What the High-Velocity Hurricane Zone Means for Your Project

If you live in Miami-Dade or Broward, you will hear contractors say "HVHZ" a lot. It usually comes up right after you ask why a window costs more than the one your cousin bought in Orlando. Here is what it actually is and how it affects the projects homeowners take on most.

What the HVHZ is

Florida has one statewide building code. Inside it are extra sections that apply only in the High-Velocity Hurricane Zone, which the code defines as Miami-Dade and Broward counties. Nowhere else. Not Palm Beach, not Monroe, not the Gulf coast.

Those sections trace back to the old South Florida Building Code, which got much stricter after Hurricane Andrew in 1992. When Florida created its statewide code, the two counties kept their tougher rules as a special zone rather than give them up.

The wind speeds

Buildings in the HVHZ are designed for specific wind speeds set in Section 1620 of the building code. For an ordinary home or business, which the code calls Risk Category II:

Those numbers drive the design pressure every window, door, roof covering and wall connection has to resist. Corners and higher floors see more pressure than the middle of a wall, so two windows on the same house can need different ratings.

The product testing

This is where the HVHZ really differs. Products that make up the outside of a building, often called the building envelope, have to pass a set of tests written for the zone:

• Large missile impact (TAS 201). A 9-pound piece of two-by-four lumber is fired from an air cannon at the product. Windows and doors near the ground have to survive it.
• Static pressure (TAS 202). The product is loaded with steady positive and negative pressure to its rated level.
• Cyclic pressure (TAS 203). After impact, the product goes through thousands of cycles of pressure pushing in and pulling out, the way gusts behave in a real storm.

A window that passes all three, with the cracked glass still holding, can be approved for HVHZ use. That testing is a big part of why HVHZ products cost more.

Product approvals: NOA or HVHZ-approved

In the HVHZ, it is not enough for a window or roof product to be "Florida approved." It has to be approved for use in the HVHZ. That happens one of two ways: a Miami-Dade Notice of Acceptance (NOA), or a Florida Product Approval whose listing specifically covers HVHZ use. Our article on Miami-Dade NOA vs Florida Product Approval walks through how to check one.

How it affects common projects

What about Palm Beach County?

Palm Beach County is outside the HVHZ, but it is still hurricane country. Homes there are designed to high wind speeds from the code's wind maps, and openings in most of the county still need impact protection. The difference is that products only need Florida Product Approval at the right design pressure, not HVHZ approval. That opens up more product choices and often lower prices.

Why this is worth caring about

• Permits and inspections. Inspectors in Miami-Dade and Broward check product approvals against what was installed. The wrong product means tearing it out.
• Insurance. Wind mitigation inspections document your openings and roof. Properly approved, properly installed products can help your premium.
• Resale. Buyers and their inspectors ask for permits and approvals on windows, doors and roofs.
• The storm itself. These rules exist because of what happened in 1992. They work when they are followed.

The bottom line

If your property is in Miami-Dade or Broward, every product on the outside of the building needs HVHZ approval and every structural piece is designed to the zone's wind speeds. Build that into your budget and your product choices from day one. We handle impact windows and doors, renovations and new homes under these rules every day. Ask us if you are not sure what your project needs.