Building Geometry

 

Locks allow the user to snap the drawing tool to various items in the model view window such as model endpoint, midpoint, grid, etc. When creating model geometry it is useful to have the lock window open so you can switch different locks on and off depending on the particular modeling task you are trying perform.

 

 

 

Snapping to the grid when building model geometry ensures the creation of an accurate compact model which enhances accuracy and performance later in the analysis. This option allows the distance between grid points to be set - in both the x and y direction. Checking the grid box in the locks menu will force the drawing tool to snap to the grid. In general it is recommended to use a grid separation distance of 4 inches (0.1m).

 

 

 

This option allows you to add or remove inner volumes from your model.

 

 

Inner volumes are used to take account of the thickness of walls, ceilings and floors. The thickness of the walls will be defined later in the Apache Constructions Database. The thickness of the wall is represented in the model by a grey line which is offset into the room by the thickness of the wall. Inner volumes are only suitable for use in models with relatively simple geometry.

 

 

 

 

 

 

 

This command opens the model settings window. Adjacency separation distance defines the maximum distance that two surfaces can be away from each other, while still being recognized by the software as being adjacent.

 

For example the two rooms in the image below on the right are 0.1m meter apart so the software would recognize them as being adjacent. Although in theory this is fine, in complex models it can cause errors to occur. It is recommended to always snap directly to the surface of the adjacent room as shown in figure below on the left. This can be done easily by using the ‘Model Endpoint’ lock.

 

 

 

 

Zoning is of critical importance to the model. Too many zones and the model becomes over complex, too few and detail is lost. Although the main focus should be on capturing core functional spaces e.g. offices in commercial buildings or living rooms, bedrooms etc. in residential buildings - it is also necessary to capture the area/volume of other miscellaneous/ancillary spaces such as elevator shafts, toilets, stairs etc.

 

The single most important aspect to note in relation to these space types is that they do not have to be represented exactly and individually to effectively convey the energy consumption of the building. In other words it is not necessary to model each and every space separately but instead zones can be outlined around each of these space types that capture all of a space type together.

 

The zoning (thermal block) requirements outlined in ASHRAE 90.1 Appendix G (proposed model thermal zones and baseline model thermal zones to be the same) should also be kept in mind when creating the building geometry. The details presented should be followed closely in order to meet the requirements of the Performance Rating Method.

 

As outlined in the concept document it is helpful that defined zones are broken-down as per the list of space types used in the prototype data:

 

 

These space types correspond exactly with the room thermal templates and provide some indication of what spaces should be grouped together.