According to the International Energy Agency, buildings represent about 40% of the energy and 75% of the electricity consumption in the world. Green building practices can substantially reduce negative environmental impacts through high-performance, market-leading design, construction, and operations practices.
The energy performance of a building depends on its design. Its massing and orientation, materials, building envelope, heating, ventilating, and air-conditioning (HVAC), systems, service hot water, lighting systems and controls determine how efficiently the building uses energy. The most effective way to optimize energy efficiency is to use an integrated, whole-building approach. Collaboration among all team members, beginning at project inception, is necessary in designing an energy-efficient building.
Some energy-efficiency measures may not require additional first costs. Many measures that do result in higher capital costs may generate savings from lower energy use, smaller equipment, reduced space needs for mechanical and electrical equipment, and utility rebates. These savings may vastly exceed the incremental capital costs associated with the energy-efficiency measures over the life of the project.
According to the U.S. Department of Energy, energy-efficient buildings allow for:
• Enhanced working environment: Healthier working environment include favorable lighting, acceptable sound levels, and thermal comfort and are affected by many energy-efficiency measures. An increasing number of surveys and studies show that natural light, proper ventilation, appropriate temperature and humidity ranges lead to healthier environments, increasing occupants well-being and productivity
• Lower construction costs / faster payback: through use of an integrated design process and project delivery, energy-efficient buildings can cost less to build than typical buildings. For example, optimizing the building envelope for the climate and designing an efficient electric lighting system can substantially reduce the size of the mechanical systems.
Some energy-efficiency strategies may cost more up front, but the energy they save means they often pay for themselves within a few years.
• Reduced operating costs: Strategic up-front investments in energy efficiency measures provide significant long-term operating and maintenance cost savings.
• Reduced greenhouse gas emissions: electricity is most often generated by burning fossil fuels, whose combustion releases greenhouse gases such as carbon dioxide which contribute to climate change.
Below are examples of energy conservation measures implemented in high performance projects:
The building sector can significantly reduce energy use by incorporating energy-efficient strategies into the design, construction, and operation of new buildings and undertaking retrofits to improve the efficiency of existing buildings. It can further reduce dependence on fossil fuel derived energy by increasing use of on-site and off-site renewable energy sources.
The concept of a Net Zero Energy Building (NZEB), one which produces as much energy as it uses over the course of a year, recently has been evolving from research to reality. As a result of advances in construction technologies, renewable energy systems, and academic research, creating Net Zero Energy buildings is becoming more and more feasible.
Minimizing the energy use through efficient building design should be a fundamental design criterion and the highest priority of all NZEB projects. Energy efficiency is generally the most cost-effective strategy with the highest return on investment, and maximizing efficiency opportunities before developing renewable energy plans will minimize the cost of the renewable energy projects needed.
Using advanced energy analysis tools, design teams can optimize efficient designs and technologies. Once efficiency measures have been incorporated, the remaining energy needs can be met using renewable energy technologies. Common on-site electricity generation strategies include photovoltaics (PV), solar water heating, and wind turbines.
LEED and energy efficiency
Within LEED green building rating system, each credit is allocated points based on the relative importance of the building-related impacts that it addresses.
LEED put a strong emphasize on energy-efficiency. For example, in LEED 2009 for New Construction and Major Renovation, up to 19 points can be earned in EA credit 1 “Optimize Energy Performance”.
As a prerequisite, LEED requires to demonstrate at least 10% improvement in the proposed building performance rating for new buildings compared with the baseline building performance. The baseline building performance is calculated according to the building performance rating method in Appendix G of ASHRAE Standard 90.1-2007 using a computer simulation model for the whole building project.
LEED encourages to achieve increasing levels of energy performance beyond the prerequisite standard to reduce environmental and economic impacts associated with excessive energy use. For New Construction projects, the project earns 1 point for each 2% energy cost savings beyond the prerequisite (minimum 10%) up to 48% energy cost savings compared with the baseline building performance rating, as shown on the table below:
Furthermore, energy use can be directly affected through the use of climatically appropriate roofing materials and careful optimization of exterior lighting. Refer to these credits:
In addition to reducing energy use through efficiency measures, project teams can mitigate energy use impacts by using renewable energy. Refer to these credits: