The Birdview Skylights TBCM is a thermally broken, curb mount, double dome skylight that can be ordered with acrylic or polycarbonate domes, in a Miami-Dade HVHZ version or a Non-Dade version. In short: pick acrylic when clear daylight is the priority, pick polycarbonate when impact resistance is, and order the Miami-Dade version, which Birdview builds with polycarbonate domes, when the building department requires a product approved for the Florida High Velocity Hurricane Zone (HVHZ).
What the TBCM is
TBCM stands for Thermal Break Curb Mount. Birdview's specification describes a factory assembled unit with sealed domes, a 0.078 inch extruded aluminum frame with a polyurethane thermal break that prevents condensation on the interior portions of the frame, and a 0.070 inch glazing retaining angle. The glazing is specified to support a 40 psf live load. We list two sizes, each as a standard version (acrylic or polycarbonate) and a Miami-Dade HVHZ version (polycarbonate):
- 51.5 x 51.5 inch inside skylight frame: 4848 TBCM (standard) or 4848 TBCM HVHZ
- 51.5 x 99.5 inch inside skylight frame: 4896 TBCM (standard) or 4896 TBCM HVHZ
Custom sizes are also available. Frame finish choices on the cut sheet are mill finish, bronze painted, white painted and clear anodized.
Acrylic or polycarbonate domes
Both materials are offered on the same thermally broken frame, and the order forms show a checkbox for each, but the Miami-Dade approval names polycarbonate domes only, so the Miami-Dade HVHZ version is the polycarbonate one; acrylic domes are ordered on the Non-Dade version. The published data points to a simple trade.
| Acrylic | Polycarbonate | |
|---|---|---|
| Visible light, single clear sheet (Birdview brochure) | 92% | 86%, based on 1/8 inch material |
| Standard colors in the brochure | Clear, bronze, white | Clear, bronze, gray, white |
| Miami-Dade HVHZ version | No. Birdview lists its acrylic TBCM options as Non-Dade | Yes. The Miami-Dade approval names polycarbonate inner and outer domes, and the Intertek large missile test specimens used a 0.118 inch UV enhanced outer dome and a 0.100 inch inner dome |
Dome color matters more than material
For a double dome unit, the cut sheet gives approximate light transmission by outer and inner dome color:
| Outer / inner dome | Approx. light transmission |
|---|---|
| Clear / clear | 84% |
| Bronze / clear | 25% |
| Bronze / bronze | 7% |
| Clear / standard white | 27% |
| Standard white / clear | 27% |
Clear over clear brings in the most daylight. White and bronze tints diffuse the light and reduce glare, and bronze over bronze cuts light the most.
When you need the HVHZ version
The High Velocity Hurricane Zone is a designation in the Florida Building Code. Miami-Dade County Product Control issues a Notice of Acceptance (NOA) for products it has approved as complying with the HVHZ provisions. The Miami-Dade TBCM cut sheet lists:
- Miami-Dade NOA 24-0401.06, 8th Edition (2023) Florida Building Code, NAMI certified. That is the number printed on the cut sheet; Miami-Dade has since revised it, see below
- Tested to ASTM E1886 and ASTM E1996, Missile Level D, Wind Zone 4
- Units can be submitted under the Miami-Dade NOA or a Florida Building Code (FL) approval. Ask us for the current FL number before you plan on that route
The approval has been revised since that cut sheet was printed. Miami-Dade County Product Control issued NOA 26-0805.04 on September 10, 2026, and its first page states that it revises NOA 24-0401.06. The current approval runs to June 1, 2028. It covers Model CMDADE curb mount at a maximum 98.5 x 60.5 inches, rated large and small missile impact resistant at Wind Zone 4 and Missile Level D with a design pressure of plus 60 and minus 140 psf, and Model 6SF self flashing. It names the inner and outer dome material as Plaskolite Tuffak or PalRam Americas polycarbonate. The Intertek report posted with our documents, run on curb mounted units with polycarbonate domes, records the same plus 60 and minus 140 psf under the TAS 201, 202 and 203 protocols.
For a project inside the HVHZ, order the Miami-Dade TBCM with polycarbonate domes and ask us for the current NOA to submit with it. Acrylic domes are a Non-Dade choice. The Miami-Dade TBCM cut sheet cites NOA 24-0401.06, which this approval revises, and the approval drawings describe the curb mount unit as Model CMDADE without naming the TBCM, so ask us to confirm your size and configuration with Birdview before you submit. Approvals are specific to a configuration and they expire, so confirm the exact model, dome material and size with your building department before you order. We can send the complete current NOA and the test documents with the quote.
Order the Miami-Dade version when the permit is in the HVHZ, or when a building official outside it asks for a Miami-Dade NOA. The NOA states that it may be used in other areas where the authority having jurisdiction allows.
The Non-Dade version
For projects without a hurricane impact requirement, the Non-Dade version comes with acrylic or polycarbonate domes. Its cut sheet lists testing to AAMA/WDMA/CSA 101/I.S.2/A440-08 with these results: design pressure of plus or minus 60.15 psf, air penetration under 0.01 cfm per square foot, water penetration at 9.19 psf, a U-factor of 0.73 and an SHGC of 0.28.
Fall protection note
The Miami-Dade cut sheet states that the unit meets the 2017 OSHA fall protection guidelines with no additional cover or screen required, citing 1910.28(b)(3)(i) and 1910.29(e). That statement is the manufacturer's and applies to the Miami-Dade unit as specified. Birdview's brochure also cautions that skylight glazing is not designed to support a person's weight, so never walk or sit on a skylight. If your safety plan still calls for a screen, or you are ordering the Non-Dade version, options sized to 4 x 4 and 4 x 8 curbs are under related products.
Sizing a replacement
The cut sheet lets you order by existing curb dimension or by inside skylight frame dimension. For a replacement, measure the outside of the existing curb including flashing, and compare it with the frame dimension on the product page. Other curb mount units are on the skylights page, and cut sheets are collected on the skylight specification sheets page.
FAQ
Is the HVHZ version only for Miami-Dade County?
No. The NOA covers Miami-Dade County and other areas where the authority having jurisdiction allows it. Birdview's cut sheet also notes that units can be submitted under a Florida Building Code (FL) approval; ask us for the current FL number first.
Can I get the HVHZ version with acrylic domes?
Not under the current Miami-Dade approval. Birdview's Miami-Dade approval names polycarbonate inner and outer domes only, and Birdview builds its impact resistant skylights with polycarbonate. Acrylic TBCM domes are available on the Non-Dade version.
What does thermally broken mean on this skylight?
The aluminum frame includes a polyurethane thermal break. Birdview specifies it to prevent condensation on the interior portions of the frame. Its brochure also cautions that double glazing reduces condensation but cannot eliminate it in every condition.
What is the warranty?
Birdview's brochure states five years from date of shipment against defects in material or workmanship when installed to its instructions, with extended warranties available on request for specific projects.
Next steps
Both sizes and their documents are on the Birdview Skylights brand page. Send the quantity, curb size, dome material, dome colors and whether the site is in the HVHZ through the skylight request for quote page and we will quote the right version.
Product data on this page comes from the manufacturer's published data sheets, drawings and installation instructions, which are posted on each product page. Code references are to the current OSHA text. Always confirm requirements with the authority having jurisdiction for your project.
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