As the mainstream facade system of modern buildings, the glass curtain wall not only needs to meet the needs of architectural aesthetics, but also needs to undertake functional missions. Among them, sound insulation and heat insulation performance are the core indicators for measuring the quality of curtain walls. This article will deeply analyze the technical path for glass curtain walls to achieve sound insulation and heat insulation, and discuss the direction of industry innovation in combination with actual cases.
1. Principles and implementation methods of glass curtain wall sound insulation technology
Sound is transmitted through air vibration. The sound insulation ability of glass curtain walls mainly depends on the reflection, absorption and attenuation of sound waves. The following are key sound insulation technologies:
1. Multi-layer composite structure
– Double/triple-layer hollow glass for glass curtain walls: Two or three pieces of glass are stacked, and dry air or inert gas (such as argon and krypton) is filled in the middle. When sound waves pass through different media, they will be reflected multiple times due to impedance differences, effectively reducing medium and high frequency noise (such as traffic noise). For example, the configuration of 6mm glass + 12mm air layer + 6mm glass can achieve a sound insulation of 35-40 decibels.
– Laminated glass: Adding PVB (polyvinyl butyral) or SGP (ionic interlayer) film between the glass can absorb vibration energy. PVB laminated glass has a significant effect on blocking low-frequency noise (such as the roar of airplanes), and the sound insulation performance is improved by more than 20%.
2. Asymmetric thickness design of glass curtain wall
Using inner and outer layers of glass with different thicknesses (such as outer 8mm tempered glass + inner 6mm Low-E glass) can avoid sound wave resonance and reduce the “matching effect”. Experimental data shows that the asymmetric structure is 3-5 decibels higher than the symmetrical structure.
3. Sealing and gap treatment
– Multiple sealing strips: EPDM (ethylene propylene diene monomer rubber) or silicone sealant is used at the joints of the curtain wall to prevent airborne sound transmission.
– Broken bridge aluminum profile: Add nylon insulation strips to the aluminum alloy frame to block the sound bridge conduction path. For example, Yuanda China uses a three-sealing system in the curtain wall project of Beijing Daxing Airport to keep the indoor noise below 40 decibels.
Case application: Shanghai Tower uses “double silver Low-E laminated insulating glass” (8mm+1.52mm PVB+8mm+16A+10mm), combined with a curtain wall system with air tightness reaching the national standard level 8, so that the 120-story observation deck can still maintain a quiet environment in strong winds.
2. Principles and innovative solutions of glass curtain wall insulation technology
Heat is transmitted through three ways: conduction, radiation, and convection. Glass curtain walls need to block each path in a targeted manner:
1. Low-E coating technology
– Principle: The glass used in the glass curtain wall is coated with a metal oxide nanolayer (such as silver and titanium) on the surface of the glass to reflect far-infrared thermal radiation. It blocks outdoor heat from entering in summer and prevents indoor heat loss in winter.
– Type:
– Single silver Low-E: visible light transmittance 70%, shading coefficient 0.5, suitable for temperate climates.
– Double Silver Low-E: Optimizes selective light transmission through two layers of silver film, and improves thermal insulation performance by 15%. It is used in super high-rise buildings such as the Burj Khalifa in Dubai.
– Triple Silver Low-E: While maintaining a visible light transmittance of 60%, the UV blocking rate reaches 99%. The representative project is Apple’s California headquarters.
2. Hollow layer design and gas filling
– Optimization of air layer thickness: 12-20mm air layer can form a stable convection barrier layer. Too thick will increase heat conduction due to gas flow.
– Inert gas filling: Argon gas has a thermal conductivity 34% lower than air, and krypton gas is even lower but the cost is higher. The curtain wall of the Beijing Winter Olympic Village is filled with argon gas, and the heat transfer coefficient (U value) is reduced to 1.1 W/(m²·K).
3. Breakthrough in glass curtain wall vacuum glass technology
– Structure: The vacuum between the two pieces of glass is evacuated to 0.1Pa, micro-supports are used to prevent collapse, and the edges are sealed with metal alloys. The vacuum layer almost eliminates gas conduction and convection, and the U value can reach 0.4 W/(m²·K).
– Challenge: The maximum size is currently limited (about 3m×1.5m), and the cost is 5 times that of ordinary insulating glass.
4. Intelligent dynamic insulation system
– Electrochromic glass: Control lithium ion migration through voltage to change the glass transmittance.
– Thermochromic material: Japan AGC’s Sunergy glass contains VO₂ coating, which automatically reflects infrared rays when the temperature exceeds 35℃, without external energy.
III. Integrated solutions and engineering practices
1. Breathing curtain wall (double-layer dynamic curtain wall)
– Structure: outer single-layer glass + inner insulating glass, with adjustable vents in the middle cavity. The cavity is closed in winter to store heat and opened in summer to discharge hot air.
– Effect: Shenzhen Ping An Financial Center uses this system, with an annual energy saving rate of 40% and a noise reduction of 25 decibels.
