This page answers a narrow question: can the glass makeup change (Low-E coating, surface, or related IGU options) while the approved framing system ID stays the same? For general impact-spec language, use the Florida commercial impact specs guide. For U-factor reporting mismatches, use the companion whole-window vs center-of-glass article.
What stays fixed when framing stays
An approved window or storefront system is not just aluminum extrusions. The controlling Florida Product Approval, Miami-Dade NOA, or other listed document (as applicable to the project) typically ties framing, glass type, interlayer, thickness ranges, and sometimes coating options into listed configurations.
Keeping the same system means keeping the same approval family and configuration envelope. Changing Low-E is still a glass-makeup change. It is not automatically “same system, free swap.”
One Low-E substitution path (checklist)
Use this as a buyout and submittal walkthrough. It is a process template, not a project record and not legal advice.
TEMPLATE ONLY. Confirm every row against the controlling approval and project specs. No invented SHGC or U-factor values.
| Step | What to verify | Pass / fail signal |
|---|---|---|
| 1. Lock the system ID | Manufacturer series, frame depth, glazed type, and approval document number currently on the submittal. | Fail if the proposed framing is a different series or unlisted variant. |
| 2. Write the current makeup | Lite thicknesses, laminate vs IGU, interlayer, spacer, Low-E surface (e.g. #2 vs #3), tint if any. | Fail if the baseline makeup is unknown. Do not price a delta from a blank. |
| 3. Write the proposed makeup | Same fields for the Low-E change only. Note what stays identical (thickness, interlayer) vs what moves (coating). | Fail if thickness or interlayer also changed without calling it a broader substitution. |
| 4. Approval match | Find the proposed makeup on the controlling approval’s listed configurations or manufacturer letter referencing that approval. | Fail if makeup is absent. |
| 5. Thermal docs | Pull U-factor and SHGC for the exact proposed configuration from manufacturer or NFRC documentation. Compare to the project basis of design using the same reporting basis (whole-window vs center-of-glass). | Fail if numbers are missing, mixed basis, or invented. Do not publish sample values here. |
| 6. Visual check | Exterior reflectance, interior appearance, tint shift, and mockup or sample lite if the owner cares about elevation match. | Fail if architect or owner rejects appearance, even when thermal and approval pass. |
| 7. Written release | Architect approval of substitution, updated glass schedule, and fabrication release only after steps 4 to 6 clear. | Fail on verbal-only release. |
Approval match check
Start with the document already stamped into the submittal. Read the glass schedule and configuration tables. Look for Low-E options by surface and type, not by marketing name alone.
If the proposed coating is listed for that system and thickness range, you may keep the framing system ID and update the glass schedule. If it is not listed, you are not doing a Low-E-only tweak inside the same approval. You are proposing a different configuration that needs a manufacturer path and an AHJ-accepted revision or alternate.
Do not treat brochure language as approval language. Manufacturer product pages for systems such as ES-8000T or ES-9500 describe products; they do not replace the controlling approval sheet for your county and opening sizes (sources: manufacturer model pages; verify current documents per project).
Thermal documentation check
Low-E changes solar heat gain and often U-factor. That does not mean this article invents numbers. Pull documentation for the exact makeup.
- Match reporting basis: whole-window U-factor vs center-of-glass. Mixing them is a common bid error. See the companion whole-window vs center-of-glass U-factor worksheet.
- Compare proposed values to the basis of design and energy-code path on the drawings.
- If NFRC label or CMA documentation exists for the commercial product, use that configuration ID in the submittal note.
No SHGC or U-factor sample values appear in this draft on purpose.
Visual and appearance check
Two Low-E coatings can both clear approval and still look different on the elevation: reflectance, color, and interior brightness. Architects often care more about this than estimators expect.
Ask for a sample lite or a manufacturer visual reference against the adjacent glass already approved. Document owner acceptance before fabrication release on large elevations.
When you cannot keep the same system
Stop calling it a Low-E-only change when any of these move:
- Glass thickness outside the approved range
- Laminate interlayer type or ply count not listed
- Monolithic to IGU (or the reverse) without a listed configuration
- Framing series, thermal break, or glazed position change
- Missile level or design pressure demand that the current approval does not cover for the opening size
Those cases need a different approved configuration or system shortlist, not a coating swap memo.
How to ask for a written answer
Send elevations, the door and window schedule, the current system and approval ID, and the proposed glass makeup in one package. State material-only or furnish-and-install. Ask explicitly: “Is this makeup listed on the controlling approval for this system?”
ACG works from West Palm Beach, Naples, and Tampa. Call (772) 486-7711. FL CGC #1531993.
Frequently Asked Questions
Can you change only the Low-E coating on an approved impact window?
Sometimes, but only when the proposed glass makeup remains inside the configurations listed on the controlling product approval for that framing system. Treat Low-E surface, thickness, interlayer, and spacer as configuration data, not a free swap. Confirm against the current approval document before buyout.
Does a Low-E change require a new Florida Product Approval or NOA?
It depends on whether the new makeup is already listed on the controlling approval. If it is not listed, you typically need a manufacturer revision path or a different approved configuration, not a field assumption.
What thermal checks belong with a Low-E substitution?
Compare the proposed makeup to the specified U-factor and SHGC using manufacturer or NFRC documentation for that exact configuration. Do not invent values. If the submittal used whole-window numbers, keep using whole-window numbers for the comparison.
How should a GC or architect ask ACG to price a Low-E change?
Send elevations, the opening schedule, the current approved system ID, and the proposed glass makeup. State whether you need material-only or furnish-and-install. Ask for written confirmation that the makeup sits on the controlling approval.