Published in Informed Infrastructure.
Buildings account for as much as 40 percent of all energy consumed in the United States... To increase the efficiency of buildings and address climate-change issues, government programs increasingly promote “net zero energy” (NZE) goals for public buildings. The following eight guiding principles for project design phases will help produce buildings that generate energy onsite using clean renewable resources through the course of a year that are at least equal to the total amount of energy consumed onsite.
1. Define Goals
The first step is to establish sustainability goals for the site. Case studies and reviews of best practices in sustainable design should be assembled to provide benchmarks for the design team. Tax incentives and rebates offered by government and utility companies should be identified. Factors such as micro-climate, orientation, water usage and occupancy (relative to energy-use targets) must be examined. The design team must work with stakeholders and agencies to reach consensus on energy-use goals.
2. Assess Building Configurations
After goals are established (and where possible), numerous building configurations (orientation, footprint, shape and massing) should be considered for the site. The building’s function and use patterns must be considered in developing the interior space plan. For instance, will it be a 24/7 operation with related power and occupant comfort considerations?
3. Set the Proposed Energy Use Intensity Target (PEUI)
The design team and building owners must agree on targets for energy-use intensity. The starting point for determining intensity is a comparison of the energy-use intensity of the proposed building design with a base-building use standard.
4. Determine Strategies for Energy Reduction
The design team should now look at multiple energy conservation measures (ECMs) to reduce energy consumption prior to exploring potential onsite renewable resources. These may include the following:
- Site Optimization — Orientation of the building and placement of glazing-affect energy use.
- Solar Shading — Exterior architectural features shade window openings from the sun at specific times; strategic planting of deciduous trees to create shade.
- Daylight and Artificial Lighting — High windows with light shelves bounce light deep into floorplans.
- Natural Ventilation — Operable windows and mechanically controlled dampers can effectively move air through spaces, decreasing the loads on mechanical conditioning equipment.
- Façade and Roof Design — Air sealing, additional roof and wall insulation; double or triple glazing in high performance framing systems such as fiberglass; and reflective or vegetated green roof can significantly reduce energy gains and losses.
- Ground-Source Heat Pumps — Liquid pumped through wells in a closed loop from mechanical equipment helps raise indoor temperatures in winter and lower them in summer.
- Displacement Air Supply — High-volume spaces are more-efficiently climate controlled by introducing conditioned air at floor level, conditioning air only in the first six to eight vertical feet of a space.
- Education — Occupants should be educated about the sustainable design of the building and how to inhabit it comfortably while saving energy.
5. Determine Renewable Energy Strategies
The design team should now assess onsite renewable energy strategies to offset anticipated energy usage, including the following:
- Solar Photovoltaic Panels
- Solar Thermal Panels for Domestic Hot Water
- Unglazed Transparent Collectors
- Biomass Boilers
- Biofuel Tri-Generation Plant
- Wind Turbines
6. Assess Energy-Generation Options
Assess all renewable energy options based on lifecycle costing. When designing building systems, the design team must view the complete picture, including initial construction costs, operating costs, evolving technologies, site design impacts and energy delivery reliability.
7. Assess Feasibility and Adopt Options
Will the energy produced onsite offset the building’s remaining energy needs after maximizing the site and building energy reduction? Site, building design, occupancy and cost constraints may preclude achieving net zero energy, but setting the goal creates a highly energy-efficient project that can adapt to changing needs and technologies—all while helping the planet!
8. Commission and Verify
During design and construction, the team must pay close attention to maintaining the goal through project design and occupancy. A Commissioning Agent should be brought on board early to provide feedback on maintaining energy-conservation integrity. For a completed project to be certified NZE, building owners collect and submit the building’s energy use and generation data for a year for third-party verification. The International Living Future Institute is one overseer.
The preceding principles are a solid starting point for seeking NZE certification, enabling design teams and owners to understand balancing between three primary interrelated elements: function, strategy and cost. Designers and owners, in partnership with municipalities, can achieve the goal of NZE (or come close) when designing, constructing and operating public projects. NZE is quite a challenge, but one that can be met through close coordination during the entire design phase—and one we must strive for to achieve a sustainable future.