{"id":10795,"date":"2026-05-27T12:40:58","date_gmt":"2026-05-27T10:40:58","guid":{"rendered":"https:\/\/aluplast.buges.sk\/slovnik-oknara\/window-thermal-transmittance-uw\/"},"modified":"2026-09-02T13:45:04","modified_gmt":"2026-09-02T11:45:04","slug":"window-thermal-transmittance-uw","status":"publish","type":"glossary","link":"https:\/\/www.aluplast.sk\/en\/slovnik-oknara\/window-thermal-transmittance-uw\/","title":{"rendered":"Window thermal transmittance Uw"},"content":{"rendered":"  <div id=\"page-header-1878570120\" class=\"page-header-wrapper\">\n  <div class=\"page-title page-header-custom z-5 dark featured-title\">\n\n        <div class=\"page-title-bg\">\n      <div class=\"title-bg fill bg-fill\"\n        data-parallax-container=\".page-title\"\n        data-parallax-background\n        data-parallax=\"-\">\n      <\/div>\n      <div class=\"title-overlay fill\"><\/div>\n    <\/div>\n    \n    <div class=\"page-title-inner container align-center flex-row medium-flex-wrap\" >\n              <div class=\"title-wrapper flex-col text-left medium-text-center\">\n          <h1 class=\"entry-title mb-0\">\n            Window thermal transmittance Uw          <\/h1>\n        <\/div>\n                    <div class=\"title-content flex-col flex-right text-right medium-text-center\">\n        <div class=\"title-breadcrumbs pb-half pt-half\"><\/div>      <\/div>\n    <\/div>\n\n     \n<style>\n#page-header-1878570120 .page-title-inner {\n  min-height: 23.6vh;\n}\n#page-header-1878570120 .featured-title {\n  background-color: rgb(0,0,0);\n}\n#page-header-1878570120 .title-bg {\n  background-position: 50% 50%;\n}\n<\/style>\n  <\/div>\n    <\/div>\n  \n\n\t<section class=\"section\" id=\"section_672399372\">\n\t\t<div class=\"section-bg fill\" >\n\t\t\t\t\t\t\t\t\t\n\t\t\t\n\n\t\t<\/div>\n\n\t\t\n\n\t\t<div class=\"section-content relative\">\n\t\t\t\n<div class=\"row\"  id=\"row-763574393\">\n\n\t<div id=\"col-281644409\" class=\"col small-12 large-12\"  >\n\t\t\t\t<div class=\"col-inner\"  >\n\t\t\t\n\t\t\t\n<h2>How much heat escapes through the entire window (frame + glass + spacer)<\/h2>\n<h3>The lower the value, the better the window insulates<\/h3>\n<p>The window thermal transmittance (Uw) is a key parameter indicating how much heat escapes through 1 m\u00b2 of a window at a temperature difference of 1 Kelvin. The lower the value, the better the window insulates; for new buildings, the standard is Uw \u2264 0.85 W\/(m\u00b2K) (new windows should be even better), which reduces heating costs and increases comfort. The Uw value is influenced by the glazing, the frame (profiles), and the installation, with smaller windows typically having a poorer value than larger ones.  <\/p>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\n\t\n\n\t<div id=\"col-1833486851\" class=\"col small-12 large-12\"  >\n\t\t\t\t<div class=\"col-inner\"  >\n\t\t\t\n\t\t\t\n\t<div class=\"img has-hover x md-x lg-x y md-y lg-y\" id=\"image_1840629894\">\n\t\t\t\t\t\t\t\t<div class=\"img-inner dark\" >\n\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"520\" src=\"https:\/\/www.aluplast.sk\/wp-content\/uploads\/sucinitel-prestupu-tepla.jpg\" class=\"attachment-original size-original\" alt=\"\" \/>\t\t\t\t\t\t\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\n<style>\n#image_1840629894 {\n  width: 100%;\n}\n<\/style>\n\t<\/div>\n\t\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\n\t\n\n\t<div id=\"col-244606141\" class=\"col small-12 large-12\"  >\n\t\t\t\t<div class=\"col-inner\"  >\n\t\t\t\n\t\t\t\n<h4>How to achieve a low Uw value<\/h4>\n<ul>\n<li aria-level=\"1\">Multiple glazing: Triple glazing is more thermally efficient than double glazing.<\/li>\n<li aria-level=\"1\">Low-emissivity coatings: Additional glass coating reduces heat transfer.<\/li>\n<li aria-level=\"1\">Insulating glass cavity filling: Noble gases (argon, krypton) between the panes improve insulation.<\/li>\n<li aria-level=\"1\">Quality frame: Choice of profile system (plastic, aluminum)<\/li>\n<li aria-level=\"1\">Spacer bar<\/li>\n<li aria-level=\"1\">Dimensions<\/li>\n<\/ul>\n<h4>Unit<\/h4>\n<p>Watt per square meter Kelvin W\/(m\u00b2K)<\/p>\n<h4>Related values<\/h4>\n<p>Uf: Thermal transmittance of the frame <a href=\"https:\/\/www.aluplast.sk\/en\/slovnik-oknara\/uf-value-frame-heat-transfer-coefficient\/\">(glazier&#8217;s dictionary)<\/a><\/p>\n<p>Uw: Thermal transmittance of the window <a href=\"https:\/\/www.aluplast.sk\/en\/slovnik-oknara\/window-thermal-transmittance-uw\/\">(glazier&#8217;s dictionary)<\/a><\/p>\n<p>Ug: Thermal transmittance of the insulating glass <a href=\"https:\/\/www.aluplast.sk\/en\/slovnik-oknara\/glazing-heat-transfer-coefficient-ug\/\">(glazier&#8217;s dictionary)<\/a><\/p>\n<p>\u03a8g (psi): Linear thermal transmittance at the frame and glass junction (spacer bar) &#8211; <a href=\"https:\/\/www.aluplast.sk\/en\/slovnik-oknara\/psi-%cf%88g-linear-heat-transfer-coefficient-at-the-frame-glass-junction-spacer-frame\/\">link<\/a><\/p>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\n\t\n<\/div>\n\t\t<\/div>\n\n\t\t\n<style>\n#section_672399372 {\n  padding-top: 30px;\n  padding-bottom: 30px;\n}\n<\/style>\n\t<\/section>\n\t\n","protected":false},"featured_media":0,"template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-10795","glossary","type-glossary","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.aluplast.sk\/en\/wp-json\/wp\/v2\/glossary\/10795","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.aluplast.sk\/en\/wp-json\/wp\/v2\/glossary"}],"about":[{"href":"https:\/\/www.aluplast.sk\/en\/wp-json\/wp\/v2\/types\/glossary"}],"version-history":[{"count":0,"href":"https:\/\/www.aluplast.sk\/en\/wp-json\/wp\/v2\/glossary\/10795\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.aluplast.sk\/en\/wp-json\/wp\/v2\/media?parent=10795"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}