by Jeffrey J. Garriga
Buildings account for as much as 40% of all energy consumed in the United States.
To make the country more energy efficient, government programs increasingly promote net zero energy usage in public buildings. Here are eight guiding principles for the project design phases that will assist in producing buildings that generate energy onsite using clean renewable resources over the course of a year that is at least equal to the total amount of energy consumed onsite.
- Define goals
The first step is to establish energy 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 the government and utility companies should be identified..
Detail and consider factors such as climate, location, orientation, water usage, and occupancy, relative to energy use targets.
Make sure all stakeholders and agencies agree on the energy use goals.
- Assess building configurations
Once goals are established, numerous building configurations (orientation, footprint, shape, and massing) should be considered for the site.
The building’s function and use need to be taken into consideration when developing the interior space plan. For instance, will it be a 24×7 operation with related power and occupant comfort considerations?
- Set the energy use intensity goal
The design team and building owners must agree on the expectations for energy consumption. A starting point for determining energy reduction is a comparison of the energy use intensity of the proposed building design with a base industry standard.
- Determine strategies for energy reduction
The design team should now look at multiple energy conservation measures to reduce energy consumption prior to exploring onsite renewable resources. These may include:
- 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; or strategic planting of deciduous trees to create shade.
- Daylight and artificial lighting – High windows with light shelves bounce light deep into floor plans.
- 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 – Large spaces are more efficiently climate controlled by introducing conditioned air at floor level while conditioning air 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.
- Determine renewable energy strategies
The design team should now assess on-site renewable energy strategies to offset anticipated energy usage.
Renewable energy resources include:
- Solar photovoltaic panels.
- Solar thermal panels.
- Unglazed transparent collector.
- Biomass boilers.
- Biofuel tri-generation plant.
- Wind turbines.
- Hydro power.
- Assess energy generation options
Assess all renewable energy options based on long-terms cost and viability. 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.
- 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; however, setting the goal creates a highly energy-efficient project that can adapt to changing needs and technologies, all the while helping the planet!
- 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 onboard 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, third party verified. The International Living Future Institute is one overseer.
Conclusion
The preceding principles are a solid starting point for design teams seeking NZE certification, enabling teams to understand how to balance three primary interrelated elements: function, strategy, and cost.
Designers and owners, in partnership with municipalities, can achieve the goal of net zero energy, or come close, when designing projects. NZE is quite a challenge, but one than can be met through close coordination during the entire design phase.
Jeffrey J. Garriga is principal, and Pat “Sherman” Morss Jr. associate principal, at Finegold Alexander Architects.
