{"id":4658,"date":"2026-09-10T02:00:00","date_gmt":"2026-09-10T02:00:00","guid":{"rendered":"https:\/\/www.26yc.com\/?p=4658"},"modified":"2026-10-08T23:36:10","modified_gmt":"2026-10-09T06:36:10","slug":"iecc-energy-recovery-provisions","status":"publish","type":"post","link":"https:\/\/www.26yc.com\/ja\/iecc-energy-recovery-provisions\/","title":{"rendered":"IECC Energy Recovery Provisions"},"content":{"rendered":"<p>\u305d\u306e <strong>International Energy Conservation Code (IECC)<\/strong> is updated on a three-year cycle (2018, 2021, 2024) and is adopted &mdash; with or without amendments &mdash; by most U.S. states. Its commercial energy-recovery rule lives in <strong>Section C403.7<\/strong>, and it is the baseline that many state codes reference. This article summarizes the C403.7 trigger and how the 2024 edition tightens ventilation.<\/p>\n<h2>C403.7 Trigger (Table C403.7.1)<\/h2>\n<p>Energy recovery is required on fan systems with both mechanical supply and exhaust when design outdoor-air supply exceeds the threshold in Table C403.7.1, which varies by climate zone and outdoor-air fraction:<\/p>\n<table>\n<tr>\n<th>Climate zones<\/th>\n<th>Outdoor air (CFM)<\/th>\n<th>Min % outdoor air<\/th>\n<th>Recovery required?<\/th>\n<\/tr>\n<tr>\n<td>3B through 8<\/td>\n<td>&ge; 5,000<\/td>\n<td>&ge; 70%<\/td>\n<td>Yes<\/td>\n<\/tr>\n<tr>\n<td>4 through 8<\/td>\n<td>&ge; 5,000<\/td>\n<td>&ge; 30%<\/td>\n<td>Yes<\/td>\n<\/tr>\n<\/table>\n<p>The device must achieve a <strong>recovery effectiveness of at least 50%<\/strong> of the enthalpy (or temperature, for sensible-only) difference between outdoor and return air. Exceptions cover economizer-equipped systems and cases where recovery is not cost-effective given climate and degree days.<\/p>\n<h2>What IECC 2024 Adds<\/h2>\n<ul>\n<li><strong>ASHRAE 62.1-2022 adoption<\/strong> by reference &mdash; ventilation is no longer optional to treat as secondary; the Ventilation Rate Procedure, IAQ Procedure, or Natural Ventilation Procedure must be demonstrated.<\/li>\n<li><strong>Demand-control ventilation (DCV) expansion<\/strong>: spaces above 500 ft&sup2; designed for more than 25 people often mandate CO<sub>2<\/sub>-based DCV, trimming 15&ndash;30% of fan and conditioning energy.<\/li>\n<li><strong>Enhanced commissioning<\/strong>: ERV\/DCV systems must be verified for airflow, sensor calibration, and control sequence.<\/li>\n<li><strong>Multifamily as commercial<\/strong>: buildings four stories or taller follow commercial paths, and the 2021\/2024 prescriptive path <em>requires ERVs in dwelling units<\/em> (the performance path can trade this out via modeling).<\/li>\n<\/ul>\n<h2>How It Relates to Other Codes<\/h2>\n<p>C403.7 mirrors the federal <a href=\"https:\/\/www.26yc.com\/ja\/ashrae-90-1-heat-recovery-requirements\/\">ASHRAE 90.1-2022<\/a> 5,000-CFM \/ 70%-OA \/ 50% rule, and aligns with <a href=\"https:\/\/www.26yc.com\/ja\/ashrae-62-1-ventilation-energy-recovery\/\">ASHRAE 62.1<\/a> on outdoor-air loads. The <a href=\"https:\/\/www.26yc.com\/ja\/building-code-heat-recovery-mandate\/\">building code heat recovery mandate<\/a> article lines these up against California Title 24 and EU Ecodesign. Pick a core at 70&ndash;75% effectiveness and it clears every regime at once.<\/p>\n<h2>Sizing Tip<\/h2>\n<p>Confirm the AHU run-hours (the &lt; 8,000 h\/yr vs &ge; 8,000 h\/yr split matters in the table) and fold the core into the <a href=\"https:\/\/www.26yc.com\/ja\/ahu-selection-calculation\/\">AHU selection calculation<\/a> before sizing the coil.<\/p>\n<h2>\u3088\u304f\u3042\u308b\u8cea\u554f<\/h2>\n<p><strong>Where is the IECC commercial recovery rule?<\/strong><br \/>In Section C403.7, with thresholds in Table C403.7.1 by climate zone and outdoor-air fraction.<\/p>\n<p><strong>What triggers recovery under IECC C403.7?<\/strong><br \/>Fan systems with both supply and exhaust, design outdoor-air supply at or above the table threshold, such as 5,000 CFM with 70% outdoor air in several zones, at 50% effectiveness.<\/p>\n<p><strong>What did IECC 2024 add?<\/strong><br \/>Adoption of ASHRAE 62.1-2022, expanded demand-control ventilation, enhanced commissioning of ERV and DCV systems, and ERV requirements in multifamily dwelling units.<\/p>\n<p><strong>How does IECC relate to ASHRAE 90.1?<\/strong><br \/>C403.7 mirrors the 90.1 five-thousand-CFM, 70%-OA, 50% rule and aligns with 62.1 on outdoor-air loads.<\/p>\n<div class=\"yc-related\">\n<h3>\u95a2\u9023\u8a18\u4e8b<\/h3>\n<ul>\n<li><a href=\"https:\/\/www.26yc.com\/ja\/pharmaceutical-cleanroom-heat-recovery-2\/\" title=\"\u88fd\u85ac\u30fb\u30af\u30ea\u30fc\u30f3\u30eb\u30fc\u30e0\u6392\u6c17\u71b1\u56de\u53ce\">\u88fd\u85ac\u30fb\u30af\u30ea\u30fc\u30f3\u30eb\u30fc\u30e0\u6392\u6c17\u71b1\u56de\u53ce<\/a><\/li>\n<\/ul>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>The International Energy Conservation Code (IECC) is updated on a three-year cycle (2018, 2021, 2024) and is adopted &mdash; with or without amendments &mdash; by most U.S. states. Its commercial energy-recovery rule lives in Section C403.7, and it is the baseline that many state codes reference. This article summarizes the C403.7 trigger and how the [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[197,241],"tags":[182,214],"class_list":["post-4658","post","type-post","status-publish","format-standard","hentry","category-encyclopedia","category-standards-codes","tag-energy-recovery","tag-standards"],"_links":{"self":[{"href":"https:\/\/www.26yc.com\/ja\/wp-json\/wp\/v2\/posts\/4658","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.26yc.com\/ja\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.26yc.com\/ja\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.26yc.com\/ja\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.26yc.com\/ja\/wp-json\/wp\/v2\/comments?post=4658"}],"version-history":[{"count":2,"href":"https:\/\/www.26yc.com\/ja\/wp-json\/wp\/v2\/posts\/4658\/revisions"}],"predecessor-version":[{"id":5177,"href":"https:\/\/www.26yc.com\/ja\/wp-json\/wp\/v2\/posts\/4658\/revisions\/5177"}],"wp:attachment":[{"href":"https:\/\/www.26yc.com\/ja\/wp-json\/wp\/v2\/media?parent=4658"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.26yc.com\/ja\/wp-json\/wp\/v2\/categories?post=4658"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.26yc.com\/ja\/wp-json\/wp\/v2\/tags?post=4658"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}