What are the best acoustic materials and strategies for green building envelope?

1 Acoustic basics

Before we dive into the specific materials and strategies, let's review some acoustic basics. Sound is a form of energy that travels as waves through a medium, such as air or water. When sound waves encounter a surface, they can be reflected, absorbed, or transmitted. The amount of reflection, absorption, or transmission depends on the properties of the surface, such as its mass, density, stiffness, and porosity. The sound level or intensity is measured in decibels (dB), and the sound frequency or pitch is measured in hertz (Hz). Human hearing ranges from 20 Hz to 20,000 Hz, and sounds above 85 dB can cause hearing damage.

2 Acoustic goals

The main acoustic goals for green building envelope are to control noise transmission and reverberation. Noise transmission is the passage of sound from one space to another through the building envelope, and it can be airborne or impact. Airborne noise is caused by sources such as traffic, aircraft, or speech, and it can be reduced by increasing the mass and insulation of the envelope. Impact noise is caused by sources such as footsteps, furniture, or machinery, and it can be reduced by adding resilient layers or isolators to the envelope. Reverberation is the persistence of sound in a space after the source has stopped, and it can be reduced by increasing the absorption of the envelope.

3 Acoustic materials

There are many types of acoustic materials that can be used for green building envelope, but they can be broadly classified into three categories: absorbers, barriers, and dampers. Absorbers are materials that convert sound energy into heat, thus reducing the sound level and reverberation. Examples of absorbers are fibrous materials, such as mineral wool, cellulose, or hemp, and porous materials, such as cork, wood, or foam. Barriers are materials that block or reflect sound waves, thus reducing the noise transmission. Examples of barriers are dense materials, such as concrete, brick, or metal, and composite materials, such as gypsum board, plywood, or sandwich panels. Dampers are materials that dissipate sound energy by friction or deformation, thus reducing the impact noise. Examples of dampers are resilient materials, such as rubber, neoprene, or springs, and viscoelastic materials, such as bitumen, asphalt, or polymers.

4 Acoustic strategies

In order to improve the acoustic performance of green building envelope, there are some design and installation strategies that should be considered, such as double or triple glazing for windows and doors and sealing any gaps or cracks around them. Sound-absorbing materials should be used for exterior cladding, roofing, and landscaping, while sound-barrier materials should be used for walls and floors with an air gap or cavity between them. Additionally, sound-damping materials should be used for joints, connections, and layers, while acoustic membranes or blankets should be used for pipes, ducts, and equipment. Acoustic vents or louvers can be used for ventilation and air conditioning, acoustic baffles or diffusers for skylights and openings, and acoustic panels or tiles for ceilings and partitions.

5 Acoustic benefits

By applying the best acoustic materials and strategies for green building envelope, you can reap a variety of benefits for your project and its occupants. These include reduced noise pollution, improved health and productivity, enhanced privacy and security, improved thermal performance and energy efficiency, increased durability and resilience, enhanced aesthetic and architectural value, and reduced environmental impact.