Design pressures for photovoltaic arrays on flat and low-slope roofs under ASCE 7-22 §29.4 — GCrn nominal net pressure coefficients resolved from panel tilt, roof zone, and parapet height, then carried through to clip and ballast uplift. Launching soon.
You're viewing the rooftop array calculator. Mounting panels on the ground instead? Switch to ground-mount →
A rooftop module lives inside the building's own separated flow. Section 29.4 captures that with net pressure coefficients tuned to tilt, position, and the parapet above it.
Each module gets a net pressure from GCrn, which the tool reads from your tilt angle, chord length, and normalized wind area — not a blanket roof number applied to hardware it was never meant for.
A module three rows in and a module on the northwest corner do not see the same wind. The calculator maps every row to its roof zone so the perimeter and corner modules — the ones that actually fail — are sized on their real demand.
The output is built to resolve. Take the net uplift straight to a per-attachment reaction for mechanically fastened rails, or to the counterweight a non-penetrating ballasted tray needs to stay put on a membrane roof.
A four-step flow tuned to a roof-mounted array, in the same clean interface as our live tools.
Design wind speed pulled from the project location, with Florida HVHZ overrides built in.
Mean roof height, parapet height, module tilt and chord, and setback to the first row.
Net pressures computed per roof zone in both directions, corners called out.
Permit-ready output with each coefficient cited to §29.4 and a zone map.
Add your email and we'll reach out the day the rooftop array calculator ships — notify-list members get in first, at launch-day pricing.
One message, the day rooftop goes live — nothing else lands in your inbox. Rather talk now? Contact sales.
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Lock the rail layout and attachment spacing to the governing zone pressures before hardware is ordered.
Produce per-zone module pressures with each GCrn traced to §29.4 for the roof-loading calc package.
Check rail and clip allowables against required uplift across tilt angles and roof-corner zones.
Confirm a ballasted array won't slide or lift on the membrane before the reviewer signs off.
Test a rooftop layout and parapet height early, while the setback is still cheap to change.
Know the downforce into the deck and the pull-out on each fastener before the crew is on the roof.
Subscribe by category and run unlimited calculations.
The other half of solar — tilted rows in open terrain.
Components & cladding for vertical walls and openings.
All roof configurations and slopes (C&C analysis).
Panels mounted on the roof of a building are covered by ASCE 7-22 Section 29.4, which supplies nominal net pressure coefficients (GCrn) for arrays on flat and low-slope roofs. The calculator works entirely within that path — it is built for modules on a roof, not for open racking in a field.
Yes. Tilt angle and chord length feed straight into the GCrn value, and a steeper module in an edge or corner row can carry noticeably more uplift than a shallow one in the interior. The tool recomputes the coefficient for each configuration rather than assuming a single worst case.
A parapet raises the separated shear layer above the roof, and whether it shelters your modules or speeds the flow over them depends on its height relative to the panels. That relative height is an input, and it shifts the coefficient the array sees near the edge.
The output is net uplift per module and per roof zone. From there you resolve it to the counterweight a ballasted tray needs, or to the pull-out on each clip for a mechanically fastened rail. You set the spacing and the racking capacity; the tool supplies the demand.
An Engineering Report listing the wind speed, exposure, roof and module geometry, the GCrn value for each zone cited to its §29.4 reference, and a zone map. Sign-and-seal by a licensed PE is available on request for the jurisdictions that require it.
Yes — a professional engineer can review and seal the rooftop calculation through the firm's licensing network, routed to a PE registered in the project's state. The software generates the report; the seal is a separate professional service you add when the permit calls for one.
Rooftop is in active build now. Join the notify list to be first in line with early access; nothing is billed until the calculator is live and you choose a plan.
Rooftop solar is in active development. Join the notify list for early access, or explore the ground-mount calculator and our free wind speed lookup in the meantime.