ICC Res Energy common mistakes
ICC Res Energy · Understand the traps and how to avoid them.
Answers a code question using the latest model-code edition without checking the permit date or the jurisdiction's adopted edition and amendments.
Study material often cites the newest IECC, so candidates memorize one edition's numbers and apply them to every scenario.
What to do instead
Make the first step of every scenario identify the governing edition from the permit application date and local adoption/amendments; if the edition is not stated, look for adoption cues before choosing a numeric requirement.
Uses a cavity insulation R-value from an envelope table as though it were an assembly U-factor, or the reverse, such as comparing R-20 wall insulation directly to a U-0.060 fenestration requirement.
Both R-values and U-factors appear in Chapter 4 tables, and U and R are reciprocals; assembly U-factors also include framing, sheathing, and air films.
What to do instead
Before looking up a number, classify the requirement as cavity insulation R-value or whole-assembly U-factor; convert with U = 1/R_total and area-weight U-factors only across similar assemblies when the code permits averaging.
Treats a blower-door envelope leakage result in ACH50 as if it satisfied duct leakage, or cites the visual air-barrier inspection as a tested leakage limit.
The code contains several air-leakage provisions with different metrics and test methods, so candidates blur the envelope test, duct test, and visual checklist together.
What to do instead
Separate the three checks: air-barrier installation/visual requirements, envelope leakage reported in ACH50 or the permitted cfm/ft2 alternative, and duct leakage reported in cfm per 100 ft2 of conditioned floor area; match the unit to the section.
Sizes heating and cooling equipment by square footage, or replaces a failed unit with the same nominal capacity, without performing a load calculation.
Rule-of-thumb sizing is common field practice and exam scenarios that give house area tempt a shortcut.
What to do instead
Residential code requires a heating/cooling load calculation per ACCA Manual J or an approved equivalent, equipment selection per ACCA Manual S, and duct design per ACCA Manual D; capacity is the calculated output, not nominal tonnage.
Accepts intermittent bathroom and kitchen exhaust fans as the only ventilation strategy in a tightly built house.
Local exhaust removes pollutants at the source but does not provide continuous whole-house ventilation, and older practice often relied on exhaust fans alone.
What to do instead
Apply the whole-house mechanical ventilation requirement separately from local exhaust; verify the ventilation system, controls, and airflow comply with the referenced residential ventilation standard, and do not let local exhaust substitute for it.
Insulates only visible or readily accessible hot-water piping and leaves recirculating lines or fittings uninsulated.
Pipe insulation is often treated as a plumbing trade practice rather than an energy-code requirement, so candidates overlook the service-water-heating provisions.
What to do instead
Apply the service-water-heating pipe insulation requirements to all hot-water piping per the table and exceptions, including recirculation lines, and verify circulation-pump controls and heat traps where required.
Applies a commercial lighting power density budget in watts per square foot to a single-family dwelling.
Lighting power density is the commercial compliance method, while the residential chapter uses fixture-efficacy and percentage provisions; candidates mix the chapters.
What to do instead
For residential projects, use the high-efficacy fixture percentage or efficacy threshold in the residential electrical power and lighting provisions; reserve lighting power density for commercial compliance.
Counts plug-in or portable lamps, or appliances such as refrigerators, toward the residential high-efficacy lighting percentage.
The lighting requirement applies to permanently installed fixtures, not cord-connected luminaires or appliances, and appliance efficiency is generally governed outside this chapter.
What to do instead
Count only permanently installed lighting fixtures; determine compliance from the fixture and the lamps shipped with it; do not use appliance standards as a substitute for the lighting requirement.
Rejects a design for not meeting prescriptive table R-values when the project is using the simulated performance or energy rating index path, or assumes the performance path waives air sealing and duct requirements.
Candidates memorize prescriptive tables and miss the chapter hierarchy: mandatory provisions apply under every compliance path.
What to do instead
Map the chapter before answering: mandatory measures such as envelope air sealing, duct sealing, ventilation, and lighting apply regardless of path; only the prescriptive tradeoff tables are path-specific, and performance paths trade envelope and systems against annual energy use.
Requires a window replacement in an existing house to trigger a full-house envelope upgrade to new-construction R-values.
Existing-building provisions are studied less often, so new-construction prescriptive tables are over-applied to alterations and replacements.
What to do instead
Use the existing-buildings provisions: alterations and replacements comply with the specific alteration requirements, such as replacement fenestration meeting the applicable U-factor and SHGC for the replacement unit, and the entire building is not brought up to new-construction prescriptive levels unless the scope triggers it.