What is a DP rating on replacement windows? Learn how Design Pressure (DP) and Performance Grade (PG) ratings measure structural strength, why they matter for Quad Cities weather, and how Darin Wilson and JR Girskis help homeowners choose durable, energy-efficient windows.
What's the DP Rating on Windows, and Should You Care?
If you've been shopping for replacement windows, you've probably heard someone mention a DP Rating, also known as a Design Pressure Rating. While it may sound like a technical specification reserved for engineers, it's actually one of the best ways to compare the structural strength and durability of different windows.
For homeowners throughout Davenport, Bettendorf, Moline, Rock Island and the greater Quad Cities, a window's DP rating can make a real difference. Our region experiences strong thunderstorms, high winds, freezing winters and humid summers. Choosing a window with the appropriate Design Pressure Rating—and having it professionally installed—helps your investment perform for decades.
What Is a DP Rating?
DP stands for Design Pressure. It is a laboratory-tested performance rating that measures how well a window resists structural loads created by wind pressure while maintaining its ability to operate properly and resist water infiltration.
During certification testing, windows are subjected to positive and negative wind pressures, structural loading, water penetration testing and operational testing. The higher the DP rating, the greater the window's ability to withstand demanding weather conditions within the scope of its design.
Why Does a DP Rating Matter?
While energy efficiency often receives the most attention, structural strength is equally important.
A properly rated window helps provide:
- Greater resistance to strong Midwest wind events.
- Improved structural stability during severe weather.
- Better protection against water penetration during driving rain.
- Long-term durability with repeated seasonal expansion and contraction.
- Smooth operation even after years of use.
Quad Cities Weather Makes DP Ratings Important
Iowa and Illinois homeowners experience nearly every type of weather imaginable throughout the year.
Winter Conditions
- Strong northwest winds
- Freezing temperatures
- Snow and ice
- Heat loss through older windows
Summer Conditions
- Thunderstorms
- Heavy rain
- High humidity
- Strong wind gusts
Windows with appropriate structural performance ratings are designed to withstand these changing conditions while maintaining proper operation and protecting the home's building envelope.
What Does AAMA and FGIA Say?
The American Architectural Manufacturers Association (AAMA), now part of the Fenestration and Glazing Industry Alliance (FGIA), helped develop many of the performance standards used throughout the window industry today.
Windows certified to the AAMA/FGIA performance standards are tested for structural loading, air leakage, water penetration resistance and operational performance using standardized laboratory procedures.
These performance classes are established under the AAMA/WDMA/CSA 101/I.S.2/A440 (North American Fenestration Standard – NAFS), which classifies windows by performance grade (PG). The familiar "DP" terminology remains widely recognized by homeowners and many contractors, although modern NAFS testing now expresses ratings using Performance Grade (PG), which incorporates design pressure along with additional performance requirements.
A High DP Rating Doesn't Replace Good Installation
Even the strongest replacement window cannot perform as intended if it isn't installed correctly.
Replacement windows are a complete system that combines product quality with installation quality. A high Design Pressure Rating only delivers its intended performance when the window is properly supported, insulated and sealed.
Professional installation includes:
- Accurate field measurements.
- Inspection of the rough opening.
- Proper leveling and shimming.
- Secure fastening.
- Perimeter insulation.
- Interior and exterior air sealing.
- Final operational testing.
Energy Efficiency Still Matters
A window's DP rating measures structural performance—not energy efficiency.
Darin Wilson and JR Girskis encourage homeowners to evaluate the complete window package by comparing:
ENERGY STAR® Certification
Designed for Northern climate energy performance.
NFRC Ratings
Compare U-Factor, Solar Heat Gain Coefficient and Visible Transmittance.
Low-E Glass Systems
Help reduce winter heat loss and unwanted summer solar heat gain.
Professional Installation
Maximizes both structural performance and long-term energy efficiency.
Darin Wilson's Expert Advice
"Homeowners usually ask about glass or price first, but structural performance is just as important. A quality window with a strong DP rating, combined with proper installation, helps your home stand up to Iowa storms while keeping your family comfortable year-round."
— Darin Wilson, Vice President, Suburban Construction
Why Homeowners Trust Darin Wilson and JR Girskis
For decades, Darin Wilson and JR Girskis have helped homeowners throughout Davenport, Bettendorf, Moline, Rock Island, East Moline, Eldridge, Le Claire and surrounding communities compare replacement windows based on more than appearance alone.
They explain the importance of DP ratings (Performance Grades), ENERGY STAR® certification, NFRC ratings, Low-E glass packages and proper installation so homeowners understand exactly what they're buying.
Their experience with Midwest weather allows them to recommend windows that balance structural strength, energy efficiency, beauty and long-term value for every home.
Strong Windows Provide Long-Term Value
Choosing a replacement window with appropriate structural performance helps protect one of your home's most valuable investments.
✔ Better Storm Resistance
Designed to withstand demanding Midwest weather conditions.
✔ Improved Energy Efficiency
Pair structural strength with ENERGY STAR® certified glass packages.
✔ Long-Term Durability
Quality construction helps maintain smooth operation and dependable performance.
✔ Excellent Return on Investment
Durable, energy-efficient windows installed correctly continue to be one of the best exterior home improvements for comfort, resale value and long-term peace of mind.
Industry Perspective
"The North American Fenestration Standard establishes performance requirements for structural loading, air leakage, water penetration resistance and operating force, providing consistent benchmarks for evaluating window performance."
— Fenestration & Glazing Industry Alliance (FGIA), formerly the American Architectural Manufacturers Association (AAMA)
Bottom Line
Yes—you should care about a window's DP rating (or Performance Grade). It provides valuable information about how well a window is designed to resist wind loads, driving rain and structural stresses. For Quad Cities homeowners, where seasonal storms and strong winds are part of life, selecting a well-built replacement window and pairing it with expert installation can provide decades of dependable performance, outstanding energy efficiency and lasting peace of mind.
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