Increasing Energy Efficiency and Decreasing Noise and Vibration

Houses and mid-rise apartments are sometimes constructed poorly, often for the sake of flipping a house or apartment building for a profit. However, it is becoming readily apparent that buildings need to be designed and constructed to last for generations rather than only a few decades.

Energy Efficiency

According to a report from the Institute for Market Transformation (IMT), increasing the energy efficiency of America’s multifamily buildings—nearly 18.5 million households—could save building owners and managers, residents, governments, energy-efficiency service providers, and financiers close to $3.4 billion annually. ICFs provide solutions to these growing energy concerns: their high thermal mass reduces conduction and convection. The result is a building with lower energy usage and improved comfort inside due to more consistent temperatures and lack of drafts. A more energy-efficient envelope means more money saved every year while reducing the project’s carbon footprint.

ICF walls are considered by the IECC and ASHRAE 90.1 as mass walls with continuous insulation. Typical whole wall ICF assemblies have an R-value between R-24 and R-26 depending on the exterior and interior finish materials compared to R-11 and R-19 for 2x4 and 2x6 wood frame. Thermal resistance (R-value) does not take into account the effects of thermal mass, and by itself does not fully describe the beneficial properties of ICFs. The damping and lag effect of thermal mass means fewer spikes in heating and cooling requirements since the mass buffers indoor temperature fluctuations, contributing to occupant comfort. Thermal mass shifts energy demand to off-peak time periods when utility rates are lower, reducing costs further. ICF walls can exceed the requirements for all climate zones for both residential and commercial thermal envelopes above and below grade because of the combination of extreme R-value and thermal mass.

Achieving a high-performance building envelope also means minimizing air leakage, and ICF walls are tighter than wood-frame or light-gauge steel walls. In tests, they averaged about half as much air infiltration as wood frame. In many cases, the air-infiltration rates are as low as 0.5 air changes per hour. Thermal bridging is also eliminated with ICF walls when compared to wood and light-gauge steel. Since the energy consumption of ICF buildings are lower, the HVAC systems can be smaller and more efficient, adding to energy savings. The result is energy savings ranging from 20 percent to as much as 50 percent depending on other energy-efficiency strategies employed for the building.

Noise and Vibration

Concrete walls and floors have long been used as the material of choice for reducing sound transmission, which is key to a better guest experience in the hospitality sector and better retention rates in multifamily housing. Occupant retention rates and financial savings will be discussed in more detail in the following section.

ICFs are often used for hotel and hospitality projects for their ability to isolate and dissipate noise. Noise transmission in residential buildings is also important to reduce noise both between units and from the outside. Most multifamily buildings, whether they are apartment buildings or hotels, are generally located in urban centers where car and truck traffic can affect occupants’ quality of life. The fact that ICFs can eliminate sound transmission at virtually no additional cost makes them attractive for any project in which peace and quiet is a selling point.

The concrete core of ICFs offer excellent noise control in two ways. First, it blocks airborne sound transmission over a wide range of frequencies. Second, concrete absorbs noise, thereby diminishing noise intensity. Because of these attributes, ICF walls and floors have been used successfully in multifamily and hospitality applications.

The International Building Code (IBC) has requirements to regulate sound transmission through interior partitions separating adjacent dwelling units and separating dwelling units from adjacent public areas. Six-inch ICF walls easily achieve a sound transmission classification (STC) rating of 55. Higher STC ratings of up to STC 70 can be achieved with additional gypsum wallboard or special isolation channels. For ICF floors, most meet STC 50 or higher and an impact insulation class (IIC) rating of 50 or higher depending on the floor and ceiling finish as required by the IBC.

Case Study: The Ricchi Condominiums

Photo courtesy of Ricchi Group

Location: San Antonio, Texas
Units: 87
General Contractor: Ricchi Group
Architect: Spazio Design + Construction

The Ricchi Condominiums located in San Antonio, Texas, are a contemporary, mid-rise building consisting of 87 luxury condominiums. The development was the first of its kind to be built in the exclusive area of La Cantera Parkway. The developers wanted to provide a first-class, secure, and quiet building. They chose insulated concrete forms (ICFs) as part of the plan to achieve their goal.

Noise reduction was a major consideration for this project. The Ricchi is located directly below the flight path for airliners approaching San Antonio International Airport and is adjacent to a U.S. Army training camp.

As a solution, the U-shaped, luxury condominium utilized more than a quarter-million square feet of ICFs. All of the exterior walls of The Ricchi, as well as the interior walls between units, carports, pool houses, and even the changing rooms, are made of ICFs. To provide views for the occupants, the architect was able to visually “break up the massive walls into smaller segments and create individual condo entrances along the 225-foot-long corridors inside.”⁵

While this meant dozens of corners and a multitude of window and embeds, the architects noted that by the time they began work on the upper levels, “‘things started to smooth out, and we were able to work very efficiently.’”⁶

Overall, the sound attenuation offered by ICFs provided resolved noise concerns throughout the development while creating significant energy savings. The higher insulation provided by the ICF walls reduced HVAC tonnage by 20 percent, resulting in significant energy savings.

Case Study: Beach Green Dunes, Rockaway,New York

Photo: © Peter Mauss/Esto

Completed in 2017, the 101-unit, 94,000-square-foot Beach Green Dunes apartment building is built in an area that was devastated by Hurricane Sandy. The Bluestone Organization selected insulated concrete forms (ICFs) for exterior, corridor, and demising walls, and precast hollow-core floors for disaster resilience and energy efficiency. The building is so energy efficient that it is certified by the Passive House institute. ICFs create a solid concrete wall with continuous insulation, resulting in a comfortable and airtight structure that lowers energy bills. The reinforced concrete system creates a structure that is strong, durable, and can stand up to fire, floods, and wind. The Bluestone Organization builds exclusively with concrete.

The project, designed by Curtis + Ginsberg Architects, incorporates many innovative features to achieve record-breaking low energy and water consumption levels. These include the use of ICFs, energy-recovery ventilation, a large rooftop solar photovoltaic system, and a natural gas fired cogeneration system that produces electricity, all of the building’s hot water needs, and serves as a backup emergency generator to supply power to safety systems in the event of a future power outage.