Reference

European Window Glossary

Every term you are likely to see on a European window quote, spec sheet, or submittal package - defined in plain English, with a link to the full guide where one exists. Start with a term below, or jump straight to a category.

Price a Window Schedule

Performance and energy

The numbers on a spec sheet that tell you how a window performs against heat, sound, and water - the same figures a plan reviewer or energy code checks first.

U-factor: How much heat a window lets through, measured in Btu/(h·ft²·°F). Lower is better. It is the number US energy code actually regulates, and the one every European system provider publishes for the whole assembly, not just the glass. U-factor by climate zone.
Uw / Ug / Uf: The European way of breaking U-factor into three parts: Uw is the whole window, Ug is the glass alone, Uf is the frame alone. US code only asks for Uw, so I always convert and quote in Uw, never Ug, to avoid an inflated-sounding number that does not match what the plan reviewer expects.
SHGC (Solar Heat Gain Coefficient): The fraction of solar heat that passes through the glass, from 0 to 1. Low SHGC glass keeps a sun-facing room cooler in summer; a good glazing package balances SHGC against U-factor and visible light rather than chasing one number.
VT (Visible Transmittance): How much visible light passes through the glass, from 0 to 1. Coatings that cut SHGC hardest also tend to cut VT, so a low-SHGC, high-VT glass package costs more and is worth specifying on a north-facing wall of glass where daylight matters.
R-value: The inverse of U-factor (R = 1/U), used in wall and insulation callouts more than window schedules. If a spec calls for R-value instead of U-factor, converting it correctly matters - see the calculator. U-factor to R-value calculator.
Air infiltration rate: How much outside air leaks through a closed window, measured in cfm per square foot at a test pressure. Tilt and turn hardware's multi-point perimeter lock is why European windows post lower infiltration numbers than a single-latch US casement.
Water penetration resistance: The wind-driven rain pressure a window is tested to withstand without leaking, expressed in psf. Coastal and high-wind projects (Florida HVHZ, Gulf Coast) specify this directly - it drives which hardware and glazing depth a system provider can offer.
DP rating (Design Pressure): A NAFS structural rating - the wind and structural load a window assembly is certified to carry, expressed as a number like DP50. Higher DP means a stronger frame and heavier hardware, which is why large lift-and-slide openings on a coastal project carry a premium.
CRF (Condensation Resistance Factor): A 0-100 score for how well a window resists interior condensation in cold, humid conditions. Higher is better; thermally broken aluminum and multi-chamber uPVC frames score well because the frame itself stays warmer on the interior face.
Acoustic rating (Rw / STC): How much a window reduces outside noise. Rw is the European lab rating, STC the US equivalent - close enough in practice to compare directly. Laminated glass and a deeper air gap raise both numbers; it is a glazing choice, not a frame choice.
Psi-install: The heat loss added at the perimeter where a window meets the wall - a thermal-bridging number used in Passive House and deep-energy-retrofit modeling. It depends more on the installation detail (buck, insulation, tape) than on the window itself.

Window types and operation

How a sash opens - the single biggest thing that separates a European window schedule from a US one.

Tilt and turn: One handle, two modes: turn 90 degrees and the sash swings inward like a door; turn 180 and the top tilts inward for secure ventilation. The default European window - see the full guide for how it compares to casement and double-hung. European tilt and turn windows.
Tilt-in / tilting window: What most US buyers mean when their drawings say "tilt-in" or "tilting" - it is the same window as tilt and turn, just a different name for the same mechanism.
Casement (European / outswing): A sash that opens outward on a side hinge, closer to a US casement than tilt and turn is, with the screen staying on the interior. Specify it when the design wants an outswing sash but the frame and glazing of a European system. European casement windows.
Hidden sash: A tilt and turn or casement window where the sash is engineered to sit flush with the frame, so from outside the window reads as one slim, uninterrupted plane instead of a visible sash line. Hidden sash windows.
Lift-and-slide door: A large sliding door where the handle lifts the heavy sash off its seals before it rolls, so one person can move a panel that can weigh several hundred pounds. The go-to for wide openings where a swing door will not fit. Lift-and-slide vs multi-slide doors.
Multi-slide door: Several sliding panels that stack to one side or pocket into a wall, opening a wall-width span. Compared against lift-and-slide in the linked guide - the choice is mostly about how much of the wall needs to disappear. Lift-and-slide vs multi-slide doors.
Bifold door: Multiple panels hinged together that fold and stack to one side, similar footprint to multi-slide but a different hardware and price point. Bifold door cost.
Pocket door: A sliding or lift-and-slide door where the panels disappear fully into a wall cavity, leaving no visible frame at the open opening. Requires a wider rough opening and structural coordination than a standard slider.
Pivot door: An entry door that swings on a pivot point set in from the edge rather than on side hinges, so it can carry a much larger, heavier slab than a hinged door of the same size. Pivot doors on luxury US projects.
Egress window: A window that meets a building code's minimum clear opening, sill height, and operability for emergency escape from a bedroom. Tilt and turn's turn mode gives a full clear opening that qualifies in most jurisdictions. Tilt and turn windows and US egress code.
Fixed light: A pane of glass in a frame that does not open at all - used to fill a wall of glass around operable units without paying for hardware on every panel.

Materials and profiles

What the frame is made of, and the engineering inside it.

uPVC: Unplasticized PVC - a rigid, multi-chamber plastic profile, steel-reinforced where a sash gets large. The best price-to-performance material I ship; not the same product as a US vinyl window, which uses a simpler, thinner extrusion. Aluminum vs uPVC guide.
Multi-chamber profile: A uPVC frame extruded with several internal air chambers instead of one hollow cavity. More chambers trap more still air, which is most of why a European uPVC frame outperforms a simpler single- or double-chamber profile on U-factor.
Steel reinforcement: A galvanized steel insert run through a uPVC profile's largest chamber so a big sash does not sag or bow. Standard on tall or wide tilt and turn sashes; the schedule tells the fabricator where it is needed.
Thermally broken aluminum: Aluminum frame split into an interior and exterior half joined by an insulating barrier, so the metal cannot conduct heat straight through. Without a thermal break, aluminum is a poor insulator - with one, it competes with uPVC on performance while carrying larger spans. Thermally broken aluminum windows explained.
Polyamide strip: A reinforced nylon bar mechanically crimped between the interior and exterior aluminum profiles - one of the two real ways to build a thermal break. Common on European systems; strong, precise, and reversible in a repair. Thermally broken aluminum windows explained.
Pour-and-debridge: The other real thermal-break method: a liquid polyurethane resin poured into the profile, cured, then the connecting aluminum web milled away to leave only the insulating resin joining the two halves. Not obsolete - both methods are current and each system provider has a reason for its choice. Thermally broken aluminum windows explained.
Aluclad: A timber window with an aluminum skin bonded to the exterior face - warm wood inside, maintenance-free metal facing the weather outside. Quoted on request; not carried in the standard estimator catalog. Aluclad vs aluminum vs wood.
Wood-alu: Another name for aluclad - a wood frame with an aluminum exterior cladding. Aluclad vs aluminum vs wood.

Glass and glazing

What is actually in the sash - the part that does most of the performance work.

IGU (Insulated Glazing Unit): The full sealed glass assembly - two or three panes separated by spacers and gas fill, sealed at the edge. "Double glazing" and "triple glazing" both describe an IGU with two or three panes.
Low-E coating: A microscopically thin metallic coating on one glass surface that reflects heat back to its source while staying visually clear - it is why modern IGUs perform so much better than plain glass without looking any different.
Argon fill: Argon gas sealed into the gap between panes instead of plain air. It conducts heat more slowly than air, which is a large part of how an IGU hits its rated U-factor. Standard on most European double and triple units.
Krypton fill: A denser insulating gas than argon, used when the gap between panes is too narrow for argon to perform well - typically triple glazing in a slim aluminum sightline. Costs more than argon, used only where the geometry needs it.
Warm-edge spacer: The strip separating the panes at the edge of an IGU, made from a low-conductivity material (foam, composite, or thin stainless steel) instead of solid aluminum. Cuts the cold line and condensation risk right at the edge of the glass.
Laminated glass: Two panes bonded to an interior plastic interlayer so the assembly holds together when broken - used for security, hurricane impact resistance, and acoustic performance rather than thermal performance.
Tempered glass: Glass heat-treated to break into small, blunt pieces instead of sharp shards. Code-required near doors, low sills, and wet areas - a safety-glazing requirement, not an optional upgrade.
Triple glazing: A three-pane IGU instead of two. Meaningfully lowers U-factor for a real cost premium - worth it in cold climates and Passive House projects, often unnecessary in mild ones. Triple vs double glazing.

Hardware

The mechanism inside the frame that most US buyers have never seen up close.

Concealed hinges: Hinges built into the frame and sash rebate rather than visible on the face of the window - the detail that gives European windows their clean, uninterrupted sightlines. Concealed window hardware.
Multipoint lock: An espagnolette mechanism that drives locking points around the full perimeter of the sash from a single handle - 4 to 8 points on a typical tilt and turn window, versus one or two latch points on a standard US casement or double-hung.
Tilt-first restrictor: A hardware setting that forces the handle into tilt mode before it can reach full turn, so a window cannot be swung open by accident - common on upper floors and near stairwells for child safety.
Handle types: Beyond finish and shape, European handles differ in function: standard turn handles, lockable handles (key-operated, for ground floor security), and tilt-first restrictor handles.
RC2 (hardware security class): A European burglary-resistance rating for window and door hardware - RC2 is the common baseline for ground-floor openings, using reinforced strike points and mushroom-head cams that resist prying.

Installation

How the window meets the wall - the part that determines whether it performs as tested.

Rough opening: The framed hole a window installs into, sized larger than the window unit to allow shimming and flashing. European window sizes are set in millimeters, so the rough opening has to be planned against the metric-to-imperial conversion, not assumed. European window rough opening sizes.
Nailing fin / flange: A flange fixed to the perimeter of the frame that nails or screws directly to the wall sheathing, matching standard US new-construction installation. An option on European systems, not the default - the default is bracket-mounted. European windows with a nailing fin.
Bracket mount: Installation using adjustable metal brackets fixed through the frame into the rough opening, rather than a nailing fin. The standard European installation method - it allows precise shimming and works in retrofit openings a nailing fin cannot reach. Installing bracket-mounted aluminum windows.
Installation clip: A smaller fixing clip used in some retrofit and light-commercial installs in place of full brackets - lower cost, less adjustment range.
Sill pan: A pre-formed or site-built pan under the sill that catches and directs any water that gets past the window back outside, rather than into the wall assembly. Good practice on any window, mandatory on most inspected jobs.
Frame depth: How deep the frame is, front to back - deeper profiles generally mean better thermal and structural performance, and it is a number worth checking against your wall assembly and interior trim detail before ordering.
mm-to-inch conversion: European systems are engineered and manufactured in millimeters. Every schedule I quote gets converted to inches for the US drawing set, but the manufacturing tolerance and the rough opening math both trace back to the metric dimension.

Codes and certification

What a plan reviewer, inspector, or energy code actually asks to see.

NFRC: The National Fenestration Rating Council - the US body that certifies and labels U-factor, SHGC, and VT for windows sold in the US. Not every European system carries an NFRC label by default; I flag which projects need it and which can proceed without. NFRC and NAFS certified European windows.
NAFS: North American Fenestration Standard - the structural and performance test standard (air, water, structural load) that produces a window's Performance Grade and Design Pressure rating. NFRC and NAFS certified European windows.
IECC climate zones: The International Energy Conservation Code's eight US climate zones, each with its own maximum allowed U-factor for windows. The single biggest driver of which glazing package a project needs. European windows by climate zone.
Title 24: California's own energy code, stricter and structured differently than the base IECC - it sets its own U-factor and SHGC targets by climate zone and requires its own compliance documentation.
HVHZ (High Velocity Hurricane Zone): The Florida building code zone (most of Miami-Dade and Broward counties) requiring windows tested and approved to a higher wind and impact standard than the rest of the state or country.
PHI / PHIUS: Passive House Institute and Passive House Institute US - the two certifying bodies behind Passive House performance targets. A window can meet Passive House performance numbers without being individually PHI-certified; certification is a separate, optional step. Passive house windows - what qualifies.
CE marking: The European Union's mandatory conformity marking, confirming a window meets EU manufacturing standards. It says nothing about US code compliance on its own - NFRC/NAFS testing is the separate step that matters for a US permit.
Egress code: The building code section (IRC R310 and local amendments) setting minimum clear opening width, height, area, and sill height for bedroom windows used as a fire escape. Tilt and turn windows and US egress code.

Importing

How a window gets from a European factory to a US job site, and what the paperwork means.

DDP (Delivered Duty Paid): An Incoterm meaning the seller's price already includes freight, insurance, customs clearance, and duty all the way to the job site. Every estimate I send is DDP - the number you see is the number you pay, with no surprise at the port. Importing European windows on DDP terms.
Incoterms: The standard international trade terms (DDP, FOB, EXW, and others) that define exactly where the seller's responsibility for freight, insurance, and customs ends and the buyer's begins.
HS code: The Harmonized System code that classifies a product for customs - it determines which duty rate applies. Window assemblies and glass are classified separately, which is part of why duty math is not a single flat percentage.
Duty: The customs tax applied to imported goods at clearance, calculated against the HS code and the country of origin. The rate depends on frame material and classification - every DDP price already has it built in, so there is nothing extra to plan for on your side.
Container: A window order typically ships as part of a shared or dedicated 20 ft or 40 ft ocean container - the unit that shipping and freight costs are calculated against.
Lead time: The span from approved order to delivery - production at the factory plus ocean transit plus customs clearance. Typically around 16 weeks for a standard tilt and turn order; some systems and large lift-and-slide units run longer. European window lead times.
Proforma (invoice): The formal pre-order document that fixes pricing, quantities, and terms before production starts - the step between an accepted estimate and a confirmed order.
RFQ (Request for Quote): A formal request sent with a window schedule and drawings asking for firm pricing - the standard way to move a project from budget estimate to an order-ready number.
Submittal package: The compiled set of drawings, performance data, and certifications a contractor submits to an architect or building department for approval before fabrication - I assemble this for every order that needs one.

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