Harvesting on-site renewable energy
“The intent of the Energy Petal is to signal a new age of design, wherein the built environment relies solely on renewable forms of energy and operates year-round in a safe, pollution-free manner. In addition, it aims to prioritize reductions and optimization before technological solutions are applied to eliminate wasteful spending—of energy, resources, and dollars.” International Living Future Institute
The Energy Petal requires net positive energy, which means at least one hundred and five percent of the project’s energy needs must be supplied by on-site renewable energy on a net annual basis, without the use of on-site combustion. As with other natural resources, The Kendeda Building must balance the energy it uses with the energy it is able to harness. Consideration is first given to climate-appropriate passive design, then energy conservation measures, which reduce the size of renewable energy system needed, and, finally, to on-site renewable energy.
The Kendeda Building has two 64-person classrooms, two 24-person class labs, two 16-person class labs, a 16-person conference room, makerspace, 176-person auditorium, rooftop apiary and pollinator garden, and an office space for co-located programs. Based upon this programming, it has a projected energy use intensity (EUI) of 30 kBTU/SF/YR, which is 72 percent more efficient than an average building of the same size and occupancy.
Passive design is a technique that designers use at the initial planning stages of a project to leverage the natural climate, solar, and energy characteristics of a building and its surroundings to lower energy demands. For The Kendeda Building, designers prioritized the following variables to enhance the building’s ability to operate passively in Atlanta’s climate, especially to reduce cooling needs and the associated energy needs.
Designing an Efficient Building Envelope
The performance of the building envelope is critical both to the energy efficiency of the building and to the comfort level of the occupants. This includes continuous insulation at walls and under slabs and triple pane window glazing which helps to reduce building loads in winter and summer.
Shading to Reduce Solar Heat
The building's photovoltaic (PV) canopy multitasks by harnassing energy, collecting rainwater, and providing shade for the south and west façades, the elevations that receive the most solar gain. The shaded areas help create a micro-climate that eases the transition between inside and outside of the building.
In addition, exterior operable and non-operable venetian blinds on the building’s west façade help manage the cooling requirements due to summer sunshine. Shades aid in solar control and daylighting optimization for occupants. Strategically placed trees also help control unwanted solar gains.
Using Daylight to Reduce Energy Demands
Daylighting design plays a large role in reducing system energy needs, improving occupant health and wellbeing, and connecting occupants to the outdoor environment. In addition, skylights and clerestory windows were designed in the large atrium space for continuous daylighting in the building.
Reducing Air Infiltration
Vestibules, air curtains at entries, and an efficient building envelope help prevent the movement of hot air and humidity into the building. Operable windows – with a system override – throughout the building is mechanically operated when outdoor temperature, humidity, and pollen count are within an acceptable range to maintain system balance.
Providing Thermal Comfort
The Kendeda Building is designed to operate within a broader range of thermal comfort than a typical building. By carefully considering air and radiant temperature, humidity, and air speed, as well as occupant activity and clothing, the building operates at higher air temperatures in the summer without sacrificing occupant comfort. This reduces energy use and the size of the mechanical system that needs to be installed.
Energy Conservation Measures
Every variable of the building’s passive design is evaluated using the energy models. The models also predict how much energy savings can be achieved by implementing additional energy conservation measures. Ultimately, the energy model determines how many photovoltaics are required to offset the energy needs of the building. Additional energy-related factors such as operating hours, thermostat set points, and plug loads become enormously important when all power must be generated onsite.
The energy demands for The Kendeda Building are higher than other certified Living Buildings. The building is open 15 hours a day Monday-Friday for 51 weeks of the year. It hosts regularly-scheduled classes, labs, tours, and evening and weekend events. The extended hours and activities result in high energy usage demands. Anticipated high pedestrian traffic increases demand on everything from toilets to lights as well as the heating, ventilating, and air conditioning (HVAC) system – all driving demand on the PV array and the net positive water supply.
Cooling and Heating the Building with Efficient Mechanical Systems
Equipped with additional condensation sensors and temperature reset strategies to mitigate moist floors, a radiant heating and cooling system in the flooring is used throughout most of the building. In addition, an energy efficient dedicated outdoor air system (DOAS) provides heated or cooled (and dehumidified) ventilation air to a majority of the building’s spaces. To accommodate large audiences, the auditorium has a dedicated variable air volume HVAC. Ceiling fans are used throughout the atrium space and classrooms for air circulation.
Borrowing Water and Energy from the Campus Central Loop
The building’s mechanical system, including the radiant flooring system and the DOAS uses chilled water from the campus’ central system. When the building needs to provide cooling, the mechanical system draws chilled water directly from the campus loop. When the building needs to provide heating, the mechanical system uses the campus heat recovery chiller to provide heat. Both the water and energy (in the form of heat) borrowed from the central plant is metered and taken into account in the annual net positive calculations.
Harvesting Energy from the Sun
The building's 330 kW (DC) solar canopy is comprised of 917 PV panels and is generates over 400,000 kWh per year that directly serves the building’s energy demands including lighting, HVAC system, water system, and plug loads. A lithium ion battery is charged exclusively by the PV array and serves as the emergency back-up system for the building in the case of power outages. The sizing of the PV array included the building’s system energy demands, a safety factor of 10 percent, plus the 5 percent net positive factor that is required for Living Building Challenge certification.
When the PV array is not producing adequate amounts of energy, the building loads run off of electricity from the grid. When the PV array is producing more electricity for the building than needed, the building supplies electricity back to the grid. The PV array has also been sized to account for energy used from the campus chilled water connection. Water from the campus connection is metered, energy is calculated, and an energy offset is supplied to the grid in order to meet the annual net positive requirements. By harnessing more energy than the building consumes, the systems create a net positive energy facility on an annual basis.