Most building energy cost comparisons and early compliance decisions can be made using annualized energy cost and consumption information. Costs are estimated using statewide, territory-wide, or nationwide average utility rates; or the customized rates you may have applied to the project.
Carbon neutrality is defined here as eliminating or offsetting fossil based electricity and fuel use. For example, if the electricity grid is 60% fossil fuel and 40% hydroelectric, reducing grid electricity use by 60% and eliminating/offsetting on-site fuel use will make the project carbon neutral. Use any combination of efficiency, natural ventilation, renewable energy, carbon credits and biofuels to reach this goal. Renewable potential is the sum of photovoltaic and wind potential shown below.
To calculate CO2 emissions for United States projects, Green Building Studio uses data from the U.S. Environmental Protection Agency; which has historical records for all the fuel and emissions of all power plants in the United States. The CARMA (Carbon Monitoring for Action) data is used for projects outside of the United States.
Access the Energy and Carbon Results in the Project Run List tab from My Project tab. Select a run and then click the Run name. The following estimated data is displayed.
In the first two rows run information is provided :
Project Template Applied
Location
Building Type
Floor Area
Electricity & Fuel Costs
Utility Data Used
The Energy and Carbon Results are categorized in multiple groups to be easy to understand:
Energy, Carbon, and Cost Summary for Base Run and Design Alternative: Includes the results for the project base run and the selected design alternative to make detail comparison.
Annual Energy Cost. The estimated total annual utility cost for all electricity and fuel used by your project.
Lifecycle Cost. The estimated total cost for all electricity and fuel used by your project over a 30-year period.
Annual CO2 emissions. Carbon emissions are based on the on-site fuel use and the fuel sources for the electricity in the region. For example, projects located in a region with electrical power plants fired by coal will have higher CO2 emissions than the same project located in a region where electrical power plants are powered by hydroelectricity.
Note: Large SUV Equivalency. Green Building Studio puts the building's annual CO2 emissions into perspective by giving an equivalency based on a sports utility vehicle (SUV). The assumptions used are: 15,000 miles (24,140 km) driven annually; 45% highway and 55% city driving; 14 miles per gallon (5.95 km per liter) city; 18 miles per gallon (7.65 km per liter) highway.
Annual Energy consumption. The estimated measure of how much electricity and fuel your project may use during a typical one-year period.
Note: Peak electric demand (kW) is the estimated highest electricity usage during any one hour for the year.
Lifecycle Energy consumption. The estimated measure of how much electricity and fuel your project may use during a 30-year period.
Alternate Run Carbon Neutral Potential. This value applies to design alternative runs and reports the CO2 emissions of the design alternative compared to the Base Run.
Onsite Renewable Potential. This value is a negative number because it represents tons of carbon you can potentially remove from your project by using renewable energy rather than obtaining electricity from your utility provider. For onsite renewable potential we calculate the Photovoltaic Potential (solar electric) and the Wind Energy Potential for your project based upon the climate, and geometry of your project. Refer to the PV Analysis page to review the various assumptions used in the photovoltaic calculations. The Wind Energy Potential calculations assume a single 15-foot diameter turbine, with cut-in and cut-out winds of 6 mph and 45 mph respectively, and located at the coordinates of the weather data.
Natural Ventilation Potential . This value is a negative number because it represents the tons of carbon you can potentially remove from your project by taking advantage of natural ventilation to cool your building, rather than using mechanical cooling systems, which require electricity. The natural ventilation potential uses your project's chosen climate data. It calculates the savings potential by determining if the outdoor air temperatures are sufficient for cooling when cooling is called for. The calculation also assumes that your building form and openings will be designed to allow for stack-effect and/or cross-ventilation that will result in 20 air-changes per hour. The calculations do not take into account your actual design opening placements.
Onsite Biofuel Use. This value is a negative number because it represents the tons of carbon you can potentially remove from your project by incorporating onsite biofuel in place of natural gas, fuel oil, or propane obtained from your utility provider.
Electric Power Plant Sources in Your Region. The U.S. Environmental Protection Agency has historical records for all the fuel and emissions of all power plants in the United States. The CARMA (Carbon Monitoring for Action) website has the same data worldwide. This section summarizes the fuel sources for electricity generated in your project's region. In order for a project to be carbon neutral, electricity consumption must be reduced or offset using renewables (such as solar electricity or wind power) by an amount equal to the portion of the electricity that comes from fossil fuels.
LEED (Leadership in Energy Efficient Design) Daylight. The LEED glazing score is the percentage of regularly occupied floor area that has a Glazing Factor greater than 0.02. Note that the analysis assumes the entire floor area of your project to be regularly occupied unless you have defined some spaces as restrooms, corridors, storage, mechanical rooms, or conference rooms (spaces not considered to be regularly occupied by LEED). The score must be more than 75 percent to qualify for LEED points and achieve full benefit from daylighting controls throughout the building.
LEED Water Efficiency. A summary is given of the estimated water use in the building based on the number of people in the building as well as the building type. Note that the water consumption is related to the number of people and not to the number of fixtures (just because you have more sinks in your project doesn't mean that people will be washing their hands more often).
Photovoltaic Potential. Green Building Studio automatically analyzes every exterior surface of the building, including roofs, walls, and windows, for their estimated potential to generate electricity using photovoltaics (solar electrictricity). The results of this analysis are summarized in this section. Note that this analysis assumes that PVs can be installed on vertical as well as horizontal surfaces as long as the surface generates significant amounts of PV power. See the PV tab for details on the surfaces that are analyzed.
Wind Energy Potential. The estimated annual amount of electricity that can be generated from one 15-foot-diameter wind turbine of conventional design, with cut-in and cut-out winds of 6mph and 45 mph respectively, and located at the coordinates of the weather data.
Energy End-Use Charts. Further breakdowns of estimated energy use for major electric and gas end uses such as lighting, HVAC (heating, ventilation, and air-conditioning), and space-heating are provided in graphical format. Additional details associated with each category can be seen by clicking the pie charts.
Building Details and Assumptions. Detailed statistics, assumptions, and information on building constructions are provided. This information allows the building designer to get an early assessment of code compliance and rough estimates of equipment sizing requirements for heating, cooling, and water heating, as well as window, wall, and floor area breakdowns.
You can use Green Building Studio to import material properties. Autodesk Revit is capable of exporting material properties to Green Building Studio. In cases where the BIM tool is not enabled to export material information ASHRAE 90.1 code-compliant default material assemblies are used instead for the baseline energy simulation. These defaults can then be modified on the web service either through Design Alternatives or by using the Project Defaults from Your Project List page. Green Building Studio determines the appropriate defaults based on where your building is located, the building type, and the size of your building.
For more detailed information, and to learn about Default Green Building Studio Assumptions, see Building Assumptions and Details.
Carbon Neutral Building:
The definition of what constitutes a carbon neutral building is in flux, with no uniform definition existing within the regulatory or design communities. Regions of the United States and of the world that use large amounts of hydro power for example, are in favor of a definition that accounts for the low carbon emissions of their regional power grid. Others feel it is more appropriate to use national averages for carbon accounting. Finally, the use of carbon credits and offsets are allowed by some carbon accounting systems and not by others.
A carbon neutral building, as defined by the Green Building Studio web service accounts for regional differences in the carbon footprint of the regional electric grid, and mandates that any fossil based electricity and fuel use be eliminated through efficiency gains or offset by onsite non-fossil based energy sources such as PV or wind energy.
Carbon neutrality is often used interchangeably with net-zero energy consumption. A Net Zero Net Zero Energy project is defined as a project/building that consumes only what it produces with respect to energy, on an annual basis. Renewable non-carbon sources are required to meet the typical definition of a net-zero energy building. Non-carbon renewable sources include wind energy, solar energy, biofuels and in some cases partial renewable energy "credits" are assigned for certain technologies such as geothermal heat pumps which utilize the earth as a heat source/sink. In principle the definitions could be quite different. For example, a building which uses only nuclear or hydro based electricity could be carbon neutral, even if it used a large amount of energy, but it would never be net-zero on an energy basis. It is more difficult under this definition to design and operate a carbon neutral building in a region that relies heavily on coal or other fossil fuels to generate most of its electricity.
Additionally, the carbon footprint can be reduced by purchasing biofuels or carbon offset credits. Applying this definition, if the regional electricity grid is 60% fossil fuel and 40% hydroelectric, reducing grid electricity use by 60% relative to a code minimum building and eliminating/offsetting on-site fuel use makes the project carbon neutral. Any combination of efficiency, natural ventilation, renewable energy, carbon credits and biofuels can be used to reach this goal. This definition assumes all calculations are based on annual energy use, generation and offsets.