Sash Windows: Compression Seals vs Brush Seals: Myths Debunked!
<h1>Why a Brush Seal is Far Superior to a Compression Seal for Draught-Proofing Double Hung Sash Windows</h1>
<p>One of the most common questions we get from homeowners looking to improve the energy efficiency of their timber sash windows is:</p>
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“Should I use a brush seal or a compression seal?”
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<p>It’s a great question — and the answer is clear. When it comes to <strong>draught-proofing double hung sash windows</strong>, <strong>brush seals</strong> (like <em>Timber Finseal</em>) are far superior to compression seals (like <em>Schlegel Aquamac</em> and similar). Let’s break down why.</p>
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<h2>Compression vs Brush Seals — What’s the Difference?</h2>
<p>To choose the right seal, it’s important to understand what each type is actually designed to do:</p>
<ul>
<li><strong>Compression Seals</strong> are made to be <em>squeezed</em> between two closing surfaces — like a casement window or a door. They work best when the seal is fully compressed to block air and water.</li>
<li><strong>Brush Seals</strong> are designed for <em>sliding applications</em>, such as double hung sash windows. They use flexible bristles to maintain contact with moving timber surfaces, sealing gaps while still allowing smooth operation.</li>
</ul>
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<h2>Why Compression Seals Don’t Work for Sash Windows</h2>
<p>Double hung sash windows slide — they don’t compress shut. Using a compression seal in this setting leads to a range of issues:</p>
<ol>
<li><strong>Too Much Friction</strong><br>
Compression seals create resistance, making the sash difficult to open and close — especially on older or heavier windows.</li>
<li><strong>Quick Deterioration</strong><br>
Constant movement against the timber frame wears out compression seals quickly, meaning more frequent replacements.</li>
<li><strong>Ineffective Seal</strong><br>
Compression seals rely on being squashed to form a seal — something sash windows simply don’t do.</li>
</ol>
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<h2>Brush Seals Are Made for the Job — And Ours Go Even Further</h2>
<p>Brush seals, like our trusted <strong>Timber Finseal</strong>, are purpose-built for sliding sash windows. They're lightweight, flexible, and ensure smooth sash operation without resistance.</p>
<p><strong>But not all brush seals are created equal.</strong></p>
<p><strong>Unlike many brush seals on the market, Lock & Latch’s seals feature a plastic fin embedded within the brush hairs.</strong></p>
<p>It’s this clever fin design that forms a <strong>complete and continuous seal</strong>. It blocks airflow far more effectively than standard brush seals, while still maintaining low-friction performance. </p>
<p><em>So if you’ve ever heard the myth that “brush seals don’t form a full seal” — you can forget it. Ours do. And they do it better than most.</em></p>
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