Rainscreen Design Calculator
Cavity depth, drainage, and ventilation for rainscreen systems.
About this calculator
Panels to Order scales directly with Wall Area and inversely with panel size (Panel Width x Panel Height), and Waste Allowance adds a straightforward percentage on top -- none of that involves Design Wind Pressure at all. Design Wind Pressure is a completely separate calculation driven entirely by Design Wind Speed, and it moves QUADRATICALLY, not linearly, because ASCE 7-style wind pressure scales with velocity squared: at this calculator's other defaults, a 10% increase in wind speed (90 to 99 mph) raises Design Wind Pressure by about 21% (21.2 to 25.6 psf), not 10%, and the full declared range swings from about 12.8 psf at 70 mph up to 104.4 psf at 200 mph -- more than 8x, even though wind speed itself only spans a 3x range.
Cavity Depth, Building Height, and Vent Open Area all feed separate outputs (Cavity Volume, Cavity Air Changes/hr, and Vent Open Area respectively) and never touch Panels to Order or Design Wind Pressure -- each of this calculator's outputs draws from its own distinct subset of the eight inputs, so changing one figure rarely means checking all the others moved too.
Inputs
Results
Panels to order
162
Design wind pressure (psf)
21.2
How to Use This Calculator
- Enter Wall Area in sq ft and Building Height in feet.
- Set Cavity Depth in inches — 1.5 in is typical for most rainscreen systems.
- Enter Panel Width and Panel Height, and Vent Open Area (%) split between top and bottom.
- Set Design Wind Speed (mph) per ASCE 7 and Waste Allowance (%).
- Review Panels to Order, Cavity Air Changes/hr, Design Wind Pressure (psf), WRB Area, and Furring Channels (LF).
How the result changes with Wall area (sq ft)
| Wall area (sq ft) | Panels to order | Design wind pressure (psf) |
|---|---|---|
| 600 | 81 | 21.2 |
| 900 | 123 | 21.2 |
| 1,800 | 243 | 21.2 |
| 3,000 | 405 | 21.2 |
What each input means
- Wall area (sq ft)
- Total exterior wall area for the rainscreen system.
- Building height (ft)
- Total height of the rainscreen facade.
- Cavity depth (in)
- Air cavity depth behind the cladding panels (typical 1-2 in).
- Panel width (in)
- Width of each rainscreen cladding panel.
- Panel height (in)
- Height of each rainscreen cladding panel.
- Vent open area (%)
- Percentage of facade area open for ventilation (top + bottom).
- Design wind speed (mph)
- Basic design wind speed per ASCE 7 (3-second gust).
- Waste allowance (%)
- Extra material for cuts and fitting.
What each result means
- Panels to order
- Cladding panels including waste allowance.
- Vent open area (sq in)
- Total ventilation opening area at top and bottom.
- Cavity volume (cu ft)
- Total air cavity volume behind panels.
- Cavity air changes/hr
- Estimated air changes per hour from stack effect and wind.
- Design wind pressure (psf)
- Component-level design wind pressure on panels.
- WRB/membrane area (sq ft)
- Weather-resistive barrier area including laps and waste.
- Furring channels (LF)
- Linear feet of vertical sub-girt/furring channels.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersWall area (sq ft) = 1200, Building height (ft) = 48, Cavity depth (in) = 1.5, Panel width (in) = 24 = 8 input(s) provided
- Calculate Panels to orderPanels to order = ceil(netPanels * (1 + wastePct / 100))162 = 162
- Calculate Design wind pressureDesign wind pressure = qPsf * 1.221.2 = 21.2
- Calculate Vent open areaVent open area = ventAreaSqFt * 1443456 = 3456
- Calculate Cavity volumeCavity volume = wallArea * (cavityDepth / 12)150 = 150
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Does raising Design Wind Speed by 10% raise Design Wind Pressure by about 10% too?
No -- it raises it by roughly double that, about 21%, because wind pressure scales with velocity SQUARED, not linearly. At this calculator's other defaults, going from 90 to 99 mph (a 10% increase) moves Design Wind Pressure from about 21.2 to 25.6 psf, and the full 70-200 mph range swings pressure more than 8x.
Does Design Wind Speed affect how many panels I need to order?
No. Panels to Order is calculated purely from Wall Area, Panel Width, Panel Height, and Waste Allowance -- Design Wind Speed only feeds Design Wind Pressure, a separate structural output for sizing panel attachments, and never enters the panel-count formula.
Does Cavity Depth change how many panels I need or how much they cost?
No. Cavity Depth only affects Cavity Volume, the airspace behind the panels used for ventilation and drainage sizing -- it never enters the Panels to Order calculation, which depends only on Wall Area, panel dimensions, and Waste Allowance.
Do Building Height and Vent Open Area affect the same outputs?
No -- they're independent. Building Height only affects Cavity Air Changes per Hour, through the stack-effect term, and Furring Channel length, while Vent Open Area only affects the calculated ventilation opening size in square inches. Neither one changes Panels to Order or Design Wind Pressure.
Related Calculators
The questions that sit next to this one — chosen by subject, including calculators filed under a different category.
More in Construction & Building Trades.