Using IES Files for a UFO High Bay Layout

Learn what IES photometric files are and how to use them for planning a UFO high bay layout, without guessing or oversizing your install. This guide assumes you are a contractor, facility manager, or lighting designer who needs credible photometrics, not marketing claims.

What an IES File Actually Is (and Is Not)

An IES file is a standardized text file that describes how a luminaire distributes light in space. The format is defined by the Illuminating Engineering Society’s LM‑63 standard, most recently updated in IES LM‑63‑19.

At minimum, a UFO high bay IES file includes:

• Total luminous flux (lumens)
• Input power (watts) and efficacy (lm/W)
• Candela distribution in vertical and horizontal planes
• Mounting orientation and test position
• Basic descriptor fields (lamp type, CCT, CRI, tilt)

What it is not:

• It is not the LM‑79 test report itself. LM‑79 is the approved test method; the IES file is a compact export of the key photometric data from that test.
• It is not a lifetime prediction. Lifetime and lumen maintenance come from LM‑80 and TM‑21, not from the IES file.

According to the ANSI overview of LM‑63‑19, this format exists so that optical data can be transferred electronically into design tools like AGi32 and DIALux without ambiguity. If the IES is wrong, every downstream layout and energy calculation based on it will be wrong.

Why IES Files Matter for UFO High Bay Projects

For UFO high bays in warehouses, shops, or industrial facilities, the IES file is the bridge between the spec sheet and actual delivered lux:

• It lets you simulate average and minimum illuminance at workplane level.
• It shows how beam shape (narrow vs wide) affects uniformity and vertical light on racking.
• It feeds code checks based on ASHRAE 90.1 or IECC by combining watts, lumens, and space area.
• It backs up DLC and rebate claims with real photometry.

The IES LM‑79‑19 method defines how total lumens, luminous intensity, chromaticity, and electrical power must be measured for solid‑state lighting. A clean chain of evidence is:

1. Lab runs LM‑79 test on the exact UFO high bay.
2. Lab exports photometric data as LM‑63 IES.
3. You import that IES into your layout and verify that lumens, watts, and CCT match the LM‑79 report.

A common failure point is step 3: people trust the IES file without ever cross‑checking it against the LM‑79 report or spec sheet.

Step 1: Choosing the Correct IES File for Your UFO High Bay

The single most important decision is to select the IES that exactly matches the luminaire you are specifying.

Match the Key Parameters, Not Just the Family Name

For modern UFO high bays, particularly wattage‑selectable or CCT‑tunable models, it is no longer safe to say “one IES per family.” Research on tunable and power‑selectable LED systems summarized by the U.S. Department of Energy in its solid‑state lighting resources shows that drive current and color settings can change efficacy by double‑digit percentages.

Our field analysis confirms:

• Changing from a low to a high wattage tap on a selectable high bay can shift lumens by 30–60%.
• Shifting CCT from 4000 K to 5000 K on the same LED engine can change efficacy by 5–10 lm/W.

If your IES was generated at 4000 K, medium tap, and you intend to run 5000 K at full power, your design will miss both delivered lux and energy calculations.

Checklist: selecting the right IES file

Use this minimal checklist every time you pull a UFO high bay IES:

1. Model / SKU – Exact model, including lumen package, beam code, driver option.
2. CCT – 4000 K, 5000 K, etc. Must match what you will order and install.
3. Input wattage – Within ±3% of catalog or LM‑79 value you are using for code/rebate.
4. Optic – Narrow, medium, wide, aisle, or special distribution.
5. Mounting orientation – Hook, pendant, or yoke; tilt = 0° unless you plan to aim.
6. Dimming/Driver setting – If the IES is for a fixed output but you plan to dim to 50% as “normal”, you should factor that into your layout.

Expert Warning: Wrong Variant, Wrong Result

Conventional wisdom suggests that “close enough” is fine—use any IES for the family and adjust quantities later. That shortcut fails with selectable high bays.

One research insight from DOE’s LED lighting resources is that changing drive current to alter lumen output directly changes efficacy; the relationship is not linear. When we compare selectable UFOs in practice, using an IES from the wrong wattage setting has produced:

• 10–20 lm/W mismatch in modeled efficacy.
• 15–25% error in calculated Lighting Power Density (LPD).
• Rebate applications rejected because the calculated lm/W no longer meets DLC thresholds when the utility re‑checks using the correct setting.

For rebate‑driven projects, always confirm that the IES file reflects the DLC‑listed configuration you intend to buy, then cross‑check the product in the DLC SSL Qualified Products List.

Step 2: Importing the IES into AGi32 or Similar Software

Most professional UFO high bay layouts today are done in tools like AGi32, DIALux, or Relux. All of them can read LM‑63 IES files.

Basic Import Workflow

The exact menu names differ, but the workflow is similar:

1. Create the room or warehouse model – Enter length, width, and mounting height. For high bays this is usually 6–15 m (20–50 ft).
2. Set surface reflectances – Ceiling, walls, and floor.
   • As‑built experience: ceilings are often 0.5 or lower in older or dusty warehouses, not the 0.8 that textbooks assume.
   • A practical starting point is 70–80% ceiling, 40–50% walls, 10–20% floor for clean spaces; reduce by 10–20 points for dirty or dark finishes.
3. Define the luminaire – Import the IES file and give it a clear name with wattage, CCT, and optic.
4. Place luminaires – Start with a regular grid for open areas, or rows following racking for aisles.
5. Assign calculation grids – Typically at 0.8–1.0 m (30–36 in) workplane height, plus vertical planes on racking faces if needed.
6. Run calculations – Review average, minimum, and uniformity ratios.

The AGi32 documentation confirms that it accepts standard IES LM‑63 files directly as luminaire definitions and uses them to compute point‑by‑point illuminance values.

Pro Tip: Confirm Orientation and Tilt

A frequent, subtle error is importing an IES with the wrong orientation. The LM‑63‑19 commentary notes that photometric origin, luminaire tilt, and axis conventions matter.

In high‑bay work, we repeatedly see these issues:

• Z‑axis flipped, causing the luminaire to emit “upwards” in the model.
• 90° rotation in plan, so a narrow aisle distribution is turned sideways.
• Tilt left at a non‑zero test angle when the real installation will be level.

Always drop a single test luminaire in an empty scene at the correct height, run a quick pseudo‑render or false‑color plot, and confirm the beam looks plausible before laying out dozens of units.

Step 3: Using IES Data to Set Spacing and Layout

Once your UFO high bay is defined in software, the IES beam pattern drives spacing, aiming, and height decisions.

Starting S/MH Ratios for Open Areas

Spacing‑to‑mounting‑height (S/MH) is the most practical quick metric. For UFO high bays:

• Many guides suggest 1.0–1.5 as a typical S/MH range.
• Our projects consistently show that in low‑reflectance industrial spaces (dark ceilings and walls), S/MH ≥ 1.5 can produce noticeable scalloping and 20–30% drops in illuminance between fixtures.

In fact, internal analysis reported in a high‑bay photometrics guide on spacing vs reflectance shows that if ceiling and wall reflectance are ≤0.3, you often need S/MH ≤ 1.0 to maintain reasonable uniformity at floor level.

Practical starting points:

• Wide distribution UFO: S/MH ≈ 1.2–1.4 in clean, light spaces; 1.0–1.2 in darker spaces.
• Medium distribution: S/MH ≈ 1.0–1.2.
• Narrow distribution (high‑rack, tall ceilings): S/MH ≈ 0.8–1.0.

From there, you refine based on calculated average lux and uniformity.

Aisle Layouts and Vertical Illuminance

For racked storage, the IES file’s vertical candela distribution becomes more important than the horizontal plane.

To keep picking faces readable:

• Use aisle or medium‑narrow optics.
• Run rows centered on aisles with S/MH ≈ 1.0–1.2.
• Stagger adjacent rows so beams overlap on the rack faces, not just on the aisle centerline.

The ANSI/IES RP‑7 recommended practice for industrial facilities suggests higher lighting levels for more demanding tasks like order picking or inspection. In practice, that means planning for:

• General storage: roughly 100–200 lux on the floor.
• Picking/packing: roughly 300–500 lux on work surfaces.
• Inspection/assembly: 500 lux and above at task level.

Use your IES‑based layout to hit these ranges with a maintenance factor applied (see below).

Layout Asset: Example Open Warehouse Scheme

Assume:

• Mounting height: 9 m (30 ft).
• Wide‑beam UFO high bay, 26,000 lm, 185 lm/W.
• Target: 250 lux average for mixed storage and light assembly.

A typical starting layout from repeated projects:

• S/MH = 1.2 ⇒ spacing ≈ 10.8 m (36 ft) between rows and along rows.
• Resulting modeled average ≈ 280–300 lux with clean 0.7 reflectance ceiling.
• After applying a 0.75 maintenance factor (see below), effective average ≈ 210–225 lux.

To reach an effective 250 lux, you either tighten spacing (S/MH ≈ 1.0–1.1) or move to a slightly higher lumen package.

Step 4: Accounting for Maintenance, Dirt, and Real‑World Losses

One of the biggest misconceptions about UFO high bay layouts is that software output equals what people will see in the finished space.

Expert Warning: Treat IES Lumens as Pre‑Discounted

Experience with real projects and a detailed analysis of high‑bay photometric performance show a consistent pattern: designs that ignore dirt and thermal losses under‑deliver.

In practice, when comparing IES‑based AGi32/DIALux predictions with handheld lux meter readings after installation, we routinely observe 10–25% lower average lux in industrial spaces, solely because designs assumed overly optimistic reflectances and no dirt depreciation. This pattern is documented in a technical discussion of modeled vs measured illuminance in a high‑bay photometric data guide.

Another field‑driven insight: in warehouses where high bays are frequently switched by occupancy sensors, sustained elevated temperatures at driver and board level can accelerate lumen depreciation. According to the U.S. Department of Energy’s analysis of LED system reliability, frequent cycling and high ambient temperatures can cause actual lumen maintenance over several years to underperform TM‑21 projections.

In real UFO high‑bay spaces, we therefore treat catalog/IES lumens as a pre‑discounted number and apply:

• 20–30% total light loss over 5–10 years in dirty, warm environments.
• 15–20% in cleaner, cooler warehouses.

Choosing a Maintenance Factor

Most design tools let you set a maintenance factor (MF) or light loss factor (LLF). For retrofit industrial projects, practical values are:

• MF ≈ 0.7 for dirty, high‑dust, or high‑temperature facilities.
• MF ≈ 0.75–0.8 for moderately clean warehouses.
• MF ≈ 0.8–0.85 only for very clean, climate‑controlled spaces.

Do not design to “as‑new” illuminance for LED high bays in harsh environments. Overshooting the target by 20–30% on day one is often justified so that year‑5 levels are still adequate.

Maintenance Factor Decision Table

Facility Type	Ambient & Dirt Level	Suggested MF	Notes
Clean logistics warehouse	Cool, low dust	0.80	White ceilings/walls, good housekeeping
Standard distribution center	Moderate dust, 24/7	0.75	Racking, forklifts, some airborne particulates
Heavy industrial / woodworking shop	High dust, warm	0.70	Build in 30% light loss over life
Food processing (washed surfaces)	Humid, frequent washdowns	0.75	IP‑rated high bays, watch for lens haze

These values are not codes; they are experience‑based planning numbers. Always validate with the facility operator’s cleaning and relamping strategy.

Step 5: Verifying Uniformity and Glare Using the IES File

The IES file allows your software to compute not just averages but also minimums and uniformity ratios. However, those metrics do not fully capture perceived quality.

Interpreting Uniformity Ratios

For horizontal layouts, two metrics are common:

• Average‑to‑minimum (U0)
• Maximum‑to‑minimum (U1)

The Illuminating Engineering Society’s definition of uniformity ratio explains that these ratios are intended to ensure that illuminance does not fall too low in any area relative to the average or maximum.

Practical guidance for UFO high bays in warehouses:

• Aim for avg:min ≤ 3:1 in open areas.
• Keep max:min ≤ 10:1 to avoid bright hotspots near fixtures.

Layouts with avg:min ≈ 2.0–2.5:1 usually feel visually comfortable for most industrial tasks.

Why Good Uniformity Can Still Feel Glary

A surprising but important real‑world finding: photometric software can show excellent U0 and U1 values while occupants still complain about glare.

The reason is that glare is strongly driven by high luminance and peak candela in the field of view, especially at high angles. A high‑bay layout can deliver smooth workplane lux while still placing very bright sources in direct line of sight at 30–60° above horizontal.

Experience with UFO high bay projects shows that when you choose optics that are too narrow and then add more fixtures to fill in the dark gaps, you often:

• Increase maximum candela at high angles.
• Create “sparkle” directly in the eyes of forklift drivers and machine operators.
• Worsen veiling reflections on glossy floors.

This aligns with the insight that simply adding more fixtures with the wrong beam often makes glare and veiling reflections worse, not better, as outlined in a high‑bay optics analysis on beam selection pitfalls.

Use the IES polar curves and intensity tables to check:

• Does peak candela occur at low angles (good for floor illumination) or at 60–80° (higher glare risk)?
• How quickly does intensity fall off beyond the main beam?

For projects where glare is a primary concern—such as production lines or detailed mechanical work—pair this article with a dedicated low‑glare discussion like the guidance in the separate resource on low‑UGR high bay lighting.

Performance Case Study: Correct vs Incorrect IES Use

To make this concrete, compare two approaches for a 4,000 m² (≈43,000 ft²) warehouse, 10 m (33 ft) mounting height, target 300 lux at workplane.

Scenario A: Correct IES, Conservative Assumptions

• IES matches exact SKU: 150 W UFO, 24,000 lm, 5000 K, wide optic.
• Ceiling reflectance 0.6, walls 0.3, floor 0.1.
• Maintenance factor 0.75.
• S/MH ≈ 1.1; 96 fixtures in a regular grid.

Results:

• Modeled average ≈ 360 lux as‑new.
• Effective design average (MF applied) ≈ 270 lux.
• Avg:min ≈ 2.5:1, max:min ≈ 6:1.

Post‑install spot checks with a mid‑range lux meter typically show 230–260 lux across representative grids—within ~10–15% of the design target, accounting for localized dirt and measurement variance.

Scenario B: Wrong IES, Optimistic Assumptions

• IES from same family but 200 W version at 32,000 lm.
• Reflectances all assumed 0.8 (textbook defaults).
• No maintenance factor applied.
• S/MH ≈ 1.5; 72 fixtures.

Modeled results look excellent on paper:

• Modeled average ≈ 420 lux.
• Avg:min ≈ 2.2:1.

Reality on site:

• Actual installed units are the 150 W version (documentation mismatch).
• Real ceiling and walls closer to 0.4/0.2.
• Measured averages: 210–230 lux.
• Large apparent scallops between fixtures, particularly in darker aisles.

Net effect: roughly 40–50% gap between modeled and perceived performance, plus a compliance risk if energy code or rebate paperwork was based on the 200 W IES.

This case illustrates why getting the IES and room assumptions right matters more than minor tweaks to layout spacing.

Common Misconceptions About IES Files and UFO High Bays

Myth 1: “If lm/W is high, the layout will be efficient.”

High efficacy is important, but delivered lux per watt depends on:

• How the beam pattern interacts with room geometry and reflectances.
• Maintenance factors over time.
• Controls strategy (occupancy and daylight dimming).

The DOE FEMP guidance on commercial and industrial luminaires sets minimum efficacy thresholds but also stresses that controls and application design determine actual savings. A poorly aimed high‑lm/W UFO can waste as much energy as a lower‑lm/W unit used intelligently.

Myth 2: “Software results are reality.”

Software is an excellent predictor when inputs are realistic and validated. However:

• Overstated reflectances, no maintenance factor, and the wrong IES variant are common.
• As noted earlier, field checks often show 10–25% lower average lux than optimistic models in industrial spaces.

Best practice is to treat software as a planning tool, then verify with a lux meter after commissioning. A short grid of 10–20 measurements provides far more assurance than a polished but unvalidated PDF.

Myth 3: “You can fix a bad layout by just adding more fixtures.”

Once you have chosen an optic that is not suitable for the space, adding more units often worsens glare and may reduce vertical illuminance where you need it. Before adding quantity, revisit:

• Optic selection (narrow vs wide vs aisle).
• Mounting height.
• Aiming to bring higher candela zones away from direct view.

Use the IES polar curves and beam angles to choose the right optic first; then adjust counts.

Practical Workflow: From IES File to Signed‑Off Layout

To make this actionable, here is a repeatable workflow for UFO high bay projects.

1. Confirm product certification and test data
   • Verify the luminaire’s listing in the DLC QPL if rebates or energy‑efficient purchasing programs are involved.
   • Obtain the LM‑79 test report and the corresponding IES file for the exact configuration.
2. Cross‑check LM‑79 vs IES
   • Total lumens and input watts in the IES should match LM‑79 within a few percent.
   • If they do not, query the lab or manufacturer before proceeding.
3. Build a realistic room model
   • Use site photos or drawings to estimate surface reflectances.
   • Apply an appropriate maintenance factor (0.7–0.8 for most industrial retrofits).
4. Select initial spacing based on optic and height
   • Start with S/MH in the 0.8–1.3 range depending on optic and reflectances.
   • Set up open area grids and aisle layouts separately.
5. Run calculations and check both averages and uniformity
   • Compare results to target lux ranges from industrial recommended practices such as RP‑7.
   • Adjust layout or lumen package as needed.
6. Review glare risk and visual comfort
   • Inspect candela distribution at higher angles.
   • If glare is a concern, consider lower output per head, more heads, and optics with better cutoff, as explored in the guide on low‑UGR high bay lighting.
7. Document and validate
   • Export calculation grids, fixture counts, and power densities for code and rebate forms.
   • After installation, sample 10–20 points with a lux meter and keep both model and field readings in the project file.

Safety, Codes, and Compliance Considerations

When you use IES files to design UFO high bay layouts, you are also implicitly addressing safety and energy code issues.

• Electrical safety and installation – Ensure that any specified high bay is certified to a luminaire safety standard such as UL 1598, which covers general‑purpose luminaires up to 600 V, and that its LED drivers comply with standards like UL 8750. The photometric layout does not replace the requirement to follow the National Electrical Code (NEC) and local regulations for wiring, overcurrent protection, and grounding.
• Energy codes and controls – Layouts driven by IES files need to be combined with appropriate controls zoning and sensor placement to comply with ASHRAE 90.1, IECC, or Title 24 where applicable. For example, warehouse high bay zones often require occupancy or vacancy sensors and, in some jurisdictions, multi‑level or continuous dimming. For a deeper dive into controls zoning in warehouses, see the resource on zoning UFO high bay dimming controls.

Because lighting design and electrical installation affect life safety and code compliance, always involve a licensed professional engineer or qualified electrician for final design approval and installation.

Wrapping Up: Key Takeaways for Using IES Files on UFO High Bay Projects

For B2B buyers, contractors, and designers, the IES file is the closest thing to an “X‑ray” of a UFO high bay’s real behavior.

If you:

• Choose the correct IES for the exact SKU and settings.
• Import it correctly into AGi32 or similar software with realistic reflectances.
• Apply an appropriate maintenance factor and check both illuminance and uniformity.
• Use the candela distribution to balance glare and visibility.
• Validate with field measurements post‑install.

…you move from guesswork to predictable, verifiable results. This approach supports rebate applications, simplifies conversations with inspectors and facility managers, and gives you defensible documentation if performance is ever questioned.

For more layout‑specific guidance, pair this article with the detailed walkthrough on designing a high bay layout for warehouse safety and the warehouse lumens guide for UFO high bay lights.

FAQ: Using IES Files for UFO High Bay Layouts

Q1. Do I need a separate IES file for each wattage and CCT of a selectable UFO high bay?

Yes, for accurate layouts and rebate calculations you should use an IES that matches the exact wattage and CCT setting you plan to deploy. Power‑selectable and CCT‑tunable fixtures change efficacy and candela distribution as drive current and spectral characteristics shift.

Q2. Can I use the same IES file for hook‑mounted and pendant‑mounted UFO high bays?

Only if the photometric lab tested the luminaire in a configuration that truly matches both installs. Even small tilts or changes in mounting hardware can shift peak candela angles by several degrees, moving bright spots on the floor. When in doubt, request separate IES files or confirm with the manufacturer.

Q3. How do I know if an IES file is trustworthy?

Cross‑check total lumens and input watts against the LM‑79 report and the DLC listing. If the numbers do not match within a few percent, ask for clarification. Visual inspection of polar curves and test layouts can also reveal implausible beam shapes or intensities.

Q4. What if I do not have access to AGi32?

You can still use IES files in other tools such as DIALux, Relux, or manufacturer‑provided layout calculators, as long as they accept LM‑63 format. The core principles in this guide—accurate IES selection, realistic reflectances, and maintenance factors—apply regardless of software.

Q5. How often should I re‑measure a warehouse after an LED retrofit?

Many facility teams schedule a quick illuminance spot‑check 6–12 months after commissioning, then at multi‑year intervals, especially in dusty or hot environments. Re‑measuring helps confirm that lumen depreciation and dirt accumulation are within expectations and can inform the timing of cleaning or relighting.

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Disclaimer: This article is for informational purposes only and does not constitute professional engineering, electrical, or legal advice. Lighting layouts and electrical installations should be reviewed and approved by a licensed professional engineer or qualified electrician familiar with local codes and standards, including NEC, building, and energy codes.