A

• Aluminum Coating 

  • Room-darkening shades have a double-pleated design with a honeycomb structure and aluminum coating between the pleats that blocks sunlight and reduces heat gain.

• Argon Gas 

  • A colorless, odorless gas used between panes of insulated glass. Denser than air, it improves thermal performance and is included in all VELUX Skylights and Roof Windows.

C

• Cladding 

  • Exterior aluminum armor that protects skylights from the elements and provides a clean, streamlined appearance.

• Combi-Flashing 

  • A flashing system designed to combine multiple skylights for expansive configurations and flexible design possibilities.

• Condensation 

  • Water droplets that form when warm, moist air meets a cold surface. VELUX skylights minimize condensation through insulated glazing with Low-E coatings and argon gas.

• Controls 

  • The method of operating a venting skylight or shade. Options include the standard KLI 310, VELUX Touch, and VELUX ACTIVE.

• Curb 

  • A site-built wood frame or pre-manufactured metal structure onto which a curb-mounted skylight is installed.

• Curb-Mounted Skylight 

  • A skylight mounted to an external curb (typically site-built) instead of directly to the roof deck.

D

• Deck (Roof Deck) 

  • The plywood or sheathing that covers roof rafters or trusses and forms the base for roofing materials.

• Deck-Mounted Skylight 

  • A skylight installed directly onto the roof deck without a curb.

• Diffused Light 

  • Soft, evenly distributed light that reduces glare, ideal for screens and workspaces. Pleated shades help diffuse incoming daylight.

E

• ENERGY STAR^® 

  • A U.S. government-backed program that promotes energy efficiency. VELUX products meet or exceed ENERGY STAR^® criteria.

F

• Finished Framing Dimensions 

  • Measurements from interior finish edge to finish edge used to determine trim dimensions inside the home.

• Fixed Skylight 

  • A non-venting skylight designed solely to bring in natural light.

• Flashing 

  • A weatherproofing system that connects the skylight with its surrounding roof material to create a watertight seal. VELUX flashing systems are designed to shed water without relying on sealants that can break down over time.

• Frame 

  • The structural support for the skylight or roof window, often made of durable Nordic Pine.

• Fresh Air Skylight 

  • A skylight that opens manually, electrically, or via solar power to provide fresh air and temperature control.

G

• Glazing (Insulated Glazing) 

  • Refers to the glass component of a skylight. VELUX offers multi-layer, argon-filled glazing with Low-E coatings for energy efficiency and UV protection.

H

• Head Flashing 

  • The uppermost component of the flashing system, interlocks with the top cover and roof underlayment for proper drainage.

• Header Framing 

  • Horizontal framing that supports the roof above a skylight opening.

I

• Identification Tag (Product ID Tag) 

  • A label on each skylight or roof window that lists the size code used for ordering blinds and replacement parts.

• Impact Glass 

  • Highly durable, laminated glass designed to withstand flying debris. Meets most U.S. coastal and high-wind zone building codes (except Dade County).

• Interior Shades 

  • Shades mounted on the interior (room side) of a skylight.

L

• Laminated Glass 

  • Two panes of heat-strengthened glass bonded around a vinyl layer. If broken, the inner layer holds the glass together.

• Light Shaft 

  • A framed tunnel between a skylight and a flat ceiling, allowing daylight to reach the room below.

• LoE³ (Low-E3) 

  • A triple-layer Low-E coating bonded to skylight glass to reduce solar heat gain and UV rays.

N

• National Fenestration Rating Council (NFRC) 

  • An independent organization that certifies and rates windows, doors, and skylights based on energy performance.

O

• Outside Frame Dimensions 

  • The total exterior measurement of the skylight or roof window frame.

P

• Pan-Flashed 

  • A skylight with integrated metal flashing, pre-attached to the frame for easy installation and water protection.

• Pitch 

  • The angle or slope of a roof, usually expressed as a ratio (rise over span).

R

• Rafter 

  • A sloped structural beam supporting the roof deck.

• Remote 

  • A handheld control that operates solar-powered and electric skylights or shades via infrared signal.

• Roof Window 

  • An operable window installed in the plane of a sloped roof, typically within reach, that opens for ventilation and egress.

• Rough Opening 

  • The framed hole in the roof deck for installing a skylight or roof window.

S

• Sash 

  • The moveable part of a skylight or roof window that holds the glazing and opens for ventilation.

• Self-Flashing 

  • A skylight designed with integrated flashing, eliminating the need for separate flashing components.

• Shades 

  • Interior light-filtering or room-darkening pleated solutions compatible with VELUX skylights.

• Shaft 

  • The passage created between a skylight and the ceiling below, often lined with drywall or other materials to direct light.

• Sill Flashing 

  • The bottom flashing piece that forms a watertight seal at the base of a skylight.

• Sill Framing 

  • The structural framing at the bottom of the skylight opening that supports the surrounding roof structure.

• Step Flashing 

  • Overlapping L-shaped flashing pieces installed with roofing materials along the sides of skylights to prevent water intrusion.

• Stick-Built 

  • A traditional framing method using individual pieces of lumber, as opposed to prefabricated trusses.

T

• Tempered Glass 

  • Heat-strengthened safety glass that shatters into small, blunt pieces rather than sharp shards.

• Truss 

  • A prefabricated structural framework used to support a roof.

U

• Underlayment 

  • Protective layers, like roofing felt or ice/water shield, installed beneath roofing materials and wrapped around skylights for added weather protection.

• UV (Ultraviolet Light) 

  • Invisible rays from sunlight that can fade interior surfaces. VELUX glazing and shades help block UV exposure.

W

• Wrapping a Skylight 

  • Applying underlayment or felt around the skylight curb or frame to enhance weather resistance and reduce condensation risk.