weather reports), roof area in square feet (length × width), and efficiency as a decimal between 0 and 1 (0.85 is typical for most roofs). All values must be positive numbers.
Q1: How accurate is this calculation?
A: It provides a good estimate but actual collection may vary due to roof material, slope, and local weather conditions.
Q2: What's a typical efficiency factor?
A: Most roofs have 75-95% efficiency. Metal roofs are most efficient (90-95%), while asphalt shingles are slightly less (85-90%).
Q3: How do I measure my roof area?
A: Calculate the footprint (length × width) of your house, ignoring roof pitch. For complex roofs, break into rectangles and add areas.
Q4: Can I use this for commercial buildings?
A: Yes, the calculation works for any roof area. Just input the correct roof dimensions.
Q5: How much rainfall can I expect in my area?
A: Check local weather records or use annual average rainfall data from government meteorological services.