Understanding Glass & Glazing Terminology

Annealed Glass

This standard float glass is common in most residential windows and buildings. It’s the most basic type of glass used in glazing and re-glazing single pane windows.

Tempered Glass

Also known as safety glass, it’s four times stronger than annealed glass. It crumbles into small pieces when broken, unlike the large shards from normal glass panes which present a higher chance of cuts. Tempered glass is often found in shower doors and commercial settings.

Laminated Glass

Laminated glass sandwiches a plastic interlayer between two annealed glass pieces. It holds its shape when broken, offering added strength, UV blocking, and sound insulation.

Wet Glazing

Wet glazing uses a silicone-based sealant to secure the glass. Silicone’s elasticity and UV resistance make it ideal for outdoor use, lasting 20-60 years.

Dry Glazing

Dry glazing uses pre-formed gaskets to secure the glass without sealants. This is suitable where sealant application may be difficult or the window is designed with gaskets. Modern dual pane windows often use gaskets and eliminate the need for wet sealing when replacing the glass. While urethane sealant is sometimes used in dry glazing for interior applications, it only lasts 5-10 years.

Single-Hung and Double-Hung Windows

Single-hung windows have a fixed top sash and a movable bottom sash. Double-hung windows allow both sashes to move, offering more ventilation control.

Double-hung windows often have larger rough openings and better ventilation. Single-hung windows can be more energy-efficient and affordable.

Casement Windows

Casement windows are side-hinged and open like a door. They offer superior ventilation control due to the fully adjustable sash.

Awning Windows

Awning windows are hinged at the top, allowing ventilation even during rain. Awning windows typically only come in smaller sizes.

Picture/Fixed Windows

Picture windows are fixed and don’t open. They are commonly used for unobstructed views.

Sash

The sash is the movable part of a window that holds the glass. It’s usually supported by weights or a spring balance mechanism. Sashes are commonly made of wood, vinyl, or aluminum.

Frame

The frame holds the sash and consists of several parts: head, jambs, and sill. In some double-hung window frames, the jamb liners can be removed. This is helpful to let you tilt the sashes inward for easy cleaning.

Compression jambs enhance the weather-tight seal. This makes double-hung windows a good choice for energy efficiency.

Grilles/Muntins

Grilles, also known as muntins, are decorative dividers within the glass. They create smaller individual pieces, sometimes called divided lites. These dividers add to security as well as the visual appeal of the windows.

U-Value/R-Value

U-value measures a window’s heat transfer rate; lower is better. Factors like frame thermal conductivity and seal integrity affect U-values.

R-value assesses resistance to heat flow, influenced by insulation’s thermal conductivity and air space. Double or triple pane windows with gas fills improve insulation, but high-performance options with specialized gases, warm edge spacers, and low-E coatings offer even greater benefits.

Low-E Coating

Low-E coatings are thin metallic layers that reflect UV and infrared rays, improving insulation and reducing heat loss.

Argon/Krypton Gas

Inert gases like argon or krypton fill the space between glass panes in insulated glass units, enhancing thermal performance. The improved thermal performance offsets the added argon gas costs quickly over time.

Rough Opening

The rough opening is the framed hole in the wall where the window unit is installed. Knowing your window’s rough opening measurement will help with proper installation and to account for potential air infiltration.

NFRC Rating

The National Fenestration Rating Council (NFRC) rates windows and doors on factors like solar heat gain, visible light transmittance, and airflow.