Design Pressure (DP) is the number you see on the label. But behind that single number are two separate lab tests at two very different pressures. Understanding the 1.5x structural multiplier and the water test ratio for each window type is the difference between a window that passes inspection in Broward County and one that gets red-tagged.
Drag the slider to change the Design Pressure and watch all three gauges recalculate instantly. The structural test pressure is always 1.5x the DP. Water test pressure depends on window type.
Every hurricane-rated window in Broward County carries a Design Pressure (DP) rating — but that single number masks a layered testing protocol mandated by ASTM standards and referenced by ASCE 7-22 and the Florida Building Code. The DP rating is not the pressure the window was tested at. It is the derived service-level pressure calculated from two separate laboratory tests performed at different intensities.
The structural test pressure (STP) at 1.5 times the DP ensures the window frame, glass, and hardware can withstand forces significantly exceeding normal hurricane conditions without permanent deformation or failure. This 50% safety margin accounts for pressure spikes, gusting patterns, internal pressurization from breached envelopes, and installation variations that occur in real buildings but are absent in laboratory conditions.
The water penetration test pressure (WTP) operates at the opposite end. Tested at a fraction of the DP — typically two-thirds for casement and fixed windows — it establishes the pressure at which wind-driven rain may begin penetrating seals and weatherstripping. This lower threshold acknowledges that water infiltration is a serviceability concern, not a life-safety failure. A window leaking water during a Category 3 hurricane is tolerable; a window collapsing inward is not.
Key pressure values found in ASTM E330/E331 reports
The maximum service-level wind pressure in psf. This is the number you match against your ASCE 7-22 calculation. Listed on the FL approval or NOA certificate.
Applied during ASTM E330 testing. The window must resist this pressure for 10 seconds without failure. Frame deflection must recover to within limits after pressure release.
Applied during ASTM E331 testing while water is sprayed at 5 gal/hr/ft². No uncontrolled water penetration allowed past the innermost glazing surface during the 15-minute test.
Different window mechanisms have different sealing capabilities, so water testing varies accordingly
| Window Type | Water TP Ratio | If DP = 50 psf | If DP = 75 psf | Why Different |
|---|---|---|---|---|
| Casement / Awning | 67% of DP | 33.3 psf | 50.0 psf | Compression seal — sash presses into frame under wind pressure |
| Fixed / Picture | 67% of DP | 33.3 psf | 50.0 psf | No moving parts — gasket seal is continuous and permanent |
| Projected (Hopper) | 67% of DP | 33.3 psf | 50.0 psf | Inward-opening sash, similar compression seal to casement |
| Horizontal Slider | 15% of DP | 7.5 psf | 11.3 psf | Sliding seal — weatherstrip only contacts by friction, not compression |
| Single / Double Hung | 15% of DP | 7.5 psf | 11.3 psf | Vertical sliding sash — similar friction seal limitations |
| Awning (CW/AW Class) | 30% of DP | 15.0 psf | 22.5 psf | Commercial-grade awnings with enhanced but non-compression seals |
What Broward County plan reviewers and field inspectors look for — and what you should verify before ordering
Inspection failure points specific to Broward County's building department
The inspector reads the permanent label on each installed window frame. The FL number and DP rating on the label must match exactly what was submitted on the permit application. If you upgraded or substituted a different model during construction, you need a permit revision before inspection. Mismatched labels are the single most common cause of failed window inspections in Broward.
Inspectors measure the distance between anchor points using a tape measure. Typical approvals specify 6" from corners and 12" on-center maximum. They also check fastener type — the wrong screw head, diameter, or material fails inspection even if the spacing is perfect. Stainless steel fasteners are required within 3,000 feet of saltwater in Broward County per the corrosion provisions.
The gap between window frame and rough opening must be sealed per the approved installation detail. Inspectors check for continuous bead of sealant (no gaps), proper backer rod where specified, and integration with the building's water-resistive barrier. Missing or inadequate flashing at the head (top) of the window is flagged because this is where water infiltration failures originate during diagonal rain events common in Broward's storm patterns.
Impact-rated glass in Broward HVHZ areas must bear a permanent etched marking showing the manufacturer, glass type, and impact rating. Inspectors look for this marking on every pane. They also verify laminated glass thickness against the NOA specification — some contractors accidentally install monolithic tempered glass that looks identical but has no impact rating. A quick tap test or edge inspection reveals the difference.
Four common project types showing how DP, STP, and WTP interact with actual building conditions
15th floor, Exposure D, corner unit facing east. Component and cladding pressures from ASCE 7-22 yield required DP of +65/-80 psf for a 4'x5' window opening in Zone 5 (corner). The structural lab test had to prove the window survived 120 psf negative pressure without failure.
Non-HVHZ, Exposure B, field of wall. Standard residential window opening 3'x4', mean roof height 12 feet. ASCE 7-22 yields approximately DP +30/-35. Horizontal slider chosen — but the water test pressure at 15% means water resistance is only 5.3 psf.
Ground floor retail, Exposure C, large storefront glazing system 6'x8'. The bigger the window, the lower the DP per square foot but higher total force. Required DP +45/-55. CW-class storefront uses the higher 30% water ratio for awning vents integrated into the system.
Risk Category III building, Exposure B, second floor classroom windows 3'x5'. Higher importance factor (1.15) pushes required DP to +48/-58. Fixed windows chosen to maximize water resistance at 67% ratio — critical for protecting educational occupancies during storms.
The North American Fenestration Standard (NAFS/AAMA/WDMA) classifies windows into four performance tiers: R (Residential), LC (Light Commercial), CW (Commercial Wall), and AW (Architectural Wall). Each tier prescribes progressively stricter structural, water, and air testing protocols. The performance class does not replace the DP rating — it adds requirements on top of it.
For Broward County residential work, R-class windows meet minimum code requirements when paired with the correct DP rating. However, LC and CW class windows provide enhanced water resistance testing and are increasingly specified by architects for oceanfront residential projects where wind-driven rain exposure is extreme. The additional cost of specifying CW-class for a coastal Broward home — typically 15-25% more than R-class at the same DP — can prevent the water intrusion damage that leads to mold claims costing tens of thousands of dollars.
AW-class is reserved for curtain wall and high-rise applications. These windows undergo thermal cycling tests simulating expansion and contraction, forced-entry testing, and water penetration testing at significantly higher pressure ratios. Any Broward high-rise over 60 feet with a curtain wall system will specify AW-class minimum per typical structural engineer requirements.
Base-level testing. Standard structural and water tests at NAFS-prescribed ratios. Adequate for single-family homes and low-rise residential in Broward. Most vinyl and basic aluminum impact windows fall in this class. Minimum DP 15.
Enhanced water and structural testing. Required for multi-story residential, mixed-use, and light commercial buildings. Adds thermal cycling and humidity resistance tests. Minimum DP 25. Commonly specified for Broward mid-rise condominiums.
Heavy-duty performance. Required for commercial buildings, institutional occupancies, and high-exposure residential. Includes forced-entry testing and higher water test pressures. Minimum DP 30. Used for Broward commercial storefronts and schools.
Maximum performance tier for curtain walls and unitized glazing systems. Adds thermal cycling, structural movement accommodation, and seismic drift testing. No maximum size limitation. Required for Broward high-rise towers and critical facilities.
Get ASCE 7-22 component and cladding pressures for every window opening in your Broward County building — with structural and water test pressure breakdowns included.
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