What is an HVHZ?
Regions that are particularly prone to hurricanes and wind-borne debris are called HVHZs. HVHZ stands for High Velocity Hurricane Zone. Because of this, it’s required that building materials meet certain standards.
HVHZs are part of the Florida Building Code. For a building to receive permit approval, the windows must be able to resist strong winds and other hurricane conditions. In other words, properties in HVHZs must have impact windows, or another adequate HVHZ approved storm protection system. It is also important to note that not every county has the same requirements. For example, Palm Beach County allows for storm shutters, while Broward County does not.
What are impact windows?
Impact windows are windows made from thick glass, upgraded hardware sealed with extra-strength adhesive, and upgraded, reinforced window frames. In an HVHZ, exterior windows must be lab-tested and proven to be able to withstand extreme wind and pressure.
Impact window glass uses laminated glass, also known as safety glass. As the name suggests, laminated glass is composed of multiple layers of glass. Impact Glass is made from at least two panes of glass that are bonded together with PVB (polyvinyl butyral) or SGP (SentryGlas Plus) interlayers. It is important to note that the interlayer is not visible.
The frames in HVHZ zones have heavy-duty frames which are secured on all four sides of the window opening. The size, type, and quantity of anchors used to hold the window in place are typically specified by engineers and then lab tested.
How are impact windows rated?
In order to ensure compliance with safety standards, window glass must have a design pressure (DP) rating. The DP rating tells you how well the glass can resist high winds and severe weather, air-born debris, and water infiltration. This rating can only be achieved if the overall window passes Structural, Water, and Air Infiltration testing.
How are impact windows Tested?
Structural test – This testing is done by firing a 9 lb., 6 ft. long piece of lumber at 50 ft. per second from a cannon at the center of the glass, the fixed center rail, and the corner of the windows main frame. Then, a pressure wall simulates negative and positive air pressure. It pushes and pulls against the glass 4,500 time each way. If the window can withstand this amount of pressure, it can effectively protect a building during a hurricane.
Water and air penetration test – The overall window is tested for its ability to resist water and air pressure. Water is applied to the outdoor-facing section of the window. A chamber is sealed to the interior section, and air is exhausted from that chamber to produce hurricane-grade pressure. A small amount of leakage is allowed, since it has minimal effect on thermal performance.
How can impact windows protect my property?
Impact windows are made with safety glass that holds together when struck by an object. By ensuring your property’s windows are made from impact resistant glass, you are protecting the people inside from potential serious injury. According to Dr. Leighton Cochran, former president of the American Association for Wind Engineering;
“The pressure created on a building’s external surface increases with the square of the wind speed. As a result, building product specification and design must be able to withstand such pressures—as well as flying debris caused by the winds.
This is key because once the building envelope is broken by a flying object during a storm, the large external pressures can move to the inside of the building and generally increase the net load seen across the remaining intact building skin, at which point further failures and water damage will ensue.”
During a storm, regular glass can “blow out.” This can cause shards of glass to explode from the frame. If a window is struck by debris, it can crack, weakening the glass and making it vulnerable to shattering. The interlayer between panes in impact windows keeps the glass bonded, even if one of them breaks. Because impact windows are so strong, there’s the added bonus of increased security in the event of an attempted break-in. The thickness of the glass also reduces sound transmission.
Do I live in an HVHZ?
Florida HVHZs include:
- Coastal Palm Beach
- The Keys
The wind map below shows Florida’s HVHZs.
If you live in an HVHZ area and need window replacement services, contact Aeroseal today. Our Florida window installation technicians can help you ensure your property is protected from severe weather conditions.