Commercial glazing guide

What is the difference between storefront and curtain wall?

Storefront is aluminum framing set inside an opening, usually one story tall, and anchored at the head and sill. Curtain wall hangs off the building's structure, outside the floor slabs, and can run past several floors. Curtain wall takes higher wind loads and drains each glass bay on its own, and it costs more.

Storefront and curtain wall compared

Feature	Storefront	Curtain wall
Where it goes	Ground-floor fronts, entrances and interior glass walls	Multi-story facades, tall lobbies and glass that crosses floor lines
Height	Usually one story, set between the floor and the structure above	Can run past several floors
How it is held	Anchored at the head and sill, inside the opening	Hung off the building structure, anchored at each floor slab
How it handles water	Water that gets into the frame drains out at the sill	Each glass bay drains on its own
How it goes up	Assembled from standard framing members, often cut and assembled by the glazing contractor	Built piece by piece on the building, or set as factory-built panels
Wind and weather	Built for lower loads and sheltered locations	Built for higher wind loads, with better water and thermal performance
Relative cost	Lower	Higher

See storefront systems and curtain wall for how each project runs.

What is Low-E glass?

Low-E stands for low emissivity. A Low-E coating is a very thin, nearly invisible metal layer on one face of the glass that reflects heat while letting daylight through. In an insulated unit it helps keep heat in during winter and out during summer.

Coatings differ. Some are tuned to block more of the sun's heat, others to let more daylight through, and the glass maker publishes performance figures for each. The project specs or your energy code review usually name what is needed.

Tempered vs. laminated glass: what is the difference?

Tempered glass is heat-treated so it is much stronger than regular glass, and when it breaks it crumbles into small, dull pieces. Laminated glass is two or more lites bonded to a plastic interlayer, so when it breaks the pieces stick to the interlayer and the lite stays in the frame. Both can qualify as safety glass, and the code and your drawings decide which one goes where.

Tempered glass cannot be cut after it is made, so it is ordered to exact size. Laminated glass also helps with security and sound, and its interlayer blocks most ultraviolet light.

What is an insulated glass unit?

An insulated glass unit, or IGU, is two or more lites of glass held apart by a spacer and sealed around the edge, with air or another gas sealed inside. The sealed space slows the heat moving through the glass. Exterior commercial glazing in a cold climate like Chicago's is usually insulated glass.

Why is there fog between the panes of glass?

Fog or haze trapped between the panes means the edge seal of the insulated unit has failed and moist air has gotten in. It cannot be cleaned because it is inside the unit. The fix is a new insulated unit, and the frame can usually stay.

See commercial glass for how a replacement runs.

What is a thermally broken aluminum frame?

Aluminum moves heat quickly. A thermally broken frame splits the inside and outside aluminum with a strip of material that conducts much less heat, such as a polyamide strip or a poured polyurethane. That keeps the inside face of the frame warmer in winter, which saves energy and cuts condensation.

How does a commercial glazing project run, from bid to install?

It starts with the drawings and specs, or a look at the opening, and a written price. On new work, shop drawings and product choices are approved before anything is ordered. Then the openings are measured, material is fabricated and ordered, and the frames, glass and doors go in, followed by sealing, adjustment and the punch list.

1. 1

   Step 1: Review and price

   We read the drawings and specs, or look at the opening, and price the scope in writing.

2. 2

   Step 2: Field measure

   Openings are measured on site before anything is ordered, because buildings are rarely exactly as drawn.

3. 3

   Step 3: Shop drawings

   On new work, elevations and details go to the general contractor and architect for approval.

4. 4

   Step 4: Material and fabrication

   Framing is cut and assembled to the approved drawings. Glass is ordered to size.

5. 5

   Step 5: Install

   Frames go in plumb, level and square. Then the glass and the doors.

6. 6

   Step 6: Seal and adjust

   Perimeter sealant goes on, and doors and hardware are adjusted until they close and latch right.

7. 7

   Step 7: Punch list

   We walk the work with you and close out every item on the list.

What does a glazing contractor need to give an accurate quote?

The best start is the drawings and specs for the glazing scope. Without them, photos of the openings, rough sizes, the building's address and your timeline are enough for a first look. Say whether it is new work or a replacement, and whether the building will be open while the work is done.

You can send all of that through the quote form, or call and talk it through.

Can the glass be replaced without replacing the frame?

Often, yes. If the frame is sound, square and not leaking, a broken or fogged lite can be swapped on its own. If the frame is bent, corroded or leaking, it is usually better to replace the framing and glass together.

Anodized or painted aluminum: what is the difference?

Anodizing thickens the aluminum's own oxide layer with an electrochemical process, giving a hard, metallic finish in clear or bronze-to-black tones. Painted finishes, such as high-performance fluoropolymer coatings, come in almost any color. Each system's manufacturer lists the finishes it offers.

Glossary of glazing terms

One-line definitions of the words you will see on glazing drawings, specs and quotes.

Anchor

A clip or fastener that ties the framing to the building structure.

Awning vent

An operable window sash hinged at the top that opens outward at the bottom.

Bite

How far the edge of the glass sits inside the frame's glazing pocket.

Butt glazing

Glass lites set edge to edge with a sealant joint instead of a vertical frame member.

Casement

An operable window sash hinged at the side.

Closer

A device that closes a door on its own and controls how fast it closes.

Continuous hinge

A hinge that runs the full height of a door.

Curtain wall

A glass and aluminum wall that carries no floor loads and hangs off the building structure, often across several floors.

Daylight opening

The visible glass area inside the frame, measured from one edge of the framing to the other.

Elevation

A drawing that shows one face of a building or wall as if seen straight on.

Exit device

Door hardware with a bar or paddle that unlatches the door when pushed, also called a panic bar.

Glazing

The glass in a building, and the work of installing it.

Glazing stop

The removable part of the frame that holds the glass in place.

Head

The horizontal member at the top of a frame.

Heat-strengthened glass

Glass heat-treated to be stronger than regular glass, but not as strong as tempered, and not a safety glass on its own.

Insulated glass unit (IGU)

Two or more lites held apart by a spacer and sealed at the edges.

Jamb

The vertical member at each side of a frame or opening.

Laminated glass

Two or more lites bonded to a plastic interlayer that holds the pieces together if the glass breaks.

Lite

A single pane of glass.

Low-E coating

A thin metal coating on glass that reflects heat while letting light through.

Mullion

A vertical framing member between two lites or units.

Pivot

Door hardware that carries the door at the top and bottom instead of along its edge.

Punch list

The list of small items to finish or fix before a job is closed out.

Setting block

A small block, usually rubber, that the bottom edge of the glass rests on inside the frame.

Shop drawings

Detailed drawings from the installer that show exactly how the system will be built, sent for approval.

Sightline

The visible width of a framing member, seen from the face of the wall.

Sill

The horizontal member at the bottom of a frame.

Solar heat gain coefficient (SHGC)

The share of the sun's heat that passes through the glass; a lower number blocks more heat.

Spandrel

The opaque panel in a curtain wall that hides the floor slab and the ceiling space.

Stick-built

A curtain wall or storefront assembled piece by piece on the building.

Stile

The vertical edge member of a door.

Storefront

Aluminum framing and glass set inside an opening, usually one story tall.

Submittal

The package of shop drawings, product data and samples sent for approval before ordering.

Tempered glass

Heat-treated safety glass that is much stronger than regular glass and breaks into small, dull pieces.

Thermal break

A low-conductivity strip that separates the inside and outside aluminum of a frame.

Transom

A horizontal framing member, or the glass above a door or above a horizontal frame line.

U-factor

A measure of how much heat passes through a window or glass unit; a lower number insulates better.

Unitized curtain wall

A curtain wall built in a factory as large panels that are lifted into place on the building.

Weep

A small opening that lets water that gets into the frame drain back out.