On the Lighter Side of the Sun (After Dark Series): • Browse the series: After Dark
(What to demand to confirm a specification is actually current):
- Publication year stated for every standard cited, not just the title
- Photometric testing reference set to IES LM-79-19, not LM-79-08
- Roadway lighting designed to ANSI/IES RP-8-25 (2025), with section numbers
- Energy code citation matched to the edition the AHJ actually enforces in this jurisdiction
- Master spec section dated within the last 12 months, not pasted from an earlier project
- AHJ adoption status verified per standard, edition by edition
- For solar and off-grid: photometric targets re-validated against current standards, not legacy HID-era illuminance levels
An LM-79-08 reference in a current specification is not a typo. It is a tell.
The Retired Rulebook Problem
The IES retired the Lighting Handbook five years ago. Half the industry hasn’t noticed.
The IES Lighting Handbook, 10th Edition was published in 2011, when LED was the underdog and HID was still the default street light. In 2020, IES retired it and replaced it with the Lighting Library, a continuously updated digital platform. The 2011 handbook is no longer authoritative.
It is still on shelves. It is still cited in active specifications. Many municipal design guides quote its illuminance tables verbatim, set the values into ordinances, and treat them as the ceiling of what is required. Those numbers were calibrated against high-pressure sodium and metal halide sources with rapid lumen depreciation, poor optics, and high dirt depreciation factors. Apply them to a modern LED with tight optical control and stable lumen output, and the result is systematic over-lighting.
The same pattern shows up in the testing references. Specifications routinely require LM-79-08 photometric testing when LM-79-19 has been current for years. Roadway specs still cite RP-8-14 or older when RP-8-25 is the current edition. AASHTO’s Roadway Lighting Design Guide reached its 7th Edition in 2018, but the 2005 edition is still embedded in some state DOT manuals.
None of this is an accident. It is the predictable output of how specifications are actually written.
The Copy-Paste Problem
A specification is only as current as the last person who actually opened the file.
Most engineering firms in North America build their specifications from master systems like MasterSpec in the US or the National Master Specification in Canada. Both are updated regularly by their publishers. The publishers are not the problem.
The problem is what happens after the firm subscribes. A senior engineer edits Division 26, Section 265119 for LED Interior Lighting and Section 265600 for Exterior Lighting to reflect the firm’s preferred manufacturers, the local AHJ’s quirks, and a few hard-won lessons from past projects. That edited version becomes the firm’s master. Junior engineers paste it into the next project. Then the project after that. Then the one after that.
The standards cited in those sections drift quietly into obsolescence. Reviewing every line against current IES, ANSI, and ASHRAE references is non-billable, time-consuming, and requires specialized expertise that retiring senior engineers are taking with them. So it does not happen. The spec ages in place, unread, until somebody finally questions it.
The Standard of Care Trap
The legal system does not reward you for being current. It rewards you for matching what everyone else is doing.
Under common law, a design professional must perform with the ordinary skill and care that a reasonably prudent peer would exercise in the same locality. That is the standard of care. It is defined by what the local industry actually does, not by what the most recent IES publication recommends.
If most lighting designers in your jurisdiction are still designing to older standards and the 2011 Lighting Handbook, that defines the regional standard of care. A designer who switches to RP-8-25 and applies current mesopic adjustments from TM-24-20 has technically improved the design. They have also walked away from the herd. If anything goes wrong on the project, the deviation can be argued against them in litigation.
E&O insurers compound the problem. They generally insure against the ordinary standard of care, not the highest. Contracts that promise the latest and best can void coverage. Defensive engineering, sticking to the older and universally accepted standard, becomes the rational legal choice. It is also the wrong engineering choice, but the incentive structure does not care.
Why Solar Specifiers Caught This Early
Batteries do not tolerate yesterday’s illuminance assumptions. They run out.
Off-grid solar lighting forces a confrontation with bad specs that grid-tied design can absorb. If a specification calls for an inflated illuminance target derived from HID-era assumptions, a grid-tied project simply pays a slightly higher utility bill. The lights stay on.
A solar project does not have that buffer. Inflated illuminance targets translate directly into more panel area, more battery capacity, larger pole structures, and higher cost. If the targets were calibrated for sources with 30 percent lumen depreciation and the actual source holds 95 percent lumen output for years, the entire system is oversized to compensate for a depreciation that never happens. The economics force the designer to question the source numbers. Once the source numbers are questioned, the spec gets a real review.
This is not a solar advantage so much as a solar pressure. The math does not let you skip the audit. Specifiers working in off-grid lighting end up doing what every specifier should be doing, which is asking whether the standard cited in their template still describes the world they are designing for.
The AHJ Lock-In
The inspector enforces what was adopted, not what is current. Those are not the same document.
Authorities Having Jurisdiction enforce the codes and standards their jurisdiction has formally adopted. If a municipal ordinance references an older AASHTO guide and the 2011 Lighting Handbook, that is the law in that city, regardless of what IES has published since.
A designer who submits a plan applying current TM-24 equivalent visual efficiency multipliers, or current RP-8-25 conflict area criteria, often gets the plan rejected. Not because the design is wrong, but because the design does not match the adopted reference. The AHJ has no authority to approve a deviation, even a technically superior one. The designer reverts to the older standard to clear the permit. The permit clears. The outdated standard is reinforced.
This is the loop that keeps the time capsule sealed.
What to Require in a Specification
If your spec does not state edition years, it does not have currency. It has nostalgia.
- Every cited standard listed with publication year and edition number
- Photometric testing reference verified as current (LM-79-19, not LM-79-08)
- Roadway lighting calculations referenced to ANSI/IES RP-8-25 (2025) by section
- Energy code citation matched to the edition the AHJ enforces, with that edition year stated
- ASHRAE 90.1 reference set to the edition currently adopted in the project jurisdiction
- Division 26 sections dated within the last 12 months and reviewed against current ANSI/IES references before issue
- For solar and off-grid: illuminance targets re-derived from current standards, not inherited from legacy HID-era assumptions
Three Questions That Expose a Time Capsule Spec
These questions sound clerical. The answers are diagnostic.
What is the publication year of every lighting standard cited in this specification, and have any of them been superseded?
When was Division 26 last reviewed against current IES, ANSI, and ASHRAE references, and by whom?
Which edition of each referenced standard is the AHJ actually enforcing in this jurisdiction, and does the design comply with that edition specifically?
If the answers are vague, the spec was not written for this project. It was inherited.
Closing Thought
The rulebook in your spec library does not age like wine. It ages like milk.
Sources and Where to Verify
- ANSI/IES RP-8-25 (2025), Recommended Practice: Lighting Roadway and Parking Facilities (current edition, supersedes RP-8-14 and earlier)
- IES Lighting Library (current, replaced the 10th Edition Lighting Handbook of 2011 in 2020)
- IES LM-79-19, Approved Method: Optical and Electrical Measurements of Solid-State Lighting Products (supersedes LM-79-08)
- ANSI/ASHRAE/IES Standard 90.1-2022, Energy Standard for Buildings (expanded scope including exterior lighting and horticultural applications)
- AASHTO Roadway Lighting Design Guide, 7th Edition (2018) and NCHRP Research Report 940, Solid-State Roadway Lighting Design
- ANSI/IES TM-24-20, Adjustments to Illuminance Criteria
- ANSI/IES LP-1-20, ANSI/IES LP-9-20, and ANSI/IES LP-10-26 (current Lighting Practice documents)
- NSPE Code of Ethics and Board of Ethical Review cases on the engineer’s duty to protect public health, safety, and welfare
- DesignLights Consortium SSL V6.0 and LUNA V2.0 Technical Requirements (current QPL specifications)
Quick FAQ
How do I tell if a master spec section is outdated without reading every standard it cites? Check the date on the section, then check the publication years on the standards it references. If the section is older than the most recent edition of any standard listed, it is outdated by definition.
Is it really a problem to design to a current standard if the AHJ enforces an older one? Yes and no. The AHJ can refuse to issue a permit if the design does not match the adopted code. Most designers comply with the older standard to clear the permit, then exceed it where they can without triggering rejection. The cost is energy and quality, paid silently across the life of the project.
Why hasn’t the industry just fixed this? Because updating master specs is non-billable work, deviating from the local standard of care creates legal exposure, and AHJs are required to enforce what was formally adopted, not what is current. The incentive structure rewards staying outdated, and that structure is what has to change.
Piotr Mikus is a roadway lighting designer and specifier focused on solar powered street lighting and controls.
Views are the author’s own and do not represent any employer or affiliated organization. See site Disclaimer.
Solar Lighting Night Shift 