Green Beat:Net Zero Energy

The next frontier in multifamily housing.

The future of real estate development lies in sustainability. Federal and local compliance are shifting toward greener standards; California’s Title 24 legislation, for example, requires all new residential construction to achieve Net Zero certification by 2020. Engineers in major cities face some of the greatest challenges in reaching these new standards. Two of the largest hurdles, versatile insulation and onsite energy production, must be overcome before Net Zero multifamily housing can become commonplace in urban environments.

The foundation to any Net Zero building starts with a well-sealed, insulated envelope. Simply finding the right insulating materials can be tricky for those developing in urban areas, especially when they must build up rather than out. Many residential Net Zero designs rely on structural insulated panels (SIPs). SIPs provide a cost-effective framing alternative that regulates internal temperature and moisture levels while adding durability and strength to the structure. The pre-cut, pre-insulated panels improve indoor air quality, limit entry of outside pollutants, and require smaller HVAC systems to keep units comfortable.

Challenges and limitations

SIPs have inherent limitations. To date, code does not approve the material for high-rise construction. Standard SIPs are composed of partially recycled EPS foam cores that are encased with oriented strand board, or OSB. Due to safety concerns, OSB products have been restricted to low-rise structures. Joe Pasma, technical manager at Premier Building Systems explains, “We have wall panels that are 8-10 feet and can hold 3,000-4,000 pounds per lineal foot. From a strength standpoint, the SIPs are ready for high-rises. Limitations come in because wood is a combustible material. Fire restrictions become a controlling factor in how tall buildings are allowed.”

It could be years before SIPs technology adapts to the regulatory and financial needs of American high-rise construction. Cementitious SIPs address fire concerns but tests for code reports could cost builders millions. Fireproof OSB SIPs have been used to construct buildings of up to 14 stories in Europe, reports Pasma. Unfortunately, the products are not financially viable for many American builders. Lastly, any SIP with an EPS petrochemical core has embodied energy that is only offset after at least three years, bringing a slower return on investment.

Alternative options

Alternative products such as Ecovative’s mushroom-based insulation will empower builders to reach Net Zero certification with less embodied energy than EPS SIPs. Though it holds promise, Ecovative’s product is still in development. Mineral wool, or slag wool, is rising in popularity due to its superior R values. With up to 70 percent recycled content, it’s a green choice from start to finish. Its weight, however, makes installation more cumbersome.

Multi-paned windows allow for high-rise construction and good insulation but they come with notable drawbacks. Evan Goldsmith, president and founder of Revoltagen energy solutions, explains the safety concerns caused by multi-paned glass high rises. “People who have been across from these buildings are being blinded and things are catching on fire because of the angle of the windows and those sorts of things. Shading is very important.”

Managing the shade in urban settings poses limitations on architects. Building in the shade of other structures minimizes natural light and weakens solar power, highlighting another challenge for Net Zero construction in cities.

Generating energy for multifamily

Net Zero buildings must produce as much energy onsite as they consume. Multifamily firms in urban areas struggle to find onsite energy sources suitable for their sites. Cogeneration, the industry’s most common technique for onsite energy production, requires closely aligned properties and at least one plot nearby for the cogeneration plant.

According to Goldsmith, “[The plant] can generate electricity onsite and the byproduct of the electricity generation is the heat, which can then be used by the buildings and their residents. Producing the energy close to the buildings minimizes the loss of energy that occurs when electricity is transported through transmission lines.” The amount of energy saved, the quantity of heat produced, and lowered utility costs are worth the installation of a small cogeneration plant—if the space is available.

Space-savvy alternatives are available, complete with their own set of obstacles in urban settings. Solar panels face limitations in the shade of other buildings. Few city corridors offer enough wind to make turbines worthwhile. Innovative algae-based power has gained a growing fan base among green builders but the living organisms are affected by both temperature and access to sunlight.

Developers have sought a combination of energy sources to fuel urban multifamily communities. Bright n’ Green in Brooklyn, a net zero energy property being developed by Robert Scarano, uses wind turbines and solar panels to generate power. The building is constructed with Oceansafe’s super-insulated SIPs. Triple-paned windows by Marvin Windows and Doors provide added insulation. Combined, the materials minimize the amount of energy required to operate the units comfortably. The solar panels and windmills can then power the building and generate enough energy to send surplus electricity to the grid.

Bright n’ Green, though a stunning example of Net Zero living, only houses six units. Until versatile insulation and energy sources can be addressed affordably, Net Zero multifamily housing is limited to relatively small projects in urban settings. The vast, ultra-luxury accommodations that propel multifamily today may prove infeasible in the future.

A change in direction could be a good thing for the industry. Reevaluating the heart of housing—its scope, its purpose, and its role amongst larger ecosystems—may help multifamily leaders conclude that less is more. Fortunately, insulating and powering less is easier in any environment.

To comment, e-mail Diana Mosher at
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