An IGU build-up is complete only when every lite, surface, cavity, spacer and treatment is identified in a fixed viewing order and linked to the project evidence that selected it.
A schedule says ‘6 + 12A + 6 Low-E tempered’. The estimator cannot tell which lite is coated, which surface carries the coating, whether both lites are tempered, what fills the cavity, which spacer and seal system apply, or whether a safety or laminated requirement exists. The string looks familiar but is not production-ready. A robust build-up combines a readable shorthand with a structured field record and elevation/mark scope. This article teaches the grammar; it deliberately supplies no glass thickness, cavity width, coating, gas, heat treatment or destination requirement for a real project.
1. Freeze the viewing direction and number every surface
Write the build-up from a declared exterior side to a declared interior side. Number surfaces consecutively across the assembly and show the same orientation on the elevation or section. A conventional double-glazed IGU may be discussed as surfaces #1 through #4, but the project record must make its own orientation unambiguous, especially where units can be viewed, installed or ordered in mirrored orientations.
Do not describe a coating as simply ‘inside’, ‘outside’ or ‘on the inner pane’. Those phrases can refer to a building side, cavity side or lite. State the manufacturer’s exact product designation, substrate if relevant and surface number, then obtain the manufacturer’s written approval for the proposed placement and processing. This article does not endorse a surface location.
Give each lite a stable identity—L1, L2 and so on—separate from surface numbers. A laminated lite can contain multiple plies and an interlayer while still occupying one position in an IGU. Record plies and interlayer within that lite rather than compressing them into an ambiguous plus-sign chain.
| Position | Project field | What the order must state | Evidence reference |
|---|---|---|---|
| Exterior reference | [defined side / elevation condition] | Fixed reading direction | [approved drawing] |
| Lite L1 | [substrate / nominal thickness / treatment] | Surfaces [# / #] | [product/process evidence] |
| Cavity C1 | [nominal width / fill / spacer-seal system] | Between L1 and L2 | [IGU system evidence] |
| Lite L2 | [monolithic or ply/interlayer construction] | Surfaces [# / #] | [product/process evidence] |
| Interior reference | [defined side] | Final orientation check | [approved section] |
| Coating/frit/film | [exact designation] | Surface [#] and extent | [manufacturer approval] |
2. Describe each lite without hiding processing inside a generic glass name
For each lite, record material/substrate designation, nominal thickness, tint or colour, coated or uncoated state, heat-treatment state, laminated ply/interlayer construction where applicable, pattern/orientation, ceramic coating or frit, edgework, holes/notches/cut-outs and any post-processing restrictions. ‘Clear tempered’ is not a complete procurement identity when coating, heat treatment, edgework or fabrication changes the order route.
ASTM’s official C14.08 page currently lists separate active specifications for flat glass (C1036), heat-strengthened and fully tempered flat glass (C1048), laminated architectural flat glass (C1172), coatings (C1376) and bent glass (C1464). Their separation is a useful drafting lesson: a reference to one material subject does not silently specify the others. The project must name the current applicable requirements and the exact product/process evidence it expects.
Do not infer safety performance from the word ‘tempered’ or infer structural suitability from thickness alone. Likewise, ‘laminated’ does not identify ply thicknesses, interlayer family/thickness, exposed-edge suitability or post-breakage role. Keep design decisions outside the shorthand and link them to approved engineering and destination-specific evidence.
| Field | Lite L1 | Lite L2 / additional lite | Unresolved if absent |
|---|---|---|---|
| Material/product identity | [record] | [record] | Substitution cannot be assessed |
| Nominal thickness | [record] | [record] | Price and processing basis unclear |
| Heat treatment | [record] | [record] | Do not infer annealed/HS/FT |
| Coating/frit and surface | [record] | [record] | Orientation and process route unclear |
| Laminate plies/interlayer | [record or N/A] | [record or N/A] | No safety/structural inference |
| Shape/edgework/fabrication | [record] | [record] | Manufacturability and price open |
3. Specify the cavity as a sealed system, not an arithmetic gap
For every cavity, record nominal width, fill composition if any, spacer family/material and colour, primary and secondary seal system, desiccant/system identity where the approved specification requires it, muntins or internal components, pressure/elevation treatment if applicable, and edge-deletion requirement for the exact coating. The responsible IGU manufacturer must confirm compatibility and manufacturability of the complete system.
ASTM E2190’s public scope addresses insulating-glass durability performance through referenced test methods; ASTM E2188 and E2189 address specific durability and fogging evaluations. A component list or one certificate does not itself prove the ordered IGU matches a tested system. Ask for a scope comparison covering glass/coating, spacer, seals, cavity construction, internal components, fabrication location and any relevant limitations.
Do not convert a nominal cavity description into a thermal or acoustic promise. Whole-window performance depends on configuration and declared methods and conditions. Preserve target values and evidence routes as separate approved requirements so the factory order does not imply an unverified calculation.
| Item | Order field | Evidence question | Do not infer |
|---|---|---|---|
| Nominal cavity | [width and tolerance source] | Does the system documentation cover it? | Thermal/acoustic result |
| Fill | [type/composition and declared basis] | How is fill controlled and verified if required? | A universal concentration or retention |
| Spacer | [system/material/colour] | Exact family and corner/joining route? | Warm-edge performance |
| Seal system | [primary/secondary identity] | Compatibility and tested-system match? | Service life or warranty |
| Coating edge | [deletion/processing instruction] | Manufacturer’s current written requirement? | Compatibility from appearance |
| Internal components | [grid/blind/other or none] | System approval and orientation? | Durability from a standard IGU |
4. Connect the build-up to opening marks, shapes and orientation
Assign a unique glass-type code to each approved build-up, then map it to every opening/panel mark. Keep configuration identity separate from cut size: many units can share a build-up while differing in dimensions and shape. The order line should carry opening mark, panel/lite position, quantity, width, height, shape/template reference, orientation, build-up code and revision.
Record dimension conventions explicitly: which edge is width, the viewing side, units, nominal versus cut/order dimensions, rectangularity or template control, and any deductions authorised by the system design. This article provides no deduction or tolerance. Reconcile the glass order to the approved frame/shop information through the project’s controlled method.
Treat handed, coated, patterned, fritted, laminated, shaped and stepped units as orientation-sensitive until the responsible team proves otherwise. Use a drawing or durable diagram, not prose alone. A rotated rectangle may fit the opening while putting the coating, pattern, frit or laminate on the wrong face.
| Identity | Geometry | Configuration | Orientation | Control |
|---|---|---|---|---|
| [opening / panel / unit mark] | [W × H / units / shape template] | [approved build-up code] | [exterior/interior and surface diagram] | [revision / release / checker] |
| [opening / panel / unit mark] | [W × H / units / shape template] | [approved build-up code] | [hand/pattern/coating direction] | [revision / release / checker] |
| [opening / panel / unit mark] | [W × H / units / shape template] | [approved build-up code] | [edge/step/cut-out orientation] | [revision / release / checker] |
5. Preserve configuration identity from quotation through production and inspection
Normalise quotations against the structured build-up fields rather than comparing abbreviated supplier strings. Require each bidder to mark match, deviation, alternative or unresolved for every lite, cavity, coating surface, process and evidence item. A lower price against a different coating, heat treatment, spacer or laminate is not a like-for-like comparison.
At technical approval, freeze the build-up code and its evidence references. At production release, verify that shop drawings, schedules, purchase orders, acknowledgements and inspection records repeat that same code and revision. Supplier shorthand may remain as a convenience, but it cannot replace the structured record.
Inspect identity and orientation at defined stages without claiming that visual checks prove hidden construction or compliance. Reconcile labels, permanent marks where required, coating-side detection records if authorised, spacer print/traceability, order acknowledgements and unit marks. Route any difference for responsible disposition before installation.
| Gate | Evidence to retain | Pass question | Unsafe shortcut |
|---|---|---|---|
| Quotation | Completed field comparison and deviations | Same requested basis? | Two similar shorthand strings |
| Technical approval | Approved build-up code, orientation and evidence | Every field resolved by authority? | Data sheet alone |
| Purchase order | Code/revision plus mark/size schedule | Order repeats approved identity? | Supplier’s generic product name |
| Acknowledgement | Manufacturer’s returned complete construction | Differences expressly reconciled? | ‘Order confirmed’ |
| Inspection | Traceability and orientation records | Observed identity matches order? | Appearance proves hidden build-up |
FAQ
Is ‘6 + 12A + 6 Low-E’ enough for a quotation?
Usually not for a controlled comparison. It omits or obscures product identity, coating surface, treatment of each lite, cavity system, orientation and evidence requirements.
Which surface should carry Low-E?
This article does not select one. Record the exact product and obtain project and manufacturer approval for the proposed surface and build-up.
Does ‘tempered IGU’ mean both lites are tempered?
Do not infer that. State the heat-treatment condition separately for every lite.
Can a laminated lite be written as one thickness?
The shorthand may be useful only if a controlled structured record also identifies each ply, interlayer and relevant processing requirement.
Does an E2190-related certificate approve the project IGU?
No automatic conclusion follows. Verify the certificate/report scope, participating system and exact proposed configuration, then use the project’s authorised acceptance route.
Continue the project review
Connect this guide with the proposed window and door systems, then review how Cavorlen approaches manufacturing and quality control. When your schedule is ready, send it through the project review form.
Official sources used
ASTM International — C14.08 active flat-glass standards list ↗ASTM International — E2190 standard specification for insulating glass performance and evaluation ↗ASTM International — E2188 insulating glass unit durability test method ↗ASTM International — E2189 insulating glass unit fogging test method ↗ISO — ISO 1279-1:2018 insulating glass units, generalities and system description ↗ISO — ISO 12543-1:2021 laminated glass, definitions and component descriptions ↗Related buyer guides
This article does not design glazing, calculate glass thickness, thermal stress, wind capacity, deflection, U-value, solar or acoustic performance; select a coating, substrate, heat treatment, laminate, cavity, gas, spacer, sealant or edge treatment; or determine safety-glazing, fire, impact, hurricane, fall, barrier or destination compliance. All bracketed values are blank project fields. Qualified responsible professionals, the governing project documents, current destination requirements and the exact manufacturers must approve the actual build-up.