A specifier's guide to strength, clarity, thermal configuration and decorative glass
Glass has moved from being the thing that fills a structural opening to being an engineered component of the building envelope — responsible for thermal regulation, acoustic control, structural performance, safety and much of a building's visual identity.
Because of that, specification matters. A poor specification produces energy waste, a failed inspection, an aesthetic that misses the design intent, or in the worst cases a structural failure. Most of the disputes we see on site trace back to a specification that was written loosely and interpreted differently by two parties.
This page is a framework for specifying glass properly: by manufacturing type and strength, by clarity and colour, by thermal configuration, and by decorative or specialist role. Each section links to a dedicated page where the detail goes further.
This is the foundational layer of any specification, because it determines break pattern, safety compliance and what can be done to the glass after treatment.
| Type | Strength | Break Pattern | Safety Glazing? | Cut After Treatment? |
|---|---|---|---|---|
| Annealed | Baseline | Large jagged shards | No | Yes |
| Heat-strengthened | ~2× | Large interlocking pieces — tend to stay in frame | No | No |
| Fully tempered | ~4–5× | Small granular cubes | Yes | No |
| Laminated | Varies by plies | Spiderwebs, fragments held by interlayer | Yes | Annealed plies only |
Annealed glass is the base substrate. All architectural glass starts here — molten glass floated on molten tin to produce a flat, uniform ribbon, then cooled slowly to relieve internal stress. It has no enhanced strength and breaks into large razor-sharp spears, so it cannot be used in safety locations. Its advantage is that it can still be cut, drilled and edged after manufacture.
Fully tempered glass is reheated to around 620°C and rapidly quenched, putting the surfaces into compression and the core into tension. Four to five times stronger, and it granulates rather than shattering into shards, which is why it qualifies as safety glazing. Code requires it in doors, shower enclosures, sidelights and low windows near walking surfaces.
The constraint that catches projects out: tempered glass cannot be cut, drilled or edged after treatment. Every hole, notch and edge detail must be finalised before it goes in the furnace. A late dimensional change means remaking the pane, not adjusting it.
Heat-strengthened glass uses the same heating with a slower quench, giving roughly twice annealed strength. It is not safety glazing — it breaks into larger pieces. That is sometimes exactly what you want, because those pieces interlock and tend to stay in the frame. It is also far less prone to the spontaneous failure that affects tempered glass, which is why it is preferred on high-rise facades and as a component inside laminated units.
Worth understanding before choosing between tempered and heat-strengthened on any facade.
Fully tempered glass carries a small but real risk of breaking with no impact at all, caused by microscopic nickel sulfide inclusions that expand slowly over years until the stored tension releases. On a ground-floor storefront that is an inconvenience. On the twentieth floor it means granules falling to the pavement.
Two responses exist. Specify heat-strengthened instead, accepting that it is not safety glazing and using it within a laminated build-up where safety is required. Or specify heat-soaked tempered glass, where panes are held in an oven at around 290°C for several hours so that vulnerable panes fail in the factory rather than on the building.
For overhead glazing, facades and anything difficult to access, the cost premium of heat soaking is small against the cost of access equipment on a completed building.
Clear float is the default. Iron oxide occurs naturally in silica sand and gives the glass a faint green cast that becomes more pronounced as thickness increases. Acceptable for most windows; noticeable against white surfaces and in thick laminated build-ups.
Low-iron glass is made with reduced-iron sand, producing a virtually colourless result with neutral edges and higher light transmittance. Specify it wherever edges are visible or true colour rendition matters — frameless shower enclosures, balustrades, museum and retail display, back-painted panels, and monumental glazing. Pair it with ultra-clear coatings for the best result; a standard coating on low-iron glass gives back some of what you paid for.
Body tints are added to the melt, so the colour is permanent and part of the substrate. Grey gives neutral colour rendition with strong glare control; bronze gives a warm tone and is a common privacy choice; green and blue tints belong to particular architectural eras and predate modern coatings.
Two things to know about tints. They work by absorbing solar energy rather than reflecting it, so the glass itself heats up — which is why dark tints usually require heat-strengthening or tempering to resist thermal stress. And they are subtractive: they reduce solar gain and visible light together. A modern Low-E coating achieves solar control while keeping the space bright, which is why tints are now specified for appearance more than performance. Tints are rarely used on the inboard lite of a sealed unit.
Reflective coatings reject solar heat and give daytime privacy, at the cost of a mirrored exterior appearance.
Laminated glass bonds two or more lites around a polymer interlayer under heat and pressure in an autoclave. The panes may crack, but the fragments stay bonded to the interlayer, so the unit holds together in the opening.
PVB is the standard interlayer, giving safety, security, acoustic damping and around 99% UV blocking — which is what protects interiors from fading.
Laminated glass is required for overhead and skylight glazing, typically on the inboard lite, so that a broken pane cannot drop on occupants below. It is also the basis of effective acoustic glazing in urban settings.
SGP, an ionoplast interlayer, is roughly five times stronger and up to a hundred times stiffer than PVB. Its value is post-breakage rigidity — a broken panel stands rather than sagging — plus superior edge stability where edges are exposed. Specify it for hurricane impact, high-security storefronts, glass floors, open-edge balustrades and structural glass fins.
One caution. SGP is the premium interlayer and is often offered as a blanket upgrade, but for noise it performs worse than PVB, because stiffness is the opposite of what acoustic damping needs. Choose the interlayer for the duty, not the price tier.
Double glazing is the default standard — two lites around a sealed cavity. See insulated glass units for full anatomy. The specifier chooses the substrate, the strength type, the coating and its surface position, the cavity fill and the spacer.
Three of those choices are where quotations quietly differ. Coatings normally go on surface 2 for solar control. Argon fill is the standard upgrade over dry air. And warm-edge spacers replace aluminium, which is a thermal bridge around the whole perimeter and the reason older units get condensation at the edges first.
Triple glazing adds a third lite and a second cavity, allowing a second Low-E coating and reaching the lowest U-values available in a conventional unit. It is the standard for passive house work and severe cold climates. The constraints are weight and thickness — the frame has to be designed for both, so it is not a straightforward upgrade to an existing system.
Vacuum insulating glass uses a very narrow evacuated cavity, under a millimetre, held apart by microscopic pillars. Removing the gas removes conduction and convection across the gap almost entirely.
Its distinctive advantage is thickness. A vacuum unit is far thinner and lighter than a triple unit of comparable performance, which makes it the option worth investigating for historic window replication and landmark work where the original frame profile cannot accept a deep unit. Availability, sizes and edge conditions need confirming per project.
Patterned and rolled glass is embossed during manufacture by passing molten glass between textured rollers. Reeded and ribbed patterns give subtle privacy for partitions and cabinet doors; frost and matte finishes give higher obscurity with even light diffusion.
Acid-etched glass dissolves a controlled amount of the surface to produce a smooth satin finish. It diffuses more uniformly than rolled frosted glass and cleans more easily. Pair it with low-iron for maximum neutrality, since the etch makes any green cast more apparent.
Switchable glass laminates a polymer dispersed liquid crystal film between two panes. Unpowered, the crystals scatter and the glass is opaque; apply a low voltage and they align and it turns clear. Suited to conference rooms, medical and consulting spaces, and residential partitions needing privacy on demand. It can be built into a sealed unit for thermal performance. Coordinate the electrical supply and control system early — and note it defaults to opaque when unpowered, which is usually the safer state but worth confirming against how the room is used.
Spandrel glass creates the opaque non-vision panels in a curtain wall that conceal floor slabs, columns and services. It is normally made by applying a ceramic frit to surface 2 and fusing it during tempering, giving a permanent, durable opaque colour. Because a frit absorbs a great deal of heat, spandrel glass must always be heat-strengthened or fully tempered — annealed glass will crack from thermal stress. Coordinate the colour deliberately: it either matches the vision glass or is a specified accent, and getting it slightly wrong is very visible across a facade.
Glass specified as a walking surface requires structural engineering rather than product selection.
These are always multi-ply laminated units using fully tempered plies — a typical floor build-up might be three 10mm tempered lites with interlayers between. The lower ply carries the structural load; the top ply is a sacrificial wear layer that can be replaced if it is damaged without compromising the floor.
The walking surface must carry a certified anti-slip treatment, either a ceramic frit or an etched pattern, meeting the required slip resistance for the location. This is not optional and it is not something to approximate.
The assembly should also be designed so that failure of any single ply does not compromise the floor. Loads, deflection limits and slip coefficients all need calculating for the specific installation — span, support condition and expected live load. Bring us in early on anything of this kind.
Four worked examples of how the layers combine.
Frameless balustrade: low-iron, tempered, laminated with SGP. Clarity because every edge is visible, tempered for strength, SGP because it holds the panel upright after breakage and resists edge delamination in the open air.
Retail storefront with security requirement: SGP laminated. The interlayer is what turns a broken pane into a barrier that still takes time and tools to get through.
Landmark window replication: vacuum insulating glass, where the original profile cannot accept the depth of a triple unit but modern thermal performance is required.
Curtain wall spandrel: heat-soaked tempered with ceramic frit, giving permanent opacity with the spontaneous failure risk mitigated on a facade that is expensive to access.
Glass technology moves quickly — coatings, jumbo sizes and vacuum unit capabilities all change year to year. For anything unusual we check current manufacturing capability rather than working from an old data sheet. Send us the openings, the performance targets and the constraints, and we will specify the build-up rather than quoting generic glass.
Insulated Glass Units Laminated Glass Tempered Glass Acoustic Glass Low-E Glass Architectural Glass
We hold and move glass through our own shop on Staten Island, working alongside a partner company in Brooklyn, and we bring architectural glass in from Oldcastle for delivery to Staten Island. That combination means we can handle both the standard sizes people need quickly and the specified architectural products that have to be ordered against a drawing.
Once material is in, you have two options. We can arrange local delivery, or you can collect from us at a time that suits you.
Direct delivery to site is available on orders over $2,500 in value. Below that we can still arrange delivery, or you can collect from Staten Island by appointment — whichever suits the job. The delivery area and lead time are confirmed when we quote, since both depend on where the building is and what is being sent.
Our Staten Island location is open by appointment only. That is deliberate rather than restrictive — it means when you arrive the glass is pulled, checked and ready, and somebody is free to go through it with you rather than serving a counter. Call 929-235-1233 or message us to arrange a time.
The range below reflects the kind of work that comes in from different parts of the city. The pattern is worth noticing: the right glass follows the exposure and the use, not the postcode alone.
Sea Gate sits at the western tip of Coney Island with water on three sides, which means strong unobstructed light and significant summer solar gain. Solarban 60 is Vitro's double-silver solar control low-e coating: in a standard one-inch insulating unit with clear glass it delivers 70 percent visible light transmittance and a solar heat gain coefficient of 0.39, for a light-to-solar-gain ratio of 1.79, with a winter nighttime U-value of 0.29 — or 0.24 with argon. Pairing it with a grey tinted outboard lite cuts transmitted light and glare further, which is what an exposed waterfront elevation usually wants.
This stretch runs through Homecrest towards Sheepshead Bay. Solarban 70, formerly Solarban 70XL, is the triple-silver coating and the step up from Solarban 60: 64 percent visible light transmittance against a solar heat gain coefficient of just 0.27, giving a light-to-solar-gain ratio of 2.37 with a U-value of 0.28, or 0.24 with argon.
That ratio is the number that matters. It means the glass admits nearly as much daylight as Solarban 60 while transmitting substantially less solar heat — you keep the light and lose the heat. It has been the most commonly specified triple-silver product in the industry since its introduction in 2005. Where a building has to meet a demanding energy target without going dark, this is usually the answer.
Printed laminated glass puts a ceramic frit or digitally printed image inside the laminate, where it is permanently protected between the plies rather than applied to a surface that can be scratched or cleaned off. It is used for privacy, for decorative work, for shading patterns, and for making large areas of glass visible to birds and people.
Manhattan work brings the extra constraints: access, hoisting, building management schedules and, in historic districts, approval. All of that is easier to solve when it is discussed before the glass is ordered rather than after.
The retail strip around Flatbush and Avenue U, running towards Marine Park and Mill Basin, is mostly straightforward commercial replacement work: storefront lites, entrance glazing, back-of-house openings. Standard low-e insulating glass covers most of it, meets the energy code, and does not carry the cost of an architectural coating that the application does not need.
Part of doing this well is not overspecifying. A shopfront that needs a clear, code-compliant insulating unit does not need a triple-silver architectural coating, and we will say so.
The Rockaways face the ocean directly, and the exposure is genuinely severe: sustained wind, salt, wind-driven rain and the flood history that came with Sandy. Triple glazing earns its cost here in a way it often does not further inland — the additional cavity and coated surface improve both thermal performance and the resistance of the assembly to that exposure.
The trade-offs are real and worth stating. Triple units are markedly heavier, which affects hardware, balances and structural support, and the thickness has to be checked against the frame depth available. On a replacement job in an existing frame that is often the deciding constraint rather than the price. See our triple glazing page for the detail.
Tell us the size, the thickness, the coating if you know it, and where the building is. If you do not know which coating you need, tell us the elevation and what the space is used for and we will work it out. We supply and deliver across the five boroughs, Northern New Jersey, the Jersey Shore, Philadelphia and the Lehigh Valley, with collection available from Staten Island by appointment.
Tell us about the opening and we will specify it for you.
