• The previous blog discussed the emergence of BIM and what data architects can include in the models that would have value to the glazing sub. This post will delineate some of the things I see coming regarding how glazing subs can use BIM models, and where this might take the industry down the road.

    Out of the box, most companies will try to use BIM with the simplest of their product lines, be they storefront or pressure wall systems. And after some trial and error, implement BIM to other product lines.

    But first, a couple of assumptions, if I may be so bold:

    1. I’m writing this as if I have my own glazing systems. As a manufacturer, TGP does. It’s recognized most of the glazing subcontractors do not. Instead, they typically buy their curtain wall and window wall products from manufacturers, such as TGP or the myriad of suppliers out there. Most, if not all, of the larger manufacturers are developing BIM models, largely for use of the architects for now. Most of the data suggestions I’m going to make below can either be imbedded in the models available from the manufacturers (through downloads or on CD), or would require some customization by the glazing subs for their individual situations.

    2. It’s highly unlikely that buying the software and opening a BIM model on your computer will make any organization ready to implement BIM across their entire processes, products, and organizations. Just as in the ’80s with the advent of CAD, there’s probably a lot of upfront software and geometry development that must precede or be part of an implementation plan. Some of what went on with the implementation of CAD was creating standard libraries and/or operating procedures, file naming, dimensional standards, etc. I don’t know this for a fact, but my guess is some of that will have to be done for BIM, as well.

    So what useful info to glaziers could be embedded or attached to a typical BIM model? I’m venturing a guess that a lot of what your company has already developed for its standard libraries can be converted to BIM models fairly easily. Take a typical horizontal or vertical detail cut, and attach data to it that includes:

    1. Working point/control point, be it at face of glass or face of cap and where it lays on the framing member centerline.

    2. Profile/part numbers of framing members, exterior caps or pressure plates, gaskets, or any other parts that run full length of the profile:

    • Some background info can be embedded to flag an alert for any part that runs longer than the longest finish or stock length allowed by the suppliers.
    • Finishing information can be attached to each part. Weights and exposed / finished surface perimeters can be added, as well.
    • Section properties can be added, especially if the part later is going to have to be analyzed for calculation purposes.

    3. Glass edge, in relation to the working point/control point mentioned above.  This will eventually establish glass sizes.

    4. Equally important will be to identify or create models of the glazing infills – be they glass, metal, granite, or other product – by thickness, manufacturer, unit construction (in the case of glass), minimum and maximum sizes, etc.

    For horizontals, information such as the shear blocks and their associated fasteners could be added, or just assembly fasteners say for a unitized wall system. The BIM model would know that for every horizontal, two shear blocks would be required, plus the quantity of fasteners needed to attach the horizontal to vertical.

    For mullions, things such as mullion splices could be added. Also, they would include the stop/start point of horizontals attached to them, so that the horizontal models would know where to start/stop in the model. By selecting that end point information or, better yet, the programming done within the software, the horizontals look for the information in the vertical model and thereby set their own length, “extruding” themselves to that point.

    3D anchors can be developed based on the system they are supporting, and/or the construction of the building frame. If the building structure were concrete, the embed type and size could be attached to the BIM model. For steel structures, the type of connecting fasteners or welding requirements could be added.

    Perimeter details can have information about sealant joint sizes and product data attached to them. Thermal insulation and/or fire-safing can be added to typical details, or as their own stand-alone models.

    For customization or fitting each job’s unique characteristics to the model, special conditions may have to be drawn from scratch, such as at a special coping, soffit, or corner conditions. Any of the attributes mentioned above – such as finish, length, relation to the control pointes, etc. – can be added to these one-off details.

    Once the base system frame system details are developed, they have to be attached to the architect’s BIM model. Using the 3D wireframe is the simplest. By selecting a grid line and associating a BIM-friendly detail to it, the total length of the part can be known based on that wireframe length. Corner mullions, horizontals, jamb details, etc. can all be attached to the model. The horizontal details are smart in that they know to stop at the side wall of the mullion, or can be told that based on the system, they should stop a fixed distance from vertical grid lines. Adding the anchor details at the frame-to-building structure will increase some accuracy of the downstream activities.

    If the glass information (or other glazing infill material) is embedded in the details, then the information from the verticals and horizontals has to close up and make individual lites of glass.

    Whew! So, lots of data can be added to BIM models that applies to glaziers. But, what can you do with all this information? That’s where the real party starts. Borrowing a line from Hollywood, tune in next time for the conclusion …

  • A couple of blogs ago, I mentioned that building information modeling (BIM) has a chance to be what CAD was to the drafting and engineering world back in the late 80s and early 90s. In reality, it has the potential to be much more because of the depth of information it can contain. But as a glazier, why should you care? BIM clearly benefits architects, but what’s in it for you? And what should they include in BIM to make your job easier?

    Most of the BIM models are going to be developed by the architects and specialty consulting firms (structural engineering for example, doing the building frame). They aren’t always thinking down the line to the glazing sub, but there’s some key information they can build into the models that would be useful to glaziers.

    From the architect’s view, and based on what I was seeing from the consulting side of the table, at project inception – from schematics through issuing construction documents – there is not a lot of value to an architect modeling a specific product within their BIM model prior to bid.

    There are too many variables that may – or, more likely, may not – result in a specific window system, for example, being used on the project. The selected glazing subcontractor may not have used that system as the basis of their bid, using a competitor’s or one of their own. If that were the case, everything in the BIM model would be of little worth. Only if a project were to be awarded based on a negotiated bid would it make any sense to utilize a fully developed model with the specific glazing system selected.

    However, taking as an example a curtain wall or window wall, what the architect can do in developing a BIM model that would really be of benefit to the eventual glazing subcontractor is fourfold:

    1. Model in 3D the curtain wall or window wall centerline-to-centerline grid dimensions. Call this a building envelope grid, but put it on its own layer.  This way the building enclosure grid, from which most, if not all, wall component geometry is basically dependent on is set, and can be used by the glazing sub in their development later.

    2. Model only the outline of the wall system framing members, the glass and any special features, like sunshades and louvers, doors or operable vents.

    • Show the aesthetics: system width, depth, special profiles, etc. – not the guts of the system. It doesn’t make sense to model a specific wall product if the winning subcontractor ends up using a different wall system when they perform the work.  If the architect selected Company A’s unitized wall and modeled it in BIM, the curtain wall portion of the BIM model is almost a complete waste if Company B uses a different wall and wins the contract.  The work to change out one for the other would have to be addressed.
    • This information can be used for preliminary budget exercises, determining the number of glass lites, the linear footage of frame members, etc, and special conditions that have to be developed through the course of the project.  It gives an overall intent of what the architect is looking for in the exterior envelope package.

    3. Indicate anchor points and connection to the structure.  The single biggest factor affecting subcontracting field labor is the types and quantities of anchoring conditions.  Seeing how many anchors go into steel or concrete, and whether the wall will be anchored to parapets or face of slab, top of concrete curbs, etc., will be of significant worth to the glazing sub in estimating their field labor rates.  Obviously, if anchor points are not in the immediate vicinity, the span of the frame member may suggest larger profile sizes, or additional / secondary steel to be furnished by either the general contractor or curtain wall sub.

    4. Next, link the specifications and other drawing packages to the model geometry, which is where BIM (at least at this stage) starts to become more of a weapon.  For example, attach the related specifications to the generic model components:  Section 088800 Glass and Glazing to the glass model, Section 084413 Curtain Wall to the curtain wall framing. And if not modeling the sealant or thermal insulation, link the spec sections to the components you know they belong to.  So that when the user selects a line of the mullion in the model, not only would the curtain wall spec come up, all the related specs would be available to select, as well, including sealants, insulation, doors, glass, etc.  Also add links to drawing packages.  If the concrete or steel structure were modeled, then it could be selected, and the drawing of the beam / edge-of-slab detail could be linked, along with all of their related specification documents or contract documents.

    There’s still some basic legwork to doing all of this that can’t be skipped by those preparing the models, be they architects, structural engineers, or HVAC systems designers (the primary users of BIM at present).  For example, the architect can’t model an 8” deep system when a 6” depth would have sufficed, or a 12” system was required for the wind load and / or span conditions.  Glass lites that are too big or too small for the glass manufacturer’s standard sizes create bidding and budgeting anomalies that have to be addressed sooner or later.  The upfront design development that now goes on still has to be completed.

    Also, this is still a GIGO world. Remember that expression – it’s true of anything computer related – the information to be gotten out of a computer is only as good as the information put in. If you don’t believe me, try adjusting your checking account register in your favor, and see how long it takes the bank to send you nasty notices.  Accuracy in checkbooks is just as critical in CAD drawings, and so it is in BIM models, too.

    This accuracy thing is why the GC’s are jumping in to BIM with both feet. If the BIM model is accurate, there are no holes in the architects’ models and controlling costs on the project gets easier. And the architects have the added responsibility of ensuring the models are complete and accurate. BIM closes a loophole in the construction process since the GC’s can now show where a building plan is based on incomplete information, not due in any part to their shortcomings (the opinions expressed herein are those of the author – and I’m sure the GC’s of the world would rise up and take issue as to their motivation for BIM, but this is just one of them – in my opinion).

    And this is now where the glazing sub or supplier can take the BIM model and do their thing:  estimating, value engineering, material takeoffs, shop drawings and structural engineering. I’ll cover that more in detail in the next blog, but first wanted to lay the foundation of what would be ideal to get out of a good, accurate and complete BIM model before the models come through the project pipeline.

    In the meantime, please shoot me a note on your BIM experience – the good, the bad and the ugly. What can and should architects and suppliers be doing differently with BIM from your perspective?

USGlass Magazine

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