A 2012 JD Power report states: “Electric cars will remain a small portion of the U.S. vehicle market unless automakers can figure out ways to cut prices.”
What a difference six years makes. Ford is now “all-in” on electric cars. General Motors and Infinity also believe in an all-electric future. If that can happen to electric cars, what's the energy future for residential buildings?
Many signs are pointing toward a future that might have already arrived.
Consider these top-down changes:
- Earlier this year, a California code draft considered requiring all future homes to be net zero by 2020, with on-site solar;
- Washington, D.C., announced a goal of converting existing buildings to net-zero status by 2032;
- In the September 2018 C40 meeting, 26 mayors, including from cities such as London, Los Angeles, and Seattle, signed an agreement to procure zero-emission buses by 2025 and ensure that a major area of their cities will be zero emissions by 2030;
- The University of California has committed to an all-electric future; and
- The U.S. DOE is performing research on a new generation of so-called Grid Interactive Efficient Buildings.
All these facts point to a zero-energy, zero-emissions future, likely through the electrification of the built environment, both ground transportation and buildings.
A Sustainable-Energy Future
While top-down policy set the stage, bottom-up forces provide the momentum for natural change. Renewable-energy costs are now at a historical low and are close to, or even lower than, grid parity. For example, while the average U.S. electricity cost is about 12 cents per kWh, in Colorado, renewable-energy developers offered the largest utility company, Xcel Energy, an average of 2.95 cents per kWh using solar photovoltaics (PVs). In Chicago, where the average residential electric rate is 10.44 cents per kWh, a solar company is willing to offer 3.5 cents per kWh to a developer for resale, and the developer can pocket the difference.
Increasingly, residents expect their home to be not only energy efficient, but also integrated into a larger community with more amenities and a greater customization of building services. Residents want to live in a community where wellness and comfort take center stage. Developers are eager to capitalize on new technologies and invest in projects that mitigate costs but ensure resident satisfaction and a profitable, resilient development. All these factors take shape within the larger move toward a sustainable energy future.
These trends require a significant change in how our buildings operate and use energy. The DOE's Building Performance Database shows that residential typologies have lower energy savings per square foot than commercial buildings. Given that the investment in homes is the biggest financial outlay people make, how can investment in residential energy efficiency and wellness align this evolving consumer awareness with market opportunity?
Building Positive + Living Well
AMLI Residential and SOM, through the design of the 2018 Multifamily Executive Concept Community, Building Positive + Living Well, used the above key characteristics of the future energy world and incorporated them as central elements of the project's building design.
The system design of the concept development, located at 900 S. Clark in Chicago, is characterized by a zero-emission, zero-energy building that is all-electric and powered by on-site solar as much as possible. Passive design, as dictated by PHIUS guidelines, is the key.
Overall, the building consumes 64% less energy than a comparable baseline (annual energy consumption of the existing building on-site), with an expected annual energy consumption of 23 kBtu/ft2. This is partially achieved through a tight building envelope that reduces infiltration, is highly insulated, and uses high-performing glass with low conductivity and solar heat-gain coefficient. The building envelope also enhances thermal autonomy, minimizes heating and cooling requirements, and allows passive survivability, allowing for a thermally resilient building that can maintain adequate indoor air temperatures in the event of a utility outage.
The project's HVAC system leverages the need for simultaneous heating and cooling as an opportunity to save energy. While typical condensing boilers have an efficiency of COP above .9, by using hot-water heat pumps, an efficiency of 2 to 3 is realized by capturing the waste heat from cooling. An innovative, three-in-one heat pump located in each residential unit generates radiant-loop floor heating, domestic hot water, and chilled water for space conditioning. This creates the option of passing on the space requirements; energy cost; and, potentially, the installation cost of the heat-pump systems to the apartment owners.
An integrated condenser water loop runs through the building, working as a “plug-and-play” infrastructure: The heat rejected into the loop during the cooling mode can be recovered to heat domestic hot water or hot water for the radiant floor loop. Moreover, the condenser water loop is linked to a series of geothermal bores located on-site that serve as an additional heat source and sink, given the relatively constant temperature of the ground. This reduces the need for cooling towers. Heating is provided also by solar thermal panels on the building roof.
On-site renewable energy at the concept community is generated partly by solar PV panels on the roof of the parking garage. The panels can supply 12% of the building's total annual energy. In addition, solar thermal panels on the roof generate 21% of the project's annual energy, equivalent to the domestic hot-water requirement.
The community's design proposes the use of groundbreaking quantum-dot technology to generate electricity. In this scenario, all windows have an applied coating that not only reduces solar heat gain but, along with a solar coating integrated into the window assembly, generates 27% of the annual electricity required for the building. Further energy can be generated from battery inverters incorporated into exercise equipment located on the building penthouse level. The remaining energy balance required to achieve net zero is provided by off-site renewable resources. On-site electric-vehicle charging stations also allow for an interactive exchange of energy between the building and resident vehicles.
A connection with nature is another key element in the design of the concept community. Selected units were shortened to allow daylighting for the entire apartment. This reduces the overall lighting energy demands and restores the daytime circadian rhythm for residents, which is further supported with artificial circadian lighting at night. Orange and red colors are avoided to maximize the daytime circadian cycle.
Cross ventilation via the corridors and central common areas allows for passive cooling of the units when climate and air-quality conditions allow. Night flushing, or night ventilation, is also enabled in the apartments. The overall goal of maximizing air movement in the project is to bring about the largest possible "breath" of outside air and use night flushing to replenish the indoor microbial biome.
Each unit also has a dedicated solarium, with operable windows: During the cold season, the windows provide a thermal buffer between the exterior and conditioned interior of the unit, acting as a double skin. During the milder and warmer months, they perform as integrated semi-outdoor spaces protected from direct sun and wind gusts.
The HVAC design of the building aims to ensure superb levels of comfort for residents. This is achieved through a radiant floor-heating system in each unit that maintains the ideal mean radiant temperature while providing high thermal efficiency. Cooling is provided by fan coil units equipped with electronically commutated motors.
In addition, through the deployment of smart-home systems, residents can monitor temperature, relative humidity, and other key unit information and control heating and cooling via a smartphone application. The system will adapt to resident selected points, schedules, and other preferences to maintain the highest levels of comfort while minimizing system losses.
Passive and Active Ventilation
Ventilation is a key aspect of the building's system design; air quality is not one size fits all. A survey of 18 countries shows that air quality is more stringent for more-vulnerable age groups (such as pregnant women, senior citizens, and children). Air-quality sensors incorporated into the building automation system will inform residents when the outdoor air is healthy and windows can be opened per specific occupants' needs. These sensors will also automatically activate any openings in the common areas. This passive ventilation strategy further improves the resiliency of the building in the event of a power outage.
As part of the project's active ventilation system, dedicated ventilators with energy-recovery wheels will provide outside air to each unit. The ventilators filter incoming air, which is pretreated before entering the unit. (The units, pending final requirements, have final filters where required.) The control of these ventilators is also integrated into the smart-home system, giving residents the highest levels of on-demand control.
This thoughtful, integrated design creates a building that is zero emission, zero energy, and resilient and that prioritizes resident comfort and well-being. A clean-energy future is possible today when we use innovative technology and forward-thinking system design, and value a vision of residential wellness.
Read more about the design of the 2018 Multifamily Executive Concept Community at www.multifamilyexecutive.com/concept-community and the cutting edge ideas from the SOM team, including Marzia Sedino, Arathi Gowda and Ali Irani.