Energy code compliance is reviewed on every commercial building permit submittal. Depending on the jurisdiction, drawings are checked against the International Energy Conservation Code (IECC) commercial provisions, ASHRAE Standard 90.1 (Energy Standard for Buildings Except Low-Rise Residential Buildings), or both. Some jurisdictions adopt the IECC but reference ASHRAE 90.1 as an alternate compliance path, while others adopt 90.1 directly. Either way, the plan reviewer is checking the same core areas: building envelope, HVAC systems, service water heating, lighting, and commissioning documentation.
Energy code corrections are among the most time-consuming to resolve because they often require recalculations, updated schedules, and coordination across architectural, mechanical, and electrical drawings. This checklist covers the 10 energy code plan review issues that generate the most comments, organized by building system.
Building envelope
1. Opaque envelope insulation values
The building envelope is the first thing energy code reviewers check. IECC Table C402.1.3 (prescriptive) and ASHRAE 90.1 Tables 5.5-1 through 5.5-8 specify minimum R-values and maximum U-factors for roofs, above-grade walls, below-grade walls, floors, and slab-on-grade foundations by climate zone. Reviewers compare the insulation values shown on the wall sections, roof details, and foundation details against the requirements for the project's climate zone. The most common violations are walls that meet the cavity insulation requirement but miss the continuous insulation requirement (for example, R-13 cavity without the required R-7.5 continuous insulation in Climate Zone 5 steel-framed walls), and slab edge insulation that is either missing or does not extend to the required depth. Check every assembly type shown on the architectural drawings: if the project has three different wall types, each one needs to meet or exceed the prescriptive minimums, or the project needs to demonstrate compliance through the building performance method (IECC Section C407 or ASHRAE 90.1 Section 11).
2. Fenestration U-factor and SHGC
Windows, curtain walls, and skylights must meet maximum U-factor and solar heat gain coefficient (SHGC) requirements per IECC Table C402.4 or ASHRAE 90.1 Table 5.5. Reviewers check the window schedule for U-factor and SHGC ratings by product, then verify these against the climate zone requirements. Common violations include window schedules that list only the glass U-factor instead of the overall assembly U-factor (which includes the frame), SHGC values that are missing entirely from the schedule, and skylights that exceed the maximum U-factor. The window-to-wall ratio (WWR) also matters: if the total fenestration area exceeds 30% of the gross above-grade wall area (IECC) or 40% (ASHRAE 90.1), additional restrictions apply or the project must use the building performance method. Reviewers calculate the WWR from the elevations and floor plans, so the fenestration areas should be clearly documented on the drawings or in a separate energy compliance form.
3. Air barrier and sealing details
IECC Section C402.5 and ASHRAE 90.1 Section 5.4.3 require a continuous air barrier across the building envelope. The air barrier must be identified on the drawings, and its continuity must be shown at all transitions: wall to roof, wall to foundation, wall to window, and at penetrations. Reviewers look for a designated air barrier material in the wall and roof assemblies, details showing how the air barrier is maintained at transitions (especially at parapet conditions, window heads and sills, and structural penetrations), and sealing details at all envelope penetrations. A common correction is a set of drawings that names the air barrier material in the specifications but never shows it in section details, leaving the reviewer unable to confirm continuity. If the project uses building envelope testing as the compliance path (0.40 cfm/sf at 75 Pa for commercial buildings under IECC), that requirement must be noted on the drawings along with a testing specification.
HVAC systems
4. Equipment efficiency ratings
Every piece of HVAC equipment shown on the mechanical schedule must meet minimum efficiency requirements. IECC Table C403.3.2 and ASHRAE 90.1 Tables 6.8.1-1 through 6.8.1-12 specify minimum efficiencies by equipment type, capacity, and heating source. For packaged rooftop units, the required metric is typically IEER (Integrated Energy Efficiency Ratio) for cooling and thermal efficiency for heating. For chillers, it is IPLV (Integrated Part Load Value) or COP by condenser type and capacity range. For boilers, it is thermal efficiency or combustion efficiency depending on capacity. Reviewers compare the efficiency values in the equipment schedule against the code minimums for each unit's type and size. The most common violation is a schedule that lists the manufacturer's rated efficiency but at a different rating condition than the code requires, or a schedule that omits the efficiency column entirely. Heat pumps have their own tables and rating conditions (HSPF2, SEER2, or COP depending on type and capacity), which changed significantly in the 2021 IECC cycle.
5. Economizer requirements
Air-side economizers are required on individual cooling systems with a cooling capacity at or above the threshold for the project's climate zone. IECC Section C403.5 and ASHRAE 90.1 Section 6.5.1 set the thresholds: in most climate zones, economizers are required on systems with 54,000 Btu/h (4.5 tons) or more of cooling capacity. The exception varies by climate zone and system type. Reviewers check each cooling unit on the mechanical schedule for capacity, then verify that units above the threshold include economizer controls. The drawings must show the control type (differential dry-bulb, differential enthalpy, or fixed dry-bulb, depending on climate zone), the high-limit shutoff setpoint, and the minimum outdoor air damper position. Systems that use water-side economizers or other exceptions must document the specific exception claimed. Common violations include units that are above the capacity threshold but show no economizer, and economizer control sequences that reference the wrong high-limit shutoff type for the climate zone.
6. Duct insulation and sealing
Supply and return ducts must be insulated and sealed per IECC Section C403.11 and ASHRAE 90.1 Section 6.4.4. Minimum duct insulation R-values depend on the duct location (conditioned space, indirectly conditioned space, or unconditioned space) and the supply air temperature. Supply ducts in unconditioned spaces typically require R-8 insulation (R-6 for heating-only ducts in some climate zones). Return ducts in unconditioned spaces require R-6 minimum. Ducts in conditioned space may be exempt from insulation but still require sealing. Duct sealing class must be specified on the drawings: Seal Class A for supply ducts upstream of the terminal, Seal Class B for supply ducts downstream of the terminal, and Seal Class C (or exempt) for return ducts in some configurations. Reviewers check the mechanical plans and details for duct insulation specifications by location, sealing class designations, and confirmation that the specified insulation meets the minimum R-value for the duct's location and function. Exhaust ducts are generally exempt from insulation requirements but not from sealing requirements.
7. HVAC controls and setback
Energy codes require specific HVAC control capabilities. IECC Section C403.4 and ASHRAE 90.1 Section 6.4.3 require programmable thermostats or DDC controls with setback/setup capability: heating setback to 55 degrees F and cooling setup to 90 degrees F (or equipment shutoff) during unoccupied periods. Zone controls must prevent simultaneous heating and cooling (deadband of at least 5 degrees F between heating and cooling setpoints). Systems with outdoor air economizers must have automatic controls that prevent economizer and mechanical cooling from operating simultaneously at cross purposes. Variable air volume (VAV) systems must have controls that reduce fan speed at part load rather than using discharge dampers. Reviewers check the mechanical schedules and control sequences for setback/setup programming, deadband settings, economizer integration, and VAV fan control strategy. The most common correction is a control sequence that describes the occupied mode operation but says nothing about unoccupied setback or optimum start.
Lighting
8. Interior lighting power density
Interior lighting must not exceed the lighting power density (LPD) allowance calculated by the building area method or the space-by-space method. IECC Table C405.3.2 and ASHRAE 90.1 Table 9.5.1 (building area method) or Table 9.6.1 (space-by-space method) set the maximum watts per square foot by building type or space type. The space-by-space method is more work but almost always yields a higher total allowance because it accounts for spaces that legitimately need more light (laboratories, retail display, medical exam rooms). Reviewers compare the total connected lighting load on the electrical plans against the calculated allowance. Common violations include lighting power calculations that omit track lighting, under-cabinet lighting, or display lighting; calculations that use gross floor area instead of net lighted area for the space-by-space method; and decorative lighting that is not included in the power total. The lighting schedule must show wattage for every fixture type, and the compliance form must show the calculation method, space areas, and resulting allowance.
9. Lighting controls
Energy codes require automatic lighting controls in addition to LPD limits. IECC Section C405.2 and ASHRAE 90.1 Section 9.4 require occupancy sensors in offices, conference rooms, restrooms, storage rooms, and other intermittently occupied spaces. Daylight-responsive controls are required in daylight zones adjacent to vertical fenestration (within 15 feet of windows for sidelighting) and below skylights (for toplit daylight zones). All enclosed spaces must have at least one manual or automatic control that independently reduces the lighting power in that space by at least 50%. Exterior lighting must have automatic controls (photocell, astronomical time clock, or both) that shut off exterior lights when daylight is available. Reviewers check the electrical plans for occupancy sensor coverage, daylight sensor locations in qualifying zones, control zoning that allows independent operation of daylight-zone fixtures, and exterior lighting control schedules. The most common correction is a floor plan that shows occupancy sensors in some spaces but not all required spaces, or a daylight zone that has no separate switching or dimming control for the fixtures within 15 feet of the windows.
Commissioning and documentation
10. Mechanical commissioning plan
IECC Section C408 and ASHRAE 90.1 Section 8.4 require mechanical system commissioning for all commercial buildings. The scope varies by building size: smaller buildings may need only functional testing of HVAC controls, while larger buildings (typically over 50,000 square feet of conditioned floor area) require a full commissioning plan including design review, construction checklists, functional performance testing, and a commissioning report. The drawings or specifications must identify the commissioning requirements, including which systems are in scope (HVAC, lighting controls, and service water heating at minimum), who is responsible for commissioning (owner's agent, contractor, or third-party commissioning authority), and the functional testing procedures. Reviewers check for a commissioning specification section or notes on the drawings that address the code requirements. The most common correction is a set of drawings that makes no mention of commissioning at all, forcing the reviewer to issue a comment requiring a commissioning plan before permit issuance. Some jurisdictions also require completed commissioning reports before issuing a certificate of occupancy, and the drawings should note this requirement to set expectations for the project team.
Catching these before submittal
Energy code compliance touches the architectural, mechanical, and electrical drawings simultaneously. A single building envelope assembly involves the architect's wall section, the mechanical engineer's load calculations (which depend on correct U-factors), and the energy compliance form that ties them together. Reviewing drawings against the IECC and ASHRAE 90.1 at the same time as the mechanical and electrical codes is where automated review tools have the biggest impact: they can cross-check insulation values, equipment efficiencies, lighting power densities, and control requirements across all sheets in one pass, catching the cross-discipline gaps that are hardest to find in a manual review.