Simulations, at their core, are models that describe a behavior. Models can be found everywhere in our world from weather forecasting to household budgeting. Simulation models include three core components:

In the example of household budgeting:

For buildings, there are many more Inputs, mathematical models (that represent the System Structure), and Outputs, but the core principles are the same. With revgen.tool, the simulation process is simplified down to the Inputs and Outputs that are aligned with a given product or equipment. The rest is all handled automatically using a multitude of standards, guidelines, and other resources that define the System Structure and Inputs.

We have already looked at the three core components of a model. Next, we will go into more details of these components within revgen.tool.

Thousands of inputs are needed to simulate something as large as a building, but do not worry! The vast majority of these can be automated with just a few key pieces of information. Only specific product or equipment inputs need to be manually defined.

The size, form, and orientation of a building will vary, however there are typical arrangements that are used by the AEC community. These building designs can be computed for any project with the Building Type and Area and the methodology found in ASHRAE Standard 209 Energy Simulation Aided Design for Buildings except Low-Rise Residential Buildings Appendix C. The same method used by revgen.tool is also used to define the U.S. Department of Energy Prototype Building Models.

Table 13 from ASHRAE 209 Appendix C is an overview of the reference buildings forms used on the platform. The general form of the building is indicated by the Aspect Ratio and No. of Floors and the Window to Wall ratio is indicated as the Glazing Fraction.

The building envelope and systems are often the input that we are investigating with our simulations. In these instances, detailed inputs are collected directly so they can be incorporated into the simulation. When these need to be automated instead, the values will come from building energy codes and engineering standards and best practice.

Both sources are used because not all aspects of a building design are dictated by energy codes. A full list of energy codes, along with the exact references to data used can be found here, and a list engineering standard practice inputs with sources can be found here.

There are two types of carbon emissions considered: operational carbon emissions and embodied carbon emissions. Operational carbon emissions are related to the energy used after a building is constructed and is being actively used by the occupants. Determining operational carbon emissions is done with grid factors which change over time. The expected change is published in the Cambium Data Set prepared by NREL and used by the platform to calculate operational carbon.

Embodied carbon emissions are related to materials and activities to construct the building, before occupancy. To calculate the embodied carbon of a project, the platform uses published Environmental Product Declarations combined with the building geometry.

Similar to carbon emissions, costs can be organized into two realms, operational or first cost. Operational costs are related to the energy used while a building is occupied and the utility rates paid for that energy. Utility rates on the platform are automated based on the location of the project entered by the user.

First costs are incurred during construction and include material costs, labor costs, soft costs and more. When studying the impact of products and equipment with simulation, the cost of these components come into focus. On the revgen.tool platform, costs are determined through market studies and working directly with manufacturers who may choose to provide direct costs within the system structure.

There are several systems used by the platform depending on the inputs and outputs required. Each system is designed to deliver accurate information with speed and ease.

The Baseline Energy Simulation is the system used to calculate the operational energy on our platform. In turn these operational energy results are used to determine operational costs and carbon with the various factors that will impact each of these outputs.

The simulation is based on the ISO 13790 Standard which is a standard method for determining building energy use. The simulation is validated through comparison to both EnergyPlus and TRACE 700 in addition to the standard test methods defined by ASHRAE Standard 140.

A second system is used to determine embodied carbon outputs. The carbon calculation is based on the input EPD and building structure which is automated to provide estimated quantitative inputs for building super-structure and sub-structure. Architecture quantities are also automated to be considered in the calculation. Industry standard methods are used to estimated the quantities, weights, volumes and other inputs of the building structure and architectural envelope.

The cost calculation system is the most familiar and common used on the platform. By using standard cost models such as price per unit or price per weight, the first cost outputs for the product and equipment are determined.

Operational costs are similar, with the rate per unit energy being used to calculate the total cost based on the total units of energy consumed.

Depending on the product or equipment, different outputs may be more or less important for selection decision. The standard outputs based on the Inputs and System Structure for the revgen.tool platform follow. Different types of outputs can be calculated such as:

Energy savings are calculated with a baseline and proposed option, which includes the specific product or equipment. It is simply defined as:

Operational carbon savings use the same simulation outputs as the energy savings and formulates to carbon emissions with grid factors.

Operational cost savings use the same simulation outputs as the energy savings and incorporates cost savings using the location specific utility rates.

Embodied carbon savings use the same geometry inputs for the baseline and proposed options. Adjustment is then made for the proposed case EPD values that reflect the specific product or equipment.

Similar to embodied carbon savings, first cost savings will use the same geometry inputs and then apply different costs based on the specified product or equipment.

In conclusion, while buildings and the models that represent them are complex, the simulation of products and equipment does not have to be! With the unique approach to breakdown the Inputs, System Structure, and Outputs of these models, revgen.tool delivers results with confidence.