IECC 2018 · Section C405 · Idaho-adopted · New construction
Design to your lighting budget, not backwards from it.
The energy code tells you how to count watts before it tells you your budget. This advisor flips that: it surfaces your power allowance first, then shows the controls each space type will expect — so you can shape a compliant design while the program is still fluid. It informs decisions; it doesn't certify them.
About this tool. LPD values are encoded from base 2018 IECC — Building Area Method from Table C405.3.2(1) and Space-by-Space from Table C405.3.2(2), read directly from the IECC Code & Commentary. Context-specific space rows are flattened to named entries; Atrium uses a height-based formula (0.03 W/ft² per ft of height, or 0.40 + 0.02 per ft above 40 ft) and is entered manually. This advisor is informational, assumes new construction, and doesn't model the IECC applicability gate or constitute a code review — always verify against your jurisdiction's adopted edition and confirm interpretations with the AHJ before permit.
00 / PHASE
Where are you in the design?
Your design phase sets which allowance method fits. BAM needs only a building type and total area — right for early design. SBSM needs the space program, gives a higher allowance, and unlocks tradeoffs and additional allowances — right once the program firms up.
01 / STRATEGY
Pick your controls strategy
A project-level choice made early, because it changes what controls each space needs. C405.2
02 / ALLOWANCE
Your power budget
Start from a building-type preset optional
Pick a building type and enter its total floor area. The tool preloads the base building area plus commonly co-located areas (multiuse split), each as an editable row with its own allowance. Use it as a starting point, then adjust areas to your program.
Related building areas — multiuse facility C405.3.2.1
A multiuse building can carry several building areas, each with its own allowance, summed. Tap to add one as its own row, then assign its area — and reduce the base area to match.
Start from a building-type preset optional
Pick a building type and enter its total floor area. The tool loads a common space-type arrangement and splits the area across it — a fast first program you can then edit, add to, or trim. Watts use the tool's own LPD table; the preset supplies only the mix of spaces.
Specific-application lighting C405.2.4
Activate the load types present C405.2.4 — tick each one that applies; its control populates the advisor
A new building can be exempt from installing daylight-responsive controls on its uncontrolled daylight zones if its total connected lighting power (TCLP, per C405.3.1) is no greater than the adjusted allowance LPA_adj. Taking this exemption means committing to LPA_adj as your binding cap — and because LPA_adj is stricter than your normal allowance (reduced by up to 40% in proportion to uncontrolled daylit area), it trades the cost of controls for a tighter power budget. This calculator is a pass/fail test meant to show those parameters and how hard the exemption is to meet. Building Area Method.
03 / CONTROLS
What each space type expects
For each space type, the advisor shows which control branches fire, the special conditions to watch, and the exemptions or additional allowances that may apply.
Required triggered now — the branch applies and must be designed in.
Conditional fires when a threshold is met (area, daylight wattage).
Watch depends on design choices you haven't locked yet.
SCOPE
Where this sits in C405
Section C405 has nine parts. This tool covers two of them — interior controls and interior lighting power. The rest are shown for orientation only.
C405.1General — scope & per-area routing (commercial vs R404.1 vs C403)reference
C405.3Interior Lighting Power — the LPD allowance (Building-Area & Space-by-Space)in this tool
C405.4Exterior Lighting Power — total connected exterior power vs allowancereference
C405.5Dwelling-Unit Submetering — individual submeters for dwelling units in commercial buildingsreference
C405.6–.9Transformers · motors · transportation · voltage drop — not lightingn/a
MAP
The interior controls map (§C405.2)
Three groups, by what's being controlled: the general lighting, any specific-application loads, and the manual switch itself.
General lighting controls every space — shutoff plus daylight where it applies
Occupancy Sensor C405.2.1
Auto-off within 20 min of vacancy, and manual-on (or auto-on to ≤50%). For the listed space types.
OR
Time-Switch C405.2.2
Scheduled automatic shutoff with a manual override ≤2 hr. The fallback where an occupant sensor isn't required.
↑ AUTO-OFF — satisfied by one of these
Daylight Harvesting C405.2.3
Triggered when a daylight zone carries more than 150 W of general lighting. Sidelit and toplit zones controlled independently; continuous dim to ≤15% in offices, classrooms, labs and library reading rooms.
LLLC (Path 2): a DLC-qualified LLLC luminaire carries an integrated occupancy sensor and photocontrol, so the fixtures absorb this whole group — occupancy auto-off, time-switch scheduling, and daylight harvesting. Only the specific-application (C405.2.4) and manual (C405.2.5) checks remain.
Specific-application controls C405.2.4 — additive, only for these load types
Display & Accent
Separate manual control, independent of general lighting, plus automatic shutoff (occupant sensor or time-switch).
Task & Case
Supplemental task and display-case lighting — same rule: dedicated manual control plus automatic shutoff.
Nonvisual
Plant-growth and food-warming loads — independent time-switch, on its own schedule (not shared with general lighting).
Sleeping Unit
Auto-off of all permanent luminaires and switched receptacles within 20 min. Card-key and patient-care areas are exempt.
The manual control is in a location with ready access to occupants.
Identification
The control is either visible from the lights it serves, or labeled to identify the area served and indicate its status.
Dwelling-unit permanent luminaires (C405.2.4 D.3) are routed to R404.1 and aren't shown here — this tool's scope is commercial new construction. They can be added if the project includes dwelling units on the commercial path.
KEY
What each control type means
Occupancy Sensor
Auto-Off / Manual-On Check
C405.2.1
Triggered
The space is one of the listed occupant-sensor types — offices, conference/meeting, classrooms, copy/print, lounges/breakrooms, restrooms, storage, locker rooms, warehouses, open-plan offices, and small full-height-partitioned rooms ≤300 ft².
Requires
Automatic shutoff within 20 min of vacancy. Sub-routes: .1.1 standard, .1.2 warehouse (per-aisle), .1.3 open plan (≤600 ft² zones).
Status
requiredconditionaln/a — required for listed types; conditional for the ≤300 ft² catch-all; N/A under LLLC, where the fixture's integrated sensor provides it.
Time-Switch
Scheduled Shutoff Check
C405.2.2
Triggered
The space isn't covered by a compliant occupant sensor under .1.1 — the scheduled-shutoff fallback.
Requires
A 7-day automatic schedule (7 day-types, holiday shutoff, 10-hr backup) with a manual override ≤2 hr covering ≤5,000 ft².
Status
requiredconditionalsatisfiedn/a — satisfied when a .1.1 sensor already shuts lights off; N/A under LLLC.
Daylight-Responsive
Sidelight / Toplight Zone Check
C405.2.3
Triggered
A sidelit or toplit daylight zone carries more than 150 W of general lighting — real glazing or skylights over a meaningful fixture load.
Requires
Photo-controls that dim or switch the daylit fixtures; continuous dim to ≤15% in offices, classrooms, labs and library reading rooms.
Status
conditionaln/a — conditional on glazing/skylights; N/A under LLLC.
Specific-Application
Separate Control Check
C405.2.4
Triggered
The space carries a special load: display/accent, supplemental task, display case, nonvisual (plant-growth / food-warming), or sleeping-unit lighting.
Requires
A dedicated control for that load, separate from the general-lighting switch. It is additive — it never replaces the general-lighting shutoff.
Status
requiredwatch — required for sleeping units; flagged as watch where it depends on what's installed.
Manual Control
Accessible Switch Check
C405.2.5
Triggered
Always — every space needs an occupant-reachable manual control.
Requires
Ready access, and either visibility of the controlled lights or a label identifying the area served and indicating status.
Status
required — required in every space. It is never discharged by an occupant sensor, time-switch, or LLLC; a separate readily accessible manual control is always needed.
STATUS
What the status colors mean
requiredThe check applies and must be designed in.
conditionalApplies only if a trigger (area, glazing, load) is met.
watchMay apply depending on what's actually installed — flag it.
satisfiedAlready met by another control — nothing more to do.
n/aNot in play here (e.g. absorbed by LLLC).
Scope: interior controls (C405.2.1–.2.5) and interior lighting power (C405.3) for commercial new construction. Exterior controls (C405.2.6), exterior power (C405.4), and dwelling-unit submetering (C405.5) are out of scope and shown on the map for orientation only. Routing reflects a strict reading of the code; where an AHJ interpretation differs, the tool surfaces a note rather than choosing silently.
Phase boundary. This advisor stops before per-room enumeration and the C408.3.1 functional-testing checklist. Once the program is fixed, hand off to Interior Compliance v8 to enumerate every room, confirm each control is installed, and document the acceptance tests. Design phase tells you what to expect and design toward; v8 confirms you built it.
04 / EXPORT
Hand off your work
Take your program forward two ways: a spreadsheet that loads straight into the Interior Compliance tool to start construction-document verification, and a PDF summary of the design-phase decisions for the record.
Compliance template (.xlsx)
A formatted workbook — Read Me, Program (or Building Areas), and Daylight Zones — carrying space type, area, count, LPD, and connected watts. The Program sheet uploads into the Interior Compliance tool; the Daylight Zones sheet feeds the Sidelit / Toplit calculators. Space-type names are translated to the compliance tool's vocabulary so rows aren't dropped on import.
Design-phase report (.pdf)
A summary of this session: method, allowance breakdown, the program with per-row power, tradeoffs applied, the daylight-controls exemption result, and the per-space control expectations.