Rubber seals in glass facades are the primary barrier against air infiltration, water ingress, and thermal movement in curtain wall systems. The wrong material or incorrect hardness allows water to bypass the frame, causes glass rattle under wind load, and degrades within 5–7 years from UV exposure. This guide covers material selection, hardness specification, and installation requirements for rubber seals in glass facades.
<h2>Why Rubber Seals Fail in Glass Facades</h2>
Most facade seal failures come from three causes: wrong compound for UV exposure, insufficient compression set resistance, and incorrect cross-section for the glazing rebate depth. EPDM handles outdoor UV and ozone better than neoprene or natural rubber. Silicone handles sustained high temperatures above 120°C where EPDM begins to soften. For standard curtain wall and window wall systems, EPDM at 60–70 Shore A hardness is the correct specification.
<h2>Which Rubber Compound to Specify</h2>
For glass facade rubber seals, two compounds are structurally appropriate:
<strong>EPDM (Ethylene Propylene Diene Monomer):</strong> UV-resistant, ozone-resistant, service temperature –40°C to +120°C, compression set below 25% after 168 hours at 70°C per ASTM D395. Standard choice for curtain wall, storefront, and window profiles.
<strong>Silicone:</strong> Rated to +200°C sustained. Used where facade panels are adjacent to HVAC exhaust or high solar gain rooflines. More expensive. Not necessary for standard glazed facades.
Neoprene is sometimes specified in older drawings. It performs adequately indoors but degrades faster than EPDM in exposed outdoor applications. Where drawings specify neoprene for external facades, substitute EPDM at equivalent hardness.
<h2>Hardness Specification for Rubber Seals in Glass Facades</h2>
Glazing gaskets — the rubber seals pressed into the channel between glass and frame — typically require 60–70 Shore A. Setting blocks and distance pieces that carry glass weight run harder at 80–90 Shore A. Specifying a single hardness across all rubber components in a facade is incorrect and causes field failures: too soft and the glass shifts under wind load; too hard and the seal does not compress enough to form a weather barrier.
Saga Elastomer manufactures EPDM <a href=”https://www.sagaelastomer.com/rubber-products/product-category/rubber-seals-and-gaskets/”>curtain wall rubber gaskets</a> in hardness grades of 50, 60, 65, 70, 80, and 90 Shore A, to ASTM D2240. Custom profiles to client drawings are available with a 4-week lead from approved drawing.
<h2>Installation Requirements</h2>
Rubber seals in glass facades must be installed clean and dry. Silicone lubricant is acceptable for easing installation; oil-based lubricants cause compound degradation within 6–12 months. Splicing corners require vulcanised joints, not cut-and-butt joints — a cut-and-butt corner seal will fail under the first thermal cycle. Compression must be uniform: if the seal requires a mallet to seat, the profile cross-section is incorrect for the rebate depth.
Saga Elastomer supplies <a href=”https://www.sagaelastomer.com/bespoke-products/”>custom rubber profiles</a> to drawing for facade contractors and system fabricators. Lead times, MOQ, and material certification are available on request.
<h2>Frequently Asked Questions</h2>
<strong>What is the standard EPDM hardness for curtain wall rubber seals?</strong>
60–70 Shore A for glazing gaskets. 80–90 Shore A for structural setting blocks. Both per ASTM D2240.
<strong>How long do EPDM rubber seals last in glass facades?</strong>
Correctly specified EPDM seals have a service life of 20–25 years in outdoor exposure. Neoprene in the same application typically degrades in 10–12 years.
<strong>Can rubber seals be replaced without removing the glass?</strong>
Snap-in gasket profiles can be replaced in place. Structural glazing seals bonded with silicone sealant require professional removal of the glass unit.
<strong>What standard governs compression set for facade rubber seals?</strong>
<a href=”https://www.astm.org/d0395-03r08.html”>ASTM D395</a> Method B at 70°C for 168 hours. Specify maximum 25% compression set for long-term facade applications.
For full material and hardness guidance, see our article on <a href=”https://www.sagaelastomer.com/2024/01/25/customising-hardness-of-rubber-compound/”>customising hardness of rubber compound</a>. For construction and <a href=”https://www.sagaelastomer.com/industries/construction-industry/architectural-industry/”>architectural industry</a> applications, Saga Elastomer supplies EPDM profiles from its facility in India, with material test certificates to <a href=”https://www.astm.org/d2240-15r21.html”>ASTM D2240</a> available on request.
