{"id":25095137,"date":"2026-08-20T14:04:34","date_gmt":"2026-08-20T12:04:34","guid":{"rendered":"https:\/\/frelons.be\/2026\/08\/20\/nid-dans-lisolation-gare-aux-guepes-et-frelons-caches\/"},"modified":"2026-08-20T14:04:34","modified_gmt":"2026-08-20T12:04:34","slug":"nest-in-the-insulation-watch-out-for-hidden-wasps-and-hornets","status":"publish","type":"post","link":"https:\/\/frelons.be\/en\/2026\/08\/20\/nid-dans-lisolation-gare-aux-guepes-et-frelons-caches\/","title":{"rendered":"Nest in the insulation: Watch out for hidden wasps and hornets!"},"content":{"rendered":"<h1>Can you have a wasp or hornet nest in your insulation?<\/h1>\n<h3 id=\"sommaire\">Contents<\/h3>\n<ul>\n<li>\n<p><a target=\"_blank\" rel=\"noopener noreferrer nofollow\" class=\"text-primary underline toc-link\" href=\"#pourquoi-les-guepes-et-frelons-choisissent-ils-votre-isolation\">Why do wasps and hornets choose your insulation?<\/a><\/p>\n<\/li>\n<li>\n<p><a target=\"_blank\" rel=\"noopener noreferrer nofollow\" class=\"text-primary underline toc-link\" href=\"#identifier-les-signes-d-un-nid-d-insectes-dans-vos-cloisons-ou-toiture\">Identify the signs of an insect nest in your walls or roof<\/a><\/p>\n<\/li>\n<li>\n<p><a target=\"_blank\" rel=\"noopener noreferrer nofollow\" class=\"text-primary underline toc-link\" href=\"#solutions-et-prevention-proteger-votre-isolant-des-nuisibles\">Solutions and Prevention: Protecting Your Insulation from Pests<\/a><\/p>\n<\/li>\n<li>\n<p><a target=\"_blank\" rel=\"noopener noreferrer nofollow\" class=\"text-primary underline toc-link\" href=\"#conclusion\">Conclusion<\/a><\/p>\n<\/li>\n<\/ul>\n<p>Yes. And it\u2019s actually much more common than you might think. When you search for \u00abinsulation nests\u00bb online, you\u2019ll find dozens of pages about birds, chickadees, and birdhouses built into building facades. That\u2019s all well and good. But the real problem we encounter in the field, ten months out of twelve, is insects: common wasps, German wasps, European hornets, and, in recent years, Asian hornets.<\/p>\n<h3 id=\"ce-qu-il-faut-retenir\">Things to remember<\/h3>\n<ul>\n<li>\n<p>While most websites focus on birds, we shed light on the little-known danger posed by insect builders<\/p>\n<\/li>\n<li>\n<p>We explain why insulation is a perfect breeding ground for hornets and how to treat an infestation without sacrificing your thermal insulation<\/p>\n<\/li>\n<li>\n<p>Why do wasps and hornets choose your insulation?<\/p>\n<\/li>\n<li>\n<p>Identify the signs of an insect nest in your walls or roof<\/p>\n<\/li>\n<\/ul>\n<p>Glass wool, rock wool, the honeycomb cardboard from old wall lining, exterior thermal insulation panels: for a queen looking for a place to establish her colony in the spring, it\u2019s a five-star spot. Warm, dry, dark, sheltered from wind and rain, and above all, inaccessible to predators. You won\u2019t find anything better within a kilometer.<\/p>\n<p>The problem is that the nest grows inside your wall or roof, often for weeks, before you notice anything. And by the time you finally do notice it, there are already a few thousand of them behind the drywall. Here\u2019s how to spot the problem early and how to fix it without tearing out half your insulation.<\/p>\n<h2 id=\"pourquoi-les-guepes-et-frelons-choisissent-ils-votre-isolation\">Why do wasps and hornets choose your insulation?<\/h2>\n<p>Imagine a mated queen emerging from hibernation in April. She flies, she searches, she inspects. Her requirements are simple: a dry cavity, a stable temperature between 20 and 30 degrees, a discreet opening, and materials to build with nearby. Your house checks all the boxes.<\/p>\n<p><img decoding=\"async\" class=\"max-w-full h-auto rounded-md\" src=\"https:\/\/nghaeknymynesecnqcmd.supabase.co\/storage\/v1\/object\/public\/article-images\/article-1787053746647-nid-dans-l-isolation-gare-aux-guepes-et-frelons-caches.png\" alt=\"Nest in the insulation: Watch out for hidden wasps and hornets!\"><\/p>\n<p>Visit <strong>glass wool<\/strong> is the material that poses the most problems. It is soft, easily hollowed out with the mandibles, and retains exactly the amount of heat the larvae need. A wasp colony doesn\u2019t even need to produce much paper: it uses the existing cavity between the vapor barrier and the roof framing as a natural shell. The result is a <strong>wasp nest in the insulation<\/strong> can grow to the size of a basketball without a single gray spot being visible from the outside.<\/p>\n<p>Rock wool holds up a little better; it\u2019s denser and more fibrous. But only a little better. European hornets, with their powerful mandibles, attack it without hesitation. As for the old honeycomb cardboard insulation still found in quite a few homes from the \u201960s and \u201970s, it\u2019s practically a buffet: the material is already made of cellulose, which is a raw material used in construction.<\/p>\n<p>Exterior thermal insulation has created a new playground. Polystyrene panels glued to the facade often leave gaps around shutter boxes, expansion joints, or poorly sealed fastening points. A hole just 8 millimeters wide is enough for a queen. Once inside, she burrows into the soft polystyrene and builds herself a custom-made nest. This leads to a host of problems: damage to the insulation, the creation of a thermal bridge, and an invisible colony.<\/p>\n<p>Visit <strong>hornet's nest on the roof<\/strong> follows the same logic. Ventilated roof underlayment, unused attic space, the junction between the wall plate and the wall\u2014these areas are designed to allow air to pass through, so they also let insects in. And the more energy-efficient your home is, the warmer the interior of the walls remains at the start of the season, which accelerates the development of the larvae. Your thermal comfort also benefits your uninvited guests. It\u2019s ironic, but it\u2019s the reality we see every summer in Belgium.<\/p>\n<h2 id=\"identifier-les-signes-d-un-nid-d-insectes-dans-vos-cloisons-ou-toiture\">Identify the signs of an insect nest in your walls or roof<\/h2>\n<p>A customer from the Namur area called us last July to report a \u00absound of running water\u00bb coming from the wall of his bedroom. There was no leak. There were 2,000 German wasps in the glass wool insulation in the roof slope. The constant scraping sound made by the worker wasps as they build their nests really does sound like a gentle trickle, especially at night when everything is quiet.<\/p>\n<p>This <strong>noise in the insulation<\/strong> is the first\u2014and most reliable\u2014sign. It grows in intensity between June and September. A steady rustling, sometimes a faint humming, when you press your ear against the wall. Unlike rodents, which make sharp, irregular, and mostly nocturnal noises, insects are constantly active and produce a more diffuse sound.<\/p>\n<p>The second sign is the \u201cballet.\u201d Stand outside for ten minutes and watch a fixed spot on your facade or roof. If you see a steady back-and-forth movement\u2014always toward the same spot\u2014with insects going in and out, you\u2019ve found the entrance. Count the traffic: if there are more than ten trips per minute, the colony is already well established.<\/p>\n<p>Next, look at the insect itself. The <strong>Asian hornet<\/strong> It can be recognized by its entirely black thorax, its yellow legs with yellow tips, and its orange stripe on the abdomen. It is slightly smaller than the European hornet, which is yellow and reddish-brown with a lot of yellow on the abdomen. The Asian hornet rarely nests in walls; it prefers treetops, but primary nests have been found under roof overhangs and in shutter boxes. In the spring, if you find a primary nest the size of an orange under a roof overhang, nine times out of ten it\u2019s an Asian hornet nest.<\/p>\n<p>Also look for the <strong>hole in the insulation<\/strong>. The insects gradually enlarge their entry hole. A clear hole in the exterior plaster, a crumbling cladding joint, or a ventilation grille with its mesh chewed through\u2014these are all signs. Inside, a brownish damp stain on the ceiling or at the top of a partition wall may reveal a large nest that is \u00absweating.\u00bb The larvae produce liquid waste that eventually seeps through the plaster.<\/p>\n<p>One last sign\u2014and this one never fails: insects appearing inside the house even though no windows are open. They\u2019ve gone the wrong way and come in through the living room, via a recessed light fixture or an electrical outlet. If this happens several days in a row, look no further\u2014the nest is in the wall.<\/p>\n<h2 id=\"solutions-et-prevention-proteger-votre-isolant-des-nuisibles\">Solutions and Prevention: Protecting Your Insulation from Pests<\/h2>\n<p>First things first, and I\u2019ll be blunt: never block the entrance hole. That\u2019s the number one instinct homeowners have, and it\u2019s the worst thing you can do. A trapped colony doesn\u2019t die\u2014it digs. It looks for another way out, and that other way out could be your ceiling, an electrical conduit, or around a recessed light fixture. We\u2019ve seen wasps emerge into a child\u2019s bedroom three days after the homeowner filled a crack in the exterior wall with some expanding foam.<\/p>\n<p>For <strong>destroy a wasp nest<\/strong> When the nest is hidden within insulation, the technique is completely different from that used for a visible nest. You do not spray randomly. Instead, you inject a powdered insecticide directly into the cavity through the entrance hole using an injection wand or a blower. The worker bees carry the product to the center of the nest as they move about. The colony collapses within 24 to 48 hours, and the structure remains in place. There is no need to cut into the drywall or remove the mineral wool. Your <strong>insulation protection<\/strong> If it's intact, so is your thermal performance.<\/p>\n<p>Should you remove the abandoned nest afterward? For wasps, not necessarily. An abandoned nest is never recolonized the following year. Leaving it in place prevents the wall from being opened up. However, if the nest is very large or located above a lived-in ceiling, we recommend removing it: the papier-m\u00e2ch\u00e9 breaks down, attracts dermestid larvae, and can cause stains. For a <strong>hornet's nest on the roof<\/strong>, removal is more often recommended, as these nests are larger.<\/p>\n<p>When it comes to prevention, a few simple steps are worth their weight in gold:<\/p>\n<ul>\n<li>\n<p>Cover all air intakes in the space between the roof and the ceiling with stainless steel mesh no larger than 5 mm, while allowing the ventilation system to continue operating.<\/p>\n<\/li>\n<li>\n<p>Repair cracks in the stucco and the exterior wall joints before March, not in July.<\/p>\n<\/li>\n<li>\n<p>Check your roller shutter boxes every spring\u2014they\u2019re the most heavily infested places in Belgium.<\/p>\n<\/li>\n<li>\n<p>For exterior insulation, check the joints around the windows and at the base of the walls.<\/p>\n<\/li>\n<li>\n<p>Do not install birdhouses directly on an exterior wall insulation system: they create a thermal bridge and provide an entry point for other pests. Use models that are mounted on brackets.<\/p>\n<\/li>\n<\/ul>\n<p>And if you have a wild beehive under your roof, don\u2019t destroy it. Call a beekeeper to rescue it. Bees are protected, and it\u2019s always better to save a colony alive.<\/p>\n<p>At <strong>hornets.be<\/strong>, we work year-round, not just during the peak season in July and August. In March and April, we remove the primary nests of Asian hornets\u2014the ones about the size of a tennis ball\u2014which we destroy in five minutes. In the winter, we conduct inspections and secure building facades. It\u2019s precisely during the off-season that we prevent major problems from arising the following summer.<\/p>\n<h2 id=\"conclusion\">Conclusion<\/h2>\n<p>A nest in the insulation can\u2019t be seen, but it can be heard; you can tell it\u2019s there by the activity on the exterior of the building, and it will cost you dearly if you wait. The good news is that a properly performed treatment won\u2019t ruin your insulation: targeted injection, the colony neutralized, glass wool or rock wool preserved, and no thermal bridges created. But you still need to act before the colony reaches its peak.<\/p>\n<p>Do you hear scratching coming from a wall? Do you see insects swarming around the same spot on your roof? Don\u2019t climb a ladder with an aerosol can, and above all, don\u2019t block anything up. Call us. We\u2019ll identify the species, locate the nest, and handle the situation properly\u2014from spring through fall and even in the middle of winter.<\/p>\n<h2 id=\"questions-frequentes\">Frequently asked questions<\/h2>\n<details class=\"faq-item\">\n<summary>How can I tell if there\u2019s a wasp nest in my insulation?<\/summary>\n<p>The most reliable sign is a continuous, muffled sound\u2014often mistaken for the sound of running water\u2014that intensifies between June and September. Also, watch your exterior wall for ten minutes: regular back-and-forth movements toward the same spot reveal the entrance. If you see more than ten movements per minute, the colony is already well established. Insects appearing inside with the windows closed confirm the presence of a nest in the wall.<\/p>\n<\/details>\n<details class=\"faq-item\">\n<summary>Why is it especially important not to block the entrance to the nest?<\/summary>\n<p>When trapped, a colony doesn\u2019t die\u2014it burrows to find another way out. This new exit may lead into a ceiling, an electrical conduit, or around a recessed light fixture. Wasps emerged this way into a child\u2019s bedroom three days after a homeowner filled a crack in the exterior wall with expanding foam.<\/p>\n<\/details>\n<details class=\"faq-item\">\n<summary>Do you need to cut the drywall to remove a nest from the glass wool insulation?<\/summary>\n<p>No. A powdered insecticide is injected directly into the cavity through the entry hole using an injection tube or a blower, and the worker bees spread it throughout the nest. The colony collapses within 24 to 48 hours without having to open the wall cavity or remove the mineral wool, thus without any loss of thermal performance.<\/p>\n<\/details>\n<details class=\"faq-item\">\n<summary>Which type of insulation is most susceptible to wasps and hornets?<\/summary>\n<p>Glass wool poses the most problems: it\u2019s soft, easy to burrow through, and just the right temperature for larvae. Rock wool, which is denser, offers only slightly more resistance to the mandibles of European hornets. The old honeycomb cardboard insulation in houses from the 1960s and 1970s is even worse, since the cellulose serves directly as a building material.<\/p>\n<\/details>\n<details class=\"faq-item\">\n<summary>Is it possible for a nest to form in exterior insulation?<\/summary>\n<p>Yes. Polystyrene panels often have gaps around shutter boxes, expansion joints, or poorly sealed fastening points, and a hole as small as 8 millimeters is enough for a queen. She then burrows into the soft polystyrene to make her home, which damages the insulation and creates a thermal bridge\u2014all while remaining completely invisible.<\/p>\n<\/details>\n<details class=\"faq-item\">\n<summary>Should the nest be removed after the colony has been destroyed?<\/summary>\n<p>For wasps, this isn\u2019t necessary: an abandoned nest is never recolonized the following year, and leaving it in place prevents the wall from being breached. Removal is recommended, however, if the nest is large or located above a living space, as the papier-m\u00e2ch\u00e9 breaks down, attracts dermestid beetles, and can cause stains. For a hornet nest on a roof, removal is more often recommended.<\/p>\n<\/details>","protected":false},"excerpt":{"rendered":"<p>Can You Have a Wasp or Hornet Nest in Your Insulation? Table of Contents Why Do Wasps and Hornets Choose Your Insulation? Identifying Signs of an Insect Nest in Your Walls or Ceiling\u2026<\/p>","protected":false},"author":2,"featured_media":25095136,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-25095137","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-non-classe"],"_links":{"self":[{"href":"https:\/\/frelons.be\/en\/wp-json\/wp\/v2\/posts\/25095137","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/frelons.be\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/frelons.be\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/frelons.be\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/frelons.be\/en\/wp-json\/wp\/v2\/comments?post=25095137"}],"version-history":[{"count":0,"href":"https:\/\/frelons.be\/en\/wp-json\/wp\/v2\/posts\/25095137\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/frelons.be\/en\/wp-json\/wp\/v2\/media\/25095136"}],"wp:attachment":[{"href":"https:\/\/frelons.be\/en\/wp-json\/wp\/v2\/media?parent=25095137"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/frelons.be\/en\/wp-json\/wp\/v2\/categories?post=25095137"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/frelons.be\/en\/wp-json\/wp\/v2\/tags?post=25095137"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}