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Adjusting Environmental Parameters
Adjusting Environmental Parameters

How to specify the site temperature, snow load, wind speed, wind exposure category and more

Updated over a week ago

We'll adjust the environmental parameters for your project at the bottom of the workspace.

Most of these fields will auto-fill, specifically:

  • Temperatures

  • Ground Snow Load

  • Wind Speed

  • Wind Exposure Category

  • Spectral Acceleration (SDS)

  • Elevation

The following fields will not auto-fill and may need to be specified depending on AHJ requirements:

  • Topographical Condition

  • Average Grade of Property


Low and high temperatures for the project are automatically populated from the nearest weather station. If we need to change the weather station or manually adjust the temperature values, scroll over the temperature area and click on the “edit” button that appears.

Ground Snow Load

The ground snow load for the project will populate automatically but it can be changed by hovering over the ground snow load modal and clicking "Edit". Ground snow load for addresses can be found here.

Wind Speed

The wind speed will auto populate based on the nearest weather station to the address but it can also be changed in the same way, by hovering over the wind speed area and clicking "Edit"

Specify if using ASCE 7-10 or 7-16, then choose the wind speed for the project. Find the wind speed for the address here. Next, specify whether the project falls into Risk Category I or II (residential projects will likely fall into Risk Category II).

Wind Exposure Category

The wind exposure category for the project can be edited by clicking on category B, C, or D. The app will default to B.

  • Category B is defined as urban and suburban areas, wooded areas or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger.

  • Category C is defined as open terrain with scattered obstructions, including surface undulations or other irregularities, having heights generally less than 30 feet (9144 mm) extending more than 1,500 feet (457.2) from the building site in any quadrant. This exposure shall also apply to any building located within Exposure B-type terrain where the building is directly adjacent to open areas of Exposure C-type terrain in any quadrant for a distance of more than 600 feet (182.9 m). This category includes flat open country, grasslands and shorelines in hurricane-prone regions.

  • Category D is defined as flat, unobstructed areas exposed to wind flowing over open water (excluding shorelines in hurricane-prone regions) for a distance of at least 1 mile (1.61 km). Shorelines in Exposure D include inland waterways, the Great Lakes and coastal areas of California, Oregon, Washington and Alaska. This exposure shall apply only to those buildings and other structures exposed to the wind coming from over the water. Exposure D extends inland from the shoreline a distance of 1,500 feet (460 m) or 10 times the height of the building or structure, whichever is greater.

Other Site Properties

Under the "Other" widget in the Environmental Parameters panel you'll find:

  • Topographical Condition

  • Average Grade of Property

  • Spectral Acceleration (SDS)

  • Elevation

Clicking Other button beside Wind Exposure Category will bring up this pop-out.

Topographical Condition, Average Grade of Property, and Elevation

Specifying the topographical condition and average grade of the property may be optional for the project, but if your AHJ requires that information, it can be done so here. Elevation will be added automatically but if it needs to be changed, this is where that is done.

Spectral Acceleration (SDS)

If provided, the Spectral Acceleration (SDS) will be displayed on the Attachment Plan and may be required by your AHJ. This information will populate automatically but can be found and verified by doing the following.

Note: SDS is required to get rail spans automatically for ASCE 7-16 projects using IronRidge mounting.

To find this information you'll go to ATC Hazards where you'll input the address and go to the Seismic information tab. Next specify the Reference Document ( ASCE 7-10 or 7-16), Risk Category, and Site Class. The Site Class varies depending on the site location but if you're unsure what value to use you can check in with your AHJ or select "D-Default." Find the SDS value and input it in the empty field in Lyra. This value will be between 0-4.

Next Steps

Continue on to define the last aspect of the site before moving on to System Design. Go here to Complete Site Info.

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