In high performance building design it is helpful, critical even, to start detailed energy modeling for the proposed design as early in the design process as possible. This allows the design team to use this modeling tool to influence the design process resulting in a more cost effective, optimized building design. Pathfinder developed the first energy model for Nuthatch Hollow during Schematic Design. Throughout the next phase, Design Development, the team will continue to update the model and use it to refine our design decisions.

One of the goals of the Nuthatch Hollow project is to be a “Net-Positive Energy” design. The project will use renewable energy on site to provide 105% or more of the annual energy that the project uses. Building simulation tools are used to help minimize energy consumption of the design and help achieve the Net-Positive goal. The first step is to enter the building geometry and floorplan into the model. Walls, windows, roofs and floors are entered along with their thermal properties. The building geometry is easily viewed and modified in a graphical interface, shown below.

 

Next, building loads are entered, consisting of occupants, equipment, lighting and hot water. The simulation represents one year of operation, so schedules are entered to describe how the loads vary hour-by-hour, as well as daily and monthly, including vacation and holiday periods per the Binghamton University school calendar. For example, a typical Monday schedule for occupancy is shown below.

 

HVAC systems (heating, ventilation and air conditioning) are entered into the model, along with thermostat schedules and the ventilation load (fresh air). Electric HVAC systems will be used to avoid using fossil fuels or other combustion. We are focusing on VRF systems (variable refrigerant flow – similar to heat pump systems). HVAC systems are controlled in the simulation to run only as needed to meet the building loads. The energy model provides detailed information about energy consumption of the proposed design. It is easy for us to make adjustments in the building loads, geometry and thermal properties, and HVAC system efficiency and controls, to see the likely impacts on energy and help us achieve our Net-Positive goal.