Selecting suitable light poles for your projects can be more complicated than you might think. Deciding how to install them and what light fixtures you will use aren’t the only factors to consider. Mother Nature plays a big part in your decision, too. Locally windy conditions can cause serious safety and reliability issues if you don’t use poles that can handle the conditions.
You’ll normally be mounting high-powered area lights and flood lights to light up outdoor areas like sports fields, streets, athletic courts, and parking lots. These fixtures will apply a load onto the tall poles that you’ll use to mount them up high so that they can properly distribute light to a wide area.
Some areas in the United States, such as around the Great Lakes, along the coast, or in the mountains encounter stronger wind conditions than other parts of the country. EPA ratings are used to determine if poles and their associated fixtures can meet the requirements of a given geographical area.
Building codes and local regulations need to be considered in your buying decisions. Before you select the light poles for your project, you’ll need to know the EPA requirements in your area. This article is intended to help you understand EPA ratings so that you can make an informed decision when purchasing them.
What is EPA and how does it relate to light poles?
EPA stands for Effective Projected Area.
The structural requirements of a light pole are affected by:
- The type of luminaire that is used for illumination.
- The number of luminaires that are mounted to the pole.
- The type of mounting bracket used to attach the luminaire(s).
The style of luminaire that is mounted to a pole makes a huge difference. Each fixture housing has a distinct EPA. The EPA is defined as a shape factor multiplied by the exposed surface area of a light fixture or bracket. You can manually calculate an EPA, but it is easier to check the specifications provided by the manufacturer. Each manufacturer performs an EPA test on its fixtures to generate their associated value.
EPA is equal to the area “visible” by the wind at a particular angle. Each grouping of fixture(s), pole, and mounting equipment will have an EPA. The weight and overall EPA mounted on any pole should not go above the pole’s maximum rating for the wind zone in which it is installed.
High wind zones are regions that encounter wind gusts that are 110 to 130+ mph. Mountainous regions and areas that experience hurricanes are examples.
The EPA of a light fixture measures the dimensions of its cross-sectional area. It is then mapped onto a two-dimensional plane. In other words, it is the measurement of a three-dimensional object on a two-dimensional area.
The EPA of any light pole system varies depending on the angles, shapes, and sizes of the systems. Even the shape of the pole can change the EPA of a complete system. For example, square poles have a larger EPA than round poles. Poles with sharp corners create more drag than rounded fixtures and therefore have a higher drag factor.
What is an EPA rating?
A fixture’s EPA is a unit of measure that determines how much load a fixture will exert on the light pole it is attached to. It is a combination of its weight and shape which affects its wind resistance.
A light pole’s EPA chart is a way to express the relationship between wind speeds and maximum loading (EPA) at each speed. As the wind speed increases, maximum loading on top of the pole decreases.
An EPA wind rating is a calculation used to determine how much force a pole-mounted fixture can handle during windy conditions. This rating will directly affect the type of pole that will be used to mount the fixture.
The fixture is expected to withstand worst-case wind conditions in the area where it is installed. These conditions are specified by the geographic region where the pole assembly is located.
As an example, cities located along the coast, like Houston or Miami, are in 180 MPH wind zones. Fixtures mounted on a tall pole must be able to handle 180 MPH winds without failure.
How is an EPA wind rating calculated?
Wind pressure values, fixture weight, and fixture EPA are combined to evaluate a fixture’s wind rating.
Worst-case historical wind pressure values are used to determine a fixture’s drag profile and wind rating, and this data has been collected over many decades. The data establishes the amount of force applied to the fixture and its mounting hardware at any time.
To make it easier to determine the wind speed in your specific location, the American Society of Civil Engineers has created a National Wind Velocity Map of the United States (shown below).
National Wind Velocity Map
A light fixture’s weight is one important factor to consider. A heavier fixture will exert more force on its pole and mounting hardware. Its weight will influence its wind rating.
The EPA is the projected area combined with the appropriate drag coefficient. The drag coefficient can be defined as the resistance created by the object or shape in a fluid environment. In this case, the fluid environment is air.
The drag coefficient will vary depending on the shape of the object. The lower the drag coefficient, the less resistance the object will create.
Projected Area (A) is the area of the fixture (measured in square feet) that is exposed to the wind. The Drag Factor (Cd) is a number that relates how much the wind ‘drags’ against the fixture based on the fixture shape; fixtures with sharp corners create more drag than rounded fixtures and therefore have a higher drag factor.
A light fixture’s EPA is its projected area multiplied by its drag factor (EPA = A x Cd).
This value is typically published by the fixture manufacturer. The EPA Rating of a pole assembly provides the maximum fixture size that can be supported by the pole assembly in a specific location.
Using the EPA Chart to Determine How to Buy
To properly read an EPA chart for a given light pole, you’ll need two pieces of information:
- What wind zone will the installation be in? Use the wind speed map of the United States to determine this.
- What is the total EPA of all the items that will be mounted on the pole?
Light fixture manufacturers typically publish the EPA ratings of their products on their associated specification sheets. This also applies to whatever brackets or adapters that the fixtures are mounted on such as bullhorns or tenons.
For example: If you have two fixtures with an EPA of 1 each and they are mounted on a bullhorn with an EPA of 2, your total EPA will be 4.
An example of a light pole with two fixtures mounted to a bullhorn.
On the chart, locate your wind zone and then find the maximum EPA for that zone. Notice that the higher the wind speed is, the lower the EPA.
Using the example above with the light pole EPA chart below for a sample pole, your configuration would meet the requirements for a 90-mph wind zone (max EPA of 5.0). It would NOT, however, meet the requirements for anything above it.
Additional tips for meeting EPA requirements:
- If you attach anything else to your light pole outside the original specifications, such as a sign or a banner, the EPA will increase and possibly go over the maximum allowed.
- If the EPA of your equipment is close to the maximum EPA allowed for a given pole, it is recommended that you purchase a different pole that can better handle the load.
Conclusion
Consulting with a local authority about building codes is the best way to ensure you are purchasing equipment that can stand up to these windy areas. The best way to determine the requirements of your project is to:
- Determine the site location.
- Determine the wind load requirement.
- Determine the total weight and EPA of the equipment.
First, you’ll select the fixture(s) according to its illumination capabilities and suitable mounting height. This information is then used to select the appropriate light pole to mount the fixture(s). The EPA of the fixture is compared with a pole’s associated EPA tables to determine if the pole assembly has an adequate structural capacity.
This can be complicated so it’s best to consult with the pole manufacturer to ensure their pole can meet the requirements. The manufacturer will not only consider the suitability of the light pole itself, but also its associated components such as the pole shaft, base plate, welded connections, and anchor bolts.
Why Choose LightMart?
LightMart stands out as an industry-leading manufacturer and supplier of light poles. Our pole assemblies exceed building codes, ensuring strength and performance. We publish EPA rating tables for every standard pole, guiding designers to make informed choices. Whether you're looking for quick ship options, custom solutions, or a range of pole kits and fixtures, we have you covered. With over 25 years in the industry and a legacy of satisfied customers, trust LightMart for all your light pole needs. Contact us today