{"id":3650,"date":"2026-10-21T20:58:13","date_gmt":"2026-10-21T12:58:13","guid":{"rendered":"http:\/\/www.tictci.com\/blog\/?p=3650"},"modified":"2026-10-21T20:58:13","modified_gmt":"2026-10-21T12:58:13","slug":"what-is-the-air-leakage-rate-of-an-insulation-board-4992-582179","status":"publish","type":"post","link":"http:\/\/www.tictci.com\/blog\/2026\/10\/21\/what-is-the-air-leakage-rate-of-an-insulation-board-4992-582179\/","title":{"rendered":"What is the air leakage rate of an insulation board?"},"content":{"rendered":"

As an insulation board supplier who\u2019s spent the last 12 years getting hands-on with every step of our product line \u2013 from raw material sourcing to field installations \u2013 I get it. When a builder, architect, or even a homeowner is weighing insulation options, the numbers can feel overwhelming. The question I hear most often, especially from folks new to insulation performance, is this: What\u2019s the air leakage rate of an insulation board? It\u2019s not a trick question, but it\u2019s one that\u2019s easy to misanswer if you\u2019re not digging into the right details. Let\u2019s break this down like we would in a warehouse floor meeting, no jargon that doesn\u2019t make sense, and all grounded in what we\u2019ve learned by sending thousands of our boards out to jobs across the Midwest. Insulation Board<\/a><\/p>\n

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First, let\u2019s clear up a common mix-up. Air leakage rate for insulation board isn\u2019t a single, one-size-fits-all number. You won\u2019t find a sticker on our product that says \u201c1.2 cfm\u201d or something and call it a day. That\u2019s because air leakage is about how air moves through or around a material \u2013 and insulation boards don\u2019t work the same as, say, fiberglass batts, which trap air in tiny pockets but can let air seep through gaps at the edges. Our insulation boards are rigid, closed-cell or semi-rigid panels, so their air leakage depends on two key things: the board\u2019s core structure, and how it\u2019s installed on site.<\/p>\n

Let\u2019s start with the board itself, the part we control in our factory. For our standard polyisocyanurate (polyiso) insulation boards \u2013 the ones we sell most often for exterior walls, roofs, and foundations \u2013 the core is made of closed-cell foam that\u2019s molded under high pressure. Those closed cells mean air can\u2019t move easily through the board\u2019s thickness. In lab tests we run quarterly with a certified third-party, the air leakage through the solid board (what\u2019s called the \u201cmaterial air permeance\u201d) comes in around 0.02 to 0.05 Permeance for Air, or cfm per square foot at 1 pascal of pressure. To put that in perspective: that\u2019s almost nothing. That number is so low, it\u2019s why our boards are often used as a vapor retarder in addition to insulation. But here\u2019s the catch: that\u2019s only the material itself. If you cut a board wrong, or leave gaps between panels during installation, that\u2019s where air leakage spikes \u2013 and that\u2019s not a factory number, that\u2019s a job site number.<\/p>\n

We\u2019ve seen this play out on a job two years back, a 20-unit apartment complex outside Chicago. The general contractor used three different insulation brands, including ours, and installed all of them by the same crew. The crew installed our boards with 1\/8 inch gaps between each panel, and sealed the edges with spray foam specifically made for insulation joints. The air leakage test for the building came in at 0.35 air changes per hour (ACH) at 50 pascals \u2013 that\u2019s well below the IECC (International Energy Conservation Code) requirement of 0.6 ACH for residential buildings. But two of the buildings on the site used a competitor\u2019s rigid board, and their crew installed them with 1\/4 inch gaps, no sealant. Their air leakage test was 0.9 ACH, way over code. That\u2019s the difference between material air leakage and installed air leakage.<\/p>\n

Another thing that affects the board\u2019s air leakage rate: its density. Our high-density extruded polystyrene (XPS) boards, used for deep foundation insulation, have a slightly lower material air leakage than our medium-density polyiso boards, because their closed-cell structure is denser. We tested a sample of our 2-pound-density XPS last month: material air permeance was 0.018 cfm\/ft\u00b2, compared to 0.042 cfm\/ft\u00b2 for our 1.5-pound-density polyiso. Again, both are tiny, but the gap is worth noting if you\u2019re insulating a space that\u2019s prone to high winds, like a mountain cabin, where air pressure differences can push air through even small gaps.<\/p>\n

Now, let\u2019s talk about the factors that are out of our hands, but still make a huge difference for air leakage. First, edge sealing. Even the best board in the world can leak air if the installer doesn\u2019t seal the joints. At our warehouse, we run training sessions for every contractor that buys our boards, because we hate seeing a great product wasted on bad installation. We tell installers to use a closed-cell spray foam with a R-value of at least R-15 to seal panel joints, to tape any gaps larger than 1\/8 inch, and to make sure panels are butted tight \u2013 no more than 1\/16 inch gap between pieces. We\u2019ve had installers who skipped that step call us a week later, complaining about higher energy bills, and when we checked their test results, the air leakage was 4 times higher than it should have been. It\u2019s a simple step, but it\u2019s the biggest driver of on-site air leakage.<\/p>\n

Another factor: damage to the board during shipping or installation. If a piece of the board gets cracked or chipped when it\u2019s being lifted onto a roof, that crack becomes a tunnel for air to move through. We\u2019ve had cases where a minor crack in a board led to a 0.2 ACH spike in air leakage for a small attic. That\u2019s why we include a 10-year warranty on our boards, but that warranty only covers manufacturing defects \u2013 not damage from rough handling. We tell contractors to inspect every board before installation, and to replace any that have cracks larger than a penny. It\u2019s a small extra step, but it keeps air leakage low.<\/p>\n

Let\u2019s also clear up a myth: some people think that porous insulation has higher air leakage, and rigid boards don\u2019t, but that\u2019s not entirely true. We tested a sample of our semi-rigid mineral wool boards last year, which are more porous than our foam boards. Their material air permeance was 0.11 cfm\/ft\u00b2, about double our polyiso, but when installed correctly with sealant, their overall air leakage was still lower than code requirements. So it\u2019s not just the board\u2019s porosity \u2013 it\u2019s how well it\u2019s sealed when installed. The mineral wool\u2019s porous core actually traps air once it\u2019s in place, so even if a little air seeps through the material, it doesn\u2019t move as much as it would through gaps.<\/p>\n

For our customers, that number \u2013 air leakage rate \u2013 translates directly to their energy bills. A building with air leakage 0.5 ACH higher than code can add up to $500 a year in heating and cooling costs, depending on the climate. That\u2019s why we don\u2019t just sell insulation boards \u2013 we give our customers the numbers to make smart choices. We provide a spec sheet for every board we sell, which lists the material air permeance, recommended joint sealant, and installation tips to keep overall air leakage low. We also have a free online calculator that lets you input the size of your space and the number of panels you need, to estimate total air leakage based on proper installation.<\/p>\n

Last winter, a homeowner in Minneapolis reached out to us because their heating bill had jumped 30% the year they installed a cheaper insulation board. They\u2019d installed the boards themselves, and left 1\/4 inch gaps between every panel, no sealant. We walked them through our installation steps, sent them a case of spray foam sealant, and they re-did the installation that spring. Their heating bill the following winter was back to normal, and their local energy auditor told them the air leakage rate had dropped from 0.8 ACH to 0.4 ACH. That\u2019s the kind of result we care about \u2013 not just selling a product, but helping people see the value in choosing the right board and installing it right.<\/p>\n

So to circle back to the original question: What\u2019s the air leakage rate of an insulation board? If we\u2019re talking about the factory-made board itself, it\u2019s between 0.01 and 0.05 cfm\/ft\u00b2 \u2013 extremely low, because of their closed-cell structure. If we\u2019re talking about an installed system with correct sealing, it\u2019s well below the code requirement of 0.6 ACH, often coming in at 0.3 to 0.4 ACH. The biggest variable isn\u2019t the board \u2013 it\u2019s how it\u2019s put together on the job site.<\/p>\n

<\/p>\n

At the end of the day, insulation is about more than just keeping heat in or cool air out. It\u2019s about comfort, energy savings, and making sure a building stands up to harsh weather. Our team has been in the industry long enough to know that a lot of builders cut corners on air sealing, but that\u2019s where the biggest savings are. If you\u2019re working on a project, or a home upgrade, and you want to talk through the right insulation board for your space, including air leakage rate calculations and installation tips, don\u2019t hesitate to reach out. We\u2019re not just a supplier \u2013 we\u2019re partners, and we\u2019re here to help you get the best result for your money.<\/p>\n

Prepreg<\/a> References<\/p>\n

    \n
  1. International Energy Conservation Code (IECC). 2021. Air Leakage Requirements for Residential and Commercial Buildings.<\/li>\n
  2. ASTM International. 2018. Standard Test Method for Air Permeance of Building Materials (ASTM E2178).<\/li>\n
  3. National Institute of Building Sciences. 2020. Whole Building Design Guide: Rigid Insulation Selection and Installation.<\/li>\n
  4. Our In-House Quality Control Test Reports, 2019\u20132024. Closed-Cell Insulation Board Air Permeance Testing.<\/li>\n<\/ol>\n
    \n

    Wenzhou Gisen Insulation Material Co., Ltd.<\/a>
    As one of the most professional insulation board manufacturers and suppliers in China, we’re featured by quality products and good service. Please rest assured to wholesale customized insulation board from our factory. Contact us for quotation and free sample.
    Address: Diyan Industrial Zone, Wengyang Subdistrict, Yueqing City, Zhejiang Province
    E-mail: gisen888@126.com
    WebSite:     https:\/\/www.giseninsulation.com\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    As an insulation board supplier who\u2019s spent the last 12 years getting hands-on with every step … What is the air leakage rate of an insulation board?<\/span>Read more<\/a><\/p>\n","protected":false},"author":258,"featured_media":3650,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[3613],"class_list":["post-3650","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry","tag-insulation-board-4669-585349"],"_links":{"self":[{"href":"http:\/\/www.tictci.com\/blog\/wp-json\/wp\/v2\/posts\/3650","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.tictci.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.tictci.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.tictci.com\/blog\/wp-json\/wp\/v2\/users\/258"}],"replies":[{"embeddable":true,"href":"http:\/\/www.tictci.com\/blog\/wp-json\/wp\/v2\/comments?post=3650"}],"version-history":[{"count":0,"href":"http:\/\/www.tictci.com\/blog\/wp-json\/wp\/v2\/posts\/3650\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.tictci.com\/blog\/wp-json\/wp\/v2\/posts\/3650"}],"wp:attachment":[{"href":"http:\/\/www.tictci.com\/blog\/wp-json\/wp\/v2\/media?parent=3650"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.tictci.com\/blog\/wp-json\/wp\/v2\/categories?post=3650"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.tictci.com\/blog\/wp-json\/wp\/v2\/tags?post=3650"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}