DEMO — fictional range. Local brief only, NOT SENT. No personal data is collected or transmitted.
LOAD
Wind pushes up as well as down.
The load on an array is not the weight of the modules. Wind acts on the underside and lifts, and it is the uplift that removes arrays from roofs.
- Dead load
- The weight of the modules, rails and fixings · the easiest case and rarely the one that governs
- Wind uplift
- Pressure on the underside, highest at edges and corners · usually the governing case
- Wind downward
- Pressure on the face, which the roof structure must carry
- Snow
- Ground load adjusted for roof pitch and exposure, held for months in some regions
- Thermal
- Expansion and contraction over the day, which moves rails and loosens fixings
- Seismic
- Horizontal, and relevant in some regions more than wind
Illustrative load record
| Case | Comes from | What it decides |
|---|---|---|
| Wind uplift | Regional speed, height, exposure, roof zone | Fixing centres and clamp count |
| Snow | Ground load, pitch, exposure | Rail span and section |
| Thermal | Daily range and rail length | Whether the rail is fixed or floating |
| Dead | Component weights | The structure beneath, rarely the array itself |
Why the edge zone governs.
Because wind accelerates over a roof edge and separates, producing pressures several times the field value. An array designed on the field pressure and installed to the edge is under-designed exactly where it matters.
The question worth asking instead.
Which load case governs, and what the fixing centres are in the edge zone. A supplier who can answer that has calculated the array rather than quoted a rail.