Glossary
The specification terms, in plain language.
Every figure that appears on a Fortwell data sheet, explained without jargon — so a drawing set can be read the same way by an architect, a builder and a homeowner.
- Design Pressure
- Design pressure (DP) is the wind load, in pounds per square foot, that a unit was tested to withstand without failing. A ± figure covers both wind pushing on the glass and wind pulling away from it. Higher numbers mean a system suited to taller, more exposed elevations.
- HVHZ
- The High Velocity Hurricane Zone covers Miami-Dade and Broward counties, where the Florida Building Code sets the strictest impact and pressure requirements in the country. Products approved for HVHZ carry a Miami-Dade Notice of Acceptance.
- NOA
- A Notice of Acceptance is the Miami-Dade County document that lists a product's tested sizes, glass make-ups, pressures and anchorage. It is what an inspector checks against, and every Fortwell system carries a current one.
- Impact Rating
- Impact testing fires a large missile (a timber section) and small missiles (steel balls) at the glazing, followed by thousands of pressure cycles. Laminated glass may crack, but it must stay in the frame and keep the building envelope closed.
- U-Factor
- U-factor measures how readily heat flows through the complete assembly of glass and frame, in Btu/h·ft²·°F. Lower numbers mean better insulation and lower cooling loads.
- SHGC
- Solar Heat Gain Coefficient is the share of the sun's heat admitted through the glazing, from 0 to 1. In Florida a low SHGC keeps interiors cooler; on shaded or north elevations a higher figure is often preferable for daylight.
- STC
- STC rates how well an assembly blocks airborne sound. Each 10 points is roughly a halving of perceived loudness; laminated impact glass already performs well, and acoustic interlayers add several points more.
- Thermal Break
- Aluminum conducts heat readily. A thermal break is a low-conductivity polyamide strut set inside the profile that separates the inside face from the outside, cutting heat transfer and condensation.
- Air Infiltration
- Measured in cubic feet per minute per square foot at a standard test pressure. Lower numbers mean a tighter seal, less dust, and less load on the air conditioning.
- Water Resistance
- Water penetration resistance is the test pressure, in psf, at which no water passes the unit while rain is sprayed against it under wind load. Higher figures suit exposed and coastal elevations.