Monday, October 12, 2009
*While the roof deck is arguably not a part of the roof system, it is not appropriate or effective to create one roof for the structure and deck and another roof above for the waterproofing system. It creates a conflict when placing components on the roof that are designed to cut a hole in the roof on placement.
§ Air/Vapor Barrier - Vapor barriers are very thin membranes typically placed between the substrate and the insulation. Even though the thickness is negligible, it is important to represent them in the model with a thickness appropriate enough to graphically display the material in a section view. Without giving the air/vapor barrier a thickness, providing call-outs or annotations of the material in detail section views is made more difficult.
§ Thermal Barrier - Roof insulation provides the thermal barrier between the building and the outside world. Just as a hat protects your head, since hot air rises, insulating a roof keeps the building’s heat from escaping. In some cases the insulation may be placed below the roof deck, and in other cases, it may be placed above the deck. In either case, its thickness should be easily adjustable and carry its R-Value in order to determine qualify the appropriate thermal protection used in a project. In addition to thermal properties, roof insulation may also provide slope, so the ability to taper the insulation independent from the roof structure is important.
§ Waterproofing Material - Shingles, membranes, metal and sprayed elastomeric coatings are all types of waterproofing. In most cases, this is the uppermost layer of the roof, and should carry some type of surface pattern to differentiate it from other roof types within the model view. Often, the roof covering is selected based on its appearance, and since there are so many options for roof coverings, it is important to have a good sample image swatch available for rendering the roof’s final appearance.
§ Roof System Attachment - Regardless of the type of roof, it needs to be attached in one fashion or another. Because it can affect how the roof performs or whether it meets the local building code’s requirements, it is important to add it as a layer in the roof system. Having it in the roof system as a layer allows the attachment method to be quickly called-out or switched if necessary.
Sunday, October 11, 2009
The Ever-Evolving Specification
BIM has two main parts to it; graphics and information. It is the responsibility of the Architect to ensure the graphics are correct and appropriate for construction, and the role of the specifier to ensure the project information is correct on the behalf of the Architect. It seems only natural then to place the responsibility of BIM information management in the hands of the specifier. Over the years, the tools of the specifier have improved. Beginning with the pen, and moving to the typewriter, followed by the word processor. Once again, the specifier is experiencing a process improvement which inevitably leads them to the database.
Databases house the salient parts of a specification for easy and repetitive retrieval while maintaining the consistency of the final delivered specification. The “Office Master” is the most common example of this. Most specifiers and architects offices have guide specifications which are used over and over in order to simplify the task of specification writing this is a rudimentary, but effective method of making a database of project information for reuse. The shortcoming of the office master is that it needs constant maintenance as products, building codes and design requirements change over the years.
AIA MasterSpec, ARCAT SpecWizard and other similar online “guide specification” libraries allow for the simplified creation of project manuals on an individual basis, by providing ready-to-use formatted specifications which can be easily implemented into projects based on either required performance values, industry standards or actual products. Which type to use is dependent on the project delivery method used on a given project. These online libraries are giving way to the concept of integrating the information from a BIM model with the project manual by providing a single database where product information is stored for multiple products. Where a specification and BIM object are sourced from the same location, and driven by the same database, there is a level of consistency not easily attainable by other means.
The possibility exists to create a short-form or outline specification, a long form specification and a BIM component all using the same series of dropdowns. Rather than a printed document being the only deliverable of a specifier, consider just how critical the responsibility of selecting the most appropriate component for a given project is. If the ability to review and select products and systems for a project extended to formatting a BIM component based on the required performance and appearance characteristics, the final project documentation and specification would be simplified considerably.
The concept of a specification is to provide documentation of specific elements of a project. It expands upon what is selected to explain why it is used. If you think of a specification in terms of what it is designed to do, much of it is broken into pairs of Attribute and Value, where the attribute is the “what” and the value is the “why”. This is the baseline concept for creating a specification from a database. Some examples of attribute and value pairs are:
§ Color: Green
§ Length: 12 inches
§ R-Value: 19
§ Tensile Strength: 1000 ksi
§ Warranty: Ten (10) Years
While not all aspects of a specification can be broken into these pairs, it can encompass most if not all of the critical aspects of product selection and implementation. The balance of the specification can be formatted through development of a pre-formatted guide specification which would act as a form which the data would be filled into.