Calculating the gains and losses from the envelope of a building is a large part of determining accurate heating and cooling loads. Doing some requires that each surface is cleanly defined and its thermal performance is captured. These two important steps occur in drawing.tool where models can either be imported or drawn natively and then assigned unique performance values per surface.

Performance values defined in drawing.tool

Currently wall (interior and exterior), window, roof, and floor (ground and interior) thermal performance can be assigned directly in drawing.tool. To assign performance to a wall or window, simply select that surface and enter the desired performance in the properties panel. For walls, the performance is defined as a R-value for projects in US units and a U-value for projects in Metric. For windows, the values are SHGC and U-value.

Roofs and floors are assigned room-by-room. Similar to walls, roofs performance is defined as a R-value for projects in US units and a U-value for projects in Metric. Floors are assigned a U-value for both unit systems. To assign performance to roofs and windows select the room containing both and update the values in the properties panel.

Default values

When geometry is first drawn or imported into the drawing.tool default values for all surfaces will be assigned. These defaults are the energy code minimum values as reflected on the Baseline Page and provide a good starting point for each project.

Assigned performance in loadmodeling.tool

All performance information is used in loadmodeling.tool for the envelope heat loss and gains calculations. Assigning the design intent envelope performance will provide accurate room loads based on the impact of each surface calculated by EnergyPlus whole building simulation engine. Using the Room Results page the % of total load coming from each surface type (window, wall, roof, etc.) can be reviewed helping to identify where higher performance will have the greatest impact on the design.

Assigned performance in Baseline energy model

Surface-by-surface performance information is area weighted averaged and then assigned on the Baseline page. This helps to add even more detail Baseline model and automates the previously manual task of determine the average envelope performance of a building with varied surfaces. Walls, windows, ground floors, and roofs are all determined via area-weighted averages when utilizing drawing.tool.

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