Window performance, explained.
Short, plain-language technical notes for architects, developers and contractors specifying high-performance fenestration.
Thermal performance: U-factor and R-value
What NFRC U-factors mean, why whole-window numbers matter, and how to read claims.
Condensation resistance
Why warm interior glass surfaces matter, and how vacuum glass and fiberglass frames change the picture.
Air infiltration and the air-barrier interface
Airtightness of the unit and of the installation: the window, the rough opening and the building's air barrier.
Frame materials compared
Fiberglass, thermally broken aluminum, wood, aluminum-clad wood and uPVC, honestly compared.
Installation
Why installation quality decides long-term performance, and how GlasFëns supports installers.
Daylighting
A short checklist for using windows to light buildings, not just to look out of them.
Key to NFRC codes
Product, frame, thermal-break, gap-fill, tint, spacer and grid codes used on NFRC certified product listings.