What are the Different Types of Hurricane Impact Windows, and Which is Best for My Home?

  • Brian Morton
  • Jan 01
  • 5 min read

Disclaimer: The following is for informational purposes only. ALWAYS consult your local building department for the most recent, up-to-date codes for your property!

Chances are, if you’ve met with 2 or more contractors about replacing your windows and/or doors, you’ve heard them talk about how great their window is, how strong it is, what wind speeds it can handle, etc. Here, we try to dispel with a lot of the shenanigans and give you the information and resources to find out on your own.

There’s no such thing as “Rated to XXX MPH wind”
This is frequently seen in marketing materials which is a false & misleading statement that comes with many unwritten disclaimers.
Windows & Doors – Impact Requirements per Florida Building Code
First – let’s look at a county map of Florida showing two important building code “zones”. Both the blue and red colored counties are areas the International Building Code (IBC) defines as areas “vulnerable to hurricanes”.

 

Wind-Borne Debris Region Zone

Shown on the map in blue, the Wind-Borne Debris (WBD for short) region are areas that are vulnerable to flying debris that can cause property damage, injury, or even death, during a hurricane.

As such, when replacing windows and doors in your home, and you live in the WBD, you are required to have some form of impact protection such as impact windows, or shutters.

 

Property Location
Map Area
Impact Requirements

Within 1 mile of the coast where the “basic design wind speed is 130 mph or greater”.

Within the Red Circles on the map.

Yes. Must meet WBD impact requirements.

Basic design windspeed is 140 mph or greater.

The blue area on the map(s).

Yes. Must meet WBD impact requirements.
High Velocity Hurricane Zone (HVHZ)

The HVHZ encompasses Miami-Dade and Broward counties, FL. Due to the higher wind speeds associated with these 2 counties, windows and doors being replaced there must pass more stringent testing requirements than those who live in the WBD.

Point #1: Generally speaking – windows and doors approved for the HVHZ zone are “stronger” than those only approved the WBD zone.

 

Types of Buildings and Their Risk Categories
As a residential window and door replacement contractor, we tend to focus primarily on single-family homes. However, as it relates to Florida Building Code, and its corresponding requirements, we’d be remiss if we did not point out that there are different types of buildings and each has their own respective requirements in the WBD and HVHZ.

 

FBC Risk Categories
Risk Category
Risk Type
Examples

I

“Low Risk”

Agricultural facilities, certain temporary structures, and buildings with a low human occupancy rate.

II

“The Default”

Office buildings, residential buildings, and commercial spaces without large assembly areas.

III

“Substantial Risk”

Buildings with a high occupancy rate, like schools, theaters, and certain healthcare facilities, as well as buildings housing or processing hazardous materials that could be dangerous if released.

IV

“Essential Facilities”

Hospitals, fire stations, emergency response centers, power generation stations, and structures vital for national defense.
Risk Category Building Types

 

 

How To Find the Windspeed and Impact Protection Type Needed for Your Home

Always check with your local building department for the most up-to-date codes for your property. For example – when looking at the WBD|HVHZ Map, Brooksville, FL does not appear to be located within a zone requiring impact protection. However, residences within the city limits of Brooksville do require impact protection when replacing windows and doors.
The American Society of Civil Engineers (ASCE) maintains an address lookup tool so you can see what the wind and impact requirements are for that particular location.

Here is the link: https://ascehazardtool.org/

ASCE Address lookup
Step 1: Input the address or place, then click on Search.
Requested Data Inputs
Step 2: Input the selections as shown.
ASCE/SEI 7-22 is for permits to be pulled 1/1/2024 or later.

 

Risk Category – input II (taken from section above).

 

Load Types = Wind.
Then, click on VIEW RESULTS.
Sample Results. Note that “Glazed openings …” refers to glass (windows, doors, etc.)
The image above shows the results page. Here are key takeaway items from this address search:

  • The windspeed rating is 139 mph.

  • The highlighted wind details portion that reads: “Glazed openings need not be protected against wind-borne debris” means:

    • Windows and doors are not required to be impact-resistant rated.

    • Non-impact resistant windows and doors are allowed to be installed at this location.

Using an address based in Pinellas County, FL, you can see from the results page that impact protection against wind-borne debris (WBD) is required.
Point #3: Use the lookup tool to find out what wind speeds your windows and doors have to meet, as well as if impact protection is required or not.

 

Searching for Approvals for Impact Resistant Windows and Doors
We’ve thus far covered the different hurricane prone zones (WBD & HVHZ), risk categories associated with different building types, and how to lookup an address to see wind speed and impact protection requirements are.
According to Florida Building Code, ALL windows and doors must go through extensive testing in order to receive approval for use in Florida. Engineers who work with, or for, window and door manufacturer’s design the products to meet, or exceed, the standards set.

 

In fact, anyone with internet access can search for product approvals directly on the Florida Department of Business and Professional Regulation website.

 

DBPR’s Product Lookup Site
Once the testing is complete on a new product, the manufacturer submits engineering plans, along with test results, to the state seeking approval. Once the state approves the product, an approval code is assigned to it. This is approval code is known as its Florida Product Approval (FPA) #.
Most window and door manufacturers have listed on their website the FPA codes associated with each product. Custom Window Systems (CWS), for example, has theirs listed here: https://www.cws.cc/downloads/

 

 

Let’s use the following 3 FPA codes from CWS’ site as an example:
  • 41973
  • 17791
  • 18689
FPA # 41973 – non-impact and NOT approved for HVHZ. This product can NOT be used in the WBD or HVHZ

 

FPA # 17791 – Impact, but NOT approved for HVHZ. This product can be used in the WBD.
FPA # 18689 – This is an impact rated product approved for the HVHZ. It can be installed ANYWHERE in Florida and pass inspection.

 

Testing Requirements for Impact Resistance in Windows and Doors
For a product to be approved as impact resistant, it must go through the following tests:

  • Water Infiltration Test

  • Air Infiltration Test

  • Cyclical Test aka Pressure Test

  • Small and/or Large Missile tests

As mentioned previously, standards related to HVHZ are higher than WBD standards.

Missile Level Testing

For our purposes, we will not touch on water or air infiltration tests.

When discussing missiles in this context, we’re not talking about bombs over Baghdad, or those used to shoot down state-sponsored spy balloons.
Rather – we’re discussing projectiles impacting the window or door system, and how well the system withstands these forces. The idea is to replicate potential flying objects during hurricane force winds.

 

Missile Level
Better Known As
Missile
Velocity

A

Small Missile Impact

10 2 gram steel balls

130 ft/sec (89 mph)

B

skylights only

skylights only

skylights only

C

Medium Missile Impact

uncommon

uncommon

D

Large Missile Impact

9 pound 2 x 4

50 ft/sec (34 mph)

E

Enhanced Impact Protection

9 pound 2 x 4

80 ft/sec (55 mph)

 

The chart above shows the basics of the test types. There are of course pass/fail guidelines, more of which you can read here and here and here.
Small Missile Impact testing is required for glazing (glass) located 30′ above grade, while Large Missile Impact testing is required for glazing within 30′ above grade.
Source: Guardian Glass https://www.guardianglass.com/content/dam/guardianindustriesholdings/collateral/usca/brochure_expert_series_EN_doc10_hurricane-impact-resistance_2021.pdf
WBD vs. HVHZ Testing Standards Differences – 2 examples

WBD

HVHZ

Large Missile Test

The 2”x4” lumber is allowed to penetrate the door, but the crack cannot be greater than 1/16” x 5”, and a 3” sphere cannot pass through the crack

The 2”x4” lumber cannot penetrate the door at all, and in a subsequent air infiltration test, no air infiltration is allowed for an HVHZ door.

Water Infiltration Test

Performed independently.

Performed alongside the pressure test. Not single drop of water may pass over the sill on the inside of the home and reach the floor.

 

Design Pressure

Unlike insurance sales, window sales is highly unregulated comparatively speaking. If we had it our way, window salesmen would NOT be able to say something like “… this window is rated to 200 mph!”

As Engineering Express correctly points out: “There’s no such thing as ‘Rated to XXX MPH wind”.

The formula that converts wind velocity to wind pressure has many variables. Each variable affects the resulting pressure for a given wind velocity. A 100mph wind velocity for example can produce pressures as low as in the mid-teens (psf) to upwards of 50psf, even 60psf, and more. These variables include such features as building height, location of the area on the building, the terrain around the building, whether the building is on or near a hill, slope of the roof, size of the area in consideration, and more. – Engineering Express
Imagine the water on this pond being a window. The bullet represents wind. At this angle, the upward pressure asserted by the pond water is greater than the downward pressure of the bullet. That’s why the bullet rebounds upwards and hits the target.

The bullet is traveling well in excess of 200 mph, probably greater than 1,000 mph, but does not penetrate the water.

Correlating this to windows and doors – you will see very important numbers on the NFRC sticker that is required to be affixed to every new window and door installed, and can NOT be removed until the building authority have jurisdiction over your property has inspected and certified the product + installation.

 

NFRC Rating Sticker – DP +/- 50
NFRC Rating Sticker – DP +/- 70
When you see “DP:” – it’s referring to Design Pressure. It is a rating usually in PSF (Pounds per Square Foot), and has both positive (+) and negative (-) numbers. The positive number relates to the “push” pressure on the window, while the negative number relates to the “pull” pressure on the window. You can probably imagine during a hurricane, with swirling winds, that the winds are both pushing and pulling on the window system.

KEY POINT – The higher the + positive and – negative numbers are, the more protection against wind, water, air pressure, and missile impacts your window and/or door unit will provide.

Fun Fact: I used to work for a company that offered impact-resistant windows in the WBD region. More often than not, we were unable to offer our windows to condo residents who lived higher than the 3rd floor due to limitations on Design Pressure ratings (building height factors into the calculation). Also, it was necessary for us as salesmen to measure (as best as possible) the distance from the edge of the window nearest to the corner of the building. Windows closest to the corner experience higher negative wind pressures than those windows in the middle of the building. Thus – the product’s engineering and testing results limited where they could actually be installed according to building code.

 

How Glass Choices Affect Impact Resistance Performance

How To Compare Impact Window Choices – and How to Make Sure You Get What’s Sold To You!

 

If I lived in the HVHZ:

To replace my windows and doors while living in the HVHZ, and I wanted to compare the impact resistance ability between different window offerings, here would be my thought process:

  1. Deal with a window and door specialist contractor servicing the area. A licensed and reputable contractor will be familiar with the building code requirements, and will pull a permit. Only HVHZ approved products will have the permit application approved.

  2. I probably would not both with asking them the FPA code for each window or door. If you want to, go ahead. Then, look up the FPA code on the DBPR product approval website, and make sure it is HVHZ approved.

  3. Compare Design Pressure ratings. Upon request, your perspective contractor should provide you the DP ratings (positive and negative) for each window. I’d compare the numbers to see which are higher than the other.

  4. I’m less worried living in the HVHZ getting an inferior window than I was expecting because in order to pass inspection, only HVHZ approved products will pass.

 

To Be Certain: There are a lot of factors involved with finding the right windows and doors for your home. A window or door’s impact resistance ratings are but one of the many factors I would consider when choosing a contractor and window for my replacement project.

 

If I lived in the WBD Zone:

 

I could get impact resistant windows that meet the WBD standards, or HVHZ standards.

If my main objective was to get the highest impact resistance possible, I’d follow the steps above. I’d verify the product was HVHZ approved, and then I’d choose the highest positive and negative DP ratings among my choices.
Installation matters! There are different installation requirements for the HVHZ and WBD Zones. It’s why building inspectors come out after the installation is complete (if a permit is pulled, as should be done 100% of the time) to ensure the windows have been installed according to building code – for that region.
If you live in the WBD but want HVHZ rated products + installation, you should hire a contractor whose installation crews have experience working in, and installing in, Miami-Dade or Broward county.
For example, if you live in Clearwater – a WBD zone – and have HVHZ products installed, the Pinellas County building department is going to ensure the windows were installed according to WBD guidelines, and NOT HVHZ.

 

Last Word of Caution – Verify What You’ve Gotten

Having been in this business for 5+ years, I have see it too often where customers have had windows installed that were not actually what they were thinking they were getting. In one instance, a customer thought they had impact resistant windows, but were actually non-impact double pane windows.

 

Rule #1 – Always get it in writing. Window salesmen (and saleswomen) can be quite persuasive – it’s their job after all – but make sure you get everything in writing.

 

Follow these steps to ensure you get what you’re expecting.

  1. Review the completed contract thoroughly before signing. Specifically look for the product information & details.

  2. Prior to signing the contract, make sure you have the Florida Product Approval Code, and look it up on the DBPR website. It will tell you if the product is non-impact, impact, and/or approved for the HVHZ.

  3. Prior to signing the contract, make sure you receive the details that will be on the NFRC sticker. If a contractor will NOT, or CAN NOT, provide you those details – then find a contractor who will. Contractors who can not or will not provide you those details are hiding something.

  4. Inspect the NFRC sticker on your new windows and doors. Verify the product approval code, and the DP ratings match up with your original order. If you don’t find the information on the NFRC sticker, you will find it in the permit paperwork that must be on-side during the installation.

My Window and Door Guy installs windows and doors throughout the greater Tampa Bay area. If you are in Hillsborough, Pinellas, Pasco, Polk, Citrus, Hernando, or Manatee county, and would like a no-cost, no pressure quote for your window and door project, reach out to us at 813-977-7500, or click the button below and we will follow up with you!

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