BIM and Roof Systems

In developing a BIM roof system, it is important to understand that the actual materials are what determine the performance and construction of the overall roof. The type of roof covering used is considered based on not just aesthetics, but roof slope and local weather conditions. The secondary roofing materials are determined based on their individual merits as well; substrates are based on the building’s overall design, structural properties and locale; a vapor barrier is selected when or if certain moisture vapor properties merit its need; insulations carry specific R-Values important to the energy performance and code compliance of a building; the roof system attachment method is typically based on requirements of local codes. It is not necessary to understand how and why to use the specific materials when developing a BIM roof object. Realize though that the roof system is not just a slab that stops water from coming in. The appearance of the materials used in the roof system will determine how the details turn out. Use an appropriate surface pattern to convey the basic appearance of the upper most layer of the roof. Layers embedded inside of the roof will never be visible, and have little or no value to the model’s success. Cut patterns assign a symbolic appearance to various types of materials. The Uniform Drawing Standard (UDS) and National CAD Standard (NCS) have uniform symbolic patterns assigned to various materials. Using industry accepted patterns allows existing technology to be implemented into BIM technology without the need for reinventing a perfectly useable process. Each material has the ability to carry its own set of performance values which can be leveraged for model analysis and quantity estimation. A model calculates the length, area, and volume of a roof or roof material, but does not consider the unit by which the material is sold (Roll, Pail, Gallon, Cartridge, etc.) Where unit coverage rates are specified for given materials, an accurate estimate of the number of necessary units can be derived from the model, considerably decreasing the amount of time required to estimate a project. Later in this chapter, we will discuss in more depth the types of calculations that are possible from roof materials which carry a substantial amount of information. Roof System Components There are five main components that make up the basis of design for a roof system. In some cases others may be added and some omitted, but the primary components that should be considered for roof systems will allow others to be built from them and easily reused. § Substrate - The roof substrate is the structural component associated with the roof system. Functionally, it is the deck on which the thermal and waterproofing products sit. There are several types of substrates which may be used, the most common being Wood, Concrete and Steel. Unless the framing members are placed individually as described in chapter 28, roof systems should contain a material layer for the structural framing in order to consider the overall thickness for potential clash detection analysis.

*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.

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.

BIM and Specifiers

So it's been a busy spring, and between AIA, CSI and other speaking engagements I was roped into (happily I will add) I haven't had time to post. From these shows and engagements, I have taken away one primary point... BIM is experiencing the largest growth that it's seen to date. Everyone is at least looking at BIM, even if they are not ready to approach it. Architects, engineers and manufacturers are embracing it more and more every day, and surprisingly enough, specifiers are as well.

Two years ago, many specifiers viewed BIM as the technology that will put them out of business. Now, it seems, the focus has shifted on how BIM can improve their workflow and make them a more necessary component of a project. I will point out that there is a clear difference between a "Spec Writer" and a "Specifier". It's not a semantic difference. A Spec Writer is really more of an editor. With guide specifications and master specifications that automate much of the authoring of a project manual, the writing of specifications (Fingers to keys) has actually become the labor aspect of the specifier's role, which is often sourced out to someone else. The Specifier is the individual who is responsible for and qualified to make educated decisions on which product is to be used on a given project, in a given location under given circumstrances. In short, a spec writer can tell you what product is selected; the specifier can tell you why it was chosen.

Now what does this all mean to BIM? BIM is a technology that is driven by information, not by graphics, so the need for more robust information is going to become essential as more people adopt it into their practice. I am finding that there is a glorious lack of individuals with ehough knowledge of products that are involved with the development and creation of BIM families, elements, objects and systems, so the responsibility lies between the manufacturer (Who doesn't understand revit) and the A/E who doesn't have the time to research the information.

Specifiers have a great opportunity to step to the plate and embrace this opening, becoming the keeper of all things technical and informational within a BIM project. I truly believe that it is the right place for them to be, and with enough individuals involved, can start a movement which will bring the specifier's role to the forefront of BIM projects.

conTENT with CONtent?

Now that BIM has stared to become widely accepted, and viewed as a necessary component of the AEC communities, the responsibility of providing product models is starting to lie in the hands of the manufacturer. Just as a manufacturer must provide Specs and CADs today in order to be competitive, tomorrow holds the requirement of BIM models. So what does that mean, "BIM Models". Some providers may lead you to believe that simple images are all that you need, but from an expert in this field, the requirements of BIM are "expanding exponentially". Thus far, the "i" in BIM is largely unexplored by content providers and certainly treated as lower case and subordinate to the "M".

The bar has been raised by those who create "Super Families" that are not only high quality graphics without sacrificing modeling speed, but contain appropriate data and family nesting to allow for high powered scheduling and maintenance study and analysis. In my humble opinion, without appropriate descriptions, proper attributed data and takeoff abilities of a BIM product model, it's about as useful as socks on a rooster... while entertaining to watch, actually makes more work for everyone.

When looking for a content provider or creating your own, there are several things to consider. Below is what I believe to be the bare minimum tht should be contained within a BIM Object.


Graphics...

• Lipstick on a pig... Graphics need to be accurate and consistent with the intent of the model without slowing down the model's performance. If you put a $5,000 paint job on a Yugo, it still will only do 55, and if Kwik-Lube tunes your Ferrari.... well, you see where I'm going here. This delecate balance needs to be managed properly. Fixtures and fittings tend to be very graphic in nature with a lot of complex curves and angles. This level of detail detail can slow down the model if not done with some care.
• Size matters... Dimensions need to be accurate enough to consider tolerances and clash detection. Most electrical devices are created considering only the visual aspect and (Hopefully) the MEP connector, BUT, an electrical device has a box embedded in a wall thats about 2"x3"x4". Adding a simple solid behind a wall plate will allow that device to be considered a clash when a 3" DWV runs right over it inside of a wall.
• NO IMPORTS!!! - And no, I'm not talking about outsourcing graphics to Asia or South America... Imported CAD files converted into BIM files are large, slow and cannot be modified. Sizes cannot be modified, and proper rendering of these files is not for the novice or impatient.

Data...

• It's not you, it's me... Data needs to consider not only those persons placing the information in the model, but those using the model later. In addition to baseline information about the identity of a product, performance aspects are used for energy and structural analysis; product lifespan is used for future budgeting and sustainablility analysis.
• Fill in the blanks... This is an enormous pet peeve of mine that I see all the time. The description parameter is used for callouts. Materials or objects that have no description or one thet's too long or too short have a worthless callout. This is really irritating to the user when they need to go back and add this during the detailing phase.
• Tell 'em what they've won, Link - Links to useful information like code compliance, specs, product data, installation procedures and sales and marketing can really simplify the research aspect of product selection, by creating a singular point of reference to search from. NOTE - If the manufacturer cannot ensure that URLs won't change, data MUST be linked through a library that will.

Family Nesting...

• More than a simplified processes... Nesting families allows more than resueable components like door slabs and window sashes. It allows for option selection and more accurate scheduling and data management, especially for the FM folks.
• What are my options?... Nesting families allows multiple components of the same type to be selected as options. Doors may have hundreds of slab (or leaf) styles, but all of them come in the same sizes. The slab becomes a "Nested" component that can be "Swapped Out" by the click of a dropdown.
• Mother always told me to share... Shared nested families allow scheduling to be made more accurate and allow for mainenance components to be their own entity with their own attributes. Lets take a light fixture... The Housing of a Recessed light is a durable product with a lifespan of 20 years. the ballast and bulb are 2 components that are both components that will not only require replacement, but have options to select from. Nesting the ballast and bulb within the light fixture allows the ballast and bulb to have independant lifespans and installation dates for every light fixture installed. The FM team can see when every bulb and ballast was installed, and when they'll need to consider replacements.

Parametrics...

• No do-overs... This one's a no brainer, but I always find myself needing to say it... If I can't modify dimensions without going into the graphics, there is something wrong. Appropriate dimensions need to be made parametric so when updates need to be made, it's not back at the drawing board.
• More than dimensions and materials... can be parametric. Equations can allow results based on other attributes. Calculations that determine if and where in the country a window meets ENERGYSTAR are created based solely on the input of a U-Factor and Solar Heat Gain.

I hope this has been an informative post and can give some insight as to what you should expect... no, demand... from your content provider. Content is being treated as something like BIMs read-headed stepchild, but the bar is raising on the level of detail required in the model. The needs of the architect are beginning to demand that content developers step up to the plate and take their BIM content seriously. The main difference between man and other mammals is the opposable thumb, and most of us choose to use it. The difference between CAD and BIM is the data... Let's use it... Don't settle for less, and don't just be conTENT with CONtent.

The Devil is in the Details

So you have this great BIM Project that has solid graphics, a respectable level of data and attributes, and all-in-all has saved you time in design. What about the drawing sheets? How much detailing work are you doing manually, and how many of your termination, intersection and other construction details are from the ACTUAL MODEL? Seems like dumping dwgs of manufacturer details onto a drawing sheet is a common practice, rather than creating the sections and drawing in the linework. Why is this? Likely it's because of the lack of detailing that is done in Families and Objects, as well as the lack of attention to materials, which ultimately drive the callouts.

The Details...

This is another issue for my style guide. Detailing associated with families should be a part of the family, so that when it is placed within a wall, the linework in section views will show up appropriately. This in itself has its pitfalls and limitations. The window goes into a wall, and has no knowledge of the type of wall, so how can the detailing be done? There are detail families which can be imported into the project file, and plunked down on the Drawing Sheets which are a good idea, since the detailing really is only important on the drawings not in the model itself... Right???... Not so fast. Yes, the detailing is only viewed on drawing sheets, but the detail should be dependant of the window, not of the wall, since the window is inserted in the wall, the wall is not placed around the window. What happens if someone wants to make a new wall section at a window... You'd need to drop in a new detail family with it as well. An instance parameter of Type - Detail Family could be nested to allow different wall type connections (Wood, Metal Concrete, CMU) to be swapped out on the fly.
I'd love to create hosted families that are more intelligent, like opening family attributes which apply to all openings of Host Type (Wall, Floor, Ceiling, Roof), so if you punch a hole in a roof, it will intuitively place base flashings, or flashing tape associated with a window. These can all be created as "Families of Type" or "Material" Instance Parameters to allow products to be swapped out without swapping out the entire family.

For instance, a window manufacturer requires that Flashing Tape be installed around their windows. If a Material Parameter named "Flashing Tape" is created within the Window Family, you can swap out the type of material by updating the material name, or importing the material from a manufacturer of Flashing tape. This works well, gets the window specified, its installation specified, and opens the door for other manufacturers to be specified alongside the window. Taking it a step further, instead of a material parameter, a Family of Type Parameter can be added to insert an entire piece of graphics and layer of information which applies to the flashing tape. Basically, create a detail family for the Flashing tape, but add the attributes and values for the product itself. Let the detail family carry information as well as graphics for a product. This allows not only a Material to be specified alongside a window, but a Product to be specified. If a competitive product wants to be specified as an equivalent, their detail family can be loaded in the window family, and voila... new options to choose from.

Now this Brings me to Materials...

Materials are the Readheaded stepchild of BIM, and it irritates me to no end. Materials are the common ground of everything built, and every material has it's specific properties that make it what it is... nobody specified "Gypsum" or "Wood". They'll specify [5/8" Type X Gypsum Wallboard meeting or exceeding ASTM Somethingorother] or [3/4" FAS American Cherry S4S] even the finish on the wood or the paint on the gypsum needs to be called out, because Someone makes that product and there are more than one set of performace characteristics for a given product. That's where inferior and superior products come from. a BIM can't calculate the VOC levels of paint if they're not listed in the material... why would anyone want the BIM to calculate VOC's of Paint??? Because it can!

Representitive Modeling of Families

OK, so everyone thinks about BIM a little differently, but at the end of the day we have the same problems implementing... Managing Data and Creating Graphics... I've decided to develop a style guide to tackle the graphics aspect of things to try to give a sense of how much is too much, and the unnecessary creation of graphics.

Lets look at a company that makes plumbing fixtures. They make 400 tubs, 600 faucets, 125 toilets, 250 sinks and in total has 1500 products which they are trying to market. A difficult proposition if you as me... Is it necessary for them to spend in the neighborhood of $300,000 just to have their graphics created ($200 each), without the addition of product data? This content developer says no. Now I am sure that there could be some product redundancies that can be taken into consideration and handled with parametrics, but this is plumbing fixtures... every one is styled a little bit differently, so for argument's sake lets say there are 1000 unique products which need to be modeled... Still, $200,000.

Now that I've told you the problem... What's the solution?

Representative modeling... This is a backbone concept behind my BIM implementation strategy and has worked well for clients that are looking to get specified rather than have a pretty picture available. The products can be broken into categories... Tubs, Sinks, Toilets, Faucets, Shower Controls, etc. For Arguments sake, let's say there are 10 categories of plumbing fixtures. Within those categories, there are types of fixtures, such as Single control and Two control faucets, Freestanding, corner and alcove tubs, wall mount and tub mount tub controls, 1 piece, 2 piece, wall mount, elongated, and urinal toilets, and it goes on, so again, for argument's sake, lets say there are 10 types for each of 10 categories. For $20,000 his creates a total of 100 unique graphic models which have the ability to represent the INTENT of the model, rather than the appearance of it, which in the big picture of BIM, is far more important. so for a fraction of the cost of modeling all 1000 products, you can model 100 of them, and allow the data behind the models to drive the other 900 just by adding a "Version" or "Instance" of the graphic.

If you pay to have appropriate product data and information added, and every instance of the products taken into consideration, you might spend another $400 each, but done properly by a skilled content developer, it will perform as though it were the actual unit, noting the finish, construction, flow rate, MEP connectors, connection sizes and types, hole spread, and any other pertinent information abut that faucet.

The Downside...

OK, you just saved $140,000 on BIM modeling... At what expense? Well, when the architect renders the BIM for graphic purposes, the faucet won't LOOK exactly like the one they specified... Not important I say!!! The rendering ability of the software is not good enough to give you enough detail on a component as ornate as a faucet anyway, so the best way to see what it will look like is at the mock up in the Plumbing Showroom.

The Conclusion...

Developing Graphics for the sole purpose of appearance and rendering is a waste of money in the BIM market. generally, at that level of detail, architects are interested in the product data, not how it renders inside of the model at a 6"=1' scale, so save your money, and spend it on developing the data about products that is so desperately needed.