Our point supported, inverted fin wall at the Lord & Taylor flagship store in Manhasset, New York, was selected for the design innovation honor from a field of incredible work throughout the industry.

This was Bellwether’s second time winning the award for Most Innovative Curtain Wall, having first won the it in 2014.  That same year, Bellwether also won the award for “Most Innovative Specialty Glass Product” for its patented line of structural glass skylights, called Insight.

The entrance wall at Lord & Taylor was one of the most challenging projects that Bellwether has completed to date.  The 41’ tall fin wall is designed to be as transparent as a retail display case, while withstanding 111 mph wind speeds.  Our design strategy was to match the architect’s design concept by creating large uninterrupted clear spans, with minimal sightlines to allow the visitor’s focus to be on the retail merchandise.  Even the 3’ tall splice plates became a unique design element with a mirror polished finish.

Read more about this year’s Glass Magazine Awards here, and for more information on the design process that goes into a glazing system like this, read our blog entitled Structural Glass Walls: Process, Design, and Engineering Options.

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While the design of truly custom wall systems is more costly than off-the-shelf systems, designers are freed up to avoid sizing and structural limitations that are often associated with pre-engineered products such as stick-built curtain wall.

Our recently completed point supported structural glass wall at the Lord & Taylor store in Manhasset, New York is a good example to illustrate our process. The main entrance wall measures approximately 41’ tall by 130’ long, with an additional “display wall” measuring approximately 24’ tall by 16’ wide, for a total of 5,700 SF.

Structural Glass Wall Design Process

Bellwether begins its work with a high level feasibility analysis of the conceptual design, to determine basic appropriateness of design, availability of materials, etc. We evaluate the requirements of the wall system from the outside inward. Wall glass make-up is reviewed first based on proposed structural support, windloads, and any other criteria such as seismic, blast, and ballistic. We then move on to the options for the structural framing system, always keeping the focus on creating a system that is as simple and visually uncluttered as possible.

High Level Feasibility Analysis

This first stage reality check identifies any major issues that would make the project impractical or impossible to build. For instance, if the Lord & Taylor fins project had been designed to feature one-piece, 40’ tall glass fins, they would carry a huge cost, and make transportation and installation difficult and very expensive. These are import factors to consider if cost is a driving criteria!

Generally, at this stage, we are doing more of an exception-check on the design, rather than setting hard limits. We consider the ways to adapt the materials to the design, rather than boxing the architect in and making them adapt their design to the material limitations.

Analysis of Wall Glass Materials

The appropriate make-up of wall glass is defined by factors ranging from the size of the largest glass lites, to the type and frequency of glass anchorage (e.g. point supports vs. patch fittings, vs. continuous two-sided structural silicone support), local windloads, etc. In the case of Lord & Taylor:

• Wall lites are large, with the largest measuring 10’-11 3/4” wide X 10’-4” tall.
  • At over 113’ SF each, and over 1,800 pounds each, these are much larger than what is found in most point supported applications.
• The specified glass was a laminated make-up, with a thickness to be confirmed by the supplier.
  • Glass thickness is often a function of limiting deflection due to wind loads. Wind loads are relatively high at the Manhasset site, at 111 MPH. We used a 1-1/16” thick make-up, utilizing two layers of 1/2” glass, with a .060 PVB interlayer.
• The conceptual design for the wall assumed just four fittings per lite of glass, with one at each corner. This was one area where we knew that the design would have to be adjusted from the start. The inclusion of a mid-span support along the 10’-4” span on the sides of each lite (for a total of six fittings per lite) was assumed to manage glass deflection. This addition of the mid-span fitting had a minimal impact on the overall aesthetic or cost.

Analysis of Glass Wall Backup Structure

The determination of the appropriate material depth, thickness, and hardware for a glass fin wall is determined by a number of standard factors, such as height of the wall, width of bays and whether the wall is hung from above, or dead loaded to the ground. In this case, due to the depth of the fins to allow for the inverted wall, the requirement to limit buckling of the fins also became the critical factor in their design.

• The height of the wall would require deep and thick fins. At 40’ tall, these are massive structural components, regardless of material.
• The depth of the fins were somewhat determined by:
  • The 2’ dimension at the base, which was driven by a desire to maximize retail floor space.
  • The degree of inversion at the head condition. We reviewed 3 degrees, 4 degrees and 5 degrees, ultimately setline on 4 degrees for engineering efficiency.

Since these dimensions were relatively settled, we evaluated the required thickness of fin glass to manage deflection and buckling. This turned out to be 2-3/8”, made up of 3 layers of 3/4” glass, with two .060 SGP interlayers.

• The fins are designed in 4 pieces, with the top components weigh over 1,100 lbs. each.
• The combination of high windloads, wide bay widths and a 40’ span introduced a need to address the potential for buckling of the fins under load. Bellwether addressed the concern through the use of the triple laminated/SGP make-ups, and splice plates that were designed in modified “H” shapes to greatly enhance stability.

Point Supported Wall Fitting Analysis

Fitting requirements on any point supported project are based on criteria such as articulation of the fitting head, bearing area (or glass bite), of the fitting head on the glass, and distance between fittings, as related to the thickness/stiffness of glass.

• Disk style fittings were the selected from the start, to provide far greater bearing area than countersunk fittings – especially important with lites of this size.
• The H shaped splice plates were developed and proposed by Bellwether during the design and engineering phase. Additional stainless straps were incorporated into splice plate design at the inverted corner, to manage deflection and buckling at this unique condition.

As with every custom project, the requirements of the base building design, and site specific environmental conditions like high wind loads, created some unexpected challenges along the way, changing material thickness and component design strategy. Bellwether’s approach through the process was to keep the project as closely centered on the architect’s original design concept as possible, with a high level of customized design and coordinated engineering.

The result is a stunning entrance with massive glass components, which completely transforms the entrance to Lord & Taylor’s flagship store, to celebrate its 75th anniversary.

Glass Magazine Award Winner

We were beyond pleased to have the Lord & Taylor project selected by Glass Magazine as the recipient of the 2017 Most Innovative Curtain Wall Project. Glass Magazine awards are given to projects that feature bold feats of glass and glazing innovation, fabrication, installation, and design. This was Bellwether’s second time winning the award for Most Innovative Curtain Wall, having first won the award in 2014 for our Hyatt Place Crinkle Wall project.

Credits
Architect:                     Highland Associates, New York, NY
Installer:                       Craftsman Storefronts & Glass, Inc., Bayshore, NY
General Contractor: EW Howell, New York, NY

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• 8-10 weeks for design, samples, and approvals from the architect and owner.
• 10-12 weeks for material production and delivery.

Compressed schedules can sometimes be accommodated, with the understanding that short timelines result in tradeoffs in design flexibility and material choices, sometimes also leading to higher costs.

Three key areas that are important to keep an eye on to manage tight schedules effectively are:

• Architectural approval turnarounds
• Material lead times
• Testing and mock-ups

We will review each of these items, using the example of the Harbor Point S4 vestibule that Bellwether designed and supplied for the developer. The schedule for this project was just 12 weeks from start to finish, accommodating an aggressive occupancy date.

Architectural Approval Turnarounds

On a typical design development timeline, we like to provide two rounds of drawings, with two approval cycles (for more, see Why Shop Drawings Should Not be the First Deliverable You Ask For):

• Profile drawings are created in 2-3 weeks to confirm basic design intent and to agree on typical details and interfaces. We typically schedule a 1-2 week architectural approval period.
• Shop drawings are created in about 2-3 weeks, with another 1-2 week architectural approval period.

The short timeline on Harbor Point S4 required profile drawings in 1 week, and shop drawings in 2 weeks, with 24 hour approval turnaround times. Since the developer was very hands-on with the design and process, and since time was the ultimate project driver, this turnaround was agreed to, at contract signing.

Material Lead Times

Material choices are limited when you have an 8 week production schedule. Two things helped on this system design:

• Patch fittings were used to anchor the glass, rather than point supported fittings. This meant that glass could be standard insulated glazing units without the need for holes which would have elongated production time.
• The patch fittings themselves were designed as simple square shapes from the initial architectural drawings, so they could go into production without changes once engineering calculations were complete. Given more time, additional shapes, materials, glass make-ups, etc. could have been considered.

Material Mock-ups and Testing

Material mock-ups and testing are typically casualties of a short project schedule. Laboratory testing and mock-ups can sometimes double the lead-time needed for a custom project: Mock-up materials used for aesthetic approvals and testing purposes can be created only after shop drawings are done. Then, if system changes are made after testing or mock-up creation, a new material production schedule must begin. In the case of the S4 vestibule, the design was based on a straightforward structural glazing system with silicone weatherseals. The performance of this design approach is well tested and proven in the field.

By approaching custom glazing system development with a motivated design team and a good understanding of project drivers and tradeoffs, it can be possible to get a very custom aesthetic in a relatively short amount of time. For more on the topic, see The Two Most Important Questions Architects Can Ask Themselves When Designing Custom Glazing Systems.

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When completing a renovation on an existing building, detailed as-built drawings seem to be the most efficient way to uncover what is hidden by various exterior cladding systems. The trouble is, these drawings are not always available or accurate and up to date. For instance, older buildings can undergo multiple renovations without updates to as-built drawings. Unfortunately, this lack of information can lead to uncertainty during the bidding stage and preliminary design stages of subsequent construction.

If accurate as-built drawings are not available, the strategy to obtain an accurate determination of existing conditions is based on access.

– Field dimensions: In cases where the area under renovation is accessible, simple field dimensions can often provide what is needed for renovation design and planning.

– 3D scanning: Scan technologies such as laser scanners allow for the creation of a detailed “point cloud” of information of existing conditions that can be converted into detailed 3D models of various formats. Building scans are particularly helpful when the project conditions are too large or inaccessible to measure manually.

– Demolition / coring: To avoid issues with unforeseen conditions later in the project, there is always a certain level of physical demolition and research that should be done to accurately document what is already in place. Coordinating with the engineer of record is a great way to get the background information and set the expectations for the demolition work. Keeping the physical demolition to a minimum is a key component, peeling back just enough to allow for access. Field measurements can then be pulled to set the parameters of the design, quantify materials, determine anchor points, etc.

The following project examples include a situation where the position of structural members was determined well after the start of construction (1350 Eye Street), and one where a laser scan was performed prior to material fabrication to insure proper coordination/fit of new system on existing structure (MIT Kresge Auditorium).

Project Examples:

1350 Eye Street

Bellwether completed a renovation to an existing building in Washington, DC consisting of an exterior glass wall with an integrated interior vestibule. During the preliminary design stages, the structural steel anchorage was believed to be within 12” of the finished ceiling based on original building architectural and structural drawings. This proximity of structure called for a simple face-mounted anchor.

When the GC proceeded to core out the existing finished to expose the structure, well after the start of material fabrication, it was discovered that the structural steel anchor point was over 3’ from the finished ceiling surface. Bellwether coordinated with the building engineer to develop a steel kicker/anchor that could handle a significant increase in torsional forces applied to the tall anchor.

Bellwether then analyzed the ability of the entire structure (wall and vestibule) to handle the imposed loads as a coordinated system. To reduce the torsion on the tall kickers and existing structure above, Bellwether used the stability of the base glass vestibule and walls to nullify the cantilever of the suspended fins. The end solution saved the installer, GC, and building owner money by looking at the complete picture and engineering a relatively low cost kicker versus finish materials such as extended glass fins or a more extensive supplemental steel support structure.

MIT Kresge Auditorium

Bellwether recently completed a renovation project at the historical Kresge Auditorium on the MIT Campus in Cambridge, MA. The main objective was to replace the existing aluminum skin system with a new laser fused stainless steel system while retaining the original curtain wall design, shapes, and dimensions.

The new system was to mount to the existing interior steel mullions. To accommodate the existing steel dimensions and tight tolerances of the new material to be fabricated, a laser scan was completed to ensure accuracy in the relationship of new to old when the pre-fabricated material arrived on site.

Materials were delivered pre-fabricated and pre-finished to accommodate efficient installation and a tight project schedule. The existing steel mullions outside tolerance were straightened and refinished, allowing the new system to fasten directly to the existing structure with minimal site work.

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When these costs are not well documented, they can become a source of disagreement further into the project regarding who is responsible for specific charges. It is critical that the design team understand the site conditions and installer limitations, and prioritize them against the parameters of the original design.

Site specific challenges posed by factors such as surrounding conditions, site logistics, material sizes, and even installation methods can vary greatly. The most efficient way to avoid these issues from arising once the project has begun is to engage in clear, up front communication between the design team and installer. Information such as glass panel weight, steel size and length, and even fabrication assumptions should be discussed in the design phase so that a strategically coordinated installation plan can be created. For instance, limited site access and equipment availability may be an argument for limiting material weights, sizes and fabrication methods.

Design Assistance Project Examples:

Edward M. Kennedy Institute

Bellwether’s structural glass wall at the EMK Institute in Boston includes glass lites that are 11’6” tall x 3’ wide. Designed to meet 105 mph wind speeds with minimal, two-sided structural support, the insulated glass units are 2-5/8” thick, and 24 lbs. per square foot. This yields a glass unit weight of 828 lbs. The final dimensions of the lite sizes was partially determined by a strategy to keep each lite below 1,000 lbs., based on the type of equipment needed to set the lites initially, and for potential re-installation after finished walkways were installed. Various design studies were undertaken during the shop drawing phase in order to fine tune the appropriate bay widths with these weight parameters.

Glass Conservatory – Private Residence

Bellwether recently completed an exterior glass conservatory project at a private residence that had very limited access to the install area. In addition to the limited access, the structure had to be designed so that it could be disassembled as needed in the future. A modular steel frame was designed with low profile connections to provide for easy assembly, without compromising the architectural design intent. Additionally, the installer was able to easily transport materials down a narrow walkway and maneuver them into place by hand.

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The design statement made by a custom glass canopy, vestibule, or wall is often just as important as its intended functional purpose. The Apple cube, for instance, has taken on a life of its own in terms of its unique aesthetic, and the simplicity of the cube also conveys the design and engineering brand attributes that are part of everything Apple does.

Design teams spend a great deal of time obsessing over project details, proportions, and materials in order to ensure that the structure conveys a specific feeling, or set of attributes. When the project is built to specifications, the architectural intent is achieved. Professional photos are taken around the time of building opening, and then everyone moves on to the next project.

Here’s where that architectural intent can sometimes break down: Have you ever returned to the site 6 months later and found dust, leaves, spider webs, tumbleweeds, etc. making your glass jewel box into a dull version of what it was meant to be? The absence of a proper maintenance plan can actually impact a company’s brand by conveying lack of upkeep and respect for the building. Likewise, it can do damage to the architect’s brand by suggesting that something was missed in the proper design of the structure.

Project specifications almost always call out detailed cleaning procedures as the last step in installation. Additionally, a care and maintenance manual is typically provided by product manufacturers for basic materials and finishes. However, an overall maintenance schedule is often overlooked in specifications.

A relatively flat skylight or canopy, for instance, will not allow water to run off as efficiently as one with a steeper pitch. Sometimes, small design tweaks can help with performance, such as the design of our glass cube at Harbor Point. Here, we integrated a slight ridge in the roof to move water off the sides of the structure, keeping them away from the front door, and not allowing “ponding” to occur on an otherwise flat roof. The ridge is barely perceptible. It does not change the overall look of the cube, but helps to keep it cleaner.

In all cases, building maintenance crews should be directed by the architect to develop a regular cleaning schedule to keep things looking clean and new. All-glass features are susceptible to finger prints, dust, and visible debris. This detracts from the reflectivity, transparency, and ultimately the architectural intent of the structure. A high-span frameless structure becomes more difficult to clean without proper lifting apparatus – while window washing anchors can be incorporated more easily into metal framed systems, they become more difficult to include in all-glass systems. Once again, cleaning and lifting equipment should also be taken into account for equipment needs.

Long lasting aesthetics require well performing custom glass structures to move water and debris off their exterior surfaces, but they also require regular maintenance for both interior and exterior surfaces. When maintained on a regular schedule, the true design intent endures as long as the structure.

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Creating custom glazing systems requires time, planning, and process that are unique to the project. Too often, as construction schedules and budgets get compressed, there is an assumption that the custom materials can be sped up accordingly. That’s unfortunately not always the case.

The most important thing to consider when starting a custom project, is that the design team will be defining all aspects of the system, from design through structural tradeoffs. This happens from project development through design-build stages. When using standard product, you have the convenience of access to existing library testing, and your material choices, sizes and thicknesses are limited to what works within those test parameters. Basically, if you stay within product parameters, you will be safe. This “transactional” type of purchase and design is fast and easy to meet tight construction schedules, but it won’t win any design awards.

Custom glazing system development gives you complete flexibility to match architectural intent. Many system solutions can be developed based on proven design methodology, which maintain performance and structural integrity. However, it takes additional time to tweak things like material sizing, anchors, and coordination with adjacent systems. It is important to launch the design stage with a full discovery process that brainstorms, identifies, and budgets all of the potential options that should be considered, so that you don’t have to go all the way back to square one when it’s time to value-engineer the system. This is the point where the team must plan the design assistance schedule within the overall construction schedule.

Material choices can have a big effect on lead times. For instance, a glass fabricator may have limited quantities of 3/4” low iron glass, but a large inventory of 3/8” low iron glass. If you have the flexibility to use a laminate of 3/8” over 3/8” glass, and understand the tradeoffs, you may be able to get the same look in a lower price, with a much shorter lead time.

Structural considerations of custom systems can also have a significant impact on the construction schedule. Oversized, tall-span glazing systems impose unique loads on the surrounding structure. One of the common considerations during the design stage is to determine where these systems will be dead-loaded conventionally at the base, or hung from above. These decisions are based partially on the characteristics of the custom materials, and partially on the limitations of the surrounding structure. The analysis doesn’t always change the base building structure, but coordination of structures should be given appropriate time to consider impact.

In the end it comes down to the definition of your systems. Are you willing to accept existing off-the-shelf products for the convenience of design simplicity, or do you want to create something with your signature on it? Off-the-shelf systems can be delivered within shorter lead times, where customization and uniqueness of the aesthetic is not a key project driver. Signature projects incorporating custom glazing systems require a well thought out design-assistance stage, complete with a system-specific timeline that allows for analysis and experimentation that will get you as close to the design intent as possible.

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• Protect it from budget cuts?
• Maintain the accuracy of the design intent?

The establishment of project drivers (aesthetics, material quality, budget, etc.) is the critical first step in defining your signature design element. These drivers will guide design teams as well as the supplier of the custom glazing system to put them on the same page with you. And we find that the two most instructive questions that you can ask in identifying the project drivers are:

1. What are the “Need-to-have” components of the project?
2. What are the “Nice-to-have” components of the project?

What we’re getting at with these questions is: What design or material elements truly define what you are trying to express, and what elements would not have an impact on that core intent if they were altered?

The answers to these questions help custom system designers to identify what is critical to you, and not spend time working on items that are not as important. If we, as systems designers, know what you absolutely can’t or won’t change for the sake of the design intent, we can advise you of the associated costs and challenges, and discuss strategies to absorb the cost impacts in other, less critical areas of the design.

This is where our creativity works in tandem with yours. You are the expert in how the building design will translate your intent. We are the experts on how to interpret that intent in the form of products and systems that meet with your aesthetic, budget, performance criteria, etc. The more we know about your preferences, how the design came about, and what you can’t live without, the better we can be at giving you options to meet your goals.

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The first question that we typically get on a new project at Bellwether, is “When will we see shop drawings?”. It’s not surprising to hear, since shops are typically the first submission on standard, off-the-shelf systems.

But shop drawings are ultimately an interpretation of how a glazing system supplier will use their system to address the perceived architectural intent. Sometimes they are a good fit with design intent, such as how a typical double hung window will fit within a standard rough opening. When it comes to developing custom, project-specific glazing systems, however, a conversation and working dialog has to be created to match the intent while presenting alternatives for various project-specific conditions. In other words, while you may have to modify your project conditions to meet the set criteria of a standard glazing system (e.g. choose rough opening sizes from the supplier’s offering), with custom design you can modify the glazing system to meet your needs exactly.

This is where the Profile Set of drawings makes sense as the first submission. As compared to shop drawings, Profiles are a scaled down set of drawings identifying key details, system sizes, shapes, anchor conditions, intersections with surrounding materials, etc. Basically, it is a conversation starter that presents our interpretation of what the architect wants, and how we would solve the project-specific challenges.

What is important to note is that the Profile set is a conversation starter. It is not meant to be as locked-down as a set of shop drawings. It is meant to lead to better shop drawings by answering some of the most common questions up front and presenting trade-offs to consider. And, this all happens while there is time to experiment with materials, structural strategies, and their budget impacts.

Profile drawings make for more accurate and efficient shop drawings, and a streamlined approval process, by:

• Getting everyone on the design, manufacturing, and installation teams in on the conversation up front. Here, we identify the impacts of the design before they are written in stone.
• Flushing out the design intent to insure that everyone is truly talking the same language.
• Identifying any discrepancies between architectural drawings, specification notes, and bid scopes of surrounding trades.
• Getting everyone working as part of the same team. This is the most important component, since multiple sets of shop drawing delivered by multiple suppliers, may each be designed in a vacuum. This approach typically requires significant coordination after the fact, when the clock is ticking loudly. Profile drawings smooth the flow through early coordination and communication among team members.

There is typically a good deal of time and effort invested by the time a full set of shop drawings is delivered. If there are critical differences of opinion identified at the shop drawing stage, there can be significantly more time lost in going back to the drawing board to coordinate after the fact.

When the process is started with a set of Profile drawings, the architectural intent is clearly identified by the whole construction team before anyone has taken too much time moving in the wrong direction. In our experience, this process is guaranteed to result in a streamlined set of shops that has a much greater chance of success during the approval process.

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