Integrating LEED and Architectural Desktop

As I promised in my last article the focus of this one will be integration of LEED requirements within a BIM environment, which in this instance means using custom tailored ADT objects for LEED project analysis.  The procedure that is outlined here could serve as a backbone for further implementation and development of automated LEED relevant data extraction from a building model.   Within the capability of Architectural Desktop 2005/2006 the only limits are those that are imposed by one's ability to recognize a project’s objectives and translate them a comprehensive set of relationships between parametric objects.   Imagine a set of objects with associated properties that carry LEED embedded information. Start with such basics as new versus existing construction; amount of recyclable content associated with construction layers that compose wall objects; product lifecycle information that is associated with space objects as well as their programmatic function and area ratios; zoning, etc.   All of these variables can be relatively easily extracted and linked to a database or even better to LEED letter submittals in the form of Excel spreadsheets.

Furthermore, this kind of planned use of software capability for data integration can provide a virtual knowledge vessel where project experience acquired through years of practice becomes a part of the everyday tools that architects or engineers use.   The true value of BIM becomes evident when transcending a gap that occurs when knowledgeable individuals move on and their experience leaves with them.  Controlling information is the very essence of one’s success and competitiveness, and the ability to use this as leverage from the very beginning of the design process can shed quite a different light on the use of CAD in any AEC firm. This, however, could be a topic for a different kind of article.

Meanwhile, let us test this concept of embedded LEED relevant information on a very simple example:

The goal of this exercise is to set up an “intelligent” window style that calculates its own Day-lighting Factor based on the formula given by LEED.

First we need to establish the values that could be associated with the window style and window object. Dimensions and Location are attributes that are specific per individual window, where Window Geometry Factor, Window Height Factor and Visible Transmittance can be associated with a window style.

We will start by modifying the existing PropertySetDefs.dwg file located in the following directory.
“C:\
Documents and Settings\
All Users\
Application Data\
Autodesk\
ADT 2005\
enu\
AEC Content\
Imperial\Documentation\
Schedule Tags”

Open the file and in the command prompt type AecPropertySetDefine. This opens a Dialogue Box that is a sub set of the Style Manger and lists all of the available property sets that can be referenced from any ADT file.

Create our own Style Based Property Set Definition by making a copy of the existing WindowStyles Property Set Definition (PSD) and naming it 01_LEEDWindowStyles (PSD).


fig.(1) (click on image for a larger view)

The same copy and rename operation will be repeated for WindowObjects (PSD) , where the newly created (PSD) will be renamed into 01_LEEDWindowObjects.

In order to have a functioning communication between these two PSDs we need to change 01_LEEDWindowStyles into a PSD that applies to all ADT objects.


fig.(2)  (click on image for a larger view)

Wthin this style we will define a set of Manual Property Definitions that are relevant for our Day-lighting Factor calculation.
LEED_GF Geometry Factor
LEED_HF Height Factor
LEED_TV Visible Transmittance
LEED_Tvmin Minimal Visible Transmittance

The format used for these newly created Manual Property Definitions will be Standard.


fig.(3) (click on image for a larger view)

You should name these factors following the same rules that apply to attribute tags.

The next step will be to modify our new Object Based Property Definition Set by introducing some logic to the way in which Window Objects relate to their associated Space Objects. For the sake of this exercise we need to define what are the variables needed to calculate DF are and where to locate them.

fig. 4 (click on image for a larger view)

One unknown that we need to obtain from the current building model is the area that is related to the placement of future window openings, and that information can be extracted from the Space Objects Property Set. This will introduce the Location Property Definition.

 
fig. 5 (click on image for a larger view)

First we need to edit 01_LEEDWindowObjects (PSD)
by adding the 001WINFLOORAREA Location Property Definition fig.(4) which relates to the Automatic Property Definition Base Area that is integral part of a Space Object. fig.(5)
We also need to calculate a window surface area for each window that gets assigned to particular space and that will be done by utilizing Formula Property Definition and naming this new Property 001WINAREA. fig.(6)


fig. 6 (click on image for a larger view)

Use the formula editor to make the following entry, and make sure that the Height and Width variables are selected from available options for the particular Object (PSD), as shown on the image. fig.(7)
RESULT=[Height]*[Width]/144


fig. 7 (click on image for a larger view)

For this formula to function properly we also need to define a custom data format that will enable multiplication of the Width and Length variables, and to do that we will create a new Property Data Format (PDF).

At the command prompt enter the following command AecPropertyFormatDefine and create a new PDF named LEED_Length.

 
fig. 8 (click on image for a larger view)

Edit LEED_Length PDF by modifying its Unit Format and Suffix. Set Unit Format to be Decimal with two decimal digits precision and for the Suffix leave an empty entry. fig.(8)

Assign this newly created PDF to Height and Width Automatic PDF within the 01_LEEDWindowObjects (PSD)This will ensure that the area calculation for the amount of available glazing functions properly, and that product of the Height and Width variables is calculated as square footage.

The next step will tie all of these elements into a formula that calculates DF for each window based on the parameters that were given in that window’s style.


fig. 9 (click on image for a larger view)

Again in the command prompt type AecPropertySetDefine and highlight the 01_LEEDWindowObjects PSD.

Proceed to edit and add another Formula Property Definition, which in this instance is the LEED formula for calculating Day-Lighting Factor.

Name this property DF fig.(9) and by selecting from the range of available variables within the formula editor create the following expression:


fig. 10 (click on image for a larger view)

RESULT=([001WINAREA]/[001WINFLOORAREA])*[01_LEEDWindowStyles:LEED_GF]*([01_LEEDWindowStyles:LEED_TV]/[01_LEEDWindowStyles:LEED_TVmin])*[01_LEEDWindowStyles:LEED_HF] fig.(10)

This simple procedure should give you an idea about the hidden potential of parametric objects and their interaction within the Architectural Desktop Environment.