An Overview of the Impact Estimator’s Input Module

From an input perspective, the user enters key building descriptors and selects from an array of building assemblies to describe a three dimensional structure. The Impact Estimator user also selects one urban center from a list of Canadian (Vancouver, Calgary, Winnipeg, Toronto, Ottawa, Montreal, Quebec City and Halifax) or American (Atlanta, Baltimore, Los Angeles, Minneapolis, New York City, Orlando, Pittsburgh, Providence, Seattle, or average USA) urban centers that best describes the building’s actual location.

With the addition of Los Angeles and Seattle, seismic effects have been added to the structural calculations for these two locations. The seismic effects for Seattle have been applied to Vancouver. In version 5.0 (2014), Portland Oregon was added as a location and has the same seismic effects added as Seattle and Vancouver.

To circumvent the problem of estimating the actual bill of materials for a specific building design, we developed a set of predetermined building assemblies that can be selected by the application user. The assemblies, in turn, have material or product quantities associated with them and those quantities are linked to the life cycle inventory databases in the software. Impact Estimator users are therefore able to select assemblies using commonly recognized design procedures, without having to go through the process of converting to masses, volumes or areas of component materials.

The assemblies included in this version of the application are recognizable units of a building structure, clearly defined in terms of size and composition, which designers can readily visualize and manipulate when developing a structural design. There are currently six categories of assemblies:

Clicking on the help file for each assembly input dialog box reveals a detailed description of the assemblies including assumptions underlying their definition and some limitations to their use.

There is also a provision for users to add additional basic materials or products to a design specified using the structural assembly choices. In fact, if a design has been previously broken down into a basic bill of materials, then it can be entered by simply entering basic materials without reference to the predetermined assemblies, but with the following limitation caveat:

We assumed foundations would always be made of reinforced concrete, but that the material quantities would vary according to:

Given the widely varying foundation configurations that can result, it was neither possible nor appropriate to establish a predetermined set of foundation assemblies. The structural inputs tables therefore establish material quantities for specific foundation dimensions rather than for predefined assemblies.

For the other three categories of assembly, structural designs were developed taking into account load, span and other engineering conditions. A series of designs for different conditions were then used to develop the relationships between given conditions and the quantity of materials per unit area for each assembly. For example, structural designs for a series of bay sizes and/or spans yielded the relationship between span and quantity of materials per unit area within a defined range of spans for each span assembly.

In addition to the provision for foundations, there are currently over 60 different assemblies specified in the application incorporating various building materials and products. However, each assembly offers flexibility in both structural and envelope product choices (e.g. the user may choose to either sheath the wood stud wall with plywood or oriented strand board or select neither product (none), insulate the wall cavity with batts (fiberglass or mineral wool) or blown cellulose, and/or insulate with rigid insulation, or any combination there of), which means there are actually more than 1200 different assemblies available to the user.

Wall Assemblies may be defined using one or more wall components. By treating walls in this manner, wall assemblies comprised of steel, wood, concrete and other wall components can be combined into a single complex wall assembly. A single envelope definition and an opening definition can be applied to the wall assembly as a whole. Individual structural wall assembly components include the following:

The Impact Estimator also determines the specifications for each assembly using a user-defined assembly load, as well as thickness or span, to ensure the chosen assembly will meet the intended task. Each assembly essentially has a workable range, some of which are bounded so the user cannot go beyond the default limits of the assembly. This helps ensure that design novices will not incorrectly specify an assembly. But the application is only a conceptual design simulation tool and should not be used to size components or assemblies for actual design purposes.