Solar Exposure — BIMO Documentation

Solar Exposure estimates how many minutes selected curtain wall panels receive direct sunlight during a configured day. It samples the sun path, checks whether each ray is obstructed in the active 3D view, and writes the result to a text parameter on every analyzed panel.

Current availability: Solar Exposure is registered in BIMO Library under BIMO > Analyze, but it is hidden in the default Ribbon scheme and associated with the OPTIMO plan. The current command implementation also contains a preview check whose trial period ended on March 1, 2026. Builds containing this check cancel the command after that date and show Command Unavailable. If the command is missing or blocked, contact support@bimo.tools; an OPTIMO entitlement alone does not bypass the current preview check.

The BIMO add-in has builds for Revit 2021-2027, and Solar Exposure has no command-specific Revit version restriction in source. The availability check above still applies to those builds.

When To Use It

Use Solar Exposure when you need to:

compare direct-sun duration between curtain wall panels;
write exposure minutes to a panel parameter for schedules or view filters;
identify intermittent exposure during the configured time range;
test a facade option against a simplified, repeatable solar model.

Solar Exposure is not a code-compliance or certification calculation. Validate the method, settings, and a sample of results before using its output for design decisions.

Before You Run

Open a Revit project. Family documents are not supported.
Activate a 3D view. The command does not run from plans, sections, elevations, sheets, or schedules.
Make the geometry that should participate in the check available in the active 3D view.
Prepare curtain wall panels or a curtain system to analyze.
Make sure every target panel has a writable text parameter for the result. The default is Comments.
Check the project's True North angle. Solar Exposure rotates its generated sun vectors by the active project location's True North angle.
Review the latitude, day, hours, and sampling step before calculating.

Warning: the command overwrites the selected result parameter on every analyzed panel.

Select Panels

Solar Exposure accepts curtain wall panels in two ways:

Preselect one or more curtain systems. BIMO expands their curtain grids and collects the panel elements.
Preselect individual curtain wall panels. If curtain systems are also selected, the directly selected panels are added to the same set.

Duplicate panels are removed. If no compatible system or panel is preselected, Revit prompts you to Pick curtain panels. Other element types are not accepted as calculation targets.

Command Settings

The main command opens the shared Daylight Measurement settings used by Solar Exposure and Preview Rays. Daylight Measurement is the settings group name, not a separate command. Defaults and validation confirmed in source are listed below.

Setting	Default	Validated Range	What It Does
`Latitude`	`55`	`0-90`	Latitude used by BIMO's solar-vector calculation. Negative latitudes are not accepted.
`Sunrise hour`	`7`	`4-20`	First whole hour sampled; this hour is included.
`Sunset hour`	`17`	`4-20`	End of the sampled range; this hour is excluded.
`Day of the year`	`112`	`1-365`	Day used for solar declination. Day 112 is approximately April 22 in a non-leap year.
`Result parameter name`	`Comments`	Writable text parameter	Parameter that receives the result. Validation checks the Curtain Wall Panels category.
`Minute step`	`5`	`1-15`	Interval between sampled sun vectors. Smaller values create more checks and usually take longer.
`Window depth (mm)`	`0`	No explicit range	Depth of the virtual opening used to reject rays blocked by a recess.
`Window width (mm)`	`0`	No explicit range	Width of the virtual opening. When the value is not positive, the calculation uses an internal width of 1000 mm for its side-obstruction check.
`Upward offset distance (mm)`	`500`	No explicit range	Moves the calculation point vertically from the panel origin.
`Minimum time range (minutes)`	`60`	`1-901`	Required length of at least one continuous period when exposure is intermittent. It affects labels, not the total minute count.
`Discontinuous label`	`Intermittent`	Text	Appended when direct exposure contains more than one period. The leading space is part of the default.
`Not enough time label`	`- No continuous hour`	Text	Appended when exposure is intermittent and every period is shorter than the minimum time range.
`Preview rays height (mm)`	`100000`	No explicit range	Shared with Preview Rays; it does not change the Solar Exposure calculation.
`Preview rays max length (mm)`	`500000`	No explicit range	Shared with Preview Rays; it does not change the Solar Exposure calculation.
`CurveHostDistanceTolerance`	`400`	No explicit range	Distance tolerance used when BIMO determines the orientation of panels hosted on curved mass faces.

Sunrise hour and Sunset hour are validated separately. The settings form does not confirm that sunset is later than sunrise. If sunset is equal to or earlier than sunrise, no time samples are generated and the result can be 0.

For predictable totals, use a minute step that divides 60 evenly, such as 1, 2, 3, 4, 5, 6, 10, 12, or 15. The current implementation counts samples and multiplies by the step; values such as 7 can overstate the duration within each hour.

Optional Per-Panel Hours

A panel can override only the global sunrise and sunset hours when it contains these integer parameters:

Panel Parameter	Behavior
`Use BIMO Settings`	Missing or greater than `0`: use the command settings. `0` or a negative value: read the two panel-specific hour parameters below.
`Sunrise Hour`	Per-panel first hour when `Use BIMO Settings` is not positive.
`Sunset Hour`	Per-panel end hour when `Use BIMO Settings` is not positive.

For a panel-specific range, sunset must be later than sunrise and both values must be from 1 through 23. Missing or invalid override parameters fail the command. Latitude, day, minute step, and all other settings still come from the selected BIMO preset.

Run The Calculation

Activate the intended 3D view.
Preselect curtain systems and/or curtain wall panels, or leave the selection empty to pick panels after launch.
Start Solar Exposure if it is enabled for your build and account.
Review the Daylight Measurement preset and settings, then click OK.
If Revit prompts for panels, select them and finish the selection.
Follow the Exposure time calculation progress indicator. You can cancel during this stage.
Review the configured result parameter on the panels.

The calculation generates sun vectors from the start hour up to, but not including, the end hour. It uses the configured latitude and day, rotates the vectors by project True North, and tests one calculation point on each panel. Every unobstructed sample adds one minute-step interval to the result.

The ray-intersection filter names Generic Models, Masses, Floors, Roofs, Ceilings, and Walls. Curtain Wall Panels are not used as shadow-casting elements. The calculation also temporarily hides categories outside Generic Models, Masses, Floors, Ceilings, and Roofs in the active 3D view and rolls that temporary change back afterward. Because this can affect Walls and linked geometry, verify occlusion behavior on a known sample before relying on the result.

Result Format

The result is text containing the total sampled exposure in minutes, optionally followed by labels.

Exposure Pattern	Example Result With Defaults
No unobstructed samples	`0`
One continuous period totaling 125 minutes	`125`
Several periods totaling 90 minutes, with at least one period of 60 minutes or more	`90 Intermittent`
Several periods totaling 65 minutes, all shorter than 60 minutes	`65 Intermittent - No continuous hour`

The command does not store the individual periods or the longest period separately. It writes only the total and applicable labels.

Presets, Variants, And Shortcuts

Solar Exposure supports BIMO presets for all Daylight Measurement settings. It also receives three generated preset variants:

the main command opens the settings window;
Variant #1, Variant #2, and Variant #3 can run with assigned presets and skip the window when their values are valid;
each variant is a separate Ribbon item and can receive a Revit keyboard shortcut.

Variants have the same visibility, plan, document, 3D-view, and preview-period restrictions as the base command. See Presets and Variants.

Changes To The Model And Cancellation

On success, the command overwrites the selected text parameter in one Revit transaction named Exposure time calculation.
The temporary visibility changes used while tracing rays are rolled back and are not intended to remain in the view.
Cancelling the progress operation stops the command before result values are written.
If writing any result fails, the result transaction is rolled back.
A completed result write can be reversed with Revit Undo.
Solar Exposure does not create preview rays, color schemes, or view filters.

Limitations

The solar model uses manually entered latitude, day, and whole-hour bounds. It does not read Revit Sun Settings, longitude, time zone, daylight-saving time, or weather data.
Latitude validation accepts only 0-90; southern-hemisphere negative latitudes are not supported by the current settings model.
The day range ends at 365; day 366 is not available.
The calculation samples one point per panel, not the full panel surface.
Results depend on panel orientation, active-view geometry and visibility, project True North, virtual-opening values, and the selected time step.
Curtain Wall Panels do not shade one another in the current intersection filter.
Source enables linked-reference searching, but the temporary hide step makes linked-model participation uncertain; validate it in your project.
The settings validator confirms the result parameter on a Curtain Wall Panel found in the document, not on every selected panel. Mixed panel families can still fail during writing.
The result is a text value. Labels make it unsuitable for direct numeric sorting without a separate workflow.

Errors And Troubleshooting

Problem	What To Check
Solar Exposure is not on the Ribbon	It is hidden in the default scheme and is plan-controlled. Check workspace/plan configuration and the current availability note above.
Command Unavailable appears	The preview period encoded in the current implementation ended on March 1, 2026. Contact `support@bimo.tools`.
BIMO asks for a 3D view	Activate a non-template 3D view and run the command again.
The settings form rejects the result parameter	Make sure the project contains Curtain Wall Panels and the named parameter is writable text.
The command asks you to pick panels	The current selection did not contain a compatible curtain system or panel.
The result is `0`	Check that sunset is later than sunrise, the panel faces the expected direction, True North is correct, and relevant geometry is available in the active 3D view.
The total looks too high	Use a minute step that divides 60 evenly and check for panel-specific hour overrides.
An error names `Sunrise Hour` and `Sunset Hour`	A panel has `Use BIMO Settings` set to `0` or lower, but its override hours are missing or invalid.
A parameter error occurs while writing	Confirm that every selected panel has the same writable text parameter, not only one panel family.
No filter or colored visualization appears	Solar Exposure writes parameter values only. Create the required Revit view filters separately.