Integration: Net-zero energy design
ASHRAE has a goal: net-zero energy for all new buildings by 2030. What do engineers need to know to achieve this goal on their projects?
>”As net-zero energy and low-energy design projects become more prevalent, engineers must be prepared to collaborate with all members of a project team including architects, energy specialists, lighting designers, builders, and owners in order to accomplish net-zero energy goals with little to no cost premium. Is this possible today or will it take another 10 or more years to get there?
There are many examples of completed projects demonstrating that not only is this possible, but it has been done in all regions of the country using readily available building products and common construction methods. So what’s the secret? It’s all about the design.
Net-zero energy defined
The term “net-zero energy” is abundantly used, but a single universally accepted definition does not exist. In general terms, a net-zero energy building (NZEB) has greatly reduced energy needs achieved through design and energy efficiency, with the balance of energy supplied by renewable energy. In an effort to clarify the issue, the National Renewable Energy Laboratory (NREL) published a paper in June 2006 titled “Zero Energy Buildings: A Critical Look at the Definition,” in which it defined the following four types of NZEBs:
Net Zero Site Energy: A site NZEB produces at least as much renewable energy as it uses in a year, when accounted for at the site.Net Zero Source Energy: A source NZEB produces (or purchases) at least as much renewable energy as it uses in a year, when accounted for at the source. Source energy refers to the primary energy used to extract, process, generate, and deliver the energy to the site. To calculate a building’s total source energy, imported and exported energy is multiplied by the appropriate site-to-source conversion multipliers based on the utility’s source energy type.Net Zero Energy Costs: In a cost NZEB, the amount of money the utility pays the building owner for the renewable energy the building exports to the grid is at least equal to the amount the owner pays the utility for the energy services and energy used over the year.Net Zero Energy Emissions: A net-zero emissions building produces (or purchases) enough emissions-free renewable energy to offset emissions from all energy used in the building annually. Carbon, nitrogen oxides, and sulfur oxides are common emissions that zero-energy buildings offset. To calculate a building’s total emissions, imported and exported energy is multiplied by the appropriate emission multipliers based on the utility’s emissions and on-site generation emissions (if there are any).
A subsequent paper was published by NREL in June 2010 titled “Net-Zero Energy Buildings: A Classification System Based on Renewable Energy Supply Options,” where four classifications of NZEBs were defined:
NZEB:A: Building generates and uses energy through a combination of energy efficiency and renewable energy (RE) collected within the building footprint.NZEB:B: Building generates and uses energy through a combination of energy efficiency, RE generated within the footprint, and RE generated within the site.NZEB:C: Building generates and uses energy through a combination of energy efficiency, RE generated within the footprint, RE generated within the site, and off-site renewable resources that are brought on site to produce energy.NZEB:D: Building uses the energy strategies described for NZEB:A, NZEB:B, and/or NZEB:C buildings, and also purchases certified off-site RE such as Renewable Energy Certificates (RECs) from certified sources. […]
Integrated building design
Integrated building design is a process that promotes holistic collaboration of a project team during all phases of the project delivery and discourages the traditional sequential philosophy. According to ASHRAE, the purpose of the integrated design process is to use a collaborative team effort to prepare design and construction documents that result in an optimized project system solution that is responsive to the objectives defined for the project. […]
Commissioning is an important part of every project, and for NZEB projects the commissioning authority should be a member of the design team and involved throughout the design process. […]”<